Method for determining a steering wheel superposition torque for transmission to a steering wheel of a steer-by-wire steering system

Abstract

A method for determining a steering wheel superposition torque (28) for transmission to a steering wheel (2) of a steer-by-wire steering system (1) of a vehicle (40) is described. The method comprises the following steps: receiving a request (22) from a driver assistance system for force or torque superposition for transmission to the wheels (5), which is proportional to a force transmitted to the wheels (5) by means of a rack (8), (11); determining a torque currently applied to the steering wheel (2) (current steering wheel torque) (23), (12); converting (32) the detected current steering wheel torque (23) into a force or torque (25) which is proportional to the force transmitted to the wheels (5) by means of a rack (8), (13);Determining a requested total force or torque (26) proportional to the force transmitted to the wheels (5) by means of a rack (8) by adding (34) the requested force or torque (22) and the force or torque (25) converted from the determined current steering wheel torque (14); determining a total steering wheel torque (27) based on the determined requested total force or torque (26) (15); and determining the steering wheel superposition torque (28) using the determined current steering wheel torque (23) and the determined total steering wheel torque (27) (16).

Description

[0001] The present invention relates to methods for determining a steering wheel override torque for transmission to a steering wheel of a steer-by-wire steering system of a vehicle, a control method for a steer-by-wire steering system of a vehicle, a control device for controlling a steering wheel actuator of a steer-by-wire steering system of a vehicle, and a vehicle. The invention also relates to a computer-implemented method, a computer program product, a computer-readable data carrier, and a data carrier signal.

[0002] Vehicles, especially motor vehicles, are commonly equipped with driver assistance functions. Some driver assistance functions, such as lane keeping assist, have been developed using modern technology in a way that requires a specific lateral response from the vehicle by requesting an overlay torque to an electronic power steering system. To control this lateral response of the vehicle using a continuous, linear control approach, the force transmitted to the wheels via a steering rack must be proportional to the requested overlay torque. In the case of conventional electronic power steering systems, this is achieved by means of a mechanical connection between a steering actuator and the steered wheels. The request of the driver assistance function can be implemented using either an overlay torque and / or a overlay force.

[0003] In newer steering systems, such as steer-by-wire systems, the described mechanical connection between the steering wheel and the wheels no longer exists. In these systems, the wheel actuator follows a fixed angle specification determined by a driver input, for example, using a steering wheel in conjunction with a steering wheel actuator. At the same time, feedback on the current driving situation is provided in the form of a feedback countertorque applied to the steering wheel. This feedback countertorque is usually based on a conversion function or a conversion table that provides input values ​​representative of the current steering force at the rack or of the current torque proportional to the force transmitted to the wheels via the rack.

[0004] In order to further implement the driver assistance functions described above, a conversion method is required to convert a superimposed force or torque, which is proportional to the steering force transmitted to the wheels, of a conventional steering system into a superimposed torque at a steering wheel in a steer-by-wire system. When this superimposed torque is applied to the steering wheel via the steering wheel actuator, it causes a steering wheel movement that balances the superimposed torque, any torque applied by a driver, and the feedback countertorque. The feedback countertorque is based on the force acting on the steering rack, which in turn is caused by the tire displacement caused by the wheel actuator as a result of the steering request input via the steering wheel actuator.The essential requirement for such a conversion process is to adapt or adjust this balance so that the vehicle response has the same characteristics as when a steering force boost is requested in a conventional, mechanically coupled steering system.

[0005] Document US 2014 / 0 005 891 A1 describes a method for converting a superimposed torque proportional to the rack force transmitted to the wheels into a superimposed torque proportional to the steering wheel torque applied by a driver. However, this conversion method is only applicable to conventional, mechanically coupled steering systems in which the driver receives an assist torque from the steering wheel actuator that is proportional to the force transmitted to the wheels and applied to the steering wheel as a superimposed torque.

[0006] The documents DE 10 2020 201 589 B4, DE 10 2022 201 402 A1, DE 10 2020 127 661 A1 and DE 10 2021 206 743 A1 describe steer-by-wire steering systems and methods for controlling them.

[0007] Against the background described above, the object of the present invention is to provide an advantageous method for determining a steering wheel override torque for transmission to a steering wheel of a steer-by-wire steering system of a vehicle. Further objects include providing a control method for a steer-by-wire steering system of a vehicle, a control device for controlling a steering wheel actuator of a steer-by-wire steering system of a vehicle, and a vehicle, as well as a computer-implemented method, a computer program product, a computer-readable data carrier, and a data carrier signal.

