Driving dynamics system, vehicle and method for operating a driving dynamics system

Abstract

The invention relates to a driving dynamics system for a vehicle, comprising: at least one wheel brake (RB1, RB2, RB3, RB4) for dissipatively braking a wheel of the vehicle; at least one braking unit (EMB, EHB) which is associated with the at least one wheel brake (RB1, RB2, RB3, RB4) and is designed to generate a dissipative braking torque by means of the at least one wheel brake (RB1, RB2, RB3, RB4); at least one electric traction motor (TM1, TM2, TM3, TM4) which can be actuated to generate a regenerative braking torque for at least one wheel or an axle of the vehicle; and a central control unit (M-ECUDomäne) which is designed to control the at least one braking unit (EMB, EHB) and the at least one electric traction motor (TM1, TM2, TM3, TM4) in combination with one another for a braking function such that a combined braking torque can be generated by means of the at least one braking unit (EMB, EHB) and the at least one electric traction motor (TM1, TM2, TM3, TM4). The braking function relates to a standard case in which a base braking torque and an additional braking torque, controlled in a closed loop, are controlled in an open loop and / or closed loop. Optionally, the base braking torque is generated by the at least one braking unit (EMB, EHB) and the additional braking torque, controlled in a closed loop, is generated by the at least one electric traction motor (TM1, TM2, TM3, TM4), or the base braking torque is generated by the at least one electric traction motor (TM1, TM2, TM3, TM4) and the additional braking torque, controlled in a closed loop, is generated by the at least one braking unit (EMB, EHB), or the at least one braking unit (EMB, EHB) and the at least one electric traction motor (TM1, TM2, TM3, TM4) together each generate the base braking torque and the additional braking torque controlled in a closed loop.

Description

[0001] Driving dynamics system, vehicle and method for operating a driving dynamics system

[0002] Description

[0003] The present invention relates to a vehicle dynamics system (FDS) with one or more electric traction motors and a high-performance central computer. The central computer controls the electric traction motor(s) and brake modules (EMB, EHB) in a synchronized manner, such that the traction motor(s) and brake module(s) (EMB, EHB) are controlled jointly in the basic braking and control mode. It further relates to a vehicle with a vehicle dynamics system and a method for operating the vehicle dynamics system.

[0004] Preferably, the brake and electric traction motors are combined as wheel modules or electric vehicle axle modules, with the wheel brake and electric traction motor being controlled synchronously via another wheel or axle module control unit.

[0005] The automotive industry is undergoing a process of disruptive change. In addition to the increasing market penetration of electric vehicles, various stages of automated driving are being developed. These are initially: Stage 3 - Highly Automated Driving (HAD), Stage 4 - Fully Automated Driving (FAD), and Stage 5 - Autonomous Driving (AD). At each stage, the demands on the systems used to control driving dynamics increase.

[0006] From Level 4 (FAD), at least 2-fold, preferably 3-fold redundancies are expected to ensure sufficient system availability, e.g., for the pedal sensors with the "2 out of 3" rule. Furthermore, redundant wheel-specific brake torque control is required for automated driving from Level 3, especially from Level 4. In Level 5 (AD), the steering wheel, brake pedal, and accelerator pedal may be completely eliminated, and the vehicle is controlled exclusively via a central computer. Since the driver can no longer intervene via a brake pedal or steering wheel in the event of system failure, fail-safe 2-fold or 3-fold redundancy with degradation of all core brake functions (brake booster, ABS, vehicle stabilization) and steering is required.

[0007] In addition, the domain structure is being introduced with control units / domains for chassis control, which includes the brakes, electric drive, steering, and optionally also the damping. Through central control, the vehicle manufacturer assumes responsibility for the aforementioned components and can therefore optimally exploit synergies. At the same time, however, the manufacturer must ensure the necessary redundancies because new requirements must be met due to the transfer of liability from the driver to the vehicle manufacturer. Furthermore, autonomous vehicles of levels 3-5 should not be parked on the shoulder of the road; at the very least, a limp-home mode is more than desirable, and continued operation in the event of a partial failure is even more desirable, since autonomous vehicles aim for a long service life.

[0008] Electro-hydraulic brake systems (EHB for short) or electromechanical brakes (EMB for short) as well as foundation brakes with brake shoes and brake discs are available as friction brake systems. Compared to EHB, EMB has the disadvantage of higher costs, as an EMB is required for each wheel. However, it has the advantage that EMB can be controlled centrally much more easily, as a central vehicle dynamics control system (FDS) with ABS and ESP functions can be developed without dependence on brake manufacturers, and integration into the domain and application of an electromechanical brake is significantly simpler than an electrohydraulic brake. This is especially true compared to standard ABS systems with open brake circuits, which require very complex and adaptively learning pressure estimation models. The increasing popularity of EMB is therefore not primarily motivated by unit costs, but rather by lower application effort and easier integration.

[0009] A typical vehicle architecture with electric drives for SAE Level 3-4 is shown in Fig. 1a (Fig. 1a was taken from: https: / / www.lsp-ias.com / our-world / chassis-control). According to WO 2019 / 214833 A1, for example, an electric friction brake system with a brake booster and an ESP unit is used. Furthermore, it is known from WO 2019 / 002475 A1 that the brake can be controlled as a pressure regulator, centrally via a central computer, namely a domain, so that the braking torques are determined in the central computer and the electrohydraulic brake serves merely as a pressure regulator to implement a target braking torque or a target pressure.

[0010] Furthermore, WO 2020 / 165255 A1 discloses an electro-hydraulic braking system in which, in the event of failure or partial failure of the pressure supply device, braking is carried out or assisted by an electric traction motor and / or an electric parking brake.

[0011] Furthermore, the so-called combi brake is known from WO 2019 / 215278 A2, where an electro-hydraulic brake (EHB) is used on the front axle and an electromechanical brake (EMB) or a hydraulically assisted electromechanical brake (H-EMB) is used on the rear axle.

[0012] WO 2020 / 128081 pursues an electric axle module where a pressure regulator supplies the hydraulic consumers, in particular the hydraulic wheel brake, with pressure.

[0013] WO 2018 / 215397 A1 pursues the idea of ​​centrally controlling the electric motor and electrohydraulic brake, with a focus on achieving the minimum time to lock (TTL). Furthermore, a braking function exclusively via the electric traction motor is introduced, depending on the driving situation, using a vehicle model.

[0014] In WO 2021 / 037658A1, another idea for the central control of the electric traction motor and electro-hydraulic brake is realized, namely the central control of the electric brake force distribution with simultaneous recuperation via the electric motor.

[0015] A holistic optimization of vehicle dynamics control and cost reduction through the use of synergies between EMB or EHB combined with electric traction motors has only been investigated rudimentarily in the current state of the art, as brake-by-wire and braking via electric traction motors are considered separate units, and braking by electric traction motors has been limited to a deceleration of approximately 0.3 g for safety and liability reasons, particularly to avoid safety-critical driving situations. Furthermore, batteries are technically limited in their energy absorption, especially at full battery state of charge (SOC), when regenerative energy is generated via the electric traction motor, which requires an energy sink.The synergy potential of joint use between drive motors and brakes is very high, because electric drive motors are becoming increasingly more powerful and dynamic thanks to high-voltage technology (especially 400 V or 800 V) in the development of electric vehicles, and thus have the potential to significantly contribute to shortening braking distances. In particular, the combined use of electric traction motors in highly dynamic braking control processes, especially ABS control, offers enormous potential for novel, innovative approaches.

[0016] In addition, the potential for downsizing and cost reduction as well as functional improvements through central control with simultaneous use of different units during acceleration and braking have not yet been investigated.

[0017] Furthermore, the application effort for a brake is currently characterized by very extensive application work. State-of-the-art brake systems (EP 2 536 607 B1, EP 3 036 136 B1) with ABS control, pre-pressure control via a plunger, pressure build-up via intake valves, and pressure reduction with time control via exhaust valves require complex pressure models that must be adapted for each vehicle. Therefore, numerous application engineers are employed for several years to apply the application to a vehicle for all driving situations and friction coefficient conditions.

[0018] The object of the invention is to provide a vehicle dynamics system (VDS) with central domain control via a vehicle dynamics domain or a central computer, as well as with wheel modules or vehicle axle modules with multiple brake units (electric traction motor, electrohydraulic pressure regulators (EHB), and / or electromechanical brake actuators (EMB)), whereby the synergies between the individual brake modules are maximized to implement a braking task. The overall costs, weight, and thermal load on the components of the braking system are to be minimized. At the same time, the braking distance is to be minimized and driving stability is to be ensured.

[0019] The wheel or axle modules should preferably be controlled in such a way that the respective wheel or vehicle axle only applies the target braking torques, and the distribution of the braking torques among the wheels or axles is calculated in a central computer, where the core functions of the anti-lock braking system (ABS), anti-skid control (ASR), electronic stability control (ESC), electric brake force distribution (EBD), and regenerative brake management are also implemented. The task of the control electronics of the wheel or axle module, in turn, is to distribute the target braking torques among the various brake units of the wheels or vehicle axle.

[0020] Furthermore, a method for controlling a vehicle in highly dynamic braking mode (AEB emergency braking function, and in particular subsequent ABS control mode) is to be provided for a vehicle with a corresponding driving dynamics system (DDS). This method is optimized with regard to braking distance and optimizes controllability in critical driving situations (ABS operation on snow or ice). Furthermore, the brake modules are to be designed in such a way that rapid application is possible and, in particular, the application can be automated.

[0021] Furthermore, the brake modules are advantageously to be designed in such a way that an interruption in normal operation is either avoided or prevented by the subsequent delivery of hydraulic volume, as taught by EP 2 580 095 B1 and implemented in two integrated brake systems on the market (DE 10 2018 212 905 A1, DE 10 2019 204 016 A1), or by dead times in a multiplex control process, or is compensated for by control interventions via electric traction motors.

[0022] Furthermore, the brake modules are advantageously designed in such a way that a diagnosable valve device is provided between the pressure supply unit and the hydraulic consumer, in particular a wheel brake or several wheel brakes of an axle, in particular a wheel valve that is resistant to closing (in the following Figure 6a as MV2k,i, MK 2k;2 , MV 2k ,3, MV 2k,4) and / or circuit isolation valve (referred to as MV2k v in the following Figure 6b), which is designed for a bidirectional volume flow, i.e. both during pressure build-up and pressure reduction, which makes it possible to isolate the corresponding consumer by closing the valve device in the event of leaks from a consumer and to continue operating the system with one less consumer.

[0023] In the prior art (EP 3 036 136 B1), for example, a check valve (referred to as inlet valve 88 and check valve 92 in EP 3 036 136 B1, Figure 1) is provided in parallel with the wheel inlet valve, which is necessary in order to be able to safely reduce the pressure in the wheel brake in any situation, in particular in the event of a failure of the ECU or the power supply.

[0024] The new design with a non-closing valve device has the decisive advantage that the failure of a wheel circuit can be clearly diagnosed because there is no uncertainty as to whether the leak is caused by the switching valve or the check valve. If the valve leak or the failure of the hydraulic line to the wheel brake or multiple wheel brakes is diagnosed, for example using a method as described in WO 2018 / 011021 A1, the hydraulic circuit can be safely isolated by closing the valve, and the braking system can continue to operate with only one less consumer. This has a decisive advantage over braking systems with typically two brake circuits and four wheel brakes (referred to in the prior art as a black-and-white brake circuit (II) or diagonal brake circuit (X)), where two wheel brakes must be deactivated directly in the event of a fault.The advantage of the innovative valve system is significant: In the event of a fault, the achievable deceleration is significantly higher with three wheel circuits instead of two, and it also allows yaw moment interventions for ESP and steering interventions to be maintained with three wheel circuits without significant performance losses. If an electric drive motor is also available to drive and brake the failed wheel and is integrated into the control system, even braking torque control with four wheel brakes is still feasible in the event of a fault.

[0025] Furthermore, the braking system should be designed in such a way that a simple application of the core functions via the central control system, in particular due to the high computing power of the central or domain computer, is possible in the application of the functions in development, and in particular also in vehicle operation via learning algorithms or artificial intelligence (AI) both before the initial commissioning of the vehicle and subsequently during operation for normal operation without errors as well as for adapted operation when an error occurs.

[0026] With the AI ​​approach, a powerful central computer with sufficient performance can take over the role of the application engineer, something that is not possible with state-of-the-art microcontrollers, such as those used in conventional control units for braking systems, due to their very limited performance and limited memory. The central computer records measurement data during vehicle operation, evaluates it, and applies various functions, particularly the safety-critical functions ABS, ESP, and AEB, while the vehicle is running or at a standstill when the vehicle is not moving and therefore the adjustment is not time-critical.

[0027] Therefore, adaptation takes place particularly after vehicle operation, when the vehicle is parked. Here, the preferred design as a closed hydraulic system, particularly with pressure build-up and pressure reduction via bidirectionally acting valves using a pressure supply unit, has the significant advantage that the non-linear relationships can be mapped by suitable sensors via characteristic maps (e.g., pressure-volume characteristic curve, relationship between motor current and brake pressure, relationship between brake pressure and / or deceleration when the wheel brake heats up). Furthermore, these characteristic maps can be adapted during operation by detecting environmental influences, for example, air in the system or heating of the wheel brake.

[0028] If the non-linear relationships are mapped in mathematical functions or characteristic maps, an automatic application of an electro-hydraulic braking system can also be carried out.

[0029] If the AI ​​approach is consistently implemented in a hydraulic braking system (EHB), the advantage of the easily adjustable or controllable electromechanical brake (EMB) disappears and the advantages of the lower manufacturing costs of the hydraulic braking system become effective because the disadvantages in the application costs largely disappear.

[0030] Furthermore, different solution approaches will be investigated depending on the electric drive architecture and the level of automated driving. Therefore, solutions are presented for the following different architectures for the arrangement of electric traction motors, which are shown in Fig. 1b: a) One electric traction motor TM1, TM2 on the rear axle (HA) or front axle (VA); b) One electric traction motor TM1 on the rear axle (HA) and one electric traction motor TM3 on the front axle (VA); c) Two electric traction motors TM1, TM2 on the rear axle (HA) for wheel-individual torque control of both wheels RI, R2; and d) Two electric traction motors TM1, TM2 on the rear axle (HA) and one electric traction motor TM3 on the front axle (VA).

[0031] Variants a) to d) can be combined as desired, with the most effective solutions b) and c) being the focus of the further embodiments of the invention.

[0032] In addition to the electric drive modules, the following brake unit configurations are to be investigated, which are shown in Fig. 2c: a) Central electro-hydraulic brake (EHB-Z) with wheel-individual braking torque control options for four wheel brakes (RI, R2, R3, R4) via solenoid valves; b) Axle modules with electro-hydraulic brake (EHB-VA) with wheel-individual braking torque control options for two wheels (RI, R2) of a front axle (VA), optionally combined with a hydraulic line to two wheel brakes (R3, R4) of a rear axle (HA) (compare, for example, Figures 6b and 6c explained in more detail below); c) Axle modules with electro-hydraulic brake (EHB1, EHB2) for two wheels (RI, R2; R3, R4) of an axle (VA, HA) with wheel-individual braking torque control via solenoid valves; and d) wheel modules with electromechanical brake (EMB1- EMB4) for each wheel (RI, R2, R3, R4) of a vehicle.

[0033] In addition, the different requirements of SAE Levels 2-5 for automated driving should be taken into account in the design of the embodiments. The solution approaches differ depending on whether only a fail-safe solution is required for SAE Level 2 and a fail-operational solution is required for SAE Levels 3-5.

[0034] - First of all, the following priorities apply to a braking system:

[0035] The following main requirements are defined based on the priorities explained above, the time delays in driver intervention, the duration and speed of autonomous ferry operation (SAE Level 3-4) and the assumption of liability by the automobile manufacturers.

[0036] The object of the invention is achieved by a driving dynamics system (DDS), a vehicle with the driving dynamics system, and a method for operating the driving dynamics system according to the independent claims. Advantageous embodiments and further developments of the invention are specified in the subclaims.

[0037] The driving dynamics system for a vehicle comprises, in particular, at least one wheel brake for dissipatively braking a wheel of the vehicle, as well as at least one brake unit assigned to the at least one wheel brake and configured to generate a dissipative braking torque by means of the at least one wheel brake. It further comprises at least one electric traction motor controllable to generate a regenerative braking torque for at least one wheel or axle of the vehicle. It additionally comprises a central control unit configured to control a braking function of the at least one brake unit and the at least one electric traction motor in combination with one another such that a combined braking torque can be generated by means of the at least one brake unit and the at least one electric traction motor.The braking function relates to a control case in which a base braking torque and a controlled additional braking torque are controlled and / or regulated simultaneously. Optionally, the base braking torque is generated by the at least one braking unit, and the controlled additional braking torque is generated by the at least one electric traction motor; or the base braking torque is generated by the at least one electric traction motor, and the controlled additional braking torque is generated by the at least one braking unit; or the at least one braking unit and the at least one electric traction motor each jointly generate the base braking torque and the controlled additional braking torque.

[0038] In one embodiment of the invention, the braking function is selected from at least one, preferably several of the following functions:

[0039] - automatic emergency brake (Automated Emergency Brake, AEB), in particular with an EBV control, in particular with an EBV control on a rear axle and a front axle of the vehicle, whereby a total braking torque is distributed between the rear axle and the front axle;

[0040] - Anti-lock braking system (ABS), in particular with a basic braking torque support via the at least one traction motor (TM1, TM2, TM3, TM4);

[0041] - Electronic Stability Program (ESP);

[0042] - electronic brake force distribution (EBD);

[0043] - Anti-skid control (ASR);

[0044] - Distance control (Automated Cruise Control, ACC);

[0045] - Recuperation management, especially for axle or wheel-specific recuperation;

[0046] - Basic brake with thermal management;

[0047] - Yaw moment control in case of wheel brake failure; and / or

[0048] - Yaw moment intervention control for steering assistance.

[0049] In particular, the central control unit comprises a central computer, wherein the central computer preferably comprises redundant microcontrollers JLLCI, p.C2, p.C3 and / or a large memory, in particular in the order of gigabytes. In a further embodiment of the driving dynamics system, the braking unit comprises an electric motor drive and is designed as an electrohydraulic braking unit or as an electromechanical braking unit.

[0050] In a further development, the brake unit is designed as an electrohydraulic brake unit with an electric motor-operated pressure supply unit, wherein a valve device is provided between the pressure supply unit and at least one wheel brake or several wheel brakes of an axle. The valve device comprises a wheel valve that is resistant to closing and / or a circuit isolation valve. In the event of a leak in at least one wheel brake, the valve device is configured to isolate the affected wheel brake by closing the valve device, and the central control unit is configured to control the at least one brake unit and / or the at least one electric traction motor such that braking torque is controlled at the other wheels of the vehicle, in particular at least three wheels. In this case, the wheel brakes of one axle of the vehicle, in particular the wheel brakes of the front axle, can be isolated by means of the valve device.

[0051] In a further development, the central control unit is coupled to at least one brake unit control unit of the brake unit.

[0052] In a further embodiment, the central control unit is configured to transmit target signals to an engine control unit of the at least one traction motor and to a brake unit control unit of the at least one brake unit during the braking function.

[0053] In one embodiment, the central control unit is further configured to control at least one electric traction motor for regenerative braking of the vehicle when the vehicle is traveling at a speed of over 80 km / h during normal operation. During regenerative braking, an electronic brake force distribution (EBD) function is simultaneously implemented on a front axle and a rear axle of the vehicle. In particular, 20-40% of the total braking torque acts on the rear axle and 60-80% of the total torque acts on the front axle of the vehicle.

[0054] In a further development, the wheel brake of one wheel of the vehicle is assigned a separate brake unit, with the brake unit being particularly electromechanical. In particular, the brake unit assigned to the wheel brake and an electric traction motor are integrated into a wheel module for each of the two wheels.

[0055] In one embodiment, a common brake unit is assigned to the wheel brakes of two wheels on one axle of the vehicle. In particular, the brake unit is electrohydraulic, with a first brake unit being assigned to the two wheels of a rear axle and a second brake unit being assigned to the two wheels of a front axle.

[0056] A central brake unit is assigned to the wheel brakes of four wheels of the vehicle, with the central brake unit in particular being electro-hydraulic.

[0057] In one embodiment, a common brake unit is assigned to the wheel brakes of two wheels of a first axle, in particular a front axle, of the vehicle. In particular, the brake unit is electrohydraulic. In particular, for the wheel brakes of the first axle, wheel-individual dissipative braking torques can be adjusted, in particular by means of solenoid valves in hydraulic lines between the brake unit and the wheel brakes. In particular, the brake unit can also be connected via a hydraulic line to the wheel brakes of two wheels of a second axle, in particular a rear axle. In particular, for the wheel brakes of the second axle, common, non-wheel-individual dissipative braking torques can be adjusted.

[0058] In one embodiment, a first electric traction motor is assigned to a first pair of two wheels of a first axle, in particular a rear axle of the vehicle, and a second electric traction motor is assigned to a second pair of wheels of a second axle, in particular a front axle of the vehicle.

[0059] In one embodiment, a first and a second wheel of a first axle, in particular a rear axle of the vehicle, are each assigned their own electric traction motor.

[0060] In a further development, the first and the second wheel are each assigned their own brake unit, wherein in particular the respective brake units are designed electromechanically. In particular for the first and second wheel, the respectively assigned electric traction motor and the respectively assigned brake unit are integrated into a wheel module each assigned to the first or second wheel.

