Method for operating a steer-by-wire steering system of a motor vehicle and steer-by-wire steering system

Abstract

The present disclosure relates generally to a method and a steer-by-wire system (12) for operating a motor vehicle (10). The steer-by-wire system (12) has at least one wheel actuator (16), a steering wheel actuator (18), and a control device (14) coupled to the wheel actuator (16) and the steering wheel actuator (18). The control device (14) receives a user input through a user interface (32). A regular feedback torque applied by the steering wheel actuator (18) is determined by the control device (14) based on an actual rack and pinion force applied. At least one driving mode is specified based on the user input. A feedback torque applied by the steering wheel actuator (18) is estimated by the control device. The feedback torque is adjusted based on a torque steering component that depends on the driving mode specified by the user input. The adjusted feedback torque is output by the steering wheel actuator (18) on a steering wheel (28) of the steer-by-wire system (12) based on a steering wheel control signal output by the control device (14) to the steering wheel actuator (18).

Description

Technical Field

[0001] The present invention generally relates to a method for operating a steer-by-wire system for a motor vehicle and a steer-by-wire system. Background Technology

[0002] Steer-by-wire (SBW) is a steering technology that eliminates the direct mechanical connection between the steering wheel and the wheels. This direct connection is replaced by two actuators: a steering wheel actuator with feedback, which generates feedback torque for the driver on the steering wheel; and a wheel actuator, which adjusts at least one (but usually several) of the steerable wheels to the desired position. The feedback torque allows the driver to perceive the lateral control status of the vehicle.

[0003] In vehicles equipped with conventional steering systems, a disturbance torque can occur on the steering wheel when speed changes, which can lead to unwanted steering. This disturbance is generated by the vehicle's driving torque and / or deceleration torque through chassis geometry, steering geometry, and specific stiffness. This disturbance torque is also known as "torque steering."

[0004] In special operating conditions, such as racing or sport mode, torque steering is beneficial to the driver because it ensures more direct and immediate feedback in lateral guidance, thus reflecting the vehicle's condition under physical limits more accurately and realistically.

[0005] SBW (Side-by-Side) steering systems decouple the feedback torque applied to the steering wheel from direct road feedback, which is unavoidable in conventional steering systems that rely on mechanical coupling. Therefore, in SBW steering systems, only a portion of the rack and pinion forces applied by the wheel actuators are considered. Consequently, the feedback torque applied to the steering wheel via the steering wheel actuators (also known as steering torque) is lower than in conventional steering systems, where the corresponding torque is caused by direct mechanical coupling. Thus, the decoupling ensured by previous SBW steering systems reduces disturbances from the road, chassis, and powertrain to the SBW steering system and steering wheel, thereby reducing the feedback torque (also known as steering torque) felt by the driver, and consequently weakening the feedback describing the vehicle's condition. Therefore, compared to conventional steering systems, known SBW steering systems based on motor vehicles operating at physical limits provide insufficient or at least reduced (weaker) feedback for lateral guidance of the vehicle. This can make operating the vehicle at physical limits, i.e., operating at high speeds and / or high speed variations, making it difficult to maintain vehicle control simultaneously.

[0006] WO 2023 / 153973 A1 discloses a power steering system for a vehicle, comprising a steering mechanism, a steering shaft, a steerable element, an electrically controllable actuator, an electronic control unit, and a feedback device connected to the control unit. The feedback device includes an electric feedback motor and a mechanical feedback device. The feedback force applied to the steering mechanism includes a combination or sum of a mechanical feedback force and an electrical feedback force provided by the electric feedback motor. The electrical feedback force is adjustable.

[0007] WO 2022 / 270164 A1 discloses a control device and control method for a steering system. The steering system includes a first motor and a second motor. The first motor controls steering via a steering wheel actuator, and the second motor controls the steering angle of the wheels via wheel actuators. The control device is configured to control both the first and second motors bidirectionally. The control device includes a basic SAT torque portion, which obtains a reference torque based on the angle of the first motor and the vehicle speed. The control device also includes a rack and pinion force estimation portion, which estimates the rack and pinion forces as reaction forces based on the steering angles of the wheels and wheel actuators. The control device is configured to switch between a first control mode for controlling the reference torque of the first motor and a second control mode for controlling the first motor based on the reaction forces estimated by the rack and pinion force estimation portion.

[0008] US 5,921,780 A discloses a simulator system for simulating racing. The simulator simulates the forces that occur when driving a real racing car. Default values ​​for relevant influencing parameters can be specified. In this way, the handling of the simulated racing car can be adapted to the handling of a real racing car that the driver is accustomed to.

[0009] Therefore, it is necessary to eliminate or at least reduce the general shortcomings of motor vehicles. In particular, it is necessary to reproduce the vehicle's state more accurately and directly for the driver during gear shifting, especially to make torque feedback achieved through vehicle lateral control more optimized to meet the driver's needs than ever before.

[0010] This objective is achieved through the subject matter of the independent claims. Advantageous embodiments are specified in the dependent claims and the description below, each of which may represent aspects of this disclosure individually or in (sub)combinations. Some features are set forth in methodological form, while others are described in SBW-to-system form. However, the relevant aspects must be converted to each other accordingly. Summary of the Invention

[0011] According to one aspect, some embodiments of this disclosure relate to a method for operating a SBW steering system of a motor vehicle. The SBW steering system has at least one wheel actuator, a steering wheel actuator, and control devices coupled to the wheel actuator and the steering wheel actuator. The method includes at least the following steps: The control device uses a user interface to receive user input. At least one driving mode is specified based on the user input.

[0012] - The regular feedback torque applied by the steering wheel actuator is determined by the control equipment based on the actual rack and pinion forces applied.

[0013] - The control unit estimates the feedback torque to be applied by the steering wheel actuators. The feedback torque is adjusted based on the torque steering component, which depends on the driving mode specified by the user input.

