How to operate the vehicle

Abstract

The present invention relates to a method for operating a vehicle (1), the vehicle (1) having at least one electric motor operable in an engine mode for driving the vehicle (1) and in a generator mode for regenerative braking of the vehicle (1), an energy storage unit and / or energy sink that supplies electrical energy to the at least one electric motor during engine operation and is charged by electrical energy regenerated during generator operation of the at least one electric motor and / or that further enables regenerative braking, a regenerative braking system for performing regenerative braking comprising the at least one electric motor and the energy storage unit and / or energy sink, and a friction braking system having friction brake devices (2) with wheel brake actuators. According to the invention, a request signal (S1, S2, S3) for a deceleration torque generated by the accelerator pedal of the vehicle (1) and / or by at least one assist function of the vehicle (1) is processed in a control unit (3) independent of the friction brake system, which checks whether the current state (Z) of the regenerative braking system allows regenerative braking, and the vehicle (1) is regeneratively braked completely in accordance with the requested deceleration torque or to the extent that the current state (Z) of the regenerative braking system allows regenerative braking.

Description

[Technical Field]

[0001] The present invention relates to a method for operating a vehicle according to the features of the preamble of claim 1 . [Background technology]

[0002] A method for controlling a brake regeneration device of a mild hybrid vehicle is known from the prior art, as described in DE 10 2016 007 838 A1. For braking, the vehicle has a brake control system with at least one hydraulic friction brake as a first brake actuator and at least one electric motor as a second brake actuator. The electric motor can operate as a generator to regenerate kinetic energy from the vehicle. The regenerated energy is charged into an energy storage device. The first and second brake actuators cannot be blended (coordinated braking), at least when the driver brakes. In a first step of the method, a target wheel torque characteristic curve for providing a predetermined target wheel torque to the vehicle's driveline, including the electric motor, is determined as a function of instantaneous brake pedal travel. The target wheel torque characteristic then varies as a function of the braking process performed before the current braking process.

[0003] DE 10 2016 201 937 A1 describes a method for determining an initial slope of a brake torque slip characteristic curve from measured brake slip of at least one vehicle wheel of a vehicle and regenerative braking torque of this vehicle wheel. In this method, the wheel speed of the braked vehicle wheel is measured, and the wheel speed of the braked vehicle wheel is determined from the wheel speed. Furthermore, the wheel speed of the non-brake vehicle wheel of the vehicle is measured, and the vehicle speed is determined from the wheel speed. The brake slip is determined from the wheel speed of the braked vehicle wheel and the vehicle speed. Furthermore, the regenerative braking torque is determined by measuring the power generated by regeneration. The initial slope of the brake torque-slip characteristic is determined from the regenerative braking torque and the determined slip.

[0004] DE 10 2012 222 507 A1 discloses a method for activating regenerative braking in a vehicle. First, a future activation strength of the regenerative braking for a preceding route of the vehicle is estimated using inputs characterizing the driving style of the preceding route. Furthermore, a maximum slip-free vehicle braking force for the route is estimated based on the inputs. Furthermore, the braking force of the regenerative braking is set to a target braking force that is equal to or less than the maximum vehicle braking force for the route. Finally, the regenerative braking is activated at the target braking force for the preceding route.

[0005] DE 10 2012 210 046 A1 describes a method for controlling a braking system of a motor vehicle. The motor vehicle can be braked by a friction brake and an electric motor operable as a generator. During the braking process, the friction braking torque applied by the friction brake and the regenerative torque applied by the electric motor are reduced during a brake torque reduction phase until a corrected total braking torque applied by the friction brake and the electric motor is reached. The regenerative torque applied by the electric motor is influenced by a first feedback loop with compensation in a second feedback loop for controlling the electric motor.

[0006] DE 10 2010 054 620 A1 discloses a method for determining the brake torque of a vehicle having a traction battery and at least one regenerative brake and at least one friction brake on a drive axle, taking into account the lateral dynamic driving state of the vehicle. In this method, at least one brake requirement is determined, and a total brake torque of the vehicle is determined. First and second brake torques of the drive axles are determined from the total brake torque of the vehicle. Furthermore, the lateral dynamic driving state of the vehicle is determined. A third brake torque of the drive axle is determined as a function of the first and second brake torques and the lateral dynamic driving state. Furthermore, a fourth brake torque of the drive axle is determined by the at least one regenerative brake and / or the traction battery. Furthermore, a fifth brake torque of the drive axle is determined by limiting the third brake torque of the drive axle with the fourth brake torque of the drive axle. The total brake torque of the vehicle is divided into the brake torque of the at least one regenerative brake of the drive axle and the brake torque of the at least one friction brake of the drive axle. Summary of the Invention

[0007] The invention is based on the problem of providing an improved method for operating a vehicle compared to the prior art.