[0008] The stated objects are achieved by a method for determining a steering wheel override torque for transmission to a steering wheel of a steer-by-wire steering system of a vehicle according to patent claim 1, a control method for a steer-by-wire steering system of a vehicle according to patent claim 9, a control device for controlling a steering wheel actuator of a steer-by-wire steering system of a vehicle according to patent claim 12 and a vehicle according to patent claim 13, as well as a computer-implemented method according to patent claim 14, a computer program product according to patent claim 15, a computer-readable data carrier according to patent claim 16, and a data carrier signal according to patent claim 17. The dependent claims contain further advantageous embodiments of the invention.

[0009] The method according to the invention for determining, e.g., calculating, a steering wheel overlay torque for transmission to a steering wheel of a steer-by-wire steering system of a vehicle comprises the following steps: In a first step, a request from a driver assistance system, in particular a driver assistance function for steering force amplification, for force or torque overlay for transmission to the wheels is received, which is proportional to a force transmitted to the wheels by means of a steering rack. In a second step, a torque currently applied to the steering wheel (current steering wheel torque) is determined, e.g., recorded.

[0010] In a third step, the detected current steering wheel torque is converted, e.g., recalculated, into a force or torque proportional to the force transmitted to the wheels via the steering rack. In a fourth step, a requested total force or torque is determined, which is proportional to the force transmitted to the wheels via a steering rack. This is done by adding the requested force or torque and the force or torque converted, e.g., recalculated, from the determined current steering wheel torque.

[0011] In a fifth step, a total steering wheel torque is determined, e.g., calculated, based on the determined requested total force or the determined requested total torque. In a sixth step, the steering wheel overlay torque is determined, e.g., calculated, using the determined, e.g., recorded, current steering wheel torque and the determined total steering wheel torque.

[0012] The method according to the invention has the advantage that it can be used to determine a superposition torque for a steering wheel of a steer-by-wire steering system, which provides a driver with a steering feel that corresponds to that of a conventional, mechanically coupled steering system.

[0013] In an advantageous variant, the current steering wheel torque is determined using a torque sensor and / or software for determining the current steering wheel torque based on known vehicle operating state variables. The steering wheel torque applied to the driver can be determined, for example, based on the currently requested steering wheel actuator torque, the current change in steering wheel angular velocity, and a moment of inertia counteracting the change in steering wheel angular velocity. In addition, the steering wheel angular velocity and a friction torque counteracting the steering wheel angular velocity can also be taken into account.

[0014] In a further variant, the detected current steering wheel torque can be converted into a force or torque using an inverse conversion function, e.g., a conversion function, or a conversion table, e.g., a conversion table. The inverse conversion function or the conversion table can be based on a conversion function or a conversion table designed to determine, e.g., calculate, a feedback counter-torque, in particular one that represents the current driving situation.

[0015] The determined requested total force or the requested total torque can be converted, for example, using a function, e.g., a calculation function, or a conversion table designed to determine, e.g., calculate, a feedback countertorque. The same conversion function or the same conversion table can be used to convert the detected current steering wheel torque into a force or torque and to convert the determined requested total force or the requested total torque. A conversion function and / or a conversion table can be used that is designed to determine a feedback countertorque based on at least one variable that represents the current rack steering force or a torque that is proportional to the steering force transmitted to the wheels.This ensures that the application of the calculated overlay torque by a steering wheel actuator corresponds to the rack force that would occur when applying an originally requested torque overlay in a conventional, mechanically coupled steering system. Furthermore, a balance corresponding to a conventional, mechanically coupled steering system is achieved between the overlay torque, any torque applied by a driver, and the counter-torque triggered by the tire deflection induced by the wheel actuator in response to a steering request.

[0016] Preferably, the steering wheel overlay torque is determined by subtracting the detected current steering wheel torque from the determined total steering wheel torque. Detected or determined input signals and / or intermediate values ​​and / or output signals can be further processed, e.g., filtered. This can reduce signal noise and / or prevent sudden, unwanted jumps in the signal values.

[0017] The inventive control method for a steer-by-wire steering system of a vehicle comprises the following steps: A steering wheel override torque of a steer-by-wire steering system of a vehicle is determined using a method according to a previously described inventive method for determining a steering wheel override torque. A current feedback countertorque at the steering wheel is determined. The aforementioned steps can be performed simultaneously or in any desired order. Subsequently, the current feedback countertorque at the steering wheel is superimposed with the determined steering wheel override torque by means of an actuator, e.g., a steering wheel actuator. The inventive control method has the features and advantages described above in connection with the inventive method for determining a steering wheel override torque.