[0014] - The adjusted feedback torque is output from the steering wheel actuator to the steering wheel of the steer-by-wire system based on the steering wheel control signal output from the control device to the steering wheel actuator.

[0015] This method is based on the knowledge that the control equipment of an SBW steering system can be used to determine the feedback torque, which is adapted and optimized for vehicle conditions and is applied at least indirectly to the steering wheel. For this purpose, the control equipment only needs information about the driving mode the driver wants to operate the vehicle in. Since there is no direct mechanical coupling between the steering wheel and the steerable wheels in an SBW steering system, the required rack and pinion forces are typically determined by the control equipment using a control model. This control model can be used to determine the torque steering component evaluated for each driving mode based on the driving mode and using adjusted parameters, and to adjust the feedback torque accordingly. Hereinafter, the torque steering component refers to the proportion of feedback torque considered when adjusting the feedback torque. Therefore, based on the torque steering component, the feedback torque can be increased or decreased to tailor the feedback on the steering wheel to the driver, particularly depending on the driving mode.

[0016] Specifically, the control devices can be used to influence the directness and immediacy of the SBW steering system's control for each driving mode. This allows the driver to have a more precise and accurate feel for the vehicle's lateral vehicle control, enabling precise control of the vehicle while maintaining vehicle control, even at physical limits, i.e., at high vehicle speeds and / or high speed variation values.

[0017] Previous SBW steering systems were unable to achieve this adaptive steering behavior because they typically diminished the driver's sense of lateral vehicle guidance. This made it more difficult for the driver to control the vehicle at its physical limits.

[0018] The torque steering component is preferably variable, depending on the desired function of the SBW steering system, the vehicle's operating parameters, and / or the selected driving mode. This allows the feedback torque to be tailored to the specific vehicle and driving situation, thereby optimizing driver comfort.

[0019] According to a further aspect, some embodiments of this disclosure relate to an SBW steering system for a motor vehicle. The SBW steering system has at least one wheel actuator, a steering wheel actuator, and control equipment coupled to the wheel actuator and the steering wheel actuator. The control equipment is at least configured as follows: - Receive user input using a user interface. Specify at least one driving mode based on user input. - The regular feedback torque to be applied by the steering wheel actuator is determined based on the actual rack and pinion forces applied. - Estimates the feedback torque to be applied by the steering wheel actuators. This feedback torque is adjusted based on the torque steer component, which depends on the driving mode specified by the user input, and - The steering wheel signal is output to the steering wheel actuator based on the adjusted feedback torque.

[0020] The steering wheel actuator is configured to output adjusted feedback torque to the steering wheel of the steer-by-wire system based on the steering wheel control signal.

[0021] The benefits achieved through the method described in this paper are also realized in a corresponding manner through the SBW steering system. In particular, this ensures the possibility of adaptively adjusting lateral vehicle guidance according to the driving mode using the SBW steering system. This provides the driver with more or less direct feedback, thereby reproducing the behavior of a conventional steering system with mechanical coupling between the steering wheel and the wheels.

[0022] The wheel actuator is at least indirectly coupled to the steerable wheel. Optionally, the wheel actuator may also be at least indirectly coupled to multiple steerable wheels simultaneously, for example, via a rack and pinion. The wheel actuator can transmit rack and pinion forces that at least indirectly cause or stabilize a particular orientation of the steerable wheel. For example, rack and pinion forces can be used to reposition the rack and pinion, which results in the repositioning of the steerable wheel, i.e., rotation about the vehicle's vertical axis.

[0023] As an alternative, the motor vehicle may also have at least a second wheel actuator, which may be coupled to the steerable rear wheel of the motor vehicle, for example, via an additional rack and pinion.

[0024] Multiple wheel actuators can be controlled by a control device.

[0025] Each wheel actuator has an electric motor for applying torque to change the orientation of the steerable wheel. For example, the wheel actuator can apply torque to a rack so that the rack position can be adjusted as needed. For example, the electric motor can have a winding set with three windings, i.e., a three-phase winding set. Optionally, the electric motor can also have more winding sets.

[0026] The steering wheel actuator is configured to apply feedback torque to the steering wheel at least indirectly, for example, through the steering column coupled to the steering wheel. The feedback torque induced by the steering wheel actuator is also used to provide torque feedback to the driver regarding lateral vehicle guidance.

[0027] Typically, a steering wheel actuator has an electric motor capable of applying feedback torque to the steering wheel. For example, the electric motor may have a winding set with three windings, i.e., a three-phase winding set. Optionally, the electric motor may also have more winding sets.

[0028] Optionally, the SBW steering system may have at least one steering wheel sensor configured to capture the steering wheel angle, i.e., the steering wheel position, and transmit it to the control device. This allows the control device to determine the driver's steering intention (steering demand) and the rack and pinion forces required for the SBW steering system to execute the steering demand.

[0029] Preferably, the steering requirements can depend on the steering wheel position of the steering wheel in the SBW steering system.

[0030] Optionally, the motor vehicle and / or SBW steering system has wheel speed sensors configured to capture the rotational speed of the wheels in the circumferential direction (rolling direction) and transmit them to control devices. For example, based on the captured rotational speed, specific wheel slip can be determined, allowing the vehicle to be characterized according to its individual driving conditions.

[0031] In some implementations, the motor vehicle and / or SBW steering system has wheel angle sensors. The wheel angle sensors are configured to capture the wheel angle of the steerable wheel relative to the steering axis of the corresponding steerable wheel and transmit it to the control equipment and / or wheel actuators of the SBW steering system.

[0032] When estimating rack and pinion forces, the control device and / or wheel actuator may take into account the captured speed and / or captured wheel angle.