[0008] This problem is solved according to the invention by a method for operating a vehicle having the features of claim 1.

[0009] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0010] The vehicle includes at least one electric motor (electric machine) operable in an engine mode for driving the vehicle and in a generator mode for regenerative braking of the vehicle, and an energy storage unit and / or energy sink that supplies electrical energy to the at least one electric motor during engine operation, is charged by regenerated electrical energy during generator operation of the at least one electric motor, and / or enables regenerative braking. The energy storage unit may also include or be designed as an energy sink, particularly for regenerated electrical energy, or vice versa, or a combination of an energy storage unit and an energy sink may be provided, particularly for regenerated electrical energy. For example, the regenerated energy may not be stored, or may not be stored at all. The energy storage unit and / or energy sink may, for example, include or be designed as at least one traction battery and / or at least one capacitor, particularly a supercapacitor, and / or at least one flywheel mass storage device and / or at least one resistor, particularly a large resistor. In particular, if the energy sink comprises only a resistor, the regenerative energy is not stored but converted into thermal energy. However, if a resistor is used, it is advantageous to provide it only in addition to the other components mentioned above, so that the regenerative electrical energy can be stored and, if this is not possible due to, for example, a full charge state or other circumstances, the regenerative braking can continue by converting the remaining regenerative electrical energy in the resistor into heat.

[0011] The vehicle further comprises a regenerative braking system for performing regenerative braking, the regenerative braking system comprising at least one electric motor and an energy storage unit and / or an energy sink. The vehicle further comprises a friction braking system comprising a friction brake device comprising a wheel brake actuator.

[0012] The friction brake system is, for example, a hydraulic brake system, but can also be designed as a different friction brake system. When the friction brake system is a hydraulic brake system, the friction brake device is therefore a hydraulic brake device, the friction brake actuator described below is a hydraulic brake actuator, the friction brake described below is a hydraulic brake, the friction brake force distribution command described below is a hydraulic brake force distribution command, the controlled friction deceleration torque described below is a controlled hydraulic deceleration torque, and the friction target brake torque described below is a hydraulic target brake torque.

[0013] In this method for operating a vehicle, according to the invention, a request signal for a deceleration torque generated by the accelerator pedal of the vehicle and / or by at least one assist function of the vehicle is processed in a control unit independent of the friction brake system, whereby it is checked whether the current state of the regenerative braking system allows for regenerative braking. The control unit independent of the friction brake system is in particular a central control unit, in particular a central control unit of an electric drivetrain of the vehicle, in particular comprising at least one electric motor and an energy storage unit and / or an energy sink.

[0014] The current state of the regenerative braking system is, in particular, the current state of availability of the regenerative braking system, i.e., the current state of availability of the electric brake system formed, in particular, by the electric drivetrain of the vehicle. The current state of the regenerative braking system is, in particular, the current state of charge of the energy storage unit or relates to this current state of charge of the energy storage unit. Thus, it is, in particular, checked whether the energy storage unit can still be charged by regenerative braking, and if so, how much energy it can still absorb generated by regenerative braking, or whether it is already fully charged. The vehicle is then regeneratively braked in accordance with the required deceleration torque, fully or to the extent that the current state of the regenerative braking system, in particular the energy storage unit, allows regenerative braking.

[0015] Furthermore, if the current state of the regenerative braking system, in particular the energy storage unit, does not allow or only partially allows regenerative braking in accordance with the requested deceleration torque, then, as shown by arrow P1, the remaining portion of the requested deceleration torque that cannot be achieved by regenerative braking is sent to the brake control system of the friction brake system, and the vehicle is accelerated by the friction brake system in accordance with the remaining portion of this requested deceleration torque that cannot be achieved by regenerative braking, which portion is sent to the brake control system of the friction brake system, and the vehicle is braked by the friction brake system, in particular its friction brake devices, in accordance with the remaining portion of this requested deceleration torque.

[0016] Assist functions that can generate a deceleration torque request signal are, for example, predictive cruise control, which adapts the vehicle speed to the road ahead, and / or distance control to the vehicle ahead, and / or vehicle automation, highly automated or autonomous driving functions.

[0017] In particular, the solution according to the invention shifts the functional scope of wheel stabilization during regenerative braking to a control unit, in particular to a drivetrain control unit for an electric drivetrain.

[0018] As a result of the solution according to the invention, the basic functional scope of the regenerative vehicle braking, in particular with regard to the deceleration torque requests from the accelerator pedal and one or more assistance systems, is externalized (outsourced) from the hydraulic brake system, in particular its brake control system and vehicle dynamics control system, and is directly coupled to and processed in this control unit, in particular a central control unit, which is not part of the hydraulic brake system, so that the regenerative braking is mainly used and only the remaining deceleration torque is realized by the friction brake system.