[0061] In a further embodiment, a third electric traction motor is jointly assigned to a third and a fourth wheel of a second axle, in particular a front axle of the vehicle. In this case, in particular, a common brake unit is assigned to the third and fourth wheel. In this case, in particular, the common brake unit is electro-hydraulic. In this case, in particular, the third electric traction motor and the common brake unit are integrated into an axle module assigned to the second axle; or in particular, a central brake module is provided, which is in particular electro-hydraulic, wherein by means of the central brake module, wheel-individual braking torques can be generated for the first and second wheels and a common braking torque can be generated for the third and fourth wheels.

[0062] In one embodiment, the central control unit is configured to distribute the base braking torque and the controlled additional braking torque to the at least one braking unit and the at least one electric traction motor as a function of the vehicle deceleration and / or as a function of a coefficient of friction of the road surface. In particular, in the case of lower deceleration and / or lower coefficient of friction, for example during ABS control on snow or ice or during deceleration in ABS braking mode, an electromotive braking unit and / or the at least one electric traction motor generates the controlled additional braking torque. In particular, in the case of greater deceleration and / or greater coefficient of friction, for example during braking on asphalt, an electrohydraulic braking unit generates the controlled additional braking torque.In particular, at medium deceleration and / or medium friction coefficient, the brake unit or the traction motor generates the basic braking torque as a constant braking torque and another brake unit or the traction motor generates the controlled additional braking torque.

[0063] In a further development, the central control unit is configured to execute an EBD control during automatic emergency braking, taking into account the braking torque gradients of the at least one brake unit and the at least one electric traction motor such that the maximum braking torque, in particular the maximum braking torque before the wheels lock, is reached simultaneously on the front and rear axles of the vehicle. In a further development, at least one of the following strategies is used during regenerative braking, in particular when a vehicle's battery is fully charged:

[0064] - Feeding the regenerated energy back into the battery up to the power consumption limit;

[0065] - field-oriented control (Id / Iq current control) of the electric traction motor in such a way that the energy in the motor is destroyed internally;

[0066] - Destroying the energy generated by the electric traction motor in generator mode, providing the generated energy for an electrical consumer of the vehicle and / or heating a

[0067] Fluid reservoirs for use with a heat pump for cooling or heating; and / or

[0068] - Use of an intermediate storage device, preferably electrical, designed for pulse power, for example a super-cap or a flywheel storage device.

[0069] In a further development, the at least one electric traction motor is operated with an inverter for switching windings of the at least one electric traction motor in series or parallel connection of three phases of the excitation coils of the brushless electric motor. In particular, the inverter enables 4-quadrant operation, namely with a quadrant 1 with a positive speed and positive torque of the electric motor, a quadrant 2 with a positive speed and negative torque of the electric motor, a quadrant 3 with a negative speed and positive torque of the electric motor, and a quadrant 4 with a negative speed and negative torque of the electric motor.

[0070] In one embodiment, the central control unit is configured to carry out the brake control based on a characteristic map, wherein in particular the characteristic map depicts a pressure-volume characteristic curve, a relationship between motor current and brake pressure and / or a relationship between brake pressure and / or deceleration when the wheel brake heats up.

[0071] In a further embodiment, the central control unit is configured to acquire sensor data during vehicle operation, particularly after initial vehicle operation, such as during ferry operation or when stationary before or after ferry operation, and to adapt the control of the braking function based on the acquired sensor data using an artificial intelligence method, particularly machine learning or neural networks. In particular, the artificial intelligence method can be executed using a computer in the central control unit. In particular, the adaptation is carried out in a safe state of the vehicle, particularly when the vehicle is parked.In particular, based on the recorded sensor data, a characteristic map is determined that depicts, for example, a pressure-volume characteristic curve, a relationship between motor current and brake pressure, and / or a relationship between brake pressure and / or deceleration when the wheel brake heats up. In particular, the characteristic map can be adapted based on the sensor data and the artificial intelligence process if a deviation from the current characteristic map is detected, for example, due to environmental influences, air in the system, or due to heating of the wheel brake.

[0072] Another driving dynamics system for a vehicle comprises at least one electric traction motor that can be controlled to generate a regenerative braking torque for at least one wheel or axle of the vehicle, and a central control unit that is configured to control the at least one electric traction motor for a braking function. The central control unit is configured to execute the braking function during braking on a road surface with a low friction coefficient, in particular on snow, ice, and / or a wet road surface, with low to moderate decelerations, in particular of less than 0.5 m / s2. In particular, the central control unit is configured to execute the braking function by means of at least one traction motor of at least one axle of the vehicle, in particular by means of two traction motors of the rear axle of the vehicle.

[0073] The vehicle according to the invention comprises a driving dynamics system according to the present description and the appended claims.

[0074] In the method for operating a driving dynamics system with at least one brake unit for generating a dissipative braking torque and at least one electric traction motor for generating a regenerative braking torque for at least one wheel or axle of the vehicle, and a central control unit for controlling the at least one brake unit and the at least one electric traction motor for a braking function, a combined braking torque is generated by means of the at least one brake unit and the at least one electric traction motor. The braking function relates to a control case in which a base braking torque and a controlled additional braking torque are controlled and / or regulated simultaneously.In this case, the at least one brake unit is optionally controlled to generate a base braking torque, and the at least one electric traction motor is controlled to generate the controlled additional braking torque; or the at least one electric traction motor is controlled to generate the base braking torque, and the at least one brake unit is controlled to generate the controlled additional braking torque; or the at least one brake unit and the at least one electric traction motor are controlled to jointly generate the base braking torque and the controlled additional braking torque.

[0075] The at least one electric traction motor for driving and braking an axle or a wheel of the vehicle has, in particular, a slave control unit on one or more axles or wheels of a vehicle.

[0076] The at least one brake unit or brake system is designed in particular for several wheel brakes, several electro-hydraulic brake modules or several electromechanical brake modules.

[0077] For example, a central vehicle model can be provided for the control system, by means of which the braking requirements for the wheel modules or axle modules can be calculated, taking into account the friction coefficient of the road surface, vehicle speed and weight distribution during braking.

[0078] Furthermore, brake control models and characteristic maps for synchronized brake torque control for the at least one traction motor and the brake unit, in particular EHB or EMB, can be provided in the sense that either the at least one electric traction motor or the brake unit, in particular EHB or EMB, provides a basic brake torque, while the dynamic brake torque control is carried out jointly by the at least one electric traction motor and the brake unit, in particular EHB or EMB, in particular by a controlled additional brake torque generated thereby.

[0079] Furthermore, sensor data from sensors can be used, whereby the sensor data is relevant for the implemented core functions and is read into the central control unit. For example, the sensor data from wheel speed sensors can be provided for an ABS function, yaw moment sensors for an ESP function, acceleration sensors and / or weight sensors for an EBD function and calibration of the functional relationship between brake pressure / brake torque and vehicle deceleration, which depends in particular on the temperature of the brake disc(s), and / or sensors for electrical recuperation strategies or emergency braking functions (AEB).

[0080] The central driving dynamics system can, for example, be used to optimize the use of at least one brake unit with a view to maximizing recuperation as well as braking or brake control performance in different driving situations. This occurs in particular depending on the braking situation, such as comfort braking or emergency braking, as well as the road surface situation, such as braking on asphalt, snow or ice, or in a so-called ^. jump or split, and the availability of the brake units. In particular, intelligent control via the driving dynamics system can reduce the costs of the brake calipers, in particular by minimizing the thermal load on the friction brake and downsizing and / or selecting the appropriate type of friction brake used, for example a drum brake or a disc brake.

[0081] Thus, in a first "Architecture I", a hydraulic braking system for wheels on the front and rear axles (EHB-Z) or a hydraulic braking system for the front axle only (EHB-VA) can be controlled together with the at least one electric traction motor via the central control unit as the braking unit. In Architecture I, a control unit (M-ECUBM, S-ECUTM,HA, S-ECUTM,VA) is provided for each of the braking units EHB-Z or EHB-VA and the at least one electric traction motor of the respective axle, which control unit has an interface to the central control unit. The central control unit M-ECUDomain transmits the synchronized target signals to the above-mentioned control units (M-ECUBM, S-ECUTM,HA, S-ECUTM,VA), wherein the target signals are in particular target braking torques or include them.

[0082] With this architecture, significant potential for an SAE Level 2 braking system with fail-safe operation can be tapped without changing the installed braking system. Such a braking system could, for example, be a common single-box braking system on the market, as described in DE102018212905A1, DE102019204016A1, or DE102019122169A1. This requires no modification of the mechanical or hydraulic structure of the braking system; instead, it merely requires an extension via an interface, such as a wheel-specific target pressure interface or a wheel-specific target torque interface. This is achieved through integration into the central control unit (domain) and intelligent control of the braking unit and the installed electric traction motors on one or both vehicle axles, or two wheels of a vehicle axle.

[0083] As an alternative to the conventional braking systems mentioned above, the brake unit (EHB) is advantageously further optimized so that the brake unit (EHB) is designed as a wheel-specific pressure regulator with wheel control valves. Each of the hydraulically actuated wheel brakes forms a separate wheel circuit and can preferably be isolated by closing the preferably non-closing wheel valves MVzk. Furthermore, an EHB pressure regulator with control valves for the front axle only (EHB-1, EHB-VA) and / or a pressure regulator with control valves for the rear axle (EHB-2) and / or a pressure regulator (EHB-Z) can be provided as the brake unit, additionally with a brake circuit for both wheels of the rear axle. The aforementioned EHB-1 and EHB-2 solutions utilize "Architecture II," which will be explained in later sections and figures.

[0084] In a version for SAE Level 4, the driver's input is no longer recorded conventionally with an actuation unit for driver input detection, but with a piston-cylinder unit, preferably with a piston and a hydraulic pressure chamber as well as a hydraulic connection to the brake circuits or via an e-pedal. The driver's input signals are redundantly read into the M-ECU module. For SAE Level 5, a pedal is no longer required. The modular design with an e-pedal has the decisive advantage over the state of the art that SAE Level 4 and SAE Level 5 can be covered modularly, and the elimination of the hydraulic connection between the actuation unit and a pressure regulator enables particularly high flexibility in locating the pressure regulator in the vehicle.In addition, noise sources are avoided because the hydraulic pressure modulation noise is generated away from the bulkhead, thus preventing structure-borne noise from being transmitted to the passenger compartment. Such embodiments of an electro-hydraulic braking system are described in more detail in Figures 6a to 6d.

[0085] Thus, the various embodiments of the brake unit (EHB) and architectures I to II explained above are enabled by a central vehicle model, by means of which functions (a) to (g) are implemented. In a first advantageous function (a), the basic braking function, the heating of the friction brake is minimized by predominantly using at least one electric motor for braking. If a braking system is designed with a blending strategy according to the state of the art (see, for example, Figure 1b), the maximum pressure during the AMS fading test is used as the basis for dimensioning (see "Brake Manual", 5th edition, Chapter 6.3.2, Figure 6.10). This means that for the AMS test, 10 subsequent braking applications from 100 km / h are simulated. Accordingly, the wheel brakes on the front axle heat up to 600°C and the wheel brakes on the rear axle to approximately 500°C.The pedal force with standard vacuum brake boosters then increases by approximately 80%, meaning that the braking system must be designed for a pressure 80% higher than the normal locking pressure in the event of fading. With an appropriate safety margin, braking systems are therefore typically designed for a maximum pressure of approximately 200 to 220 bar. Typical biending strategies do not provide for regenerative braking at speeds above 60 km / h ("Brake Manual", Chapter 19.3.2, Figure 19.12); the potential braking power of electric motors is therefore not utilized. This limitation of regenerative braking to speed ranges below 60 km / h is due, on the one hand, to limitations in volume absorption during blending, such as the volume absorption by an accumulator chamber of the ESP unit in a 2-box braking system with electric secondary brake boosters.On the other hand, the brake manufacturer's liability and the legislation speak against expanding regenerative braking. Furthermore, these limitations may be due to the limited energy storage capacity of the battery, especially when fully charged.

[0086] With central FDS control, the potential of regenerative braking can be fully exploited. Furthermore, the heating of the friction brake and thus also the fading effect can be significantly reduced because the braking energy no longer leads to significant heating of the friction brake. For example, the at least one electric traction motor can be operated with an inverter that enables 4-quadrant operation (quadrant 1: positive speed, positive torque; quadrant 2: positive engine speed, negative engine torque; quadrant 3: negative engine speed, positive engine torque; quadrant 4: negative engine speed, negative engine torque). In this case, an electric traction motor with an exemplary drive power of 130 kW with a torque of 250 Nm can be connected to the rear axle of a mid-size vehicle (cf. BMW i3 vehicle with max.Braking torque 2000 Nm at the rear wheel / 3000 Nm at the front wheel) can also be braked in the second quadrant with approximately the same torque and power. The regenerative braking torque of the electric traction motors is slightly higher than the drive braking torque of the electric traction motor, as losses in the motor and transmission also have a braking effect, while during acceleration the losses reduce the drive torque. Thus, with this type of design, at a speed of 100 km / h, approximately 60-70% of the braking energy can be recovered at the rear axle through regenerative braking. If such a motor is also installed on the front axle, a deceleration of approximately 50% can also be achieved on the front axle.When braking via electric traction motors, one or more energy management strategies are pursued, whereby through efficient selection or combination of strategies, braking via the electric traction motor is de facto only limited by the torque limits in the 4-quadrant operation of the inverter.

[0087] The following four basic energy management strategies are available:

[0088] (1) Feeding back into the battery up to the limit of power consumption: This depends, among other things, on the energy absorption capacity of the battery, in particular on the current state of charge (SOC) of the battery.

[0089] (2) Field-oriented control (Id / Iq current control) of the electric motor such that the energy is dissipated internally in the electric traction motor: Internal energy dissipation is limited by the resistance of the excitation windings of the electric traction motor's stator, eddy current losses, and the motor's cooling capabilities. Since electric traction motors are designed for water or oil cooling, and the heating during pulsed braking, which is normally completed in 5-10 seconds during full braking, is dampened by the large thermal mass of the electric motor, the energy absorption by the electric motor during pulsed operation is relatively uncritical and can therefore usually be fully utilized.

[0090] Furthermore, a cooling circuit of the electric traction motor can be fed into a water reservoir, which in turn is used by a heat pump for particularly efficient cooling and heating of the vehicle's interior. This allows the energy "wasted" in the traction motor to be utilized, particularly with a heat pump efficiency of more than 300%.

[0091] (3) As a third option, the energy generated by the electric traction motor in generator mode can be used via a wear-free eddy-current brake, as is known from engine test benches, or another medium (e.g., water) can be heated in a similar way to a kettle. The generated heat can also advantageously be used via a heat exchanger for particularly efficient cooling or heating of the vehicle. Preferably, the energy from one or more electric traction motors is fed to a heat sink.

[0092] (4) As a fourth option, an intermediate electrical storage device designed for pulsed power can be provided, for example, a supercapacitor or flywheel energy storage device. Supercapacitors or flywheel energy storage devices are particularly well suited for pulsed power and, in contrast to batteries, can absorb significantly higher peak power. The energy temporarily stored in the supercapacitor or flywheel energy storage device can be used when accelerating the vehicle after braking or for other purposes in the vehicle.

[0093] Regenerative braking with energy management can reduce friction brake heating in the AMS test by more than 50%, and even by up to 70-80%. This effect can be advantageously used to simplify the friction brake on the front axle and to advantageously use a cost-effective, lightweight drum brake on the rear axle. Alternatively, this effect can be used to design the hydraulic brake for significantly lower maximum braking pressures, for example, 120-140 bar instead of 200-220 bar, which has a positive impact on the cost of the braking system because the pressure supply can be equipped with a smaller electric motor. Furthermore, the hydraulic volume of the pressure supply unit can be reduced.

[0094] Furthermore, by appropriately designing the interface between the vehicle dynamics system and the braking system with access to the electronic brake force distribution (EBD) function, the dynamics of the automatic emergency braking (AEB) can be further increased in a second advantageous function (b), which has a significant impact on the braking distance, particularly at high vehicle speeds. If braking is performed via the electric motor, the vehicle dynamics system must ensure that driving stability (see above - priority 2) and steerability (see table above - priority 3) are maintained in order to meet legal requirements and ensure vehicle safety. This means, for example, that the rear axle must not lock before the front axle, and if the wheels, especially the front axle, lock, the ABS must be activated.The interface between the vehicle dynamics system and the braking system must therefore be designed in such a way, and preferably the EBD function must be controlled in such a way that the maximum braking torque (wheel lock limit) is reached on the front and rear axles almost simultaneously. As explained below with reference to Figure 4, this can reduce the time from the start of braking to maximum deceleration (TTL time) from 140 ms to 90 ms even with an electric traction motor with an average power of 130 kW on the front and rear axles of a mid-size vehicle. At speeds exceeding 100 km / h, this can lead to a braking distance reduction of several meters. If the TTL time reduction is not feasible, for example due to chassis limitations, the braking effect of the electric motor can alternatively be advantageously used to make the braking system more cost-effective and smaller.This means that the pressure supply of the brake unit can be driven by a motor with lower torque and / or by a less powerful motor, or possibly by a cost-effective brush motor.

[0095] In a third advantageous function (c), axle-by-axle recuperation can be implemented via electric motors. Here, too, access from the vehicle dynamics system to the solenoid valves of the brake unit (EHB) or a suitable interface to the brake unit (EHB) must be defined so that the ABS operating state intervenes in critical fault cases. In the case of interaction between the brake unit (EHB) and the electric traction motors controlled via the vehicle dynamics system, the pressure build-up and pressure reduction must be controlled accordingly via inlet valves or isolating valves to the brake circuit of the front axle for the blending. This can be achieved during pressure build-up, for example, via PMW control of the inlet valves; during pressure reduction, alternatively via the MUX process via inlet valves or isolating valves, or via pressure reduction using outlet valves.The solution in the brake units EHB-Z and EHB-VA, as described below with reference to Figures 6a-6d, is simpler and significantly more flexible, especially when the wheel inlet valves are designed as pull-tight solenoid valves MVzk (also referred to as inlet / outlet valves below) designed for bidirectional volume flow, so that the pressure can be maintained due to the lack of check valves when the pressure supply has a lower pressure level than the wheel brake and the hydraulic braking torque is to be kept constant in the recuperation strategy.While in the embodiment of the EHB according to Figure 9a or in the variants of Figures 6a-6d, where no outlet valves are provided or only on some wheel brakes, the pressure reduction occurs exclusively via the inlet / outlet valves, in the embodiment according to Figures 6a to 6d and Figure 9b, the degrees of freedom for braking torque reduction exist via the inlet / outlet valves or via outlet valves. This is advantageous in the implementation of very dynamic braking torque interventions. In the embodiment according to Figure 6b, the axle-specific recuperation strategy is also only minimally affected, since pressure reduction occurs optionally via the inlet / outlet valves MVzk, 1-4 or outlet valves AV1-AV4. In the recuperation strategy via the driving dynamics system, the braking torque curve can be synchronized by the electric traction motor and the brake unit (EHB) in such a way that recuperation is maximized.If recuperation via the electric traction motor is limited, for example, when the battery is fully charged, the kinetic energy is dissipated via the brake unit (EMH). If the battery allows energy to be fed in, recuperation occurs primarily via the electric traction motor. With the wheel-specific degrees of freedom, axle-by-axle recuperation with an X-brake force distribution is also easily implemented.

[0096] When designed as an axle pressure regulator (EHB-1, EHB-2), preferably with a structure according to Figures 9a and 9b, the recuperation strategy is very simple and does not require valve confirmation, since the braking torque build-up and braking torque reduction can be carried out very precisely with the known PPC pressure regulation or pressure control.

[0097] In a fourth advantageous function (d), the at least one electric traction motor can generate a base braking torque during control operation. This is made possible by the use of modern electric traction motors with high power and torque (>200 Nm, <100 kW) and operating them at a high operating voltage (400 V, in particular 700-900 V). Such traction motors can implement braking torque changes with high dynamics (typical values: 15,000 Nm / s, 30,000 Nm / s are achievable), they can operate in 4-quadrant mode, and they are very dynamic in braking torque buildup and braking torque reduction. At low target braking torques, they are more dynamic than a hydraulic brake unit (EHB). Depending on the torque available across the entire speed range (1,000 Nm in Figure 3 up to the maximum vehicle speed), the maximum pressure of the brake unit (EHB) can be reduced by the maximum torque.Since a new type of ASR control is possible using electric traction motors (see ATZ 2 / 2014: "Control algorithms for recuperation and traction in electric vehicles"), high pressures are no longer required for ASR control compared to the previous state of the art, so that the maximum pressure of the brake unit (EHB) is determined by normal braking operation.

[0098] In a fifth advantageous function (e), the at least one electric traction motor can be used to support the brake system in the event of a brake unit (EHB) failure. Newer single-box brake systems, such as those shown in DE102018212905A1, are designed such that, in the event of a pressure supply failure, only a deceleration of 0.3 m / s is achieved via the driver's foot force. 2 which meets the legal requirements of ECE-13-H with a minimum deceleration of 0.244 m / s 2and also meets regional requirements in China. If the brake unit (EHB) is integrated into the vehicle dynamics system, the braking force in the event of a fault can be reduced to 0.58 m / s, as proposed in WO 2020 / 165255 Al. 2 This can be achieved by utilizing the braking power of electric drive motors. Furthermore, the electric drive motors, such as a TM1 motor on the rear axle and another TM3 motor on the front axle, can achieve a driving stability function comparable to a two-box braking system (iBooster + ESP-hev). This allows SAE Level 2+ to be achieved by integrating the brake unit (EHB) into the central control system of the driving dynamics system.