[0018] The current feedback countertorque at the steering wheel can be determined based on a current rack torque applied to the wheels of the vehicle, e.g., by means of a wheel actuator. The determined current feedback countertorque and / or the steering wheel superimposed torque can be adjusted if the current feedback countertorque depends on at least one variable or parameter that is not representative of a current rack torque applied to the wheels of the vehicle. The adjustment can be performed, for example, by multiplying by a constant or a dynamically calculated factor. Advantageously, the dynamically calculated factor or the constant is representative of the relationship between components of the countertorque that depend on the rack force and components of the countertorque that do not depend on the rack force.

[0019] The control device according to the invention for controlling a steering wheel actuator of a steer-by-wire steering system of a vehicle comprises a device for receiving a request from a driver assistance system for a force or torque overlay for transmission to the wheels, a device for determining a steering wheel overlay torque using a method according to the invention for determining a steering wheel overlay torque described above, and a device for determining a current feedback countertorque at the steering wheel. The control device is designed to execute a previously described control method according to the invention for a steer-by-wire steering system. It has the features and advantages already described above.

[0020] The vehicle according to the invention comprises a steer-by-wire steering system and a previously described control device according to the invention. The vehicle has the advantages already described. The vehicle can be a motor vehicle or a vessel. The motor vehicle can be a passenger car, a truck, a bus, a minibus, a motorcycle, or a moped. Furthermore, the vehicle can be an electric vehicle or a hybrid vehicle (HEV - hybrid electric vehicle).

[0021] The computer-implemented method according to the invention comprises instructions which, when the program is executed by a computer, cause the computer to execute an inventive method described above. The computer program product according to the invention comprises instructions which, when the program is executed by a computer, cause the computer to execute an inventive method described above for determining a steering wheel override torque for transmission to a steering wheel of a steer-by-wire steering system or an inventive control method described above for a steer-by-wire steering system of a vehicle. The computer program product according to the invention is stored on the computer-readable data carrier according to the invention. The data carrier signal according to the invention transmits the computer program product according to the invention.The computer-implemented method according to the invention, the computer program product according to the invention, the computer-readable data carrier according to the invention and the data carrier signal according to the invention have the features and advantages already mentioned above.

[0022] The invention will be explained in more detail below using exemplary embodiments with reference to the accompanying figures. Although the invention is illustrated and described in more detail by the preferred embodiments, the invention is not limited to the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0023] The figures are not necessarily detailed or to scale and may be enlarged or reduced to provide a better overview. Therefore, the functional details disclosed herein are not to be interpreted in a limiting sense, but merely as an illustrative basis for teaching one skilled in the art how to variously employ the present invention.

[0024] As used herein, the term "and / or," when used in a series of two or more elements, means that any of the listed elements may be used alone, or any combination of two or more of the listed elements may be used. For example, if a composition is described containing components A, B, and / or C, the composition may contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination. Fig. 1 shows a schematic diagram of a steer-by-wire steering system of a vehicle. Fig. 2 schematically shows a control method according to the invention for a steer-by-wire steering system in the form of a flow chart. Fig. 3 schematically shows the signal transmission and processing within the framework of a control method according to the invention. Fig. 4 shows schematically a vehicle according to the invention.

[0025] The Fig. 1 schematically shows a steer-by-wire steering system 1 of a vehicle. The steering system 1 comprises a steering wheel 2, a steering rod 3, and a steering wheel actuator 4, which are mechanically connected to one another. The steering system 1 further comprises a number of steerable wheels 5, tie rods 6, a rack 8, and a wheel actuator 7, which are mechanically connected to one another. The tie rods 6 connect the rack 8 to the wheels 5. The steering system 1 further comprises a control device 10, which is connected to the steering wheel actuator 4 and the wheel actuator 7 for signal transmission. The signal transmission is indicated by arrows 9. The control device 10 can also be designed to receive additional signals.

[0026] A steering request is transmitted by a driver via the steering wheel to the handlebar and from there to the steering wheel actuator 4. The steering wheel actuator 4 is in turn designed to transmit torque to the handlebar 3. The wheel actuator 7 is designed to transmit a force or torque to the steering rack 8 and to determine, for example, to measure or receive a force or torque applied to the steering rack 8.