[0019] The solution according to the invention avoids, among other things, a signal loop. Previously, all deceleration torque requests from the accelerator pedal and one or more assistance systems, which were initially recorded in a control unit independent of the friction brake system, were transmitted by this control unit to the friction brake system, in particular to its brake control system and / or to a vehicle dynamics control system previously assigned to the friction brake system. From there, the respective proportion of the requested deceleration torque to be generated by regenerative braking was transmitted back to this control unit, which is not part of the friction brake system. This resulted in a regenerative signal loop. By avoiding this regenerative signal loop, functions related to regenerative braking in particular can be performed faster and better.

[0020] In a possible embodiment of the method, a request signal for deceleration torque generated by the vehicle's brake pedal is processed by a brake control system of the friction brake system. This checks whether the current state of the regenerative braking system, particularly the energy storage unit, allows regenerative braking. To the extent that the current state of the regenerative braking system, particularly the energy storage unit, allows regenerative braking, the requested deceleration torque is forwarded to a control unit that is not part of the friction brake system, which then brakes the vehicle accordingly. The vehicle is braked by the friction brake system, particularly the friction brake device, according to the remaining percentage of the requested deceleration torque. This also means that regenerative braking takes priority over friction braking. However, when deceleration torque is requested by the brake pedal, the brake control system is intended to check whether regeneration is possible. This also has the advantage of a short signal propagation time, because the brake pedal is coupled to the brake control system, and therefore its request signal must first be forwarded to a control unit, particularly a central control unit, that is not part of the friction brake system for evaluation. This is avoided in the present solution, since the signal processing relating to the friction brake is carried out entirely within the brake control system, i.e. no control unit independent of the friction brake system, in particular no central control unit, is responsible for this, so that the friction braking can also be carried out very quickly, and in this respect longer signal propagation times are also avoided.

[0021] The solution described herein therefore retains the existing architecture of signal detection and forwarding: the demand signals from the accelerator pedal and the assist function were previously also detected by a control unit, in particular a central control unit, independent of the friction brake system, and the demand signals from the brake pedal were previously also detected by the brake control system, and this will continue to be the case. The processing of the demand signals from the brake pedal in the brake control system is also retained to avoid longer signal paths. The previous transmission of demand signals from the accelerator pedal and the assist function to the brake control system, which would have led to the above-mentioned signal loop, has been modified and is now avoided.

[0022] In particular, the current state of the regenerative braking system, in particular the energy storage unit, is determined by a control unit that is independent of the friction braking system and transferred to the brake control system, thereby ensuring that the current state of the regenerative braking system, in particular the energy storage unit, is available to both the control unit that is part of the friction braking system and the brake control system and can be used in the manner described above.

[0023] In an alternative embodiment, the brake pedal deceleration request is processed in the same manner as the accelerator pedal and assist function deceleration requests, i.e., primarily in a control unit, particularly a central control unit, independent of the friction brake system. This means that the deceleration torque request signal generated by the vehicle's brake pedal is also processed in a control unit that is not part of the friction brake system, which checks whether the current state of the regenerative braking system, particularly the energy storage unit, allows regenerative braking. The vehicle is then regeneratively braked in accordance with the requested deceleration torque, either fully or to the extent that the current state of the regenerative braking system, particularly the energy storage unit, allows regenerative braking. In this alternative embodiment, in particular, if the current state of the regenerative braking system, particularly the energy storage unit, does not allow or only partially allows regenerative braking in accordance with the requested deceleration torque, the remaining portion of the requested deceleration torque not generated by the regenerative braking system, which cannot be achieved by regenerative braking, is transferred to the brake control system of the friction brake system, and the vehicle is braked in accordance with this remaining portion of the requested deceleration torque by the friction brake system, particularly its friction brake devices.

[0024] In particular, the deceleration torque for regenerative braking is transmitted as an electric target braking torque from a control unit independent of the friction brake system to a drivetrain control unit of an electric drivetrain of the vehicle which comprises at least one electric motor.

[0025] More specifically, the vehicle dynamics control unit transmits a minimum drive speed of the electric motors to the drivetrain control unit, and the drivetrain control unit controls the at least one electric motor according to an electrical target brake torque to perform regenerative braking only until the minimum drive speed is reached. Thus, once the minimum drive speed is reached, the regenerative braking, i.e., the regenerative torque, is reduced to maintain the specified minimum drive speed. Thus, once the minimum drive speed is reached, the drivetrain control unit transmits the remaining deceleration torque that cannot be achieved by regenerative braking to the vehicle dynamics control system.