[0033] For example, the user interface could be a multimedia device configured to output notifications to the driver and receive user input, such as audio- or haptic input. Based on the user input, the driver can specify the desired driving mode and make additional detailed specifications and adjustments.

[0034] Preferably, the control device is at least coupled to the user interface. This allows user input to be transmitted directly from the user interface to the control device. Furthermore, the control device can then immediately output notifications to the driver via the user interface. In this sense, the user interface can be configured for two-way interaction with the driver.

[0035] In some implementations, the method further includes the following steps: - The actual rack and pinion forces applied to the rack of the SBW steering system by the wheel actuators are estimated by the control equipment.

[0036] - The optimized rack and pinion forces are estimated by the control equipment, depending on the vehicle's operating parameters.

[0037] - The torque steering component is estimated by the control device by subtracting the optimized rack and pinion force from the estimated actual rack and pinion force.

[0038] According to the previous method, the control device has already estimated the amount actually applied to the rack by the wheel actuators. Instead, the control device can determine an optimized rack and pinion force, which differs from the actual rack and pinion force and takes into account various operating parameters of the vehicle. Therefore, there is a difference between the actual applied rack and pinion force and the optimized rack and pinion force. This difference can be determined by the control device and used to estimate the torque steering component. In this case, the torque steering component of the feedback torque is therefore a measure of the deviation relative to the steering wheel feedback under driving conditions. It can thus be used by the control device to provide appropriate torque feedback to the driver at the steering wheel via the steering wheel actuators. Therefore, the torque feedback to the driver depends on the corresponding driving situation operating parameters of the vehicle and the optimized rack and pinion force dependent on them, thus ensuring that the torque feedback can more accurately and directly reproduce the actual lateral vehicle control.

[0039] Preferably, the vehicle's operating parameters include at least one of vehicle speed, yaw rate, lateral speed variation, steering angle of the steerable wheel around the corresponding wheel steering axis, and combinations thereof.

[0040] For example, the actual applied rack and pinion force can be estimated using the applied electrical power of the electric motor of the rack and pinion sensor and / or wheel actuator.

[0041] Rack and pinion sensors can be configured to capture the output force of the wheel actuator on the rack.

[0042] Optionally or incrementally, the rack and pinion sensor may also include a position sensor configured to detect the rack position relative to a reference position and transmit it to a control device.

[0043] In an alternative, the actual rack and pinion forces applied to the rack by the wheel actuator can also be estimated based on the operating parameters of the wheel actuator, such as current consumption and / or voltage consumption, i.e., electrical power consumption.

[0044] In some implementations, the control device takes into account a model of the SBW steering system and / or the vehicle when estimating the optimized rack and pinion forces. Therefore, the control applied by the control device is particularly closely adapted to the structural implementation, such as the mechanical functional chain, for example, between the rack and pinion and the steerable wheels. This enables the realization of the practical results of the control method executed by the control device.

[0045] Optionally or incrementally, when estimating the optimized rack and pinion forces, the control device considers at least one of the vehicle speed, yaw rate, lateral velocity variation, and steering angle of the steerable wheels. The control device can use these parameters to more accurately determine the vehicle condition at any given time. Therefore, the optimized rack and pinion forces can then be determined in a dimensionally appropriate manner based on the corresponding vehicle condition.

[0046] Optionally, the estimated rack and pinion forces optimized for the driving mode are stored in a data memory coupled to the control device. This data memory contains a database of feedback characteristics for the torque steering component of the feedback torque applied by the steering wheel actuator. This means that the optimized rack and pinion forces estimated for a vehicle configuration (such as a driving mode) only need to be determined once and then stored in the database for that vehicle configuration. If the same vehicle configuration occurs again in the future, it is not necessary to estimate the optimized rack and pinion forces again. Instead, the control device can simply access the database and read the corresponding parameter values. This significantly reduces the control load.

[0047] According to one aspect, the method may also include the following steps: - The feedback torque is determined by the control device by adding the estimated torque steering component to the regular feedback torque determined by the control device.

[0048] Of course, the SBW steering system has a standard control program for determining the feedback torque of the steering wheel, which reflects the lateral guidance of the vehicle and is applied to the steering wheel by the steering wheel actuators. This program determines the feedback torque corresponding to the desired feedback torque based on the actual rack and pinion forces output by the wheel actuators, which is typically filtered for interference. However, this program does not account for modifications related to the driving mode concerning the torque steering component.

[0049] However, to provide the driver with more immediate and direct feedback on the vehicle's lateral guidance, a feedback torque is determined by a control device based on the aforementioned aspects, which adds a torque steer component to the regular feedback torque. For example, the feedback torque to the driver on the steering wheel varies according to the driving mode, thus adjusting its intensity. This makes the feedback more direct than a conventional SBW steering system and can simulate the behavior of a conventional mechanically coupled steering system, resulting in a more sporty overall feel. Therefore, vehicle control for the driver is simplified compared to existing methods.

[0050] In some implementations, the method may further include the following steps: - The preferred torque steering component is estimated by the control equipment based on optimized rack and pinion forces that depend on estimates of the vehicle's operating parameters, and - The control device determines the feedback torque by adding the estimated preferred torque steering component to the determined conventional feedback torque.

[0051] This design is particularly advantageous for vehicles that produce only small or almost no torque steering component, such as rear-wheel-drive vehicles, which typically have low rack and pinion disturbance forces. Therefore, the preferred torque steering component for such vehicles can be determined based on estimated optimized rack and pinion forces and the vehicle's operating parameters. This allows for feedback torque simulation of sporty vehicles, for example, taking into account the torque steering component compared to conventional SBW steering systems.

[0052] Optionally, some implementations of the method may further include the following steps: - The control device determines the feedback torque by subtracting the estimated torque steering component from the determined conventional feedback torque.