[0027] The control device 10 is designed to receive signals from the steering wheel actuator 4, which in particular comprise an estimated or measured current torque and a steering wheel rotation angle. The control device 10 is also designed to receive signals from the wheel actuator 7, which comprise measured or estimated signals that include the current steering angle and / or a torque overlay request from a driver assistance function, as well as a torque or a corresponding force currently applied to the steering rack 8. The signals transmitted from the control device 10 to the steering wheel actuator 4 represent, for example, a calculated total torque request based on the measured or estimated force or the corresponding torque on the steering rack, the measured or estimated steering wheel torque, and an external torque overlay request, for example, a steering force boosting assistance function.

[0028] The Fig. Figure 2 schematically shows a control method according to the invention for a steer-by-wire steering system in the form of a flowchart. In step 11, a request from a driver assistance system for force or torque superposition for transmission to the wheels, which is proportional to a force transmitted to the wheels via a rack, is received. In step 12, a torque currently applied to the steering wheel (current steering wheel torque) is determined.

[0029] In step 13, the detected current steering wheel torque is converted, e.g., converted, into a force or torque proportional to the force transmitted to the wheels via a rack. In step 14, a requested total force or torque is determined, which is proportional to the force transmitted to the wheels via a rack, by adding the requested force or torque and the force or torque converted from the determined current steering wheel torque.

[0030] In step 15, a total steering wheel torque is determined based on the determined requested total force or the determined requested total torque. In step 16, the steering wheel override torque is determined using the determined current steering wheel torque and the determined total steering wheel torque. In step 17, a determined current feedback countertorque on the steering wheel is superimposed on the determined steering wheel override torque using an actuator 4.

[0031] The Fig. Figure 3 schematically shows the signal transmission and processing within the framework of a control method according to the invention. Signal 21 represents the current rack force on the wheel actuator. Using a conversion function or conversion table 31 for converting the torque based on the current rack force, signal 21 is converted into a signal 24, which represents a feedback countertorque.

[0032] The signal 22 represents the torque superposition request from a driver assistance function, in particular a superposition force to be applied to the rack 8 for transmission to the wheels 5. The detection of the signal 22 corresponds to step 11 in the Fig. 2. The signal 23 represents the torque currently applied to the steering wheel 2.

[0033] The signal 23, the reception of which corresponds to step 12 described above, is converted into a signal 25 by means of an inverse conversion function or conversion table 32 for calculating the rack force based on a current steering wheel torque. The signal 25 represents the calculated rack force. The conversion step corresponds to step 13 in the Fig. 2.

[0034] The signal 22 is added to the signal 25 by an adder 34. This corresponds to step 14 in the Fig. 2. The resulting signal 26 is then converted by a conversion function or a conversion table 31 into a signal 27, which represents a total torque requirement at the steering wheel. The signal 23 is then subtracted from the signal 27 by an adder 35. This corresponds to step 16 in the Fig. 2. The resulting signal 28 represents the steering wheel overlay torque. This is then added to the signal 24 by an adder 36. This corresponds to step 17 in the Fig. 2. The resulting signal 29, which corresponds to the total torque to be applied to the steering wheel, is applied to the steering wheel 2 by means of the steering wheel actuator 4.

[0035] The Fig. 4 schematically shows a vehicle 40 according to the invention. The vehicle 40 according to the invention comprises a steer-by-wire system 1, which has a control device 10 according to the invention, that is to say a control device 10 which is used for carrying out, for example, a Fig. 2 and Fig. 3 described procedure. List of reference symbols 1 steering system 2 steering wheel 3 Handlebar 4 steering wheel actuator 5 wheel 6 Tie rod 7 Wheel actuator 8 rack 9 Signal transmission 10 11 Control device Receiving a request from a driver assistance system for force or torque superposition for transmission to the wheels, which is proportional to a force transmitted to the wheels by means of a rack 12 Determining the current steering wheel torque 13 Converting the detected current steering wheel torque into a force or torque that is proportional to the force transmitted to the wheels via a rack 14 Determining a requested total force or a requested total torque 15 Determining a total steering wheel torque based on the determined total requested force or the determined total requested torque 16 Determination of the steering wheel overlay torque using the determined current steering wheel torque and the determined total steering wheel torque 17 Superimposing the current feedback counter torque on the steering wheel with the determined steering wheel overlay torque by means of an actuator 21 Signal 22 Signal 23 Signal 24 Signal 25 Signal 26 Signal 27 Signal 28 Signal 29 Signal 31 Conversion function or conversion table 32 inverse conversion function or conversion table 34 adders 35 adders 36 adders 40 vehicles QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2014 / 0 005 891 A1

[0005] DE 10 2020 201 589 B4

[0006] DE 10 2022 201 402 A1

[0006] DE 10 2020 127 661 A1

[0006] DE 10 2021 206 743 A1

[0006]