[0026] In particular, the deceleration torque for the friction brake is transmitted from the brake control system to the friction brake device as a friction target brake torque.

[0027] In particular, the vehicle motion control unit transmits the minimum wheel speed to the friction brake device, and the friction brake device performs friction braking by activating the friction brake actuator according to the friction target brake torque, but only until the minimum wheel speed is reached. Thus, when the minimum wheel speed is reached, the friction brake, i.e., the friction brake torque, is reduced to maintain the specified minimum wheel speed. When the minimum wheel speed is reached, the friction brake device transmits the remaining deceleration torque that cannot be achieved by friction braking to the vehicle motion control system.

[0028] In one possible embodiment, the vehicle motion control system for stabilizing the vehicle transmits to a control unit independent of the friction brake system, particularly a central control unit, and / or a brake control system of the friction brake system, a configurable electric deceleration torque, i.e., a deceleration torque that can be regeneratively deactivated by at least one electric motor at a corresponding time. Advantageously, this is taken into account during regenerative braking and / or friction braking accordingly, i.e., the vehicle is braked and / or friction braked accordingly. The applicable electric deceleration torque is, in particular, the maximum applicable electric torque. For example, if the deceleration request cannot be fully decelerated by regenerative braking due to a slippery road surface or other condition, particularly a condition detected by the vehicle motion control system, only the portion of the deceleration that can be decelerated by regenerative braking is transmitted. This is the dissipable electric deceleration torque, i.e., the deceleration torque that can be dissipated by regenerative braking by at least one electric motor at a corresponding time. Thus, a control unit that is not part of the brake control system or the friction brake system, particularly a central control unit, knows that any additional requests via the brake pedal, accelerator pedal, or assist function can no longer be made electrically but must be made via the friction brake.

[0029] In one possible embodiment, the vehicle motion control system sends brake force distribution commands to a control unit independent of the friction brake system, in particular a central control unit, and / or to a brake control system of the friction brake system.

[0030] The vehicle dynamics control is, for example, externalized (outsourced) from the friction brake system, particularly from an independent unit, such as an independent control unit, and therefore is not integrated into a control unit that is not part of the friction brake system, particularly a central control unit.

[0031] The vehicle dynamics control's specification of a minimum driving speed allows the vehicle's electric drivetrain to control a target brake slip based on the vehicle dynamics control's dynamic driving limit specification, thereby enabling regenerative braking up to this limit. The minimum driving speed, for example, includes a specified maximum wheel slip, e.g., 3%, that must not be exceeded because otherwise there is a risk of unstable driving. Previously, regeneration was turned off when slip occurred. However, in the solution described herein, regenerative torque, i.e., the deceleration torque generated by regenerative braking, is reduced only when the specified minimum driving speed is reached or not reached, and this regenerative torque is restored when the specified minimum driving speed is exceeded.

[0032] Traditionally, the negative torque of the electric drivetrain has been monitored and reduced as needed by the vehicle dynamics control system, which means that all braking requests, i.e., all deceleration torque requests, must always pass through the vehicle dynamics control system, resulting in the regeneration signal loop described above.

[0033] In the method described herein, deceleration torque is monitored directly by the driveline control unit and reduced as necessary. In particular, electric braking demand, i.e., regenerative braking demand, is limited directly by the driveline control unit, so that the vehicle no longer becomes unstable. Therefore, using the described method, braking demand, i.e., deceleration torque demand, can be made directly by different requestors, for example, the accelerator pedal, the longitudinal control assist function, and the brake pedal. The vehicle dynamics control simply specifies a minimum drive speed for the electric driveline, i.e., at least one electric motor, and a minimum wheel speed for the friction brake system so that maximum slip is not exceeded. Electric torque, particularly regenerative torque, is no longer monitored by the vehicle dynamics control system, but by the electric driveline, particularly its driveline control unit. Friction brake torque is monitored by the friction brake system.

[0034] In particular, the described solution allows for increased availability of regeneration. Regeneration, i.e., regenerative braking, is always fully enabled as part of vehicle dynamics control until a specified minimum driving speed threshold is reached. In particular, the described procedure avoids vehicle instability due to negative torque.

[0035] As already mentioned, previously, regenerative braking was completely shut off when slip occurred. This was achieved by setting a slip bit. With the method described here, this slip bit, and therefore the immediate shut-off (hard switch-off) of regenerative braking when a predetermined slip threshold is exceeded, is no longer necessary. This is made possible by targeted protection against vehicle instability by specifying and maintaining a minimum driving speed threshold, up to which regeneration can continue. This means that regenerative braking only needs to be slowed down to not fall below the minimum driving speed, but is not turned off completely.