[0099] If the braking system described in WO 2020 / 165255 A1 is further developed in such a way that electric drive motors generate a basic braking torque according to function (d) and the pressure supply is also designed to be partially redundant with redundant windings, for example by being designed with 2x3 phases, (partially) redundant electronics (DV1-ECU1, DV-ECU2) and connections to two on-board networks and / or power supplies (BN1, BN2) as well as data lines (DS1, DS2), the pressure supply can be operated at half power or half torque even in the event of a winding or power semiconductor failure of a motor output stage, which is the most common failure in EC motors. With a preferred design at 140-160 bar, a pressure of 70-80 bar can still be generated. This allows for fully functional ABS control even in the event of a partial failure of the pressure supply.If, in this fault case, at least one traction motor is used to set the basic braking torque to generate a basic braking torque, ABS operation with maximum deceleration, in particular approximately 1 to 1.4 g, can also be achieved.

[0100] If, in a 1-box brake system, such as that according to WO 2020 / 165255 A1, inlet / outlet solenoid valves or switching solenoid valves (SV1-SV4 of Fig.7 of WO 2020 / 165255 A1) designed for bidirectional volume flow are used between the pressure supply and the wheel brake in both brake fluid flow directions, i.e. from the pressure supply to the wheel brake and from the wheel brake to the pressure supply, each wheel circuit can be reliably diagnosed and separated from the brake system in the event of a fault. This is not possible with the wheel inlet valves otherwise used in the prior art, since non-diagnosable and non-safely closable check valves (such as reference numerals 50a-50b of Figure 1 of DE 10 2013 222 281 A1) are used parallel to the inlet valves (such as reference numerals 6a-6d of Figure 1 of DE 10 2013 222 281 A1).This allows the vehicle dynamics system to operate in three-channel wheel pressure control mode even in the event of a fault, enabling a vehicle stabilization function comparable to the ESP function, as well as maintaining pressure in the wheel brake circuit. This, in turn, provides additional degrees of freedom in braking torque control, particularly with wheel-specific recuperation. This type of novel activation valve is also preferably used in the inventive EHB solutions shown in Figures 6a-6d and Figures 9a and 9b, explained in more detail below.

[0101] In any case, a 2-channel ABS function must be provided on the front axle to ensure steerability according to priority 3. This can also be implemented if no bidirectional, non-closing valve (switching solenoid valve MVzk) is provided on the wheel brakes. In this case, a separating valve is provided between the front and rear axles. Pressure control can alternatively be achieved via the MUX pressure control method with pressure build-up and pressure build-up via switching valves, whereby the switching valves are preferably designed such that the valve seat of the solenoid valves is connected to the wheel brake to ensure that the brake pressure is not trapped in the wheel brake. Optionally, outlet valves can also be provided so that, as an alternative to MUX pressure reduction, pressure reduction takes place via outlet valves into the reservoir. In this context, reference is also made to Figures 9a and 9b, which are explained in more detail below.

[0102] Another alternative is to implement standard ABS control, where a pre-pressure is set via the pressure supply, and pressure build-up is achieved via PWM control of the switching valves, and pressure reduction is achieved via time control of the outlet valves. In this case, the valve seat is connected to the pressure supply, enabling proportional control of the flow cross-section. Shrink-proof switching valves are particularly important here, ensuring that the brake pressure is not trapped in the wheel brake in the event of a failure due to high differential pressures.

[0103] In a sixth advantageous function (f), yaw moment interventions for steering assistance can be implemented by specifying a setpoint value from the vehicle dynamics system. For this purpose, pressure buildup and pressure reduction can be controlled accordingly via intake valves (see, for example, reference numeral 11 of DE 10 2018 212 905 A1), so that the hydraulic braking force is modulated with the electric braking force. This can be achieved during pressure buildup via PMW control of the intake valves; during pressure reduction, alternatively, via the MUX method via intake valves or isolation valves, or via pressure reduction via exhaust valves.

[0104] The solution with EHB-Z and EHB-VA according to Figure 6a and Figure 9a is simpler, especially if the wheel inlet valves are designed as inlet / outlet valves that are resistant to closing and designed for bidirectional volume flow. This allows pressure to be maintained due to the absence of check valves when the pressure supply has a lower pressure level than the wheel brake and the hydraulic braking torque is to be kept constant in the recuperation strategy. Furthermore, the degrees of freedom for braking torque reduction exist via the bidirectional inlet / outlet valves while simultaneously retracting the piston of the piston-cylinder unit of the pressure supply device or via outlet valves into the reservoir, which is advantageous for implementing highly dynamic braking torque interventions.

[0105] In a seventh advantageous function (g), wheel-specific braking torques for wheel-specific recuperation can be generated by specifying a setpoint value from the driving dynamics system. For this purpose, pressure buildup and pressure reduction must be controlled accordingly via intake valves (see reference numeral 11 of DE 10 2018 212 905 A1) so that the hydraulic braking force is modulated with the electric braking force. This can be achieved during pressure buildup via PMW control of the intake valves; during pressure reduction, alternatively, via the MUX process via intake valves or isolation valves, or via pressure reduction via exhaust valves.

[0106] The solution with EHB-Z and EHB-VA according to Figures 6a, 6c and 9a-9b explained in more detail below is simpler and significantly more flexible, especially when the wheel inlet valves are designed as non-return inlet / outlet valves MVzk, so that the pressure can be maintained due to the lack of check valves when the pressure supply has a lower pressure level than the wheel brake and the hydraulic braking torque is to be kept constant in the recuperation strategy. While in the embodiment of the brake unit (EHB) according to Figure 9a or in the variants of Figures 6a-6d, where no outlet valves are provided or only some of the wheel brakes, the pressure reduction takes place exclusively via the inlet / outlet valves, in the embodiment according to Figures 6a to 6d and Figure 9b, the degrees of freedom for braking torque reduction exist via the inlet / outlet valves or via outlet valves.This is particularly advantageous for implementing highly flexible braking torque interventions to maximize recuperation. In the recuperation strategy via the vehicle dynamics system, the braking torque curve of at least one electric traction motor and the brake unit (EHB) can be synchronized to maximize recuperation. If recuperation via the at least one electric traction motor is limited, for example, when the battery is fully charged, the kinetic energy is dissipated via the brake unit (EHB); if the battery allows for energy to be fed in, recuperation occurs primarily via the electric traction motor.

[0107] For functions (e), (f), and (g), a close-resistant and cost-effective inlet / outlet valve MVzk is important because it can prevent brake circuit failure and allow a wheel circuit to continue operating even if the switching valves leak. In this way, 4-channel wheel pressure control operation can be maintained even if the switching valves leak, or if a wheel circuit is switched off, emergency steering or steering assistance can still be performed with the 3-channel wheel pressure control operation, which can simplify the redundancy requirements of the electric power steering for higher levels of automated driving (SAE Level 3-4). These functions (e) and (f) are particularly important for the overall costs of the primary chassis control actuators for brakes and steering. If an electric power steering system is designed to be completely redundant, two steering actuators are required.However, the brake, through function (f), can become a valid solution approach as a redundancy function for the steering system to meet SAE Level 3-4 requirements. It also has the advantage that a non-identical unit can be used for the redundant steering function, thus eliminating production quality defects as a source of error in identical steering units. The steering function via the brake unit (EHB) can also be provided as a third fallback level of an already redundant electric power steering system EPS with two steering actuators, or as a second fallback level of an EPS with no or only partially redundant design, for example, with a steering actuator with 2x3 phases and a redundant control unit.In addition, the steering unit (EHB) can support the steering on a second axle where no EPS is provided, or can also carry out yaw moment interventions to stabilize the vehicle in addition to steering interventions, for example when braking on a split.

[0108] Thus, with the functions explained above, the SAE requirements for autonomous driving of level 3 can be met with a hydraulic braking system with only one pressure supply. For the fulfillment of SAE levels 4 and 5, all requirements are also met with the inventive extension of a

[0109] A single-box braking system according to Figures 6a and 6b is created. An emergency braking function with a commercially available dynamic response of 150 ms can also be ensured if the pressure supply is redundant and electric traction motors, as in function (b), support the build-up of braking torque. Although the maximum dynamic response of 90 ms of the inventive solution cannot normally be achieved, a TTL of 150-200 ms can be achieved with acceptable losses. This corresponds to the performance data of commercially available brake boosters.

[0110] In comparison, brake systems for SAE Level 3 and 4 (see WO 2018233854 Al) can only rely on the pressure dynamics of the ESP pump in the event of a brake booster failure, which, according to the current specifications, only allows a pressure build-up of 450 ms to 50 bar. The driving dynamics system also offers the option of supporting the pressure build-up via the ESP pump with the braking torque build-up dynamics of an electric traction motor. Depending on the power of the electric traction motors, a

[0111] A two-box braking system with a weak ESP pump can achieve a TTL of approximately 150-250 ms. The emergency braking function in the event of a fault is then equivalent or nearly equivalent to normal operation.

[0112] The integration of braking systems into a central control system, with the synergies and functional support described above, ultimately offers the potential to eliminate the hydraulic fallback function via a brake pedal (see Figures 6-6c) and either introduce an electric pedal or eliminate the pedal altogether. Thus, a braking system with only one pressure supply in a single unit (single-box braking system) with the inventive FDS certainly has the potential to achieve AD Level 5 qualification.

[0113] In a second "Architecture II", axle modules are provided instead of a hydraulic brake system controlled centrally via the domain. For example, an axle module has at least two brake modules, selected from:

[0114] - electric drive motor,

[0115] - electromechanical brake (EMB) for each wheel,

[0116] - electro-hydraulic pressure regulator (EHB-VA, EHB-HA) for each axle with wheel control valves for braking torque control for both wheels of the axle.

[0117] For example, an axle module can comprise an electric drive motor by means of which the wheels of an axle (VA, HA) can be driven and braked generatively, as well as an electromechanical brake unit (EMB) for each of the two wheels of the axle or a common electrohydraulic brake unit (EHB-VA, EHB-HA) for both wheels of the axle (VA, HA).

[0118] In contrast to the first embodiment, the second embodiment provides a control unit (S-ECUVA, S-ECUHA) for each axle. This control unit has a communication interface to the central control unit (M-ECU domain) and synchronizes the selected brake modules of the axle. Synchronization is particularly advantageous for control operation, as opposed to normal brake operation, because different delay times and time profiles in the build-up and reduction of braking torque are optimally coordinated by the various brake modules. Furthermore, such a structure resolves adhesion issues because the supplier of an e-axle is then responsible for the entire drive and brake management.In this second embodiment, various variants are possible: a) Electromechanical brake unit EMB combined with an electric traction drive, particularly advantageous for the front axle of a vehicle (see Figure 12a); b) Electromechanical brake unit EMB combined with an electrohydraulic EHB pressure actuator with wheel control valves, particularly advantageous for the front axle (see Figure 12b); c) Electric traction motors for each wheel of an axle combined with an electrohydraulic EHB pressure actuator with wheel control valves, particularly advantageous for the rear axle (see Figure 12c); and d) Electric traction motor for one axle combined with an electrohydraulic EHB pressure actuator with wheel control valves, generally advantageous for the front axle and rear axle (see Figure 12d).

[0119] The combination of an electric motor or electromechanical brake unit (EMB) with an electrohydraulic brake unit (EHB) is particularly advantageous because the advantages of both braking torque generators can be ideally combined: a) Electrohydraulic brake units (EHB) are highly dynamic in their pressure reduction at high braking torques and are insensitive to high braking torques, whereas electric drive motors or electromotive brake units (EMB) have their greatest advantages in braking torque gradients at low braking torques. Their costs also increase when designed for higher loads. b) Electrohydraulic brake units (EHB) are significantly more cost-effective than electromotive brake units (EMB). Compared to a pressure regulator for a rear axle with wheel control valves for two wheel brakes, the costs of the electromotive brake (EMB) are approximately twice as high.The costs for electro-hydraulic pressure actuators for the front axle with wheel control valves for two wheel brakes are only 10% higher, while the costs for the electromechanical brake EMB for the front axle are a further 50% higher than for the rear axle. The reason for the disproportionately high cost increase for the electromechanical brake EMB is the higher braking torques that must be achieved for the front axle and the necessity of providing two motors per wheel in luxury vehicles or SUVs. c) A combination of the electro-hydraulic brake unit EHB in the pressure actuator version with the PPC Gen2 pressure control process described below with an electric traction motor or electromechanical brake units EMB can exploit the advantages of the innovative PPC Gen2 pressure control with very precise braking torque control.Dead times in the PPC-Gen2 process, for example due to partial multiplex pressure control operation, can be compensated by control via traction motors or EMB, since such brake units can achieve comparable braking torque gradients.

[0120] To illustrate the advantages, the achievable pressure torque gradients are further illustrated in Figures 13a and 13b using a powerful electric traction motor and a typical braking torque gradient of EMB, EHB with AV / EV technology and PPC Gen2 operation and explained in more detail below.

[0121] The basic hydraulic principle used is the embodiments shown in Figures 9a and 9b, which are explained in more detail below.

[0122] The functions (a)-(g) performed in "Architecture I" can all also be performed in "Architecture II", even with more degrees of freedom, because two pressure supplies with pressure control valves per axis are available, which are also preferably designed redundantly.

[0123] In a third "Architecture III," wheel modules are provided instead of a conventional electro-hydraulic EMS braking system, with each wheel module equipped with an electric traction motor and an electromechanical brake (EMB). Wheel modules with electric traction motors enable very high flexibility in platform design. Such a concept is maximally flexible and has more redundancies than a conventional braking system, since in the event of a wheel module failure, all core functions of braking and brake control, vehicle stabilization, and steering can still be performed with the remaining wheel modules. The disadvantage is the high complexity, as an electric traction drive and an electromechanical brake unit (EMB) are required for each wheel. Furthermore, the electrical components are located in the area of ​​the unsprung masses and are therefore subject to high mechanical loads.The advantage is that the EMB can also map the parking brake function and therefore reduce costs.

[0124] As explained in the first embodiment, a synchronized use of the electric traction motor and the electromechanical brake unit EMB via the driving dynamics system is advantageous, especially when the braking power is divided in the basic braking function (see in particular function (a) of "Architecture I"). This allows the fading effect caused by the heating of the friction brake to be prevented or reduced, and in the case of an emergency braking function AEB, the braking torques of the traction motor and the electromechanical brake unit EMB can be summed (see function (b) of the first embodiment "Architecture 1").

[0125] In contrast to function (g) of "Architecture I", wheel-specific recuperation can also be implemented more easily. Axle-specific recuperation (function (c) in "Architecture 1") can of course also be implemented.

[0126] The decisive factor is the application of function (f), where a basic braking torque is generated via the traction motor during normal operation and the braking torque is modulated in the control system by means of the electromechanical braking unit EMB. Alternatively, the basic braking torque can also be generated via the electromechanical braking unit EMB and the braking torque modeled via the electric traction motor. For critical driving situations (for example, during a ^. jump), the joint braking torque can even be built up or reduced simultaneously using the electromechanical braking unit EMB and the electric traction motor, so that overall highly dynamic braking torque adjustment is available. Joint control of the braking torques is easily achieved if each wheel has a control unit (M-ECU-Wheel1, M-ECU-Wheel2, M-ECU-Wheel3, M-ECU-Wheel4) that controls the synchronized braking torque control of the EMB and the electric traction motor.This also allows time delays in braking torque changes to be minimized.

[0127] The advantage of coordinated braking torque reduction is significant because the technical challenges of the electromechanical brake (EMB) are particularly evident at high braking torques. The EMB tends to become tense at high actuation torques, and the release process of the brake shoes is problematic and leads to high costs. This problem is significantly alleviated by applying a base braking torque via the traction motor. Furthermore, the support function allows the costs of the electromechanical brake (EMB) to be significantly reduced, although this effect increases more than proportionally with the actuation forces or braking torques. For example, if 30% of the required base torque is applied by the electric traction motor, the costs of the electromechanical brake (EMB) can be reduced by more than 30%, as the electromechanical brake (EMB) can be dimensioned accordingly smaller.Due to the axle load distribution during braking (typically 60-70% of the load on the front axle, 40-30% of the load on the rear axle), it is advantageous to make the electric traction motors on the front axle more powerful than the electric traction motors on the rear axle. This allows identical parts of the EMB electric motor brake units to be used for both the rear and front axles, because the axle load distribution during braking is balanced by the increased braking power provided by the motors on the front axle.

[0128] The vehicle dynamics system with wheel modules is a solution that, due to its redundancies, certainly meets the requirements of SAE Level 5. However, due to the high costs (four traction motors + four electromechanical brakes), this solution is more of a niche solution for special applications from a chassis control perspective. However, the additional costs are offset by other advantages, such as flexibility in the production and design of different vehicle concepts.

[0129] In a further embodiment of the driving dynamics system, a special combination brake with a hydraulic brake for the front axle is provided, with one pressure regulator for each wheel of a front axle (EHB-VR, EHB-VL) and electromechanical brake units as EMB modules (EMB1, EMB2) on each wheel of a rear axle, preferably with an integrated electric parking brake, for example, by redundantly designing the electronics of the EMB1, EMB2 or implementing a self-locking mechanism for the transmissions of the EMB1 and EMB2, for example, by using a trapezoidal plastic spindle. The electrohydraulic EHB-VR or EHB-VL pressure regulator can be designed as a piston-cylinder unit without wheel control valves or, in a simplified form, as a pump, in particular with a gear pump for each pressure regulator.If a piston pump, for example a 2k pump of a standard ESP unit, is used, at least one valve device is required to reduce the pressure, while a gear pump can take over the function of the piston-cylinder unit and can both build up and reduce braking torque.

[0130] "Architecture II" is particularly suitable for the special Combi brake, where the pressure actuators of each axle are combined and the synchronization of functions a) to f) can be easily coordinated via an axle control unit S-ECUVA and S-ECUHA. However, another architecture is also conceivable, in which the control unit of each brake torque actuator communicates with the central control unit M-ECU, and the central control unit transmits the target braking torques to the control electronics of the brake torque actuators (EHB-VR, EHB-VL, EMB-HL, EMB-HR) of the wheel brakes and to at least one traction motor (TM1, TM2, TM3, TM4).Regardless of the chosen architecture, the driving dynamics system functions (a) - (g) explained above can also be implemented. Here, too, the greatest potential lies in the cost and weight optimization of the friction brake, for example, by using a drum brake on the front axle and a smaller disc brake on the rear axle for electromechanical brake units (EMB). Therefore, it is particularly advantageous to utilize the braking effect of an electric traction motor on the front axle for the combined brake.

[0131] Although the special Combi solution is more complex than the solution with electro-hydraulic brake units (EHB-1 or EHB-ZA) with wheel control valves on the front axle and electromechanical brake units (EMB) on the rear axle (e.g., Figure 6c without a hydraulic connection to the rear axle), it has the advantage of greater freedom in positioning the EHB-VR and EHB-VL modules close to the wheels and enables easier scaling than with electromechanical brake units (EMB) on the front axle. Furthermore, it makes the pressure control unit manufacturer, especially new companies, independent of suppliers of solenoid valves and the required pressure control technology with solenoid valves, which are firmly in the hands of established brake manufacturers.

[0132] In addition, the special Combi-Brake is easier to apply, comparable to an electromechanical brake unit (EMB). Using a gear pump instead of a piston-cylinder unit also makes it possible to implement a solution at a reasonable cost. In particular, the cost-reduction potential offered by the vehicle dynamics system and functions (a) - (g), as explained below for other embodiments and architectures, is also significant for this solution.

[0133] The following inventive goals with major functional, redundancy and cost advantages are pursued with the vehicle dynamics system control of architectures I-III and with the special Combi brake:

[0134] Improvement of function / application / new functions:

[0135] - Use of electric traction motors in ABS operation, particularly on road surfaces with low friction coefficients (snow, ice) in normal operation to shorten braking distances, where the larger braking torque gradients of the electric traction motors have advantages compared to known ABS systems with storage chamber (compare standard ESP systems with slow pressure reduction in a storage chamber).

[0136] - Use of electric traction motors for ASR operation through torque control and engine speed control when starting, instead of the known solutions by braking the rear wheel using the electro-hydraulic brake EHB.

[0137] - Improvement of the emergency braking function AEB with braking torque increase to 100 ms instead of 150 ms with the corresponding shortening of the braking distance, especially at high speeds and when there is a risk of accidents.

[0138] - Combined yaw moment interventions for vehicle stabilization or steering by using torque interventions generated by the electric traction motor and a braking torque by an electro-hydraulic brake unit EHB.

[0139] - Combined braking interventions in normal operation by the electric traction motor and electro-hydraulic brake EHB, for example in the event of dynamic changes in the road surface characteristics, such as in the case of a ^. jump, where rapid pressure reduction is required.

[0140] - ABS control with electro-hydraulic brake unit EHB in multiplex process with torque control via electric traction motors, thus avoiding dead times of the multiplex system.

[0141] - Leveraging the advantages of the closed hydraulic braking system for rapid application of the core ABS and ESP functions and automation of new software functions via central over-the-air updates, for example, implementation of software upgrades during the transition from SAE Level 2 to SAE Levels 3-5. - EBD control with electric traction motor on the rear axle and electrohydraulic brake (EHB) on the front axle.

[0142] - Implementation of a redundant ASR function through the electric traction motor or the electro-hydraulic brake unit EHB.