Claims

[1] Method for determining a steering wheel overlay torque (28) for transmission to a steering wheel (2) of a steer-by-wire steering system (1) of a vehicle (40), characterized by that the procedure includes the following steps: - receiving a request (22) from a driver assistance system for force or torque superposition for transmission to the wheels (5), which is proportional to a force transmitted to the wheels (5) by means of a rack (8), (11) - Determining a torque currently applied to the steering wheel (2) (current steering wheel torque) (23), (12) - converting (32) the detected current steering wheel torque (23) into a force or torque (25) which is proportional to the force transmitted to the wheels (5) by means of a rack (8), (13) - Determining a requested total force or a requested total torque (26), which is proportional to the force transmitted to the wheels (5) by means of a rack (8), by adding (34) the requested force or the requested torque (22) and the force or the torque (25) which was converted from the determined current steering wheel torque, (14) - Determining a total steering wheel torque (27) based on the determined requested total force or the determined requested total torque (26), (15) - Determining the steering wheel overlay torque (28) using the determined current steering wheel torque (23) and the determined total steering wheel torque (27). (16) [2] Method according to claim 1, characterized bythat the current steering wheel torque (23) is determined by means of a torque sensor and / or by means of software for determining the current steering wheel torque (23) based on known operating state variables of the vehicle (40). [3] Method according to claim 1 or 2, characterized by that the detected current steering wheel torque (23) is converted into a force or a torque (25) by means of an inverse conversion function or a conversion table (32). [4] Method according to claim 3, characterized by that the inverse conversion function or the conversion table (32) is based on a conversion function or a conversion table (31) which is designed to determine a feedback counter torque (24). [5] Method according to one of claims 1 to 4, characterized bythat the conversion of the determined requested total force or the requested total torque (26) is carried out by means of a function or a conversion table (31) which is designed to determine a feedback counter torque (24). [6] Method according to one of claims 1 to 5, characterized by that the same conversion function or the same conversion table (31, 32) is used to convert the detected current steering wheel torque (23) into a force or a torque (25) and to convert the determined requested total force or the requested total torque (26). [7] Method according to one of claims 1 to 6, characterized bythat a conversion function and / or a conversion table (31) is used which is designed to determine a feedback counter torque (24) based on at least one variable which represents the current rack steering force or a torque which is proportional to the steering force transmitted to the wheels (5). [8] Method according to one of claims 1 to 7, characterized by that the steering wheel superposition torque (28) is determined by subtracting the detected current steering wheel torque (23) and the determined total steering wheel torque (27). [9] Control method for a steer-by-wire steering system (1) of a vehicle (40), characterized by that the procedure includes the following steps: - Determining a steering wheel superposition torque (28) of a steer-by-wire steering system (1) of a vehicle (40) by means of a method according to one of claims 1 to 8, - determining a current feedback counter torque (24) on the steering wheel (2), - superimposing the current feedback counter torque (24) on the steering wheel (2) with the determined steering wheel superimposition torque (28) by means of an actuator (4) (29). [10] Method according to claim 9, characterized by that the current feedback counter torque (24) on the steering wheel (2) is determined based on a current rack torque applied to the wheels (5) of the vehicle (40). [11] Method according to claim 10, characterized by that the determined current feedback counter torque (24) and / or the steering wheel overlay torque (28) is adjusted if the current feedback counter torque (21) depends on at least one variable / parameter which is not representative of a current rack torque applied to the wheels (5) of the vehicle (40). [12] Control device (10) for controlling a steering wheel actuator (4) of a steer-by-wire steering system (1) of a vehicle (40), characterized by that the control device (10) comprises a device for receiving a request (22) from a driver assistance system for a force or torque superposition for transmission to the wheels (5), a device for determining a steering wheel superposition torque (28) by means of a method according to one of claims 1 to 8 and a device for determining a current feedback counter-torque (24) on the steering wheel and the control device (10) is designed to carry out a method according to one of claims 9 to 11. [13] Vehicle (40) comprising a steer-by-wire steering system (1) and a control device (10) according to claim 12. [14] A computer-implemented method comprising instructions which, when the program is executed by a computer, cause the computer to carry out a method according to any one of claims 1 to 11. [15] A computer program product comprising instructions which, when executed by a computer, cause the computer to carry out a method according to any one of claims 1 to 11. [16] A computer-readable data carrier on which the computer program product according to claim 15 is stored. [17] A data carrier signal carrying the computer program product according to claim 15.

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