[0036] The method described herein also allows for improved vehicle stability through targeted slip control, thereby improving vehicle stability at dynamic operating limits.

[0037] Furthermore, this process improves regeneration efficiency, especially in so-called one-pedal driving, i.e., when the vehicle is driven using only the accelerator pedal and the vehicle is decelerated by regenerative braking as the accelerator pedal is gradually released, and during assisted braking. When the vehicle is braked only by regenerative braking, there is no positive displacement of brake fluid to the low-pressure reservoir and no application of brake pads to the brake discs.

[0038] Specifically, the method builds on the traditional signaling scheme, but replaces the time-critical torque command signal with an inertia signal, i.e., a speed command in the form of vehicle speed minus brake slip. This is achieved by monitoring the aforementioned minimum wheel speed or minimum drive speed specified by the vehicle dynamics control. The method described here also distributes control to the control unit that can most quickly execute the control command. For example, in the driveline control unit, a deceleration torque command is converted into a driveline speed value every 1 millisecond, whereas in the past, torque was calculated in the driveline control unit every 20 milliseconds and had to be transmitted to the control unit via a network.

[0039] Conventionally, there is a latency in the control loop due to the transmission time of the target torque through the network of the control loop: Vehicle Dynamics Control - Central Control Unit - Drivetrain Control Unit. In the method described here, the latency is outside the control loop, which allows for higher dynamics within the control loop. The control loop is then closed at the drivetrain control unit.

[0040] In the procedure described here, two coordinators are used for braking requests: a control unit independent of the friction brake system, specifically a central control unit for regenerative braking and a brake control system for friction brakes. Previously, everything was coordinated together within the vehicle dynamics control system, resulting in the aforementioned regenerative signal loop.

[0041] In the method described herein, each brake actuator, i.e., both electric driveline and friction brake device, has its own actuator-related control that is based not only on torque but also on torque and a predetermined minimum speed, i.e., minimum drive speed or minimum wheel speed.

[0042] In the method described here, the brake pedal request, i.e. the deceleration torque requested via the brake pedal, can also be performed electrically as described above, thereby enabling regenerative braking, and the accelerator pedal request, i.e. the deceleration torque requested via the accelerator pedal, can be performed via the friction brake system, thereby enabling friction braking.

[0043] This is made possible by the two coordinators mentioned above exchanging or coordinating their respective delay requests with each other and making requests to their partner control units via an interface as needed.

[0044] In the method described here, a prescribed minimum driving speed ensures vehicle stability, allowing regenerative braking even in the event of slippage.

[0045] The method described herein allows for accomplishing both the tasks of stability by allocating the friction braking system and electric drivetrain actuators, and the regenerative function of maintaining and allocating the respective deceleration torque demands.

[0046] In the method described herein, a delay-insensitive signal in the form of a speed command is used instead of a delay-sensitive signal in the form of a torque command. The speed command is delay-insensitive because it is an inertial variable that corresponds to the current vehicle speed. The torque command is delay-sensitive because it requires high torque strokes to be executed quickly, and in the previous procedure is sent from the vehicle dynamics control system via the central control unit to the driveline control unit, with associated latencies in the bus and control unit.

[0047] In the method described herein, a control unit that is not part of the friction brake system, particularly a central control unit, directly commands the desired deceleration torque to the driveline control unit. Previously, the regenerative torque command from the central control unit was always routed through the vehicle dynamics control and then forwarded to the driveline control unit. Here, the reduction of the regenerative torque is now performed directly by the driveline control unit based on the deceleration torque command from a control unit that is not part of the friction brake system, particularly the central control unit, and the minimum drive speed specified by the vehicle dynamics control. Previously, the reduction of the regenerative torque was performed by the vehicle dynamics control system and forwarded to the driveline control unit via the central control unit.

[0048] This solution allows one-pedal driving to be extended over the entire available recuperation range. The recuperation level can be set flexibly. Because the friction brake system is not activated, fast torque settings similar to accelerator pedal movements are possible. This means, for example, that the electric brake booster of the friction brake system does not need to be activated. This also avoids the corresponding noise, which could have an unpleasant effect. This process allows for a direct response behavior of the electric drivetrain without unnecessary latency generation and filtering.

[0049] This process increases the availability of regenerative braking and also enables regenerative braking up to the dynamic operating limit. For example, this process enables regenerative braking when cornering with high lateral acceleration and after intervention of the dynamic brake control system, where regenerative braking was previously turned off. Thus, this process enables regenerative braking even at low road friction values ​​up to the dynamic operating limit.