[0143] Benefits of cost and weight reduction:

[0144] - Use of electric traction motors to reduce the thermal load on the brake calipers during multiple braking applications (so-called AMS fading test) and thus downsizing the electro-hydraulic braking system, for example designing the electro-hydraulic brake unit EHB to the blocking pressure and an additional reserve of 20-40%, i.e. 120-140 bar, instead of 200-200 bar, optionally even designing for lower pressures than the required blocking pressure (60-80 bar) with successful implementation of the brake via electric traction motors with reliable energy management even with a full battery.

[0145] - Use of electric traction motors to reduce the thermal load on the brake calipers and enable the use of cost-effective drum brakes on the rear axle.

[0146] - Reduction of fine dust and wear on the braking systems by braking primarily using the electric traction motors.

[0147] - Downsizing of the electromotive brake unit EMB through braking torque support by the electric traction motor, especially on the front axle of the vehicle, but also on the rear axle.

[0148] - Use of an electro-hydraulic brake EHB with a simple 2-component pump with relatively low power instead of a 1-box with a powerful EC motor and representation of the emergency braking function in 150 ms through corresponding power of the electric traction motors in combination with a standard ESP device with TTL = 500 ms.

[0149] - Use of smaller solenoid valves by mapping highly dynamic pressure build-ups using the electric traction motor.

[0150] Improvement through redundancy:

[0151] - Use of the electric traction motor for braking in the event of a failure or partial failure of the braking system. - Use of the electric traction motor to maintain rapid emergency braking (AEB) with a TTL of 150 ms, even in the event of a failure of the primary braking system.

[0152] - Use of the electric traction motor to maintain the EBV function even if the rear axle brake circuit fails.

[0153] - Use of the electric traction motor in case of brake circuit failure.

[0154] - Use of the electric traction motor if the ESP function fails.

[0155] - Use of the electric traction motor in the event of a steering function failure or support of the steering interventions on the front axle by yaw moment interventions on the rear axle.

[0156] - Implementation of a redundant ASR function by the electric traction motor or an electro-hydraulic brake unit EHB

[0157] The invention is described below using several exemplary embodiments, which are explained in more detail with reference to the figures. Herein:

[0158] Fig. la: Fading effect in the AMS test as a basis for the design of a standard braking system;

[0159] Fig. lb: Blending strategy with regenerative brakes according to the state of the art without driving dynamics system;

[0160] Fig. 2a: Driving dynamics system “Architecture I”: Hydraulic braking system EHB-Z, EHB-VA in combination with electric traction motors TM1, TM2, TM3;

[0161] Fig. 2b: Driving dynamics system “Architecture I”: Hydraulic braking system in combination with electric traction motors;

[0162] Fig. 3: Novel blending strategy with driving dynamics system and powerful electric traction motor or powerful electric traction motors;

[0163] Fig. 4: AEB time saving with braking via electric traction motor and electro-hydraulic brake unit EHB with adapted EBV function;

[0164] Fig. 5: ABS control mode with electro-hydraulic brake unit EHB and

[0165] Generation of the basic braking torque by electric traction motor;

[0166] Fig. 5a: Typical ABS time curve with wheel speed, pressure and valve times for brake torque control with electro-hydraulic brake unit EHB;

[0167] Fig. 5b: Optimized ABS time curve with wheel speed, pressure, and valve timing for brake torque control with an electric traction motor; Fig. 5c: ABS control operation during a ^. jump with an electrohydraulic brake unit (EHB) in combination with an electric traction motor;

[0168] Fig. 5d: ABS control mode in the low-case mode with electro-hydraulic brake unit EHB in combination with electric traction motor on the rear axle;

[0169] Fig. 6a: Concept A for driving dynamics system “Architecture I”: EHB-Z for wheel-individual control for the front axle and the rear axle in combination with electric traction motor on the front axle and on the rear axle;

[0170] Fig. 6b: Concept B for driving dynamics system “Architecture I”: EHB-Z for wheel-individual control for the front axle in combination with a basic braking torque for the rear axle, ABS control on the rear axle by means of electric traction motors;

[0171] Fig. 6c: Concept B for driving dynamics system “Architecture I”: EHB-Z for wheel-individual control for the front axle in combination with a basic braking torque for the rear axle, ABS control on the rear axle by means of electromechanical brake unit EMB;

[0172] Fig. 6d: Concept D for driving dynamics system “Architecture I”: EHB-VA for wheel-individual control of the front axle, brakes and ABS control on the rear axle exclusively with electric traction motors;

[0173] Fig. 7a: 250 KW engine map with powerful motor & power boost via innovative RSP-4Q inverter;

[0174] Fig. 7b: Structure of a novel RSP-4Q inverter;

[0175] Fig. 8-8c: Tightening inlet / outlet valve MVzk for pressure build-up and pressure reduction at high pressure gradients and brake pressures;

[0176] Fig.9a: New pressure control with inlet / outlet valve MVZK (PPC-Gen-Vl);

[0177] Fig. 9b: Novel pressure control with inlet / outlet valve MVZK (PPC-Gen2-V2);

[0178] Fig.10: Driving dynamics system “Architecture II”: E-axle modules with

[0179] Axle control electronics S-ECUVA and S-ECUHA;

[0180] Fig.11a: Driving dynamics system “Architecture II”: E-axle module I with two electromotive brake units and one electric traction motor;

[0181] Fig.11b: Driving dynamics system “Architecture II”: E-axle module II with an electro-hydraulic brake unit and two electromotive brake units; Fig.11c: Driving dynamics system “Architecture II”: E-axle module III with an electro-hydraulic brake unit and an electric traction motor;

[0182] Fig.1 ld: Driving dynamics system “Architecture II”: E-axle module IV with an electro-hydraulic brake unit and two electric traction motors;

[0183] Fig. 12: Comparison of braking torque gradients of electric traction motor TM, electro-hydraulic brake unit EHB, electromotive brake unit EMB and operating ranges;

[0184] Fig.12a: Decision heuristics with evaluation of characteristic maps, core data and signals;

[0185] Fig. 13: Driving dynamics system “Architecture III”: Wheel modules with wheel control electronics for electromotive brake unit and electric traction motor; and

[0186] Fig.13a: Driving dynamics system "Architecture III": wheel modules with four electric brake units and four electric traction motors.

[0187] Figure 1d shows a typical simulation of an AMS test, according to which a braking system is designed according to the state of the art. In this simulation, 10 subsequent braking applications from 100 km / h are simulated. If the so-called AMS fading test is used as a basis for dimensioning the maximum pressure (Brake Manual, 5th Edition, Chapter 6.3.2, Figure 6.10), the wheel brakes on the front axle typically heat up to about 600°C, and the wheel brakes on the rear axle to about 500°C. The pedal force on standard vacuum brake boosters then increases by about 80%, meaning that the braking system must be designed for a pressure 80% higher for the fading event than would be required for normal locking pressure. With an appropriate safety margin, typical braking systems are therefore designed for a maximum pressure of 200-220 bar.

[0188] Figure 1e shows the currently commercially available brake management system with an electro-hydraulic brake when blended with an electric traction motor. The process is described in more detail in the Brake Manual, 5th Edition, Chapters 19.3.2 and 19.3.3, and is reproduced in Figure 1a. This management system is now being expanded as one of the core concepts of the invention. It is characteristic that at the beginning of braking at low vehicle speeds (range B), hydraulic braking is applied, while regenerative braking is gradually increased at speed vi and gradually reduced up to speed v2. This means that at low vehicle speeds (vi<10 km / h, range B) and high vehicle speeds (v2>60 km / h, range E2, D), hydraulic braking is used, not regenerative braking. In addition, the available potential of regenerative braking, for example, stronger braking above the braking torque of M max between vi and V2 and regenerative braking in the speed range >V2 is not fully utilized. This means that although a higher braking torque could be available up to Mmax M, it is not utilized in this speed range (range El). This is often due to technical reasons, for example, if the braking position used is not designed for higher recuperation. For example, in the system described in DE 10 2012 211 278 A1, this is limited by the fact that the storage chamber of the ESP-hev unit can only accommodate a limited amount of volume, so the blending is limited.

[0189] At higher decelerations and speeds, safety aspects also play a role: For example, regenerative braking is not used if, in the event of ABS, the braking torque of the electric traction motor could lead to wheel lock. Only the vehicle dynamics system of the invention provides a remedy here by centrally controlling the electric traction motor and the electro-hydraulic brake unit. Therefore, the blending strategy according to the state of the art does not provide for regenerative braking in the E1 and E2 ranges.

[0190] For the reasons mentioned above, the potential of regenerative braking and the optimization of the friction brake for the AMS fading scenario is not fully exploited in existing systems, since the AMS fading scenario occurs precisely at speeds above approximately 100 km / h and during emergency braking. According to the state of the art (see Figure 1), braking is purely hydraulic. If, for example, 30% of the braking power in the AMS test were to be provided by the electric traction motor (M ei.TM, AMS), the fading effect would be significantly reduced, as the heating of the braking system would be significantly lower. The braking system could then be designed for a significantly lower maximum pressure, approximately 140-160 bar. Maximization using the inventive vehicle dynamics system control would have three effects with significant cost and weight savings: 1. Regeneration could be maximized, which would increase the range of electric vehicles and could be used to operate heat pumps.

[0191] 2. The friction brake could be simplified, for example through easier cooling, less wear and smaller brake discs, and cost-effective drum brakes could replace disc brakes,

[0192] 3. Downsizing of the electro-hydraulic brake would be possible, in particular with a smaller EC motor for lower maximum torques, a design of the wheel control valves for lower maximum pressures, a weight reduction of the electro-hydraulic brake unit EHB and a smaller volume of the pressure supply unit of the electro-hydraulic brake unit.

[0193] Figure 2 shows the advantageous driving dynamics system "Architecture I" for a joint operation of electric traction motors on the front axle (TM3) and / or on the rear axle (TM1, TM2), combined with an electro-hydraulic braking system of the EHB-Z or EHB-VA topology according to Figure 2. The central control unit controls the braking torques of the electric traction motors TM1, TM2, TM3 and the electro-hydraulic braking units EHB-Z, EHH-VA for at least one of the following functions:

[0194] • (A) Basic brake with thermal management and energy management of the supplied and dissipated energy (electrical energy, thermal energy) of the traction motor;

[0195] • (B) Emergency brake AEB with electronic brake force distribution (EBD);

[0196] • (C) Regenerative braking on multiple axles;

[0197] • (D) ABS control with basic brake torque support and / or joint brake torque control;

[0198] • (E) Braking operation in the event of failure of the electro-hydraulic brake unit EHB-Z, EHB-VA;

[0199] • (F) Yaw moment interventions by means of wheel-specific braking torque interventions; and / or

[0200] • (G) wheel-specific braking torque interventions for wheel-specific regenerative braking.

[0201] The driving dynamics system sends target values ​​to the various components, with the target values ​​primarily including target braking torques or target braking pressures. For certain functions (such as functions (C), (E), (F) described above), target signals for pressure control or pressure regulation are also specified, such as control signals for solenoid valves for functions such as the switching duration of the opening time or a PWM frequency during throttle operation, and / or pre-pressures for the pressure supply device for pressure build-up or pressure reduction.

[0202] Furthermore, the M-ECU module can also interface with the control unit or autonomous driving domain (M-ECUAD) and can evaluate additional information useful for effective and predictive control. This includes, for example, camera information about the road surface (snow, ice, rain) or information about the surroundings (distances to pedestrians and / or other vehicles).

[0203] Figure 2a shows the exemplary structure of a vehicle architecture with the driving dynamics system, including hydraulic lines and signal lines between the units and sensors. The central control unit M-ECU, preferably comprising three microcontrollers JLLCI, p.C2, .C3 to implement a 2-out-of-3 architecture, communicates with the control unit of the electrohydraulic brake unit (M-ECUBM) as well as the electric traction motors TM1 (optionally TM2) of the rear axle and the electric traction motor TM3 of the front axle, particularly via redundant data lines.

[0204] The central control unit (M-ECU) can, in particular, comprise at least one very powerful microcontroller and a large memory (in the gigabyte range) so that an automatic application can be implemented via artificial intelligence (AI) before the vehicle's initial commissioning and / or during vehicle operation. Alternatively, a central computer can be used instead of a domain computer, or the typically larger resources of a central computer designed for processing multimedia data can be used, especially for the application via AI.

[0205] The central control unit M-ECUoomäne receives data from wheel speed sensors of the wheels VRI - v R4and preferably further sensor signals SI, S2, Si, etc. The sensor signals SI, S2, Si can be provided by yaw moment sensors, acceleration sensors, and / or weight sensors, which are important for the central control of a vehicle model because these sensors enable or at least facilitate the optimization of the central control. Thus, the weight sensor can be used advantageously to adapt the recuperation strategy depending on the weight. Yaw moment sensors are helpful for vehicle dynamics interventions, such as torque vectoring or ESP yaw moment interventions, and acceleration sensors help calibrate the relationship between the brake pressure of a hydraulic brake unit (EHB) and the achieved braking torque or brake pressure and the achieved vehicle deceleration.Additional sensors or data from the autonomous driving system, such as data from cameras and lidar sensors, map material or data in the interaction with the environment and other vehicles, for example in Car2X (V2x) or Car2Car (V2V) communication, can also be used to implement traffic-specific braking torque interventions or to decelerate the vehicle in a targeted manner and, in the event of a fault, for example in the event of a partial failure with reduced maximum deceleration, to operate the vehicle at an adjusted speed or to decelerate early.

[0206] In addition, the electric power steering (EPS) on the front axle and optional electric parking brakes (EPB1, EPB2) on the rear axles are advantageously provided for communication with the central domain. The integration of the EPS enables coordinated driving dynamics interventions, such as torque vectoring and ESP yaw moment interventions via the electrohydraulic brake unit (EHB), in addition to the steering or to support the vehicle's electric power steering in the event of a failure or partial failure of the EPS. Furthermore, the integration of the electric parking brake (EPB) is advantageous because, in addition to ensuring a standstill, the parking brake can also perform dynamic braking functions or emergency functions, as described, for example, in WO 2020165255 A1.

[0207] Figure 2b shows the exemplary structure of another vehicle architecture of the inventive driving dynamics system with EHB-Z with hydraulic lines and signal lines between the brake units and sensors. The central control unit M-ECU, preferably comprising three microcontrollers JLLCI, p.C2, p.C3 to implement a 2-out-of-3 architecture, communicates with a control unit of the hydraulic brake unit (M-ECUBM) with two redundant control units ECU IEHB and ECU2EHB, as well as the electric traction motors TM1, TM2 of the rear axle, and the electric traction motor TM3 of the front axle, in particular via redundant data lines. In contrast to Fig.2b, the EHB-Z does not have an integrated pedal, and only one hydraulic line to the rear axle wheel brakes is provided, along with an electric traction motor for each rear axle wheel. Thus, the braking torque control for various functions (ABS, ASR, ESP, EDB, and regenerative braking) is performed by the electric traction motors, while the electro-hydraulic brake unit EHB-Z only provides a base braking torque. Further details on the hydraulic layout of the EHB-Z are shown in Figure 6b.

[0208] The central control units (M-ECUs) receive data from wheel speed sensors of the wheels VR1 - VR4, as well as preferably other sensor signals SI, S2, Si, etc. The sensor signals SI, S2, Si can be provided by yaw moment sensors, acceleration sensors, and / or weight sensors, which are important for the central control of a vehicle model because these sensors enable or at least facilitate the optimization of the central control. Thus, the weight sensor can be used advantageously to adapt the recuperation strategy depending on the weight. Yaw moment sensors are helpful for vehicle dynamics interventions, such as torque vectoring or ESP yaw moment interventions, and acceleration sensors help calibrate the relationship between the brake pressure of a hydraulic brake system (EHB) and the achieved braking torque, or brake pressure and achieved vehicle deceleration.Additional sensors or data from the autonomous driving system, such as data from cameras and lidar sensors, map material or data in the interaction with the environment and with other vehicles, for example in Car2X (V2x) or Car2Car (V2V) communication, can also be used to implement traffic-specific braking torque interventions or to decelerate the vehicle in a targeted manner and, in the event of a fault, for example in the event of a partial failure with reduced maximum deceleration, to operate the vehicle at an adjusted speed or to decelerate early.

[0209] In addition, the electric power steering (EPS) of the front axle and, optionally, the electric parking brakes (EPB1, EPB2) of the rear axles are advantageously also provided for communication with the central domain. The integration of the EPS enables coordinated driving dynamics interventions, such as torque vectoring or ESP yaw moment interventions via the hydraulic brake unit (EHB), to supplement the steering or to support the vehicle's electric power steering in the event of a failure or partial failure of the EPS. Furthermore, the integration of the electric parking brake (EPB) is advantageous because, in addition to ensuring a standstill, the parking brake can also perform dynamic braking functions or emergency functions, as described, for example, in WO2020165255A1.

[0210] Figure 3 shows the blending strategy of the driving dynamics system, with the full utilization of the braking force of an electric traction motor across the entire vehicle speed range and up to the maximum braking torque of the electric traction motor used. Full utilization of the driving dynamics system is possible because, as shown in Fig. 2a, the central domain has all the important information and can therefore very quickly adjust the braking effect via the electric motor with minimal time delay in a critical driving situation, such as during ABS control operation. New high-voltage electric motors (>700V) can very dynamically increase or decrease the electric braking torque via the electric motor by 10,000 to 30,000 Nm / s.In an ABS case, the electric traction motor on the axle in the case of electric axle drives (see table) or in the case of a wheel with individual wheel drive or in the case of electric axles with torque vectoring modules can therefore reduce the braking torque almost as quickly as with a hydraulic brake (typically 1,000 to 2,000 bar / s = 20,000 to 40,000 Nm / s) before the electro-hydraulic brake unit (EHB) takes over ABS control. A control strategy in ABS operation together with the electric traction motor and the electro-hydraulic brake unit (EHB) is further described in Figure 5a. Although the first control cycle is not entirely optimal, there is no safety-critical situation where the vehicle could become unstable. Furthermore, in critical driving situations where an automatic emergency brake (AEB) is used, the disadvantages of the first control cycle can be overcompensated by shortening TTL.

[0211] The illustration uses the torque-speed map of an electric drive motor of a plug-in hybrid or electric vehicle (e.g., a BMW i3) with a vehicle weight of 1,365 kg as an example. In this case, the electric traction motor has a maximum power of approximately 130 kW and a maximum torque of 250 Nm and operates with a gear ratio of 9.5, meaning that a torque of up to 2,400 Nm can be used on the vehicle's axles for propulsion and deceleration. Assuming a permissible maximum vehicle weight of 1,710 kg and a weight distribution during braking with maximum deceleration of 40% on the rear axle and 60% on the front axle, an axle braking torque of 3,400 Nm on the front axle and 2,465 Nm on the rear axle is required. This allows the rear axle to be braked entirely electrically up to a speed of approximately 70 km / h.

[0212] At the design point for the AMS fading test, at a speed of 100 km / h, approximately 50% of the braking power can be delivered on the front axle, and nearly 70% on the rear axle. This, in turn, means that the brakes on the front axle experience only half the friction power, and the rear axle only 30%.

[0213] The high additional braking torque available over a wide speed range can be used to significantly reduce friction brake heating, not only under the AMS test conditions at 100 km / h but also at high speeds, where a large amount of kinetic energy is absorbed by the friction brake. This is advantageous for sports cars, where very expensive ceramic brakes are typically used. Furthermore, the rear axle can be completely thermally relieved in the speed range up to 70 km / h; it can be significantly relieved, especially during the critical AMS test. This allows the use of a cost-effective drum brake.

[0214] The central control unit of the driving dynamics system, which preferably also detects the weight of the vehicle, can then increase braking through regenerative braking even at low loads, so that the recuperation strategy is adapted depending on the vehicle load.

[0215] The battery's ability to absorb high pulse power is problematic, especially when the battery is at a high state of charge. For this special case, it makes sense not to feed the power back into the battery, but to dissipate it at least partially internally in the electric traction motor using intelligent field-oriented vector control (Id, Iq), so that no energy is returned. Alternatively, an additional resistor can be used to dissipate the heat. The heat generated by a resistor can then be advantageously used to heat the vehicle or, via a heat exchanger, to cool the vehicle. The energy management options have already been described in more detail above.

[0216] If a special inverter is also used, which allows the motor windings to be connected either in series or in parallel (RSP-4Q inverter), a torque boost is also possible at higher engine speeds or at higher vehicle speeds. This also allows the braking torque to be increased for regenerative braking at higher vehicle speeds, thus recuperating even more kinetic energy. Alternatively, the TTL (time-to-lock) time can be further reduced at high speeds, as shown in Figure 4. This can also be advantageously used to shorten braking distances, as electrical braking can be applied in addition to the hydraulic brake.

[0217] Figure 4 illustrates how the inventive function of the emergency brake (AEB) (function B) can be implemented with the inventive control of the driving dynamics system. In the electric emergency brake, in addition to the braking effect via electric traction motors, the EBV control is also appropriately adapted to shorten the braking distance. Figure 4 uses an electric traction motor with the performance data shown in Figure 3 (130 kW, 250 Nm, gear ratio of 9.5) and a torque gradient of 15,000 Nm / s as an example. The electro-hydraulic EHB system assumes a black / white brake circuit layout, i.e., one brake circuit for the front axle and a second brake circuit for the rear axle of the vehicle. The curves BMTMI-VA and BMTM2-HA show the braking torque increase of the electric traction motor on the front axle VA and rear axle HA, respectively, in particular with a braking torque gradient of 15,000 Nm / s.This increase is taken into account for the electronic brake force distribution (EBD) in such a way that the pressure curve is distributed to the front axle and the rear axle via an advantageous hydraulic braking system, as further explained in Fig. 6a to 6d, in such a way that the front axle and the rear axle reach their maximum braking torque, for example for 1 g deceleration, at the same time and at the same time it is ensured that design priorities (see Table 1 of the priorities) are taken into account.