[0053] The procedure used to determine the conventional feedback torque does not take into account modifications related to the driving mode regarding the torque steering component. However, to provide the driver with more convenient feedback on the vehicle's lateral guidance, the control unit determines (adjusted) the feedback torque. To do this, the control unit subtracts the torque steering component from the estimated conventional feedback torque. For example, depending on the driving mode, the driver's feedback on the steering wheel can be reduced or minimized, thus lowering the intensity and making the feedback more comfortable than, for example, a conventional SBW steering system. Therefore, vehicle control is less disruptive to the driver compared to existing methods.

[0054] In an alternative approach, the feedback torque is determined by subtracting a preferred torque steering component, estimated based on the vehicle's operating parameters, from a predetermined conventional feedback torque using control equipment. As mentioned above, the preferred torque steering component is determined by control equipment based on optimized rack and pinion forces.

[0055] In general, the estimated torque steering component or preferred torque steering component can be added to or subtracted from the conventional feedback torque by the control device in order to determine the feedback torque suitable for the adjustment of the driving mode.

[0056] The control device can also optionally adjust the estimated torque steering component or preferred torque steering component relative to a specified driving mode before adding or subtracting, and can determine the torque steering component optimized depending on the driving mode, and then take it into account during addition or subtraction. For example, while the optimized rack and pinion forces are initially determined independently of the specified driving mode, as it could be determined purely based on the corresponding operating parameters of the vehicle, taking the specified driving mode into account provides additional degrees of freedom for adjusting the feedback on the steering wheel in the way the driver expects.

[0057] This means that users can optionally specify, based on user input via the user interface, whether the feedback torque output to the steering wheel is added additively or subtracted subtractively. Preferably, this adjustment can also be made by the user according to the driving mode.

[0058] When determining the optimized torque steering component that depends on the driving mode, the control device preferably considers a prefactor. Therefore, the control device has further degrees of freedom in terms of the adaptability of the adjustment feedback to the vehicle's operating state (e.g., regarding the degree of adjustment).

[0059] Driver input can involve different driving modes, such as normal mode, comfort mode, sport mode, and racing mode.

[0060] In addition, user input can optionally specify an intensity level, which defines the characteristics of the mode. In other words, user input can also specify the intensity level of the driving mode. The intensity level indicates how comfortably or sportily the driver receives feedback regarding the vehicle's lateral guidance.

[0061] Driving mode and / or intensity level can be used by the control equipment to determine the pre-coefficient, which is taken into account when adding estimated feedback torque.

[0062] For example, the control device can be coupled to a database with an association table that has predetermined pre-coefficients associated with driving modes and / or intensity levels.

[0063] In some implementations, if the intensity level is greater than or equal to an intensity threshold and / or if a specific driving mode is selected based on user input, the control device outputs a notification to the user to hold the steering wheel with both hands. The database may contain associations between the notifications to be output and the corresponding driving modes and / or intensity levels.

[0064] Preferably, the notification is output to the driver via a user interface. For example, the notification can be output as a visual or audible notification via a display and / or a speaker.

[0065] In a further aspect, this disclosure also relates to a computer program product comprising commands that, when executed by a computer, cause the computer to perform the methods described herein. The benefits achieved by the methods described herein are also achieved in a corresponding manner by the computer program product.

[0066] According to an additional aspect, this disclosure also relates to a computer-readable storage medium containing commands that, when executed by a computer, cause the computer to perform the methods described herein. The advantages achieved by the methods described herein are also achieved in a corresponding manner through the computer-readable storage medium.

[0067] According to another aspect, some embodiments of this disclosure relate to motor vehicles having the SBW steering system described herein.

[0068] The advantages of the SBW steering system described in this article are also realized in motor vehicles in a similar manner.

[0069] For the purposes of this disclosure, motor vehicles may specifically include land vehicles, particularly off-road vehicles and highway vehicles such as passenger cars, buses, trucks, and other commercial vehicles. Motor vehicles may be manned or unmanned. Motor vehicles are at least partially electrically driven, i.e., they have an electric motor that serves as the drive unit. Furthermore, motor vehicles may optionally have an internal combustion engine.

[0070] All features explained in terms of each aspect can be combined individually or in a (sub-combination) manner with other aspects. Attached Figure Description

[0071] The present disclosure, as well as other advantageous embodiments and developments thereof, are described and explained in more detail below with reference to the embodiments shown in the accompanying drawings. In the drawings: - Figure 1 A simplified schematic diagram of a motor vehicle with an SBW steering system according to an embodiment is shown, and - Figure 2 A simplified schematic diagram of a method for operating an SBW steering system according to an embodiment is shown. Detailed Implementation

[0072] The following detailed description, taken in conjunction with the accompanying drawings, in which like numbers refer to like elements, is intended to describe different embodiments of the disclosed purpose and is not intended to represent only these embodiments. Each embodiment described in this disclosure is intended only as an example or illustration and should not be construed as superior to or advantageous to other embodiments. The illustrative embodiments contained herein are not exhaustive, nor are they intended to limit the claimed subject matter to the exact forms disclosed. Various variations of the described embodiments will be readily recognized by those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of the described embodiments. Therefore, the described embodiments are not limited to the embodiments shown, but have the widest possible scope of application compatible with the principles and features disclosed herein.

[0073] All features disclosed below with respect to exemplary embodiments and / or drawings may be combined individually or in any sub-combination with features of various aspects of this disclosure (including features of preferred embodiments), provided that the resulting combination of features is reasonable to those skilled in the art.

[0074] For the purposes of this disclosure, the phrase "at least one of A, B, and C" means, for example, (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), and if more than three elements are listed, all other possible combinations are included. In other words, the term "at least one of A and B" generally means "A and / or B," i.e., "A" alone, "B" alone, or "A and B."

[0075] Figure 1 A simplified schematic diagram of a motor vehicle 10 with an SBW steering system 12 according to an embodiment is shown.