[0050] This process also improves vehicle stability during regenerative braking.

[0051] Regenerative braking is always maximized within dynamic drive limits, particularly within a specified wheel slip. If the specified wheel slip is exceeded, the driveline control unit reduces regenerative braking by the amount of deceleration torque required to bring the wheel slip back below the specified slip threshold.

[0052] This process allows braking without friction braking, particularly without using a one-box (brake pedal and vehicle dynamics control in one component), and without a separate braking system for the one-pedal drive and assist function, improving efficiency. When decelerating using the one-pedal drive and assist function, there is no residual brake pressure in the system and no friction braking is applied because there is no need to transfer hydraulic volume.

[0053] NVH (Noise, Vibration, Harshness) issues, i.e., brake system noise and vibration issues, are improved because the friction brake system only needs to operate when the friction brakes are in use.

[0054] As already mentioned, this method minimizes latency as a time sensitive signal in the form of a torque command is replaced by a slower signal, i.e. a speed command in the form of vehicle speed minus brake slip; the signal is sent directly without delays due to loops and waiting for feedback signals, and control is distributed to the control unit that can execute the control command most quickly, as already mentioned.

[0055] This method uses a drive torque interface in the electric braking portion of the longitudinal controller, thereby simplifying the longitudinal controller interface to use the same interface for both drive and regenerative braking modes, and eliminating the need for a separate recovery function in the longitudinal controller.

[0056] Examples of embodiments of the invention are explained in more detail below with reference to the drawings. [Brief explanation of the drawings]

[0057] [Figure 1] 1 shows a schematic diagram of a vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0058] 1 shows a schematic diagram of a regenerative braking torque modulation system with stability protection for a vehicle 1. For clarity, only the friction and regenerative braking system components of the vehicle 1 are shown.

[0059] The vehicle 1 has at least one electric motor operable in an engine mode for driving the vehicle 1 and in a generator mode for regenerative braking of the vehicle 1. The vehicle 1 further has an energy storage unit or energy sink that supplies electrical energy to the at least one electric motor during engine operation and is charged by electrical energy regenerated during generator operation of the at least one electric motor or that enables further regenerative deceleration. The vehicle 1 also has a regenerative braking system for performing regenerative braking, including the at least one electric motor and the energy storage unit and / or energy sink. The vehicle 1 also has a friction braking system having friction brake devices 2 including wheel brake actuators.

[0060] In this method for operating a vehicle 1, request signals S1, S2, S3 for a deceleration torque generated by the accelerator pedal of the vehicle 1 and / or at least one assist function of the vehicle 1 are processed in a control unit 3 that is not part of the friction braking system. This will be referred to hereinafter as the central control unit 3. First, a setpoint 5 for manual or assisted driving is generated from the request signals S1, S2, S3. The system then checks whether the current state Z of the regenerative braking system, in particular the charge state of the energy storage unit, allows regenerative braking, i.e., in particular whether the energy storage unit has a sufficient potential to absorb regenerative energy. The vehicle 1 is then regeneratively braked in accordance with the requested deceleration torque, either completely or to the extent that the current state Z of the regenerative braking system, in particular the energy storage unit, allows regenerative braking.

[0061] If the current state Z of the regenerative braking system, in particular the energy storage unit, does not allow regenerative braking according to the requested deceleration torque, or only allows it partially, then the remaining part of the requested deceleration torque that cannot be achieved by regenerative braking is sent to the brake control system 4 of the friction brake system, as shown by arrow P1, and the vehicle 1 is accelerated according to the remaining part of this requested deceleration torque that cannot be achieved by regenerative braking, which part is sent to the brake control system 4 of the friction brake system, in particular its friction brake devices 2, as shown by arrow P1, and the vehicle 1 is braked according to this remaining part of the requested deceleration torque. This check and, if necessary, the distribution 6 of the requested deceleration torque is thus carried out in the central control unit 3.

[0062] A request signal S4 for a deceleration torque generated by the brake pedal of the vehicle 1 is processed in a brake control system 4 of the friction brake system. First, a setpoint 7 for manual braking is generated from the request signal S4. Next, the system checks whether the current state Z of the regenerative braking system, in particular the energy storage unit, allows regenerative braking. For this purpose, the current state Z of the regenerative braking system, in particular the energy storage unit, is determined by the central control unit 3, as indicated by arrow P2, and sent to the brake control system 4. Furthermore, this determined state Z of the regenerative braking system, in particular the energy storage unit, is also used in the central control unit 3, as described above.