[0218] In simplified terms, the braking torque continues to increase after reaching the maximum braking torque (indicated in the figure as approximately 1 g) to illustrate the further temporal braking torque curve and thus also TTL for higher decelerations (e.g., up to 1.4 g for sports cars). If an ABS event occurs, typically at a deceleration of approximately 1 g, the braking torque is subsequently reduced, and ABS control operation ensues, as further explained below with reference to Figures 5, 5a, 5b, and 5c.

[0219] The curve BMEHB-HA shows the braking torque curve for the electro-hydraulic brake of the rear axle; the curve BM H A,EHB+TM2-HA shows the sum of the braking torque curve for the electro-hydraulic brake of the rear axle and the traction motor TM2 assigned to the rear axle.

[0220] The curve BMEHB-VA also shows the braking torque curve for the electro-hydraulic brake of the front axle; the curve BM VA,EHB+TM I-VA shows the sum of the

[0221] REVISED SHEET (RULE 91) ISA / EP braking torque curve for the electro-hydraulic brake of the front axle and the traction motor.

[0222] The upper horizontal line BLM-VA represents the braking torque corresponding to the locking pressure for the front axle (front axle). The lower horizontal line BLM-RA represents the braking torque corresponding to the locking pressure for the rear axle (rear axle).

[0223] Where the curves for the braking torque achieved by the brake units EHB-VA, TM1, EHB-HA, and TM2 intersect the horizontal lines BLM-VA and BLM-HA, the respective locking pressure is obtained. The time until this point is reached is referred to as the time-to-lock (TTL).

[0224] The TTL for the electrohydraulic brakes EHB-VA and EHB-HA alone is approximately 140 ms, while when the regenerative braking torques of the traction motors TM1 and TM2 are also used, it is approximately 90 ms. This means that by controlling the vehicle dynamics system, the TTL in the simulation can be reduced by a difference ΔT of 140 ms to 95 ms, which has a significant impact on the braking distance. At a speed of 100 km / h, for example, these 45 ms correspond to a distance traveled of approximately 1 m. This is already a significant improvement compared to typical braking distances of 25 m with ABS braking.

[0225] Such an improvement in braking distance by 1 m is a very ambitious goal for ABS braking system applicators.

[0226] Figure 5 illustrates another fundamental idea of ​​the synergistic use of the braking torques of electric traction motors and the braking torques of electro-hydraulic brake units using a typical ABS control curve at high pressures on asphalt, i.e. in the so-called "high-case".

[0227] Since, as already explained above, a traction motor can build up and reduce braking torque very quickly, the use of the electric traction motor in ABS control is unproblematic.

[0228] Figure 5 shows a curve for the deceleration of the vehicle, as well as curves for the wheel speeds of the vehicle's four wheels. Advantageously, the electric traction motor generates a base braking torque VA in ABS mode, which is illustrated in Figure 5 for an exemplary arrangement of the electric traction motor on the front axle. This results in the pre-pressure of the electro-hydraulic brake unit EHB being reduced by the base braking torque of the electric traction motor. This means that the locking pressure can be generated more quickly, as shown in Figure 4, and the required pressure of the EHB for ABS control is reduced.

[0229] This can be used to downsize the braking system, which typically requires a pre-pressure 20-40% higher than the maximum wheel pressure. However, if 50% of the base braking torque is generated by the electric traction motor, only a pressure of 70-80 bar is required for ABS operation instead of the typical 120-140 bar. Furthermore, since the heating of the braking system is significantly reduced by generative braking (see the above explanation with reference to Figure 3), a design of the EMS at 100 bar is sufficient for safe control operation.

[0230] Figure 5 shows how the base braking torque at the front axle (VA) is provided by the electric traction motor. The difference between the pre-pressure and the desired pre-pressure for the front axle (VA) is then relatively small. The pressure control for the two wheels of the front axle (VA) accordingly accommodates variations with a small amplitude, allowing the electro-hydraulic brake unit to be smaller.

[0231] This has significant effects on the braking system because, on the one hand, the pressure supply requires a smaller volume to provide the necessary fluid volume, and the electric motor of the electro-hydraulic brake unit (EHB) can only generate 50% of the braking torque. Furthermore, the valve design of the hydraulic control unit (HCU) of the EHB can be adapted by using smaller or less expensive valves that can be designed for significantly lower pressure resistance. With these fundamental ideas, the costs of an EHB can be reduced by around 10%. Furthermore, the friction brake can be designed significantly more cost-effectively because the thermal load is reduced and less braking torque needs to be transferred to the brake shoes. In sports vehicles, expensive ceramic brakes can be replaced with significantly more cost-effective gray cast iron brakes.Figures 5a and 5b show the delays of ABS control with electric traction motors compared to standard ABS systems. The temporal progressions of the wheel speed vRl are illustrated for comparison.

[0232] Figure 5a shows a typical sequence at the beginning of a control cycle of pressure reduction in ABS operation with a standard ESP system or a 1-box system, shown on a low friction coefficient, for example on snow.

[0233] The upper diagram shows the wheel speed as a function of time t. The lower diagram shows the pressure as a function of time t (upper curve); furthermore, the opening state of a valve is shown schematically over time t (lower curve).

[0234] After a time to, due to a dead time of the system, the locking of a wheel is detected, since the wheel speed v differs by Av from the reference speed v ref. The outlet valves are then opened to reduce the pressure. A time tvM passes until the valve is open. During this time phase, the wheel speed continues to fall by Avi. After the valve opening phase, the pressure is reduced over the time period tab, which is shown linearly for simplicity. During this time phase, the wheel speed continues to fall by Av2 until the wheel stabilizes. The valve is then closed again. This is followed by a gradual pressure build-up (not shown) to bring the wheel speed back to the level of the reference speed v re f, which is preferably done via small, step-by-step pressure increases via inlet valves.

[0235] Figure 5b shows ABS control of a wheel via traction motors.

[0236] The upper diagram shows the wheel speed as a function of time t. The lower diagram shows the pressure as a function of time t.

[0237] If the ABS control system with traction motors described here preferably uses wheel speed sensors with high resolution and short latency times for data transmission to the central control unit (M-ECU domain), an ABS event, characterized by a wheel speed deviation from the reference value, can be detected more quickly, particularly due to precise modeling of a vehicle model in the central computer. Consequently, the delay time t in the control of the driving dynamics system according to the invention is shorter, and thus the speed difference Av is also smaller.Furthermore, since ABS control with electric traction motors does not require a valve and the time delay of the torque change in an inverter of a high-performance traction motor is negligible, the braking torque reduction occurs immediately after the initial deceleration t0 without any further time delay tMv, especially with a low road friction coefficient and a larger braking torque gradient (see illustration of the braking torque gradients in Figure 12). Furthermore, due to the higher resolution, improved wheel acceleration control with central domain control can be implemented, so that the target wheel torque can be reached more quickly and without overshoot.If the braking torque increase then follows without any delay in valve actuation and also with the precision of a motor control with torque and motor speed control cascade (in particular taking into account the torque / current of the electric motor of the pressure regulator, the position of a piston in a piston-cylinder system of the pressure regulator, and an actuator speed, i.e. a speed of adjustment of a piston of the pressure regulator), the reference speed v. ref is also reached much faster without oscillations in the braking torque curve. Due to the smaller deviations from the reference speed, the braking distance can be reduced when controlling with electric traction motors in the ABS compared to a standard ABS system, while at the same time reducing noise due to the low pressure oscillation control. Viewed differently, the same control quality can be achieved with smaller braking torque gradients when controlling with traction motors compared to braking torque gradients of an electro-hydraulic brake unit (EHB), because the critical time delay t caused by the solenoid valves V M is eliminated. In addition, the powerful computer and wheel speed sensors with higher resolution can reduce the reaction time t0, meaning that a wheel lock is detected earlier and can be corrected more quickly.

[0238] Figure 5c shows a further advantage of the joint braking torque modulation according to the invention in normal operation, for example for a negative ^. jump, i.e. when the vehicle comes from asphalt onto snow.

[0239] Figure 5c shows the pressure or the corresponding braking torque at the front axle VA and at the rear axle HA as a function of time t. Curves are shown for the braking torques generated by the traction motors on the front and rear axles, as well as the total braking torques at the front and rear axles. In Figure 5c, it is assumed for simplicity that both wheels on the front axle have the same braking torque or the same braking pressure, and that both the front and rear axles have a traction motor on the axle that contributes a base braking torque to the total braking torque of the respective axle. The braking torque of the traction motors Mbrems,TM,vrad or Mbrems,TM,Hrad and the hydraulic braking torque (not shown) of the electro-hydraulic braking unit EHB of the front wheels or the rear wheels act additively to the total braking torque Mbrems,ges,vrad or Mbrems,ges,Hrad.When the braking torque is reduced, the braking torque on the front axle Mbrake,TM,vrad can be reduced first without any time delay, followed by the pressure reduction by the EMS with the time delay to described above. This means that the braking torque can be advantageously adjusted very quickly, and the gradient increases as soon as the EMS can reduce the pressure. This has a positive effect on the drop in speed of the front wheels (not shown). The braking torque on the rear axle, or rather the reduction in the braking torque Mbrake,ges,Hrad, follows with a short time delay. This braking torque - as described above for the front axle - benefits from the rapid onset of braking torque by the electric traction motor Mbrake,TM,Hrad without any further time delay to, so that the wheel speed does not drop as sharply here either.

[0240] Figure 5d shows the inventive approach for a different control situation in which the vehicle is operated on a largely homogeneous road surface, for example with snow (so-called low-case).

[0241] The braking torque Mbrake generated at the front right VR, front left FL, rear right HR and front right VR wheels are plotted as a function of time t.

[0242] Here, the front axle is advantageously controlled with the EHB, while the lower braking torques for the rear axle are obtained by the two traction motors TM1 and TM2, whereby the concept of the following explained Figures 6b or 6d is used as a basis.

[0243] Alternatively, the control system can also be applied to drive concepts in which an electromechanical brake unit (EMB) is provided on the rear axle according to the concept shown in Figure 6c, and an electrohydraulic brake unit (EHB) is provided on the front axle. An electromotive brake unit (EMB) offers comparable advantages to traction motors, such as a high braking torque gradient and precise braking torque control through torque and acceleration control of the EMB motor. The electromotive brake (EMB) is even superior to electric traction motors in terms of braking torque gradient (see illustration in Figure 12). Furthermore, the brake shoe tension effect of the EMB is eliminated at low friction values.

[0244] Figure 6a shows a hydraulic braking system for four wheel brakes, advantageous for integration into the vehicle dynamics system according to the first embodiment ("Architecture I"), with electric traction motors TM1 on the rear axle and TM2 on the front axle of the vehicle. This braking system can also have a redundant pressure supply in the form of a piston-cylinder unit driven by an electric motor and spindle drive. The pressure supply can be equipped with a current sensor i / U and an angle sensor a / U, as well as optionally with temperature sensors T / U, which measure the motor temperature of the EC motor. The piston-cylinder unit can also have redundant phase connections, redundant electronics, and / or redundant on-board power supply connections BN1 and BN2, and data lines DS1 and DS2 for communication with the chassis domain of a central control unit (M-ECU chassis domain).The braking system can further comprise an e-pedal with a sensor ECU and sensors, in particular a force-displacement sensor based on the principle of differential displacement measurement (see US13 / 883,192), applied to the e-pedal concept for detecting pedal force. The sensor ECU can be in direct communication with the central control unit of the chassis domain.

[0245] In addition, special bidirectional inlet / outlet valves (simplified as MVzk) can be used for each wheel brake, whereby pressure can be built up or reduced by simultaneously moving the piston of a piston-cylinder unit forwards and backwards. Alternatively, different valve connections can be provided so that the cross-sections of the valves can be controlled by suitable current supply either during pressure build-up or pressure reduction. If, for example, the valve seat is connected to the wheel brake, different pressure gradients can be achieved during pressure reduction so that the pressure in several wheel brakes can be reduced simultaneously and quietly. The pressure is then built up via volume control by the pressure supply unit, either simultaneously or in a multiplex process. If the valve seat is connected to the pressure supply, the pressure is built up via a classic pre-pressure control.For the latter method, outlet valves AV1-AV4 are advantageous but are not necessarily intended for pressure reduction. Furthermore, it is advisable to use the outlet valves only in extreme situations, as this results in the volume of the pressure supply being lost to the reservoir. In the case of a relatively lengthy control intervention, it is then necessary to return volume from the reservoir by retracting the piston, compare a control strategy according to EP 2580095 B1. The volume reduction via the outlet valves must therefore be dimensioned such that, in order to avoid a critical control interruption, a braking operation can be completed completely and that subsequent delivery only needs to take place after the braking operation has been completed. Alternatively, a continuously delivering double-acting piston can be provided for the pressure supply, as described in EP 3 145 771 B1, or the electric traction motors can take over the braking torque control during the interruption phase.

[0246] Such a system solution offers the flexibility of optional pressure reduction via the intake / exhaust valves (MVzk) or via exhaust valves. The use of exhaust valves is therefore optional, and one to four exhaust valves can be provided. The exhaust valves simply offer an additional degree of flexibility in the pressure reduction options. It makes sense to equip all wheels with exhaust valves when the system is introduced, with their number being gradually reduced later as part of product maintenance.

[0247] Alternatively, the well-known multiplexing method on two wheel brakes can be combined with the classic pressure control on two additional wheel brakes via inlet / outlet valves. Optionally, standard inlet valves are used instead of the inlet / outlet valves, or the MVzk valves are used only for pressure build-up and pressure reduction in brake booster mode. The electric traction motors can also be advantageously used in the context of downsizing (see Figure 5) to implement an efficient blending strategy, providing a base braking torque during ABS operation and / or being used in the emergency braking function (AEB) (see Figure 4) to achieve a faster TTL.

[0248] In addition, a targeted braking torque intervention is advantageously specified via the domain as a setpoint or setpoint curve, which advantageously also determines the temporal progression of the braking torque increase or decrease, allowing efficient synchronization with the braking torque curve of the electric traction motors. The intervention can be performed on an axle-specific or wheel-specific basis. Wheel-specific intervention is primarily used for yaw moment control, for example, for torque vectoring interventions, and is also advantageously synchronized with the steering intervention of the electric power steering (EPS).

[0249] The use of MVzk valves also has the advantage that the failure of a wheel circuit can be diagnosed and the wheel circuit can be isolated in the event of a fault by closing the MVzk valves. This allows for 3-channel control operation even if a wheel circuit fails, which can be used for ABS control, as well as yaw moment interventions for steering assistance or emergency steering in the event of a failure or partial failure of an electric power steering system.

[0250] In addition, the brake units are preferably designed redundantly, for example with redundant windings and electronics, so that the individual brake units can still operate even in the event of a partial failure. This allows two- to three-fold redundancy of the braking function to be achieved with a high degree of reliability. Even if braking performance is reduced, critical situations can still be managed. If the pressure supply fails partially, 50% of the maximum braking torque is still generated with reduced dynamics of the 1x3 instead of 2x3 phases, i.e., approximately 70 bar with a design of 140 bar. This allows full ABS operation on both axles up to the locking pressure, because the electric traction motors can then provide supporting torque to one or both axles.

[0251] The hydraulic braking system with the vehicle dynamics system of the present description has a very simple and cost-effective design (few solenoid valves, downsized pressure supply) and meets all redundancy requirements of SAE Level 4, as specified above.

[0252] Figure 6b shows a second embodiment of the electro-hydraulic brake unit (EHB) with two electric traction motors TM1 and TM2 on the rear axle and one traction motor TM3 on the front axle. The traction motor TM3 can be omitted, with the two traction motors TM1 and TM2 being system-relevant and depicting topology B in Figure 2.

[0253] Only one hydraulic line leads from the pressure supply of the electro-hydraulic brake unit EHB to the two wheel brakes RB3 and RB4 of the rear axle and, advantageously, only one cost-effective drum brake is used on the rear axle.

[0254] The electric traction motors TM1 and TM2 are powerful, with more than 50 kW per wheel. Braking torque buildup and reduction are carried out dynamically. The traction motors TM1 and TM2 control the braking torque, while the EHB is used only to apply a base braking torque to the rear axle during normal operation.

[0255] Normal operation is comparable to the case shown in Figure 5, with the difference that the roles of the EMS and the traction motors are reversed, and this time the EMS generates the base braking torque instead of the electric traction motors. On the front axle, however, ABS control is carried out via the EMS, and the optional TM3 traction motor provides the base braking torque. If an optional TM3 traction motor is used on the front axle, a cost-effective drum brake can also be used here.

[0256] In the event of an initial failure, for example, if the hydraulic connection to the rear axle wheel brakes fails, the connecting line is disconnected via the isolation valve, and the traction motors take over full control. This may limit rear axle deceleration depending on the performance and speed of the traction motors. However, all safety-critical functions (p-step, ABS to low-p) can still be controlled very safely, and steerability (priority 3) is ensured by the front axle pressure control and / or by controlling the EPB steering system via the vehicle dynamics system.

[0257] It makes sense to limit the vehicle's speed in such a fault scenario (e.g., to 75 km / h with an engine configuration as shown in Figure 3). Without a speed limit, this fault scenario results in a longer braking distance but is otherwise not critical from a safety perspective.

[0258] If, in a second fault scenario, the rear axle's electric traction motors TM1 and TM2 fail, ABS is controlled axle-by-axle via the pressure supply system. Steering interventions are then preferably carried out via EPS control by the vehicle dynamics system. If only one traction motor fails, steering interventions can also be carried out via the still active traction motor. Pressure control can be maintained even in the event of a partial failure of the pressure supply, for example, if a winding of an electric motor fails, albeit with reduced power, by having the second branch of the 2x3 phases take over control with 50% of the power. In this case, the traction motors on the rear axle can also take over the anti-skid control (ASR) as well as torque vectoring or yaw moment interventions.

[0259] The hydraulic brake system embodiment shown in Figure 6b is even simpler than the system shown in Figure 6a, as it requires fewer solenoid valves and hydraulic lines, and a drum brake can be used. The embodiment shown in Figure 6b also meets the redundancy requirements of SAE Level 4, as specified above.

[0260] Figure 6c shows a third embodiment with two electromechanical brakes EMB1 and EMB2 on the rear axle and a traction motor TM3 on the front axle.

[0261] The TM3 traction motor can be omitted, although the EMB1 and EMB2 electromotive brake units are system-relevant and represent topologies B and D in Figure 2. Only one hydraulic line leads from the pressure supply of the EHB to the two wheel brakes RB3 and RB4 on the rear axle. In particular, only a cost-effective drum brake can be used on the rear axle.

[0262] The electromechanical brake units EMB 1 and EMB 2 are designed to dynamically build up and reduce braking torque and are responsible for controlling the braking torque. The electrohydraulic brake EHB is used in normal operation only to apply a base braking torque to the rear axle. Control operation is similar to that explained above with reference to Figure 5, except that the roles of the EHB and the EMB are reversed, and the EHB generates the base braking torque. On the front axle, however, ABS control is carried out via the EHB, and the optional traction motor TM3 provides the base braking torque. If an optional traction motor TM3 is used on the front axle, a cost-effective drum brake can also be used here.

[0263] In the event of an initial failure, for example, if the hydraulic connection to the rear axle wheel brake fails, the connecting line is disconnected via the isolation valve, and EMB1 and EMB2 fully assume control of the individual rear axle wheels. This allows all safety-critical functions (p jump, ABS to low-p) to be controlled very safely, even without hydraulic support from the EMS. Steerability (priority 3) is ensured by the front axle pressure control and / or by controlling the EPB via the vehicle dynamics system.

[0264] The electromechanical brake units EMB1 and EMB2 are sensibly designed for the locking braking torque with a small reserve for fading (20% reserve); however, for cost reasons, the electromechanical brake units EMB1 and EMB2 can also be advantageously designed for a braking torque below the locking limit (approximately 50% of the locking braking torque). In normal operation, the EHB support allows the braking torque required for control at maximum deceleration to be reliably achieved without excessive thermal stress on a drum brake. In the event of a hydraulic line failure, it is perfectly acceptable for the rear axle to contribute less braking torque to the overall deceleration than the front axle, as the effect on the increased stopping distance is relatively small. Control operation at low-p and p-step is primarily important. In this case, 50% of the locking torque is sufficient for safe ferry operation.

[0265] If, in a second failure scenario, the electromechanical brake units EMB1 and EMB2 on the rear axle fail, ABS is controlled axle-by-axle via the pressure supply system. Steering interventions are then preferably carried out via EPS control by the vehicle dynamics system. If only one electromechanical brake unit EMB (EMB1 or EMB2) fails, steering interventions can also be carried out via the electromechanical brake unit EMB (EMB2 or EMB1) that is still active.

[0266] Pressure control can be maintained even in the event of a partial failure of the pressure supply, for example, due to the failure of a winding in an electric motor, albeit at a lower level, as the second phase of the 2x3 phases takes over control with 50% of the torque. In addition, the electromechanical brake units EMB1 and EMB2 on the rear axle handle anti-skid control (ASR) as well as torque vectoring and / or yaw moment interventions.