[0076] The SBW steering system 12 includes a control device 14, a wheel actuator 16, and a steering wheel actuator 18.

[0077] Wheel actuator 16 is indirectly coupled to the steerable wheel 20 of motor vehicle 10. For this purpose, wheel actuator 16 is coupled to rack and pinion 22, which is coupled to the steerable wheel 20 of motor vehicle 10. Deflection of rack and pinion 22 causes a change in orientation of steerable wheel 20, that is, steerable wheel 20 rotates about the vertical axis of the vehicle.

[0078] The motor vehicle 10 also has a wheel speed sensor 24. The wheel speed sensor 24 can also be part of the SBW steering system. The wheel speed sensor 24 is configured to capture the speed of the wheel 20 in the circumferential direction and transmit it to the control device 14. Thus, for example, the specific wheel slip can be determined by the control device 14.

[0079] Furthermore, the vehicle 10 has a wheel angle sensor 26, which may also be part of the SBW steering system 12. The wheel angle sensor 26 is configured to capture the wheel angle of the steerable wheel 20 relative to a reference position (such as a straight position) and transmit the captured wheel angle to the control device 14. In the straight position, the steerable wheel 20 is oriented parallel to the longitudinal direction of the vehicle 10.

[0080] In an alternative, optional sensors, such as rack and pinion sensors, can also be coupled to rack and pinion 22 and can capture the deflection of rack and pinion 22 relative to a reference position (such as a center position). Since rack and pinion 22 is coupled to steerable wheel 20, the orientation of steerable wheel can also be determined.

[0081] The SBW steering system 12 also includes a steering wheel 28, with a steering wheel actuator 18 (e.g., via the steering column) at least indirectly coupled to the steering wheel 28. The steering wheel actuator 18 is configured to apply feedback torque to the steering wheel 28, so that the driver of the vehicle 10 feels lateral guidance of the vehicle 10.

[0082] The steering wheel actuator 18 has an electric motor. The electric motor of the steering wheel actuator 18 includes at least one winding group. Each winding group of the electric motor is three-phase and is configured to drive the rotor of the electric motor. Therefore, feedback torque can be provided to the driver on the steering wheel 28 of the motor vehicle 10 by the electric motor, so that the driver can feel the lateral control of the motor vehicle 10.

[0083] Using the steering wheel 28, the driver of the motor vehicle 10 can give the steering requirements of the motor vehicle 10.

[0084] Furthermore, the SBW steering system 12 includes at least one steering wheel sensor 30, which is configured to capture the steering wheel angle of the steering wheel 28 relative to a reference position (e.g., center orientation (zero position)), i.e., the steering wheel position. Therefore, the steering wheel sensor 30 can be used to capture the steering needs of the driver of the motor vehicle 10 using the steering wheel 28.

[0085] In this embodiment, the steering wheel sensor 30 is integrated with the steering wheel actuator 18. However, in other embodiments, the steering wheel sensor 30 may be separate from the steering wheel actuator 18. The steering wheel sensor 30 is configured to transmit the captured steering wheel angle to the control device 14.

[0086] Control device 14 includes data processing equipment. Optionally, when outputting a wheel orientation signal to wheel actuator 16, control device 14 may consider other parameters of the motor vehicle 10, such as vehicle speed or speed variation. Of course, these values ​​may also be considered when controlling the feedback torque applied to steering wheel 28 by steering wheel actuator 18, i.e., when outputting steering wheel control signals.

[0087] The vehicle 10 also has a user interface 32 coupled to the control device 14. Notifications for the vehicle user or user input from the vehicle user can be transmitted bidirectionally between the user interface 32 and the control device 14. This means that the control device 14 can use the user interface 32 to output notifications to the vehicle user and can receive user input via the user interface 32.

[0088] Optionally, the user interface 32 may be part of the SBW steering system 12. However, the user interface 32 is typically formed in such a way as, for example, through a multimedia device, that the driver can use the user interface 32 to use other functions of the motor vehicle 10, such as air conditioning or entertainment functions.

[0089] According to this embodiment, the user of the motor vehicle 10 can transmit user input to the control device 14 through the user interface 32, thereby allowing the user of the motor vehicle 10 to specify a desired driving mode, and optionally also specify the desired intensity level of the corresponding driving mode.

[0090] Optional driving modes include, for example, Sport mode and Racing mode. Optionally, driving modes may also include Normal mode or Comfort mode. Intensity level indicates fine-tuning of the driving mode.

[0091] The driving mode and / or intensity level indicate what kind of direct and immediate feedback the driver expects to receive via the steering wheel 28, which is presented in the form of feedback torque for lateral vehicle control.

[0092] The SBW steering system 12 also has at least one data memory 34 coupled to the control device 14. The data memory 34 has at least one database 36 storing feedback characteristics. These feedback characteristics indicate the feedback torque to be applied to the steering wheel 28 by the steering wheel actuator 18. Feedback characteristics dependent on various parameters can be provided, such as the steering wheel angle captured by the steering wheel sensor 30, the wheel angle of the steerable wheel 20 captured by the wheel angle sensor 26, the vehicle speed of the motor vehicle 10 which can be indirectly determined, for example, by the wheel speed sensor 24, and the rack and pinion force applied to the rack and pinion 22 by the wheel actuator 16. The rack and pinion force applied by the wheel actuator 16 can be determined, for example, based on the operating parameters of the wheel actuator 16. For this purpose, for example, the voltage and current drawn by the wheel actuator 16 can be captured, and typically the electrical power consumption of the wheel actuator 16 is obtained. Alternatively, the rack and pinion force applied to the rack and pinion 22 by the wheel actuator 16 can also be determined using a dedicated sensor (such as a rack and pinion sensor) that is part of the SBW steering system 12.