[0063] The requested deceleration torque is transferred to the central control unit 3 in the form of a double-headed arrow P1, to the extent that the current state Z of the regenerative braking system, in particular the energy storage unit, allows for regenerative braking. The vehicle 1 is accordingly regeneratively braked. The vehicle 1 is then friction braked according to the remaining portion of the requested deceleration torque. Thus, the checking and distribution 8 of the requested deceleration torque is performed in the brake control system 4.

[0064] The portion of the required deceleration torque for regenerative braking is initially subjected to torque processing 9 in the central control unit 3 as an electrical setpoint brake torque ESM. This processing includes torque shaping and, if necessary, torque distribution for reasons of efficiency and driving dynamics. Torque shaping serves to ensure a deceleration gradient so that complete deceleration is not performed suddenly. Torque distribution for efficiency and driving dynamics is performed when the vehicle 1 has several electric motors, in particular an electric motor on the front axle and another electric motor on the rear axle. In this case, the electrical setpoint brake torque ESM can be distributed to these electric motors, in particular in such a way that regeneration is achieved as efficiently as possible and / or in accordance with the driving dynamics.

[0065] The deceleration torque for regenerative braking, in this case the electric target braking torque ESM thus processed, is then sent by the central control unit 3 to a driveline control unit 10 of the electric driveline of the vehicle 1, which comprises at least one or more electric motors, and which is then transmitted to each electric motor, as indicated diagrammatically by the output arrow P3, and actuated accordingly.

[0066] To ensure the driving stability of the vehicle 1 even during regenerative braking, and in particular to avoid excessive slip, the drivetrain control unit 11 transmits a minimum driving speed MAD of the electric motor or motors to the drivetrain control unit 10, which controls the at least one electric motor or motors to perform regenerative braking according to an electrical setpoint brake torque ESM only until the minimum driving speed MAD is reached. Once the minimum driving speed MAD is reached, the drivetrain control unit 10 transmits the remaining, i.e., adjusted, electrical deceleration torque AEV that cannot be achieved by regenerative braking to the vehicle dynamics control unit 11. The resulting maximum settable electrical torque is transmitted by the vehicle dynamics control unit 11 to the central control unit 3 and the brake control unit 4 as a settable electrical deceleration torque 13.

[0067] The required deceleration torque of the friction brake is first subjected to torque processing 12 in the brake control unit 4 as a friction target brake torque RSM including torque distribution from the viewpoint of stability, particularly distribution to the front and rear axles of the vehicle 1.

[0068] The friction brake deceleration torque thus processed, in this case the friction brake target torque RSM, is transferred by the brake control unit 4 to the friction brake device 2. This is transmitted to the friction brake actuator, as shown diagrammatically by the output arrow P4, and is actuated accordingly. The friction brake device 2 also receives information from the antilock braking system ABS of the vehicle 1.

[0069] To ensure the running stability of the vehicle 1 even during friction braking, and in particular to avoid excessive slippage, the vehicle motion control unit 11 transmits a minimum wheel speed MRD to the friction brake device 2, and the friction brake device 2 performs friction braking by activating the friction brake actuator according to the friction target brake torque RSM only until the minimum wheel speed MRD is reached. Once the minimum wheel speed MRD is reached, the friction brake device 2 transmits the remaining, i.e., adjusted, friction deceleration torque ARV that cannot be achieved by friction braking to the vehicle motion control unit 11.

[0070] To stabilize the vehicle 1, the vehicle motion control unit 11 transmits a deceleration torque 13 to the friction brake system central control unit 3 and the brake control system 4, which is regeneratively released by at least one electric motor at a corresponding time. This deceleration torque feeds into and is taken into account in the respective distributions 6, 8 of the required deceleration torque, so that the vehicle 1 is regeneratively braked and / or friction braked accordingly.

[0071] In addition, in the illustrated example, the vehicle dynamics control unit 11 transmits an electric brake force distribution command 14 or a friction brake force distribution command 15 to the central control unit 3 and the brake control system 4 of the friction brake system. In the illustrated example, the electric brake force distribution command 14 is taken into account in torque processing 9 in the central control unit 3. In the illustrated example, the friction brake force distribution command 15 is taken into account in torque processing 12 in the brake control system 4. [Explanation of symbols]

[0072] 1 vehicle 2 Friction brake device 3 Control units / central control units that are not part of the friction brake system 4. Brake Control System 5. Generating setpoints for manual or assisted driving 6. Distribution of the required deceleration torque in the central control unit 7 Generating setpoints for manual braking 8 Distribution of required deceleration torque in the brake control system 9. Central control unit torque processing 10 Drivetrain control unit 11 Vehicle motion control unit 12 Torque processing in brake control system 13 Deductible Electrical Deceleration Torque 14 Electric brake force distribution command 15 Friction brake force distribution command ABS Anti-lock Braking System AEV Reduced Electrical Deceleration Torque ARV Reduced Friction Deceleration Torque ESM Electrically set brake torque RSM friction brake torque MAD Minimum Drive Speed MRD minimum wheel speed P1 Arrow P2 Arrow P3 Output P4 Output Arrow S1 Demand signal generated by accelerator pedal Request signal generated by the S2 assist function Request signal generated by the S3 assist function S4 Demand signal generated by the brake pedal Z Current state of the regenerative braking system