[0267] The hydraulic brake system embodiment shown in Figure 6c is simpler than the system shown in Figure 6a, as it requires fewer solenoid valves and hydraulic lines, and a drum brake can be used. The embodiment shown in Figure 6c also meets the redundancy requirements of SAE Level 4, as specified above.

[0268] Such a solution is useful when no electric traction motor is provided on the rear axle or neither an electric traction motor is provided on the rear axle nor on the front axle for interventions to generate braking torque by the vehicle dynamics system, for example for hydrogen vehicles or hybrid vehicles, where the electric motor is closely connected to an internal combustion engine and is therefore not dynamic.

[0269] Figure 6d shows a fourth variant of the electro-hydraulic brake unit EHB for integration into the driving dynamics system, whereby only one electro-hydraulic brake is provided for the front axle and, as in Figure 6b, an electric traction motor TM 1 and TM2 is also provided for each wheel on the rear axle.

[0270] In contrast to the system in Figure 6b, the rear axle is not supported by a basic braking torque via the EHB. This means that the traction motors are advantageously designed with correspondingly higher performance and can apply braking torque up to the locking limit and also regulate it dynamically. This type of configuration is advantageous for sports cars or premium vehicles with powerful engines, as the motors are sufficiently powerful and an electro-hydraulic brake unit EHB for the rear axle is no longer required. With this type of arrangement, the friction brake on the rear axle is completely eliminated. The traction motors TM1 and TM2 perform many functions (ESP interventions, ASR interventions, ABS interventions, EBD braking torque setting) and are controlled synchronously via the vehicle dynamics system with the electro-hydraulic brake units EHB on the front axle. This means that the braking torque setpoints are also synchronized in time.

[0271] Fig. 7a shows two curves of engine torque-speed maps, scaled with a transmission ratio to the speed of a 1,800 kg vehicle up to a maximum speed of 200 km / h, and therefore presented as an engine torque-vehicle speed map. The braking torques for a deceleration of 1 g = 9.81 m / s 2are calculated with a weight distribution VA / RA of 65% / 35% and are shown as dashed lines for the braking torques of the front axle (upper horizontal line, dash-dot) and rear axle (lower horizontal line, dashed). A first engine torque-vehicle speed map 1 (referred to as "Mbrems_normal" in Figure 7a) assumes a typical motor design with a typical inverter, since the electric traction motor is designed for constant power and thus, from a certain point PI, the power hyperbola is primarily limited by the voltage. Here, the maximum braking torque on the rear axle can still be generated by the electric traction motor in generator mode up to a speed v2.

[0272] To optimally utilize the traction motor's braking torque for braking even at maximum speed, an inverter can be advantageously used, which enables switching the coils from a series connection to a parallel connection of coil windings. This halves the inductance, and with a given voltage, a higher torque can be generated at the same speed. At the same time, the torque dynamics are increased by 100%, which is very advantageous for highly dynamic braking torque control in ABS operation. Furthermore, the inverter should be designed in such a way that, comparable to a 2x3-phase inverter concept, operation is still possible even if one or more components (power semiconductors, coil windings) fail, in order to prevent a complete failure of the electric traction motor as a braking unit.

[0273] In further embodiments, other topologies known from the prior art and similar in effect can also be used to achieve the functionality required above. However, these typically have between 24 and over 42 switching elements to implement redundancy (2 x 3 phases) and switchability between series and parallel connection during operation. They can also be used for the boost function.

[0274] Figure 7b shows a converter which, in contrast to similar prior art systems, requires only 18 switching elements instead of 30 to over 40 switching elements and which, like standard converters for brushless motors, can also be operated in 4-quadrant mode. The four quadrants result from positive or negative torque and positive or negative speed. 4-quadrant operation enables a motor torque boost mode, in which the torque is temporarily increased by up to 100%, and also provides redundancy in the event of one or more components failing (circuit breaker, coil windings). Converters with the capabilities described above are still more complex than a standard three-phase converter, which typically has six switching elements, due to the complexity of the circuitry and components.The application for the driving dynamics system described here is particularly attractive if, as shown in Fig. 6c, exclusively regenerative braking of the rear axle can occur in normal braking mode and in ABS control mode, thus potentially resulting in significant cost and weight savings due to the elimination of the friction brake. Furthermore, while converter redundancy is not absolutely necessary for SAE Level 2, the requirements for SAE Level 3 are met because control operation on the rear axle is still possible even in the event of a partial failure of the electric traction motors. Alternatively, SAE Level 3 also justifies a state-of-the-art inverter concept with 30 to 40 components, because comparable braking systems, such as 2-box braking systems, are significantly more complex than typical 1-box braking systems for SAE Level 2.

[0275] The configuration of the novel converter according to the invention (referred to as the "RSP-4Q converter"), described in detail below, makes it possible to realize a converter with only 18 switching elements (a total of only six connecting switching elements and twelve supply switching elements), which makes it possible to switch from a series connection to a parallel connection of the phases and vice versa during operation of the electric motor. In parallel connection, the twelve supply switching elements are active, while in series connection, the six connecting switching elements and six of the twelve supply switching elements are active. "Active" can be understood here as meaning that these switching elements are controlled in a clocked manner, while the other switching elements are, for example, in freewheeling mode.

[0276] In addition, switching from the series connection to the parallel connection or vice versa occurs depending on the failure of one or more operating elements. In the present case, the operating elements can be understood to mean, but are not limited to, the switching elements, for example, supply switching elements and connecting switching elements, and / or the coils of the individual phases. This configuration makes it easy to continue operating the electric motor in the event of a failure of one or more operating elements by switching from the series connection to the parallel connection. The converter shown in Figure 7b, as described, for example, in WO 2021 / 179980, is connected to an electric motor 4 with six phases U, V, W, U', V', W', which is shown only schematically with a circuit and its connections.

[0277] Each phase U, V, W, U', V', W' has at least one coil 6. Two phases

[0278] U, V, W, U', V', W' are combined to form a phase. In Figure 7b, a phase is shown as an example by circling the phases that make up the phase. Each of the two phases U, V, W, U', V', W' of the phase is electrically rotated 180 degrees to the other phase U, V, W, U', V', W' of the same phase 8, i.e., connected inverted. The inverted phases U', V', W' are marked with a line to distinguish them from the other phases U, V, W. In the exemplary embodiment, phase U' is the phase inverted to phase U, phase V' is the phase inverted to phase V, and phase W' is the phase inverted to phase W.

[0279] The converter also has six switching units 10, represented by dashed rectangles. Each switching unit 10 is assigned to a phase U, V, W, U', V', W'. Furthermore, the switching units 10 of the two phases U,

[0280] V, W, U', V', W' of a phase form a switching module. In the figure, the switching units 10 each form a switching module, so that the converter according to the invention according to Figure 7b has three switching modules. Each switching unit 10 is connected to a supply voltage supplying the individual phases U, V, W, U', V', W'. For this purpose, each switching unit 10 has two supply switching elements 16. The supply switching elements 16 are designed as MOSFETs in the exemplary embodiment.

[0281] Depending on the operating mode of the electric motor 4, the two phases U, V, W, U', V', W' of each phase are connected in parallel or in series. For this purpose, the converter 2 has a control unit configured to control the supply switching elements 16 and the connecting switching elements 20.

[0282] In addition, the converter 2 has a fuse unit (not shown in Figure 7b), which is also referred to as a "circuit breaker module" and is arranged between the electric motor 4 and the converter 2. The fuse unit has switching elements (not shown) that are designed to preferably galvanically isolate the electric motor 4 from the converter 2 in the event of a fault. Due to its simplicity, the RSP-4Q inverter described here is used for the control strategy with torque boost, as described in Fig. 7a. In further embodiments, however, other inverters that enable switching of the inductances during operation may also be suitable, such as an inverter with switching between delta and star connection or another inverter such as those used, for example, in DE 11 2018 000 733 T5 or DE 11 2018 001 213 T.

[0283] Figure 8 shows an advantageous embodiment of a pull-tight bidirectional inlet-outlet valve MV2k, which is used for implementing the pressure control functions in the EHB brake systems of Figures 6a to 6d or for an axle pressure adjuster according to Figures 9a and 9b.

[0284] Figure 8 shows a special MVzk valve required for the above-mentioned embodiments, which functions reliably in both flow directions. This means that the valve's functionality is guaranteed, even at large flow rates, such as 100 cm 3 / s - 120 cm 3 / s, or large pressure differences across the valve, such as 160 bar - 220 bar.

[0285] In particular, for the above-described ranges of parameters, this valve MV 2k ensured that it does not close automatically.

[0286] The valve MV2k basically has the typical structure of a solenoid valve with electromagnetic circuit EMI with an armature 6, a valve actuator or valve stem 7 and a valve seat 8 as well as a return spring 13. The return spring can be omitted if the additional force device, which in Figure 8 is formed by an electromagnetic circuit EM2, is designed accordingly.

[0287] The magnetic circuit EMI generates (see Figure 8a) a strong progressive force curve FM1 over a stroke h and the return spring 13 generates a progressive restoring force FRF over the stroke h to reset the armature.

[0288] In the left part of Figure 8, the armature 6 is coupled to a second force-generating element, which forms an additional force device. This can consist of a second electromagnetic circuit EM2 with armature 6a, whose switchable force FM2 counteracts the force FMI of the first magnetic circuit EMI. As a more cost-effective variant, a permanent magnetic circuit can also be used as a passive additional force device, comprising a small permanent magnet 9 with a pole plate 10.

[0289] The force effect of FM2 counteracts FMI and acts with a relatively strong force when the valve is open with a strong desired drop in force over the stroke h.

[0290] The force FM2 (see Figure 8b) is still large enough when the end of the stroke is reached to take over the usual armature return and therefore can optionally replace the usual return spring 13.

[0291] Figure 8c shows the interaction of the force sources FMI as a function of the current and FM2 for the permanent magnet.

[0292] In the closed valve position, the pressure difference P2-P1 acts on the valve seat with the force FP, which is directed towards the valve opening if the pressure P2 is greater than the pressure PI.

[0293] In the open valve position, the hydraulic force FH described above acts on the valve seat due to the volume flow Q through the valve, which could tear the valve shut without countermeasures, both during the pressure build-up P aU f and also during pressure reduction Pab, depending on how the solenoid valve MV2k is connected to a pressure supply DV and a wheel brake cylinder RZ, and depending on the direction of the volume flow. This is the basis for the pressure control with pressure supply device and wheel brakes shown in Figures 9a and 9b below.

[0294] If the solenoid valve is in an open position, a force FH acts upon flow through the valve, starting from the valve armature connection (14) toward the valve seat connection (16), depending on the volume flow Q due to the Bernouilli effect. If the volume flow Q is very high, for example, with high pressure differences, this can result in the valve being forced closed solely by the flow force FH. This causes the valve to close and can no longer be opened.

[0295] To prevent this effect, the force of the auxiliary force device FM2 counteracts the force FH and prevents the valve from closing, even in the case of large pressure differences that can occur during braking system operation. The auxiliary force FM is preferably highest when the valve is open, which can be achieved, for example, using a permanent magnet circuit. It acts across the entire stroke range and supports the restoring force of the valve spring FRF in such a way that the valve is always returned to the open valve position when a volume flow Q is applied, regardless of the valve position, i.e., in particular, even in a half-closed state.

[0296] With appropriate design, the valve return spring 13 can also be omitted.

[0297] The valve must also be designed in such a way that when the valve is energized by activating the magnetic circuit EMI, the primary valve force FMI can overcome the sum of both forces (FMZ+FRF) so that the valve can close when energized.

[0298] Large volume flows can occur, for example, when the wheel brake is connected to the switching valve via the armature connection, as is typically the case with a wheel valve configuration with inlet / outlet valves (see Fig. 6a - 6d for this embodiment), and the ECU or power supply of the brake system fails at this time, thus preventing pressure reduction via outlet valves because they are closed by the differential pressure and can no longer be opened because a remaining residual pressure greater than the return force FRF of the valve spring keeps the valve closed. Valve closing can also occur when the pressure of the wheel brake is reduced with a very high pressure gradient, for example when pressure is reduced by a very rapid return movement of the piston of the pressure supply unit.

[0299] A valve design that resists closing is also relevant when the pressure supply device is connected to the armature connection (see Figures 9a and 9b), and pressure is built up very quickly with the pressure supply unit. Rapid pressure buildup occurs, for example, in the automatic emergency brake (AEB) or in the multiplexing process with pressure curve control via volume control / control of the pressure supply device instead of pre-pressure control, as well as pressure curve control via volume flow throttle control of the PWM control of the intake valves.

[0300] The closing effect can be limited by a pressure difference limitation in the control of the pressure supply unit or preferably by means of a throttle not shown in the figures, wherein the throttle is mounted in front of the armature connection of the valve connection in a hydraulic line.

[0301] Alternatively, it is conceivable to arrange a pressure relief valve in a hydraulic parallel circuit to the switching valve. This valve opens at high differential pressures, thus limiting the hydraulic force FH acting through the Bernoulli effect and thus eliminating the need for the auxiliary force device FM2. This simplifies the valve design but limits the pressure change dynamics via the hydraulic pressure supply.

[0302] If the braking torque change is controlled in parallel via a traction motor, such measures are not necessary because the dynamic demands on the hydraulic braking system are lower. Standard valves can then be used without an auxiliary power device and without a throttle or pressure relief valve.

[0303] In the event of a wheel circuit failure, a wheel circuit can be isolated by closing an inlet valve (SV) located between the wheel brake and the pressure supply. The hydraulic braking system with n wheel circuits can then operate with one fewer wheel circuit, i.e., with nl wheel circuits. For example, instead of a 4-circuit braking system control, three circuits can be used. This means that in the event of a wheel circuit failure, even after the inlet valve (SV) closes, very high deceleration can still be achieved, and yaw moment control with three wheel brakes or an ESP function can be maintained. If an electric motor is available on the failed wheel circuit, this can take over the braking torque control of the failed wheel brake, thus maintaining a 4-circuit braking torque control with no or only minor restrictions, for example, due to the maximum braking torque of the traction motor.

[0304] The valve tappet 7 can also have a special shape which provides the counterforce through hydraulic flow forces and can reduce the closing force.

[0305] Figure 8c shows the electrical control of the valve via a current i. The current i1 is selected in the closed valve position so that FMI is greater than FM2. The current can then be varied in the closed valve position, at current i2, depending on the hydraulic differential pressure P2-P1 across the valve. Since the force FM2 in this position is within the range of the usual spring force for the reasons described above, the valve can also be operated, for example, with a current control or current regulation.

[0306] To keep the valve in the closed position, the differential force

[0307] Fv,zu = FM 1,ZU ■ FM2,ZU must be greater than the force FP resulting from the differential pressure P2-P1 across the valve in the closed position.

[0308] Figure 9a describes the design of a pressure regulator in the form of a piston-cylinder unit driven by an electric motor via a transmission, to which two wheel brakes RI and R2 and optionally additional hydraulic consumers Vx are connected via hydraulic lines. Additional hydraulic consumers Vx can be additional wheel brakes or other hydraulic consumers, for example, hydraulic pistons of clutch(es) or a hydraulic power steering system or other actuating pistons of a vehicle axle. Preferably, the pressure regulator is also connected to a valve device with a reservoir VB.

[0309] The pressure regulator preferably has 2x3-phase connections to two control units ECU I EHB and ECU2EHB, whereby current sensors i / U and angle sensors a / U are provided, which are preferably also designed redundantly and which are used for high-precision PPC pressure control or pressure control via piston position or current.

[0310] A pressure sensor p / U is preferably provided at the pressure supply outlet, which is primarily used for calibration purposes. However, pressure regulation or control can also be performed without this pressure sensor if the relationship between the EMS braking torque and the current or piston position is established in another way, for example, by using acceleration sensors or by comparing it with the braking torques or vehicle deceleration due to braking torques from electric traction motors TM1-TM4.

[0311] Bidirectional inlet / outlet valves, referred to here as "MV2k", are used as solenoid valves. The MV2k valves are operated in such a way that pressure can be built up and released via the solenoid valves, with the pressure change occurring particularly dynamically, i.e., at > 1000 bar / sec, preferably > 2000 bar / sec. The valves must be designed to be resistant to closing according to the system specification, i.e., according to the required maximum pressures and maximum flow rates.

[0312] Preferably, solenoid valves with a first soft iron magnetic circuit EMI and a second permanent magnet circuit EM2 are used as shown in Figures 8-8c.

[0313] Alternatively, modified inlet valves of a standard ESP unit can be used as MVzk, i.e. normally open solenoid valves with a standard valve opening cross-section and 6 mm magnet armature diameter without a second permanent magnet circuit EM2, which in the classic design can also be designed to be resistant to closing, in particular due to the lower maximum pressures occurring in the present driving dynamics system and the therefore lower closing forces when the pressure changes with maximum pressure gradients.

[0314] If inlet valves of an ABS / ESP unit are used as MVzk valves, they must be designed according to the pressure differences and pressure change rates, for example with a stronger magnetic circuit with a larger armature and / or stronger return springs.

[0315] Alternatively, the pressure gradient and / or pressure differences can be limited via the control during pressure build-up using software, so that a dynamic pressure build-up does not lead to the solenoid valves closing.

[0316] Due to the fact that the pressure range for the control of the driving dynamics system described here is smaller than for standard braking systems, and because a braking torque can also be built up via the electric traction motor, the requirements for the MV-2K valves are lower than for standard braking systems.

[0317] What is specific to the MVzk valve - regardless of the variant selected - is that the solenoid valves are designed without a parallel-connected check valve or that no check valve is arranged in parallel in the hydraulic line in the hydraulic connection between a wheel brake R1, R2 or a hydraulic consumer Vx and the pressure supply device.

[0318] The purpose of this is to maintain a constant pressure in one wheel brake while changing the pressure in other wheel brakes. This is a major difference from standard braking systems, where pressure in one wheel brake can only be maintained via a pre-pressure regulator. This severely limits the degrees of freedom in pressure control in standard braking systems and also makes diagnosing a wheel brake failure considerably more difficult, if not impossible, since in the event of a wheel circuit failure, it is impossible to determine whether the solenoid valve, the check valve, or the hydraulic system is the cause.

[0319] If an MVzk valve is used, the wheel brake can be safely disconnected from the pressure supply, regardless of the cause of the failure. This makes it possible to switch from an m-circuit electrohydraulic braking system (EHB) to an ml-circuit braking system. In Figure 9a, for example, a 2-circuit EHB with two wheel brakes becomes a 1-circuit EHB, or a 3-circuit EHB with Vx becomes a 2-circuit EHB.

[0320] In the case shown in Figure 6a, a 4-circuit EHB becomes a 3-circuit EHB, in Figure 6b a 3-circuit EHB becomes a 2-circuit EHB.

[0321] A special feature of this first configuration is that the valve seat of the MVzk valve is connected to the wheel circuit and that its armature chamber is connected to the pressure regulator.

[0322] Such a setup enables innovative pressure control with bidirectional inlet / exhaust valves, forward and backward movement of the piston of a piston-cylinder unit via current or piston control, and simultaneous pressure gradient-controlled pressure reduction. In one embodiment, the pressure buildup occurs sequentially using the known multiplexing method. Alternatively, the dead time of pressure buildup can be avoided by a braking torque gradient generated by an electric traction motor, which is possible if an electric traction motor for individual wheel drive is available. Alternatively, the braking torque buildup can also be achieved via the traction motor of only one axle, which is particularly possible if both wheels on an axle have the same braking torque increase.

[0323] If simultaneous pressure buildup is required and no electric traction motor is available for support, pressure buildup can also occur simultaneously through timing of the valves. This means that a variable pre-pressure is set by the piston, and one valve closes earlier than the second. Pressure reduction occurs simultaneously at several wheel brakes via piston control using the pressure-volume characteristic curve, as well as PWM control of the valves or current control of the valves. This means that a variable flow cross-section is set via a current, allowing different pressure reduction gradients to be achieved.

[0324] Such a control is referred to as PPC-Gen2-Vl (2nd generation Piston Pressure Control with valve connection VI: valve seat inlet / outlet valve MVzk on wheel brake).

[0325] Figure 9b describes the design of a pressure regulator with an electric motor-driven piston-cylinder unit with MVzk switching valves. Unlike Figure 9a, the valve seat is connected to the hydraulic line to the pressure regulator and the armature chamber is connected to the wheel brake. Optional exhaust valves are also provided.

[0326] With such a setup, a second variant of a PPC-Genl-V2 pressure control system can be implemented, with bidirectional inlet / outlet valves MVzk and forward and backward movement of the piston of a piston-cylinder unit via current or piston control, as well as simultaneous pressure gradient-controlled pressure buildup. The valve design of the MV2k valves is similar to the configuration shown in Figure 9a and thus transferable, as is the PPC pressure control or pressure control, as well as the preferably redundant design of the motors with redundant electronics ECU IEHB, ECU2EHB, and sensors a / U, i / U.

[0327] In one embodiment, the pressure reduction takes place in the known multiplex process sequentially with a time delay AtMux or via a time control of exhaust valves, as known from classic ABS systems.

[0328] In contrast to the state of the art, pressure reduction can also occur simultaneously in one wheel circuit (R2) via intake / exhaust valves using piston control based on the pressure-volume characteristic, while in a second wheel circuit (RI') it occurs via exhaust valves. This avoids the time delay AtMux.