[0093] Control device 14 outputs a wheel orientation signal to control wheel actuator 16. Based on the wheel orientation signal, wheel actuator 16 outputs the required output torque. The output torque is applied to rack and pinion 22 via wheel actuator 16 in the form of rack and pinion forces, thereby indirectly changing the deflection of the steerable wheel 20. In determining the required rack and pinion forces, control device 14 specifically considers the steering demand on steering wheel 28, as well as the driver's desired driving mode and / or the intensity level specified by the driver of motor vehicle 10 based on user input.

[0094] To control the steering wheel actuator 18, the control device 14 outputs a steering wheel control signal. Based on the steering wheel control signal, the steering wheel actuator 18 outputs the required feedback torque. Then, the steering wheel actuator 18 outputs feedback torque, which at least indirectly affects the orientation of the steering wheel 28.

[0095] The SBW steering system 12 can of course also have multiple components of the same type and roughly the same function, such as multiple steering wheel sensors 30 to ensure redundancy.

[0096] Here, the SBW steering system 12 is shown as a front axle steering system. The motor vehicle 10 and the SBW steering system 12 may optionally have additional steerable wheels 20, such as the rear wheels coupled to an additional common wheel actuator 16.

[0097] Each wheel actuator 16 has an electric motor. The motor has at least one winding group comprising a set of windings. Each winding group is configured such that when a power supply signal, such as a phase voltage, is provided, a phase current suitable for driving the rotor of the electric motor is generated in the underlying windings. The rotor can then be coupled to corresponding components of the SBW steering system, such as the rack and pinion 22, thereby enabling movement of the steerable wheel 20. Generally, the electric motor may also have more than one winding group.

[0098] Typically, each winding group is three-phase, so the entire motor is at least three-phase, and optionally six-phase or nine-phase.

[0099] If there are multiple winding groups, each winding group allows the rotor of the electric motor to move independently of the other winding groups. This means that the winding groups are independent of each other.

[0100] Figure 2 A simplified schematic diagram of a method for operating the SBW steering system 12 according to an embodiment is shown. Optional steps are shown in dashed lines.

[0101] The method first includes step S1, in which the control device 14 receives user input using the user interface 32. Based on the user input, at least one driving mode desired by the driver is specified. Thus, the control device 14 is informed of how the feedback to the driver of the motor vehicle 10 on the steering wheel 28 will be adjusted.

[0102] Step S1 can be extended by optional step S2, wherein if the intensity level is greater than or equal to an intensity threshold and / or if the driver wishes to obtain the predetermined driving mode to which the notification is targeted via user input, the control device 14 outputs a notification to the user to hold the steering wheel 28 with both hands. This notification can be output by the control device 14 to the driver of the motor vehicle 10 via the user interface 32.

[0103] Since the intensity level selected by the driver of the motor vehicle 10 affects the feedback on the steering wheel 28, it is conceivable that the driver of the motor vehicle 10 holds the steering wheel 28 with both hands, for example, in order to be able to withstand particularly high feedback torque and to be able to adjust the lateral guidance of the motor vehicle 10 as desired, even though the driver has selected a specific motion and direct feedback.

[0104] Starting from step S1, the method may optionally have step S3, in which the optimized rack and pinion force to be applied by the wheel actuator 16 to the rack and pinion 22 of the SBW steering system 12 is estimated by the control device 14.

[0105] Therefore, determining the optimized rack and pinion forces in step S3 allows for the reproduction of the torque steering component of a conventional steering system, i.e., a non-SBW steering system with direct mechanical coupling between the steering wheel 28 and the steerable wheel 20. For example, the optimized rack and pinion forces can be determined by the control device 14 in such a manner that it models the rack and pinion forces applied to a conventional steering system of a motor vehicle operating under physical limits 10.

[0106] Step S3 can be extended by optional step S4, wherein the control device 14 considers the model of the SBW steering system 12 and / or the vehicle 10 when estimating the optimized rack and pinion forces. This allows the control device 14 to consider how forces are transmitted from individual components of the SBW steering system 12 to their other components. For example, friction effects can also be taken into account in this way. Finally, the model of the SBW steering system 12 used by the control device 14 is customized for the corresponding SBW steering system 12.

[0107] Step S3 can also be extended by optional step S5, wherein the control device 14 takes into account the vehicle speed, yaw rate, lateral velocity variation and / or steering angle of the steerable wheel 20 around the corresponding wheel steering axis when determining the optimized rack and pinion forces.

[0108] For example, the steering angle of the steerable wheel 20 can be captured by the wheel angle sensor 26. The vehicle speed of the motor vehicle 10 can be determined at least indirectly by the wheel speed sensor 24. To determine changes in yaw rate and / or lateral velocity, the SBW steering system 12 can have additional sensors or can use sensors already present in the motor vehicle 10. These parameters can be used to optimize the determination of rack and pinion forces based on driving conditions, thereby making the determination more accurate.

[0109] Furthermore, the method may optionally include a step S6 in which the estimated, optimized rack and pinion forces are stored in a data memory 34 coupled to the control device 14. The data memory 34 has a database 36 of feedback characteristics for the feedback torque to be applied by the steering wheel actuator 18. This allows for the simulation of torque steering components for a motor vehicle 10 (such as a rear-wheel-drive motor vehicle 10), which typically provides little or no torque feedback to the driver.

[0110] Starting from step S1, the method also includes an optional step S7, in which the actual rack and pinion forces applied by the wheel actuator 16 to the rack and pinion 22 of the SBW steering system 12 are estimated. This can be determined, for example, using operating parameters of the wheel actuator 16, which can be captured by appropriate sensors and transmitted to the control device 14. For example, the electrical power consumption of the wheel actuator 16 can be evaluated.