Claims

1. A method of operating a vehicle (1), the vehicle (1) comprising: at least one electric motor operable in an engine mode for driving the vehicle (1) and in a generator mode for regenerative braking of the vehicle (1); an energy storage unit and / or energy sink that supplies electrical energy to the at least one electric motor during engine operation and is charged by regenerated electrical energy during generator operation of the at least one electric motor and / or further enables regenerative braking; a regenerative braking system for performing the regenerative braking, the regenerative braking system comprising the at least one electric motor and the energy storage unit and / or energy sink; a friction brake system having a friction brake device (2) with a wheel brake actuator; and a request signal (S1, S2, S3) for a deceleration torque generated by an accelerator pedal of the vehicle (1) and / or at least one assist function of the vehicle (1) is processed in a control unit (3) independent of the friction brake system, A method in which it is checked whether the current state (Z) of the regenerative braking system allows regenerative braking, and the vehicle (1) is regeneratively braked in accordance with the required deceleration torque, either fully or to the extent that the current state (Z) of the regenerative braking system allows regenerative braking.

2. 2. The method of claim 1, wherein if the current state (Z) of the regenerative braking system does not allow or only partially allows regenerative braking according to the requested deceleration torque, the remaining part of the requested deceleration torque that cannot be achieved by regenerative braking is sent to a brake control system (4) of the friction braking system, and the vehicle (1) is braked by the friction braking system according to the remaining part of the requested deceleration torque.

3. a demand signal (S4) for a deceleration torque generated by a brake pedal of the vehicle (1) is processed in the brake control system (4) of the friction brake system; checking whether the current state (Z) of the regenerative braking system allows regenerative braking; the required deceleration torque is sent to the control unit (3) independent of the friction brake system, to the extent that the current state (Z) of the regenerative braking system allows regenerative braking, and the vehicle (1) is regeneratively braked accordingly; 3. The method of claim 2, wherein the vehicle (1) is braked by the friction brake system according to the remaining portion of the required deceleration torque.

4. 4. The method of claim 3, wherein the current state (Z) of the regenerative braking system is determined by the control unit (3) that is not part of the friction braking system and is sent to the brake control system (4).

5. 4. The method according to claim 1, wherein the deceleration torque of the regenerative brake is transmitted by the control unit (3), which is not part of the friction brake system, as an electric setpoint brake torque (ESM) to a driveline control unit (10) of an electric driveline of the vehicle (1) comprising the at least one electric motor.

6. 6. The method according to claim 5, wherein a vehicle dynamics control unit (11) transmits a minimum driving speed (MAD) of the electric motor to the drivetrain control unit (10), the drivetrain control unit (10) performs regenerative braking by operating the at least one electric motor according to the electrical setpoint braking torque (ESM) only until the minimum driving speed (MAD) is reached, and the drivetrain control unit (10) transmits a remaining deceleration torque (AEV) that cannot be achieved by regenerative braking to the vehicle dynamics control unit (11) when the minimum driving speed (MAD) is reached.

7. The method according to any one of claims 2 to 6, wherein a deceleration torque for the friction brake is sent from the brake control system (4) to the friction brake device (2) as a friction target brake torque (RSM).

8. The vehicle motion control unit (11) transmits a minimum wheel speed (MRD) to the friction brake device (2), and the friction brake device (2) executes the friction brake by operating a friction brake actuator according to the friction target brake torque (RSM) only until the minimum wheel speed (MRD) is reached.

8. The method according to claim 7, wherein the friction brake device (2) transmits a remaining deceleration torque (ARV) that cannot be achieved by the friction brake to the vehicle motion control unit (11) when the minimum wheel speed (MRD) is reached.

9. 9. The method according to claim 6, wherein the vehicle motion control unit (11) for stabilizing the vehicle (1) transmits a settable electric deceleration torque (13) to the control unit (3) independent of the friction brake system and / or to the brake control system (4) of the friction brake system, and accordingly the vehicle (1) is subjected to regenerative braking and / or friction braking.

10. The method according to any one of claims 6 to 9, wherein the vehicle motion control unit (11) transmits a brake force distribution command (14, 15) to the control unit (3) independent of the friction brake system and / or to the brake control system (4) of the friction brake system.

Images