[0329] This allows pressure to be reduced very quickly in critical driving situations, for example at high-p or when the pressure jumps. In another control state, such as low-p, i.e. when controlling on ice and snow, control can be carried out using the well-known multiplex method. By combining the pressure reduction methods, very short braking distances can be achieved in all driving situations. The combination of pressure reduction via exhaust valves with inlet / outlet valves has the further advantage that it is not necessary to use MVzk valves designed for high pressure differences and volume flows. This is because the MVzk valves do not need to be subjected to high flow rates during pressure reduction, as pressure reductions with high pressure gradients occur via exhaust valves.

[0330] Furthermore, the MVzk valves are subjected to lower stress during pressure reduction because the electro-hydraulic brake unit (EHB) described for the vehicle dynamics system is designed for a maximum pressure of 140 bar, and the valves do not need to be pressure-resistant to 160 bar - 220 bar, as shown in Figure 8a. This means that modified standard inlet valves of an ESP unit with typical valve opening cross-sections, but without parallel check valves, can be used in this embodiment. The advantages of not using parallel check valves were described above with reference to Figure 9a and apply analogously to Figure 9b.

[0331] Thanks to the advantageous combination with exhaust valves, pressure can be reduced quickly in all driving situations, which also significantly reduces the dynamic demands on the pressure regulator's drive motor. If the MUX method is used for most operating conditions, the hydraulic brake circuit can be operated primarily in a closed brake circuit. This eliminates the need for the critical replenishment of hydraulic fluid during normal operation—typical for open systems according to the state of the art (DE 10 2018 212 905 A1), which are controlled according to the method described in EP 2 580 095 B1. The replenishment of volume in open systems is increasingly viewed as critical, as a time interruption of more than 100 ms can lead to critical driving situations.

[0332] In addition, a braking system embedded in the driving dynamics system described here can perform more functions beyond pure ABS control, such as additional braking torque interventions such as torque vectoring. This could result in a loss of hydraulic volume in the open circuit.

[0333] If the MV2K valve according to the invention is also used as the switching valve, a wheel circuit failure can be diagnosed analogously to the case described with reference to Figure 9a, and the wheel circuit can continue to operate even with a minor leak, which is not possible in state-of-the-art systems with parallel-connected check valves. Such a control system is referred to here as PPC-Gen2-V2 (2nd generation Piston Pressure Control with valve connection V2: valve seat inlet / outlet valve MVzk on pressure supply).

[0334] As an alternative to the MVzk solenoid valves, standard inlet valves from an ABS / ESP unit can also be used. These valves are designed to suit the pressure differences and pressure change rates, for example, with a stronger magnetic circuit and / or stronger return springs. Due to the fact that the pressure range of the control of the driving dynamics system described here is smaller than that of standard braking systems, the demands on the solenoid valves are lower.

[0335] As an alternative to the piston-cylinder unit with inlet / outlet valves, a simple pump can also be used, for example, a 2-piston pump according to the state of the art for ABS pumps or a gear pump according to WO 2021 005 151 A1. With a 2-piston pump, pressure reduction is controlled via outlet valves, and pressure build-up is controlled via a pre-pressure and PWM control of the inlet valves. If a gear pump is used, the same degree of freedom exists as with the piston-cylinder unit, because pressure can be applied either via outlet valves or via the gear pump by changing the direction of rotation. This design has cost advantages but disadvantages in the precision of the braking torque control due to leaks in the gear pump.

[0336] Figure 10 shows the advantageous "Architecture II" of the driving dynamics system for electric axles, with several brake units acting on the front and rear axles.

[0337] Braking units include traction motors TM1, TM2, and TM3, hydraulic pressure regulators EHBHA and EHBVA, and / or EMB modules for wheel brakes. The central control unit regulates the braking torques and sends target signals to the axle control units S-ECUVA and S-ECUHA. This, analogous to "Architecture I," preferably implements the following functions:

[0338] • (A) Basic brake with thermal management and energy flow management of the traction motor;

[0339] • (B) Emergency brake AEB with electronic brake force distribution (EBD);

[0340] • (C) Regenerative braking on multiple axles; • (D) ABS control with basic brake torque support and / or joint brake torque control;

[0341] • (E) Braking operation in the event of failure of the electro-hydraulic brake unit EHB-Z, EHB-VA;

[0342] • (F) Yaw moment interventions or wheel-individual braking torque interventions; and / or

[0343] • (G) wheel-specific braking torque interventions for wheel-specific regenerative braking.

[0344] The driving dynamics system sends target values, particularly those relating to braking torques or brake pressures. For certain functions (such as functions (C), (F), (G) described above), target signals for pressure control or pressure regulation are also specified. These include control signals for solenoid valves for functions such as switching duration, opening time, PWM frequency, or alternatively, current profiles for pressure changes with throttled valve cross-sections, and / or pre-pressures for the pressure supply device for pressure build-up or pressure reduction.

[0345] Furthermore, the M-ECU domain can also have an interface to the control unit or autonomous driving domain (M-ECUAD) and can evaluate additional information useful for effective and predictive control. These include, for example, camera information about the road surface (snow, ice, rain) or information about the environment (distances to pedestrians and / or other vehicles).

[0346] A first embodiment of an axle module is described with reference to Figure 11a. In this example, electromotive brake units EMB1, EMB2 are provided on each wheel, and an electric traction motor TM1 is also provided for the axle.

[0347] A control unit of the axle S-ECU-axle communicates with the electric motor brake units EMB1, EMB2 and the electric traction motor TM1 and sends corresponding target signals such that a braking torque is preferably controlled simultaneously by the electric motor brake units EMB1, EMB2 and the traction motor TM1. In this case, the braking torques preferably act additively on the wheels even during control operation. For example, a base braking torque is preferably generated with the traction motor TM1, which reduces the braking torque amplitude of the EMB modules (see the above description with reference to Figure 5). In addition, the base braking torque of the traction motor TM1 can also be reduced simultaneously with the EMB braking torques of the wheel brakes, allowing higher braking torque gradients to be achieved. This is particularly important in critical driving situations such as a .-jump (see the above description of control situations with reference to Figure 5b).This can also be used advantageously for downsizing the EMB modules with low maximum forces and lower power of the EMB drive motors.

[0348] A further embodiment is described with reference to Figure 11b. An electrohydraulic pressure regulator (EHB) is combined with EMB modules in an axle module. The pressure regulator is preferably constructed according to Figures 9a and 9b and enables wheel-specific control.

[0349] This allows individual wheel control either via the EMB modules or via the electro-hydraulic brake unit EHB.

[0350] This allows maximum degrees of freedom in pressure control.

[0351] It also enables redundancies in the wheel-specific pressure control, as required for SAE Level 4-5, for example, so that the ABS control function can be implemented redundantly and with two different brake torque controller designs. This is particularly advantageous with regard to meeting redundancy requirements.

[0352] Such a configuration is designed especially for the front axle of an autonomously driving vehicle, where higher requirements must be met than on the rear axle, for example with regard to steerability and the major influence on the braking distance.

[0353] Such an axle configuration can also be used to simplify steer-by-wire systems, which typically have two steering actuators, with one steering actuator also being equipped with a 2x3 phase winding. In this way, the steering can be simplified using the braking torques, because safe, redundant steering can be ensured through braking torques. This leads to cost savings of up to €100 for the steering system. Alternatively, a pressure regulator with only one hydraulic line to two wheel brakes is also conceivable, although this is not shown in Figure 11b. As an alternative to a piston-cylinder unit, a simple rotary pump in the form of a gear pump is also conceivable, by means of which pressure can be built up and released. In this embodiment, a braking torque can be applied per axle.The hydraulic pressure regulator then supports the control system in a similar way to the traction motor, but due to the lack of power restriction, it can also achieve a deceleration until the locking pressure is reached. This enables axle-by-axle ABS function, which is absolutely sufficient for controlling a rear axle if individual wheel control is implemented on the front axle.

[0354] If the system of Figure 11b is provided for the rear axle and combined with a system of Figure 11a for the front axle, a 3-channel ABS operation and a yaw moment control can be realized.

[0355] Referring to Figure 11c, another embodiment with an electrohydraulic brake unit (EHB) and two electric traction motors (TM1 and TM2) is explained. One traction motor is provided for each wheel.

[0356] Alternatively, the electro-hydraulic brake unit EHB is designed for individual wheel control as shown, but the electro-hydraulic brake unit EHB can also be designed with only one circuit.

[0357] A vehicle's rear axle is sensibly equipped with such a configuration, and the electrohydraulic brake unit (EHB) is used for redundancy purposes for ABS and yaw moment control for stability and steering interventions. ABS is controlled via the traction motors at low-speed and supported by the EHB, while at high-speed ABS is controlled via the EHB and supported by traction motors. Anti-skid control is provided exclusively by the traction motors TM1 and TM2. Such an axle is sensibly equipped with a cost-effective drum brake.

[0358] With reference to Figure 11d, a further embodiment is explained in which a traction motor TM1 is combined with an electrohydraulic brake unit EHB. This variant is comparable to the embodiment shown in Figure 11a, with the difference that the electromotor brake unit EMB is replaced in its function by an electrohydraulic brake unit EHB. Figure 12 shows the maximum braking torque gradients as a function of vehicle deceleration using exemplary designs of the typical brake unit 1 box (curve 1210), ESP standard with storage chamber (curve 1220), electric traction motor (curve 1240), electric traction motor with RSP-4Q inverter (curve 250) and pressure regulator with PPC-2Gen-Vl or V2 pressure control (curve 1260) designed for high braking torque gradients, preferably with a pull-tight MVzk valve, for an exemplary maximum speed of 200 km / h.

[0359] In addition, the corresponding curve for "MUX 2.0" is shown (curve 1230), whereby MUX 2.0 encompasses the 2nd generation multiplexing processes, such as the pressure controls PPC-Gen2-Vl and PPC-Genl-V2, which are described in this description (see description with reference to Figures 9a and 9b). These systems, in particular, utilize non-closing valves, and a distinction is made between different valve connections and pressure control processes. In PPC-Gen2-Vl, the valve seat is connected to the wheel brake; in PPC-Gen2-V2, the valve seat is connected to the pressure supply unit. In both processes, bidirectional flow through the valves occurs, and the pressure is changed in one pressure change direction via volume control; in another pressure change direction, the pressure is optionally throttled by means of the valve opening cross-section control, or the valve is changed only via time control.These second-generation multiplexing methods differ from first-generation multiplexing methods (MUX 1.0) in that, with the MUX 1.0 method, the pressure is changed exclusively via volume control in both pressure change directions. In addition, pressure reduction is achieved via at least one outlet valve on a wheel brake. This results in higher overall pressure change gradients than when using a single-box and ESP.

[0360] In addition, three areas I-III are defined:

[0361] In the range of smaller decelerations, the EMB electromotive brake unit and electric traction motors can, by design, achieve particularly high braking torque gradients. A standard ESP system with a storage chamber has the lowest gradients because there is counterpressure in the storage chamber, whereas single-box braking systems reduce the pressure in the reservoir and therefore have advantages. In range I, which is typically relevant for ABS control on snow and ice or deceleration during normal ACC braking, for example, EMB electromotive brake units or traction motors are preferably used for braking torque control.

[0362] In area III, on the other hand, during long decelerations, electro-hydraulic systems (pressure regulators with preferably PPC Gen2 control, 1-box) have the great advantages and preferably take over the ABS control.

[0363] In the intermediate range, all of the above-mentioned brake units can Sufficient braking torque gradients are achieved. Preferably, a first braking torque controller with a low braking torque gradient supports the ABS control with a constant braking torque, while the ABS control is taken over by a more dynamic pressure controller.

[0364] If the additive braking torques are linearized across the entire deceleration range by adding the braking torque gradients of two braking torque controllers, a high braking torque gradient can be ensured across the entire deceleration range. Ideally, this preferred characteristic is used to downsize the brake units: For example, motors with low drive torques and power can be used for EMB and EHB, and / or smaller control valves can be used. In such a case, a cost-effective EHB pressure controller with a trapezoidal spindle can be implemented, which is only suitable for lower pressure ranges due to the spindle load caused by higher pressures.

[0365] If a pressure regulator is operated sequentially with a MUX control, dead times in the control cycles due to braking torque interventions from other components can be reduced, thus restoring the relevance of MUX control, which had previously lost significance due to its disadvantages in extreme situations (e.g., at high-p). This has the particular advantage that a braking system is then completely closed, and the control can be modeled using mathematical models. This eliminates the need for complex pressure estimation models and calibration work required for the calibration of open ABS systems. Automated calibration is also possible.

[0366] With reference to Figure 12a, an example is given of how the target braking torques for the wheel brakes on the vehicle's front axle are obtained from the control units. A vehicle model implemented in the central control unit M-ECUchassis control includes, for example, modeling data on weight distribution, a coefficient of friction of the road surface, a tire condition, and a brake pressure effect on the vehicle's deceleration. In particular, the following values ​​are transferred to a control unit M-ECUVA of the front axle: Target values ​​for the target braking torque of the right M SO II,VR and left front wheel M SO II,VL, a speed of the vehicle VF Z9 , a speed of the right VVR and left VVL front wheel, a difference moment of the right AM SO II,VR and left front wheel AM SO II,VL and a friction coefficient of the road surface.

[0367] In particular, the M-ECUVA control unit of the front axle stores an Mn characteristic map of the traction motor TM, which indicates a dependence of the deceleration achieved by the traction motor on the speed of the vehicle or the speed of the traction motor, as well as a further characteristic map that indicates the relationship between the achievable braking torque gradient and a deceleration of the vehicle for the available braking units or the traction motor.

[0368] Based on this data, the M-ECUVA control unit determines the target torque for a first M S0 H,TMI and second traction motor M S0 H,TM2 of the front axle, target torques for electromechanical brake units of the first M S0 H,EMB,RI and second wheel M SO II,EMB,R2 as well as target torques for electro-hydraulic brake units for the first M SO II,EHB,RI and second wheel M S0H,EHB,R2. The procedure is adapted to which brake units are actually available.

[0369] These values ​​then result in a target braking torque of the right M S0 H, brake, VR and left front wheel M S0 H, brake, VL.

[0370] The same procedure can be carried out analogously for the rear axle or for all wheels of the vehicle.

[0371] With reference to Figure 13, an advantageous "Architecture III" of the driving dynamics system for wheel modules is explained, with two brake units acting on each wheel. Traction motors TM1, TM2, TM3, TM4 and electromotive brake units EMB modules EMB1, EMB2, EMB3, EMB4 for wheel brakes can be used as brake units.

[0372] The central control unit controls the braking torques and sends target signals to the S-ECURadi, S-ECURad2, S-ECURad3, S-ECURad4 control units of the individual wheels or axles.

[0373] Analogous to architectures I and II, the following functions are preferably implemented: • (A) Basic brake with thermal management and energy flow management of the traction motor;

[0374] • (B) Emergency brake AEB with electronic brake force distribution (EBD);

[0375] • (C) Regenerative braking on multiple axles;

[0376] • (D) ABS control with basic brake torque support and / or joint brake torque control;

[0377] • (E) Braking operation in the event of failure of an electromotive brake unit EHB-Z, EHB-VA;

[0378] • (F) Yaw moment interventions or wheel-specific braking torque interventions; and / or

[0379] • (G) wheel-specific braking torque interventions for wheel-specific regenerative braking.

[0380] When implementing the functions, the braking torque is distributed between the electric traction motor and the EMB according to characteristic maps, in particular the braking torque gradients, as shown in Figure 12, depending on the deceleration of the vehicle. In contrast to the other architectures, the braking torque modulation is preferably carried out by the electromotive braking units EMB in all driving conditions and only a basic braking torque is provided via the electric traction motor of the respective wheel, which is used in particular for downsizing the electromotive braking units EMB. This is preferably used to a greater extent when the wheel brake heats up. If one braking unit fails, control operation is then taken over by the other braking unit, possibly with restrictions on the maximum achievable deceleration, but with fully redundant control functions on all wheels.

[0381] An exemplary embodiment of this architecture is explained with reference to Figure 13a. In a wheel module, an electromechanical brake EMB (EMB1-EMB4) is combined with an electric traction motor (TM1-TM4), so that each wheel module forms an assembly and is controlled by a wheel module control unit (M-ECU-Rad1 - M-ECU-Rad4). The respective wheel module control unit synchronizes the torque control of the electric traction motor and distributes the braking torque differently between the EMB and the traction motor TM depending on the driving situation, such as the coefficient of friction or speed.

[0382] Preferably, the traction motor and the EMB each have an additional control unit (ECU-EMB, ECU-TM), which in particular contains the output stages of the converter and the motor control and operates with a faster cycle time, while the decision heuristics and characteristic maps are preferably mapped in the wheel module control unit M-ECU-Wheel.

[0383] The darmodule control units (M-ECU-Radl to M-ECU-Rad4) also communicate with the central control unit (M-ECU domain), where in particular wheel speeds VRI-VR4 and in particular other sensor signals SI, S2, Si are read in.

[0384] It is conceivable that the wheel module control units (ECU-Rad1 to M-ECU-Rad4) also record wheel speeds VRI-VR4 as well as sensor signals SI, S2, Si. They can also redundantly execute functions of the central control unit (M-ECU domain).

[0385] This allows for wheel-specific control either via the EMB modules or the traction motor. This allows for maximum freedom in pressure control, but also redundancies in wheel-specific pressure control, as required, for example, for SAE Level 4-5. In particular, an ABS control function can be implemented redundantly and with two different brake torque controller designs, which is particularly advantageous with regard to meeting redundancy requirements. If one wheel module fails, a much safer and more reliable control system with short braking distances and yaw moment control options can still be achieved with three wheel modules. If either the EMB electromotive brake unit or the traction motor fails within a wheel module, the other, non-failing component takes over control of the braking process.

[0386] There are different design variants: a) The electromotive brake unit EMB is designed to achieve the blocking pressure so that if the traction motor fails, braking can still be carried out with maximum deceleration via the electromotive brake unit EMB; however, the generous reserve for fading (typically 100%) is omitted, i.e. the electromotive brake unit EMB only has a small reserve in addition to the maximum braking torque without heating, for example 20-40%. b) The electromotive brake unit EMB and the electric traction motor TM are designed so that maximum deceleration is achieved through a combination of the braking torques of EMB and TM and the friction brake is designed according to the maximum braking torque of the electromechanical brake unit EMB.In addition, as explained above with regard to "Architecture I", suitable precautions and control strategies are required to ensure that braking via the regenerative braking torque of the traction motor does not lead to damage to the battery, especially when the battery is fully charged. These include (1) feeding energy back into the battery up to the limit of power consumption, (2) field-oriented control (Id / Iq current control) of the electric motor such that the energy is dissipated internally in the motor, (3) otherwise dissipating the energy generated by the electric traction motor in generator mode, or (4) using an electrical buffer designed for pulsed power, such as a supercapacitor.

[0387] Variant b) is the preferred design because it offers the greatest potential for cost and weight reduction. However, in an initial introduction scenario for the technology, variant a) may be more appropriate in terms of risk minimization.

[0388] The two variants a) and b) mentioned above provide sufficient safety for SAE Level 5 because, in the event of a wheel module component failure or the entire wheel module failure, the vehicle can still be decelerated with high vehicle stability and even ABS operation. The only reductions are in braking distance at high speeds and decelerations.

[0389] The systems described here, in particular the driving dynamics system, the vehicle, and the method, enable significant cost savings for the core components of the vehicle's braking and steering systems. Furthermore, significant weight savings can be achieved, which in turn leads to further cost savings.

[0390] By optimally exploiting the potential of regenerative braking using the electric traction motor(s), dissipative braking systems can be smaller, as they only have to apply a smaller portion of the total braking torque. The problem of fading caused by excessive heating of the friction brake can thus also be reduced.

[0391] A: AD Level 2

[0392] If, for example, as described above for the FDS variant Al, the basic braking function (function a) is optimized with a driving dynamics system and central control as well as a blending strategy according to Figure 3, i.e., for example, 51% of the braking is regenerative via the traction motor on the front axle and 71% on the rear axle, then the heating of the wheel brake can be minimized.

[0393] This has two positive effects on costs: Firstly, the braking system can be designed for a lower pressure, which reduces the cost of the electro-hydraulic brake unit (EHB). Secondly, the foundation brake can be significantly lighter. This can be achieved, for example, by using smaller brake discs, smaller brake shoes, and more cost-effective materials. This allows a cost-effective drum brake to be used on both the front and rear axles.

[0394] In an FDS variant A2, for example, to simplify the electrohydraulic braking system shown in Figure 6b, the traction motor on the rear axle can be designed so that torque can be generated for each wheel individually, either by a traction motor with a torque vectoring module or, preferably, by dividing the power of a 130 kW motor into two electric traction motors TM1, TM2, each with 65 kW. The latter embodiment with two motors is advantageous because dynamic braking torques at both wheels can be varied independently of each other.

[0395] If, as explained above, a braking torque is synchronously controlled via the driving dynamics system via the electric traction motor and the electro-hydraulic braking module EHB, with one braking unit in particular providing a basic braking torque while the second braking unit provides an additional controlled braking torque (control strategy according to Figure 5), the costs and weight of the system can be further significantly reduced.

[0396] Firstly, the costs of the electro-hydraulic brake unit (EHB), particularly according to the embodiment shown in Figure 6a, can be reduced by using fewer and more cost-effective valves and even lower maximum pressures and volumes. For example, a cost-effective trapezoidal spindle can be used instead of a ball screw drive. Furthermore, it is possible to use a drum brake on both the front and rear axles.