[0111] Starting with optional steps S3 and S7, the method has an optional step S8. In step S8, the control device 14 estimates the torque steering component by subtracting the optimized rack and pinion force from the estimated actual rack and pinion force. The torque steering component is a measure of the difference between the actual applied rack and pinion force and the optimized rack and pinion force. This difference can then be used indirectly to adjust the feedback torque on the steering wheel 28 in a customized manner.

[0112] Furthermore, the method includes step S9, which follows optionally step S7. In step S9, the control device 14 determines the conventional feedback torque to be applied by the steering wheel actuator 18 based on the actually applied rack and pinion forces. Optionally, other parameters, such as vehicle speed, lateral speed variation, yaw rate, and / or wheel angle, may also be considered. Thus, this represents the conventional determination of the feedback torque applied to the steering wheel 28 by the steering wheel actuator 18, and corresponds to the normal operating state of the SBW steering system 12 outside the methods described herein.

[0113] Due to the difference between the rack and pinion force actually applied by the wheel actuator 16 and the optimized rack and pinion force, adjustment of the feedback torque applied to the steering wheel 28 by the steering wheel actuator 18 is now provided.

[0114] Therefore, following optional step S3, the method includes optional step S10, in which control device 14 estimates the preferred torque steering component based on the estimated optimized rack and pinion forces according to the operating parameters of vehicle 10. In other words, the torque steering component can be estimated even if the rack and pinion forces actually applied by control device 14 are ignored, as an optional and / or as a comparison variable and / or as a criterion for the reasonableness of the torque steering component estimated according to step S8. For this purpose, control device 14 considers only the optimized rack and pinion forces from optional step S3, and optionally other operating parameters of the vehicle from optional steps S4 to S6. In particular, this makes it possible to estimate the torque steering component independently of the actually applied rack and pinion forces.

[0115] The method may then include an optional step S11, beginning with steps S8 and S10. In this step, the control device 14 may optimize the determined torque steering component relative to the driving mode selected in step S1, regardless of how it is estimated (based on the subtraction according to S8 or solely on the optimized rack and pinion forces according to S3). This means that the control device 14 estimates the optimized torque steering component based on the driving mode. On the other hand, the torque steering component estimated from steps S8 and S10 has no or only an indirect driving mode dependency. Since the driver defines specific types of feedback on the steering wheel 28 based on user input, such as driving mode and / or feedback intensity level, this has an impact on the lateral control performance of the motor vehicle 10. This is used by the control device 14 in the optional step S11 to determine the torque steering component optimized for the corresponding settings desired by the user, which will be taken into account when adjusting the feedback torque.

[0116] For example, optional step S11 can be extended by optional step S12, wherein the control device 14 considers a pre-coefficient when estimating the optimized torque steering component. This results in the torque steering component being artificially amplified or attenuated, thus allowing customization for the corresponding SBW steering system 12. In this case, the pre-coefficient can be specifically based on the driving mode and / or intensity level specified by the user input.

[0117] Optionally, the user input can also specify further information, such as the desired intensity of feedback on the steering wheel 28, which allows for the determination of the pre-coefficient. The data storage 34 can hold the corresponding information about the pre-coefficient. This enables tailored estimations of the torque steering component.

[0118] To actually adjust the driver's feedback at the steering wheel 28, the method includes step S13, which begins with steps S9 and S11. In this step, the control device 14 determines a feedback torque that is adjusted for an optimized torque steering component, which in turn depends on the driving mode specified by the driver according to step S1.

[0119] This method can enhance the feedback on the steering wheel 28 (more direct feedback behavior) and weaken the feedback (less direct feedback behavior).

[0120] Therefore, step S13 can also be designed in different ways according to the desired driving mode and / or driving conditions of the motor vehicle 10.

[0121] According to an optional step S14 as part of step S13, the control device 14 determines the adjusted feedback torque to be applied to the steering wheel 28 by adding the estimated optimized torque steering component from the optional step S10 to the conventional feedback torque determined by the control device 14. This enhances the feedback. The driver perceives this as a more direct feedback behavior regarding the lateral control of the motor vehicle 10 on the steering wheel 28.

[0122] Alternatively, step S13 may also include an optional step S15, in which the control device 14 subtracts the estimated optimized torque steering component from the determined conventional feedback torque to determine the adjusted feedback torque. This weakens the feedback. The driver perceives this as less direct feedback behavior on the steering wheel 28 regarding the lateral control of the motor vehicle 10.

[0123] In steps S14 and S15, the estimated optimized torque steering component can be based on the estimated torque steering component from step S8 and the preferred torque steering component from step S14. The corresponding pre-coefficients from step S12 can also be considered.

[0124] Depending on optional step S14 or S15, whether the feedback torque on the steering wheel 28 is increased or decreased can be specifically specified by user input via user interface 32 according to step S1.

[0125] In the subsequent step S16, a correspondingly adjusted feedback torque is output through the steering wheel actuator 18 on the steering wheel 28. For this purpose, the control device 14 outputs a corresponding steering wheel control signal to the steering wheel actuator 18. Specifically, the feedback torque applied to the steering wheel 28 by the steering wheel actuator 18 is adjusted by an optimized torque steering component, corresponding to either step S14 or S15.

[0126] Therefore, an SBW steering system 12 and a method are provided that enable customized adjustment of the driver's feedback on the steering wheel 28 based on the driving mode and / or intensity level selected by the driver of the motor vehicle 10. Specifically, this allows for the reproduction of the torque steering component of a conventional steering system with a mechanical connection between the steering wheel 28 and the steerable wheels 20. In this way, sporty, direct, or more comfortable (less direct) feedback can be achieved based on user input.

[0127] The specific embodiments disclosed herein use circuits (e.g., one or more circuits) to implement the standards, schemes, methods, or techniques disclosed herein to functionally couple two or more components to generate information, process information, analyze information, generate signals, encode / decode signals, convert signals, transmit and / or receive signals, control other devices, etc. Any type of circuit can be used.

[0128] In one embodiment, the circuitry, such as that of a control device, includes one or more data processing means, such as a processor (e.g., a microprocessor), a central processing unit (CPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a system-on-a-chip (SoC), or the like, or any combination thereof, and may include discrete digital or analog circuit elements or electronic devices, or combinations thereof. In one embodiment, the circuitry includes hardware circuitry implementations (e.g., implementations in analog circuitry, implementations in digital circuitry, etc., and combinations thereof).

[0129] In one embodiment, the circuit system includes a combination of circuitry and computer program products with software or firmware instructions stored in one or more computer-readable storage media, which work together to cause a device to perform one or more of the schemes, methods, or techniques described herein. In one embodiment, the circuit system includes circuitry such as a microprocessor or microprocessor components that require software, firmware, etc., to operate. In one embodiment, the circuitry includes one or more processors or components thereof, along with associated software, firmware, hardware, etc.

[0130] This disclosure may refer to quantities and numbers. Unless explicitly stated otherwise, these quantities and numbers should not be considered as limitations, but rather as examples of possible quantities or numbers relating to this disclosure. In this context, the term "plural number" may also be used to refer to a quantity or number. In this context, the term "plural number" refers to any number greater than one, such as two, three, four, five, etc. The terms "approximately," "approximately," "close to," etc., indicate a value plus or minus 5%.

[0131] Although this disclosure has been presented and described with respect to one or more embodiments, equivalent changes and modifications will be able to be made by those skilled in the art after reading and understanding this specification and the accompanying drawings.

Claims

1. A method for operating a steer-by-wire system (12) of a motor vehicle (10), wherein the steer-by-wire system (12) comprises at least one wheel actuator (16), a steering wheel actuator (18), and a control device (14) coupled to the wheel actuator (16) and the steering wheel actuator (18), wherein the method comprises at least the following steps: - The control device (14) receives user input via a user interface (32), wherein at least one driving mode is specified based on the user input. - The control device (14) determines the normal feedback torque to be applied by the steering wheel actuator (18) based on the actual rack and pinion forces applied. The control device (14) estimates the feedback torque to be applied by the steering wheel actuator (18), wherein the feedback torque is adjusted based on the torque steering component, and wherein the torque steering component depends on the driving mode specified by the user input. - The steering wheel actuator (18) outputs adjusted feedback torque to the steering wheel (28) of the steer-by-wire system (12) based on the steering wheel control signal output from the control device (14) to the steering wheel actuator (18).

2. The method according to claim 1, characterized in that, The method further includes: - The control device (14) estimates the actual rack and pinion forces applied by the wheel actuator (16) to the rack (22) of the steer-by-wire system (12). - The control device (14) estimates an optimized rack and pinion force depending on the operating parameters of the motor vehicle (10), the optimized rack and pinion force being applied to the rack (22) by the wheel actuator (16), and - The control device (14) estimates the torque steering component by subtracting the optimized rack and pinion force from the estimated actual rack and pinion force.

3. The method according to claim 2, characterized in that, The method further includes: - The feedback torque is determined by adding the estimated torque steering component to the conventional feedback torque determined by the control device (14), or - The feedback torque is determined by subtracting the estimated torque steering component from the conventional feedback torque determined by the control device (14).

4. The method according to claim 2, characterized in that, The method further includes the following steps: - The control device (14) estimates the preferred torque steering component based on the estimated optimized rack and pinion forces, and - The control device (14) determines the feedback torque by adding the estimated preferred torque steering component to the determined conventional feedback torque, or - The control device (14) determines the feedback torque by subtracting the estimated preferred torque steering component from the determined conventional feedback torque.

5. The method according to claim 3 or 4, characterized in that, When adding or subtracting using pre-coefficients, the estimated torque steering component is taken into account.

6. The method according to any one of the preceding claims, characterized in that, When estimating the optimized rack and pinion forces, the control device (14) states: - Considering the model of the steer-by-wire system (12) and / or the motor vehicle (10), and / or - Consider at least one of the following: vehicle speed, yaw rate, lateral velocity variation and wheel angle of the motor vehicle (10).

7. The method according to any one of the preceding claims, characterized in that, The estimated rack and pinion forces optimized relative to the driving mode are stored in a data memory (34), which is coupled to the control device (14) and has a database (36) of feedback characteristics for the feedback torque to be applied by the steering wheel actuator (18).

8. The method according to any one of the preceding claims, characterized in that, The user input additionally specifies the intensity level of the driving mode.

9. The method according to any one of the preceding claims, characterized in that, If the intensity level is greater than or equal to the intensity threshold, the control device (14) outputs a notification to the user to hold the steering wheel (28) with both hands.

10. A steer-by-wire system (12) for a motor vehicle (10), wherein the steer-by-wire system comprises at least one wheel actuator (16), a steering wheel actuator (18), and a control device (14) coupled to the wheel actuator (16) and the steering wheel actuator (18), wherein the control device (14) is configured to at least: - Receive user input using a user interface (32), wherein at least one driving mode is specified based on the user input; - The conventional feedback torque to be applied by the steering wheel actuator (18) is determined based on the actual applied rack and pinion forces. - Estimate the feedback torque to be applied by the steering wheel actuator (18), wherein the feedback torque is adjusted based on the torque steering component, and wherein the torque steering component depends on the driving mode specified based on the user input. - The steering wheel signal is output to the steering wheel actuator (18) based on the adjusted feedback torque. Furthermore, the steering wheel actuator (18) is configured to output the adjusted feedback torque based on the steering wheel control signal on the steering wheel (28) of the steer-by-wire system (12).

11. The steer-by-wire system (12) according to claim 10, characterized in that, The control device (14) is at least coupled to the user interface (32).

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