[0397] For an FDS variant A3, for example, in a third optimization step, only one twin traction drive (TM1, TM2) with, for example, 230 kW of power can be used on the rear axle. If the RSP-4Q inverter described here is also used according to Figure 7b, the operating range of regenerative braking can be significantly expanded again according to the motor map in Figure 7a.

[0398] This allows the rear axle to be decelerated exclusively via the electric traction motor throughout the entire vehicle speed range up to the maximum speed. Furthermore, if the control function described here is performed via the electric traction motors TM1 and TM2, the foundation brake on the rear axle can be completely dispensed with.

[0399] In addition, no hydraulic lines to the rear axle or a control valve are required, so the electro-hydraulic brake unit (EHB) needs to be designed exclusively for the front axle of the vehicle (see Figure 6c). A cost-effective trapezoidal thread can also be used.

[0400] B: AD Level 3-4

[0401] If an electro-hydraulic braking system as shown in Figure 8 is used in a variant Bl of the driving dynamics system with a 2-box system (e.g. X-Boost3 and ESP) and integrated into the driving dynamics system as described, both the redundancy requirements of SAE Level 4 can be met and the electro-hydraulic braking unit EHB can be designed more cost-effectively through downsizing.

[0402] Furthermore, the friction brake can be reduced in terms of cost and weight even in the basic braking function (a) by providing brake assistance via electric traction motors. Costs can be reduced even further by using a cost-effective disc brake on the front axle and a drum brake on the rear axle.

[0403] If, in a variant B2 of the driving dynamics system with a central EHB-Z, an electro-hydraulic braking system as shown in Figure 6a is used, and the traction motors on both axles are used for support in accordance with the driving dynamics system control described here for the basic brake and control function, then a functional redundancy level for AD Level 3-4 can be achieved with the additional redundancy functions described above with reference to Figure 6a and with a redundant design of the pressure supply system. It is also assumed here that the hydraulic braking system has a four-circuit design and can still be operated with three circuits in the event of a failure.

[0404] C: AD Level 5

[0405] For a CI variant of the driving dynamics system with an electromechanical brake unit (EMB), the third embodiment described above is used, where a control ECU (S-ECUkadi, S-ECURad2, S-ECURad3, S-ECURad4) is provided for each wheel module, which jointly controls the torque of the drive motor and the EMB. This allows for various cost and weight reductions both in the basic braking function and in normal operation through simultaneous braking torque control via the driving dynamics system.

[0406] In a first step, the EMB can be significantly downsized, as lower maximum torques are required.

[0407] Compared to a two-box solution, the EMB described here is also significantly easier to apply and integrate into a central control system for the vehicle dynamics system. Another advantage is its independence from a brake manufacturer.

[0408] If the EMB is used in wheel modules according to the "Architecture III" of the vehicle dynamics system, the optional EPS electric power steering can be omitted because steering can be performed via the wheel motors using different motor speeds. Even in an FDS variant C2 with EHB axle modules with piston-cylinder units, the EHB can be significantly downsized, as lower maximum torques must be achievable. By braking together using the traction motor and EHB, the friction brake can also be designed significantly lighter and more cost-effectively. Two pressure actuators thus achieve a lower cost level and also provide the necessary redundancy for SAE Level 5.

[0409] The use of a drum brake makes further cost reduction possible.

[0410] If, in contrast to the optimization 2 mentioned above, a variant C3 is used for the rear axle's EHB with a simple pump (2-piston pump, gear pump), the pump generally cannot achieve the same control quality as a piston-cylinder unit; however, this is less critical on the rear axle. Furthermore, the pump can only generate the base torque, while the traction motor(s) on the rear axle generate the controlled additional braking torque.

[0411] Here, too, the use of a drum brake on the rear axle enables further cost reduction.

[0412] For a variant 04 with a central EHB-Z, suitability for AD Level 3-4 has already been investigated, and suitability for AD Level 5 has even been described. Therefore, one operating unit can be omitted.

[0413] The use of a drum brake on the rear axle enables additional cost and weight reduction compared to an electromechanical brake unit EMB.

[0414] In summary, the variants C2-C4 described here achieve the cost level of an SAE Level 2 solution, but meet all redundancy requirements for SAE Level 5. They can therefore be classified as effective solutions for autonomous driving at the highest level of development.

[0415] Compared to the EMB variants, the solutions have the great advantage that components that are manufactured in large quantities, such as the hydraulic pressure supply or solenoid valves, are already available, thus enabling rapid series introduction without high capital costs.

[0416] In addition, another example is described:

[0417] In the further example, a vehicle dynamics system (FDS) or electric vehicle with a central control system with a vehicle dynamics system (FDS) with one of the FDS architectures I, II or III

[0418] • at least 1 wheel brake (RB1-RB4),

[0419] • at least 1 electric traction motor (TM1, TM2, TM3, TM4) used both to drive and brake an axle or wheel,

[0420] • at least 1 braking device (EMB, EHB) used to generate braking torque(s) on one or more wheel brakes,

[0421] • a central computer (M-ECU unit), by means of which both the at least one electric traction motor (TM1-TM4) and at least one braking device (EHB, EMB) are jointly controlled during braking operations via a control unit (M-ECU domain, S-ECU axle, S-ECU wheel) and sends target signals to the control units of the traction motor(s) (TM1-TM4) and braking device (EHB, EMB) for execution,

[0422] • a central computer with at least one of the core functions ABS, ESP, EBV, ASR, ACC, AEB, Reku management with regenerative brakes via electric traction motors on several axles and / or at least one of the core functions (A)-(G) is regulated or controlled via the central computer, whereby

[0423] • with normal braking, braking is carried out with the electric traction motor (TM1 - TM4) even at high speeds (>80 km / h) of the vehicle and when braking via the electric traction motor (TM1-TM4) an EBV function (EBV = electronic brake force distribution to the front axle and rear axle) is implemented at the same time, and / or

[0424] • in normal operation (e.g. ABS, ESP) a braking torque is generated with at least one traction motor (TM1-TM4) and at least one EHB or EMB at the same time and a braking torque control is carried out on at least 3 wheels of a vehicle using a braking unit (EMB, EHB) and / or electric traction motor (TM1-TM4), such that a braking torque can be controlled on three wheels of a vehicle in any vehicle position.

Claims

Patent claims 1. Vehicle dynamics system, comprising - at least one wheel brake (RBI, RB2, RB3, RB4) for dissipative braking of one wheel of the vehicle; - at least one brake unit (EMB, EHB) assigned to at least one wheel brake (RBI, RB2, RB3, RB4) and designed to generate a dissipative braking torque by means of the at least one wheel brake (RBI, RB2, RB3, RB4); - at least one electric traction motor (TM1, TM2, TM3, TM4) that can be controlled to generate a regenerative braking torque for at least one wheel or axle of the vehicle; and - a central control unit (M-ECU domain) configured to control the at least one brake assembly (EMB, EHB) and the at least one electric traction motor (TM1, TM2, TM3, TM4) in combination for a braking function such that a combined braking torque can be generated by means of the at least one brake assembly (EMB, EHB) and the at least one electric traction motor (TM1, TM2, TM3, TM4); characterized in that - the braking function concerns a standard case in which a basic braking torque and a regulated additional braking torque are controlled and / or regulated simultaneously; wherein - optionally, the basic braking torque is generated by at least one brake unit (EMB, EHB) and the controlled additional braking torque is generated by at least one electric traction motor (TM1, TM2, TM3, TM4); or - the basic braking torque generated by at least one electric traction motor (TM1, TM2, TM3, TM4) and the controlled additional braking torque generated by at least one brake unit (EMB, EHB); or - that at least one brake unit (EMB, EHB) and at least one electric traction motor (TM1, TM2, TM3, TM4) jointly generate the basic braking torque and the controlled additional braking torque. Vehicle dynamics system according to claim 1, characterized in that the braking function is selected from one of the following functions: - automatic emergency brake (AEB), in particular with an EBV control, especially with an EBV control on a rear axle and a front axle of the vehicle, wherein a total braking torque is distributed to the rear axle and the front axle; - Anti-lock braking system (ABS), in particular with basic brake torque support via at least one traction motor (TM1, TM2, TM3, TM4); - Electronic Stability Program (ESP); - Electronic brake force distribution (EBD); - Traction control system (ASR); - Distance control Automated Cruise Control, ACC); - Recuperation management, especially for axle- or wheel-specific recuperation; - Basic brake with thermal management; - Yaw moment control in case of wheel brake failure (RBI, RB2, RB3, RB4); and / or - Yaw moment intervention control for steering assistance. Vehicle dynamics system according to one of the preceding claims, characterized in that the brake assembly (EMB, EHB) comprises an electric motor drive (M) and is designed as an electro-hydraulic brake assembly (EHB) or as an electromechanical brake assembly (EMB). Vehicle dynamics system according to one of the preceding claims, characterized in that the brake assembly (EHB) is designed as an electro-hydraulic brake assembly (EHB) with an electric motor-driven pressure supply unit; wherein a valve assembly is provided between the pressure supply unit and at least one wheel brake (RB1, RB2, RB3, RB4) or several wheel brakes (RBI, RB2, RB3, RB4) of an axle (HA, VA); wherein the valve assembly comprises a closed-circuit wheel valve (MV2k,i, MK2k,2, MV2k,3, MV2k,4) and / or a circuit isolating valve (MV2k,Tv), wherein in the event of a leakage of at least one wheel brake (RBI, RB2, RB3, RB4) the valve device is configured to disconnect the affected wheel brake (RBI, RB2, RB3, RB4) by closing, and the central control unit (M-ECU) is configured to control the at least one brake assembly (EMB, EHB) and / or the at least one electric traction motor (TM1, TM2, TM3, TM4) in such a way that brake torque control is carried out on the other wheels of the vehicle, in particular on at least three wheels; wherein - in particular, the wheel brakes (RBI, RB2) of an axle (VA) of the vehicle can be disconnected by means of the valve device, especially the wheel brakes (RB1, RB2) of the front axle (VA).

5. Vehicle dynamics system according to one of the preceding claims, characterized in that the central control unit (M-ECUoomäne) is coupled with at least one brake unit control unit (S-ECUAchse, S-ECURad) of the brake unit (EMB, EHB).

6. Vehicle dynamics system according to one of the preceding claims, characterized in that the central control unit (M-ECU domain) is configured to transmit target signals to an engine control unit (ECU-TM1, ECU-TM2, ECU-TM3, ECU-TM4) of the at least one traction motor (TM1, TM2, TM3, TM4) and to a brake unit control unit (S-ECU axle, S-ECURad) of the at least one brake unit (EHB, EMB) during the braking function.

7. Vehicle dynamics system according to one of the preceding claims, characterized in that the central control unit (M-ECU) is further configured to control the at least one electric traction motor (TM1, TM2, TM3, TM4) for regenerative braking of the vehicle when the vehicle speed exceeds 80 km / h during normal operation; wherein, during regenerative braking, an electronic brake force distribution (EBD function) is simultaneously implemented on a front axle and a rear axle of the vehicle; wherein, in particular, 20-40% of the total braking torque acts on the rear axle and 60-80% of the total torque acts on the front axle of the vehicle.

8. Vehicle dynamics system according to one of the preceding claims, characterized in that the wheel brake (RBI, RB2, RB3, RB4) of a wheel (RI, R2, R3, R4) of the vehicle is assigned its own brake assembly (EMB1, EMB2, EMB3, EMB4); wherein - in particular the brake assembly (EMB1, EMB2, EMB3, EMB4) is electromechanically designed; wherein - in particular, for each of the two wheels (RI, R2, R3, R4), the brake assembly (EMB1, EMB2, EMB3, EMB4) associated with the wheel brake (RBI, RB2, RB3, RB4) and an electric traction motor (TM1, TM2) are integrated into a wheel module. A vehicle dynamics system according to one of the preceding claims, characterized in that a common brake assembly (EHB1, EHB2) is assigned to the wheel brakes (RBI, RB2, RB3, RB4) of two wheels (RI, R2, R3, R4) of an axle (HA, VA) of the vehicle; wherein - in particular the brake unit (EHB1, EHB2) is electro-hydraulically designed; wherein - in particular, a first brake assembly (EHB1) is assigned to the two wheels (RI, R2) of a rear axle (HA) and a second brake assembly (EHB2) is assigned to the two wheels (R3, R4) of a front axle (VA). A vehicle dynamics system according to one of the preceding claims, characterized in that a central brake assembly (EHB-VA) is assigned to the wheel brakes (RBI, RB2, RB3, RB4) of four wheels (RI, R2, R3, R4) of the vehicle; wherein - in particular the central brake assembly (EHB-VA) is electro-hydraulically designed. Vehicle dynamics system according to one of the preceding claims, characterized in that a common brake assembly (EHB-VA) is assigned to the wheel brakes (RBI, RB2) of two wheels (RI, R2) of a first axle (VA), in particular a front axle (VA), of the vehicle; wherein - in particular the brake unit (EHB-VA) is electro-hydraulically designed; wherein - especially in the case of the wheel brakes (RBI, RB2) of the first axle (VA) individual dissipative braking torques are adjustable, in particular by means of Solenoid valves in hydraulic lines between the brake assembly (EHB-VA) and the wheel brakes (RBI, RB2), wherein - in particular the brake unit (EHB-VA) can also be connected via a hydraulic line to the wheel brakes (RBI, RB2) of two wheels (RI, R2, R3, R4) of a second axle (HA), in particular a rear axle (HA); wherein - in particular, common, non-wheel-individual dissipative braking torques are adjustable for the wheel brakes (RB3, RB4) of the second axle (HA). A vehicle dynamics system according to one of the preceding claims, characterized in that a first electric traction motor (TM1) is assigned to a first pair of two wheels (RI, R2) of a first axle (HA), in particular a rear axle (HA) of the vehicle, and a second electric traction motor (TM3) is assigned to a second pair of wheels (R3, R4) of a second axle (VA), in particular a front axle (VA) of the vehicle. A vehicle dynamics system according to one of the preceding claims, characterized in that a first (RI) and a second wheel (R2) of a first axle (HA), in particular a rear axle (HA) of the vehicle, are each assigned their own electric traction motor (TM1, TM2).Vehicle dynamics system according to claim 14, characterized in that the first (RI) and the second wheel (R2) are each further assigned their own brake assembly (EMB1, EMB2); wherein in particular the respective brake assemblies (EMB1, EMB2) are electromechanically designed; wherein. - in particular for the first (RI) and second wheel (R2), the respective associated electric traction motor (TM1, TM2) and the respective associated brake unit (EMB1, EMB2) are integrated into a wheel module assigned to the first (RI) or second wheel (R2), respectively. Vehicle dynamics system according to claim 14 or 15, characterized in that a third electric traction motor (TM3) is also jointly assigned to a third (R3) and a fourth wheel (R4) of a second axle (VA), in particular a front axle (VA) of the vehicle; wherein - in particular, a common brake assembly (EHB2) is assigned to the third (R3) and fourth wheel (R4); wherein, in particular, the common brake assembly (EHB2) is electro-hydraulically designed; wherein, in particular, the third electric traction motor (TM3) and the common brake assembly (EHB2) are integrated into an axle module assigned to the second axle (VA); or wherein - in particular a central brake module (EHB-Z) is provided, which is in particular electro-hydraulic, wherein wheel-individual braking torques can be generated for the first (RI) and second wheel (R2) by means of the central brake module (EHB-Z) and a common braking torque can be generated for the third (R3) and fourth wheel (R4). Vehicle dynamics system according to one of the preceding claims, characterized in that the central control unit (M-ECU) is configured to distribute the basic braking torque and the controlled additional braking torque to the at least one brake assembly (EMB, EHB) and the at least one electric traction motor (TM1, TM2, TM3, TM4) depending on the vehicle deceleration and / or depending on a coefficient of friction of the road surface; wherein - particularly in the case of lower deceleration and / or lower coefficient of friction, for example in ABS control on snow or ice or in deceleration in ACC braking mode, an electromechanical brake unit (EMB) and / or at least one electric traction motor (TM1, TM2, TM3, TM4) generates the controlled additional braking torque; wherein - particularly in the case of greater deceleration and / or greater coefficient of friction, for example when braking on asphalt, an electro-hydraulic brake unit (EHB) generates the controlled additional braking torque; wherein - particularly at medium deceleration and / or medium coefficient of friction, the brake unit (EHB, EMB) or the traction motor (TM1, TM2, TM3, TM4) generates the basic braking torque as a constant braking torque, and a further brake unit (EMB, EHB) or the traction motor (TM1, TM2, TM3, TM4) generates the controlled additional braking torque. Vehicle dynamics system according to one of the preceding claims, characterized in that the central control unit (M-ECU domain) is configured to execute EBV control during automatic emergency braking (AEB); wherein The braking torque gradients of the at least one brake unit (EMB, EHB) and the at least one electric traction motor (TM1, TM2, TM3, TM4) are taken into account such that the maximum braking torque is achieved simultaneously at the front axle (VA) and the rear axle (HA) of the vehicle. A vehicle dynamics system according to one of the preceding claims, characterized in that during regenerative braking, particularly when the vehicle's battery is fully charged, at least one of the following strategies is used: - Feeding the regenerated energy back into the battery up to the limit of power consumption; - field-oriented control (Id / Iq current control) of the electric traction motor such that the energy is destroyed internally in the motor; - Dissipating the energy generated by the electric traction motor (TM1, TM2, TM3, TM4) in generator mode, supplying the generated energy to an electrical consumer of the vehicle and / or heating a fluid reservoir for use with a heat pump for cooling or heating; and / or - Use of an electrical buffer designed for pulse power, for example a supercapacitor. Vehicle dynamics system according to one of the preceding claims, characterized in that the at least one electric traction motor (TM1, TM2, TM3, TM4) is operated with an inverter for switching windings of the at least one electric traction motor (TM1, TM2, TM3, TM4) in series or parallel connection of three strands of the excitation coils of the brushless electric motor; wherein - in particular, a 4-quadrant operation is enabled by means of the inverter, namely with a quadrant 1 with positive speed and positive torque of the electric motor, a quadrant 2 with positive speed and negative torque of the electric motor; a quadrant 3 with negative speed and positive torque of the electric motor, and a quadrant 4 with negative speed and negative torque of the electric motor. A vehicle dynamics system according to one of the preceding claims, characterized in that the central control unit (M-ECU) is set up to perform brake control based on a characteristic map; wherein - in particular, the characteristic map depicts a pressure-volume characteristic curve, a relationship between motor current and brake pressure, and / or a relationship between brake pressure and / or deceleration when the wheel brake heats up. A vehicle dynamics system according to one of the preceding claims, characterized in that the central control unit (M-ECU) is configured to acquire sensor data during vehicle operation, in particular in a state after initial vehicle start-up, such as during ferry operation or when stationary before or after ferry operation, and to adapt the control of the braking function based on the acquired sensor data using an artificial intelligence method, in particular machine learning or neural networks; wherein - in particular, the artificial intelligence process can be carried out using a computer of the central control unit (M-ECUoomäne); wherein - in particular, the adjustment is carried out in a safe condition of the vehicle, especially in a parked state; wherein - in particular, a characteristic map is determined based on the recorded sensor data, which, for example, depicts a pressure-volume characteristic curve, a relationship between motor current and brake pressure and / or a relationship between brake pressure and / or deceleration when the wheel brake heats up; wherein - in particular, the characteristic map can be adapted based on sensor data and artificial intelligence if a deviation from the current characteristic map is detected, for example due to environmental influences, air in the system, or heating of the wheel brakes. Vehicle dynamics system for a vehicle, comprising - at least one electric traction motor (TM1, TM2, TM3, TM4) that can be controlled to generate a regenerative braking torque for at least one wheel or axle of the vehicle; and - a central control unit (M-ECU domain) configured to control at least one electric traction motor (TM1, TM2, TM3, TM4) for a braking function; characterized in that the central control unit (M-ECU) is designed to activate the braking function when braking on a road surface with a low coefficient of friction, especially on snow, ice and / or wet roads, with low to moderate decelerations, particularly of less than 0.5 m / s² 2 to perform; - wherein, in particular, the central control unit (M-ECU domain) is configured to execute the braking function by means of at least one traction motor of at least one axle of the vehicle, in particular by means of two traction motors of the rear axle of the vehicle. Vehicle with a vehicle dynamics system according to one of the preceding claims. Method for operating a vehicle dynamics system with at least one brake unit (EMB, EHB) for generating a dissipative braking torque and at least one electric traction motor (TM1, TM2, TM3, TM4) for generating a regenerative braking torque for at least one wheel or axle of the vehicle, and a central control unit (M-ECU domain) for controlling the at least one brake unit (EMB, EHB) and the at least one electric traction motor (TM1, TM2, TM3, TM4) for a braking function, wherein in the method: - a combined braking torque is generated by means of the at least one brake unit (EMB, EHB) and the at least one electric traction motor (TM1, TM2, TM3, TM4); wherein - the braking function concerns a standard case in which a basic braking torque and a regulated additional braking torque are controlled and / or regulated simultaneously; wherein - optionally, at least one brake unit (EMB, EHB) is controlled to generate a basic braking torque, and at least one electric traction motor (TM1, TM2, TM3, TM4) is controlled to generate the regulated additional braking torque; or - which at least one electric traction motor (TM1, TM2, TM3, TM4) is controlled to generate the basic braking torque, and which at least one brake unit (EMB, EHB) is controlled to generate the controlled additional braking torque; or - that at least one brake unit (EMB, EHB) and at least one electric traction motor (TM1, TM2, TM3, TM4) are controlled to jointly generate the basic braking torque and the controlled additional braking torque.

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