Control unit, steer-by-wire steering system and method for generating a counter torque on a steering wheel of a steer-by-wire steering system

Abstract

Control unit (9) for an actuator (8) for generating a counter torque (M R ) on a steering wheel (4) of a steer-by-wire steering system (1), wherein the control unit (9) is designed to determine from a steering wheel angle (φ), a steering wheel angular speed (φ̇), a manual torque (M H ) on the steering wheel (4), a vehicle speed (V) and a rack force (F Z ) a resulting counter moment (M R ), whereby the resulting counter moment (M R ) contains a component for an active reset and a component due to the feedback from the road, wherein the control unit (9) contains a module (20) which is designed to calculate the steering angle (φ), the steering wheel angular speed (φ̇) and the manual torque (M H ) a rack force (F ZAR) based on the active return, wherein the control unit (9) has at least one adder (22) which calculates the rack force (F Z ) and the rack force (F ZAR ) due to the active return to a total rack force (F Zges ), characterized in that the control unit (9) has a further module (21), wherein the further module (21) is designed in such a way that from the total rack force (F Zges ) and the vehicle speed (V) the resulting counter torque (M R ), or the module (20) is designed to additionally generate a counter moment (M AR ) on the steering wheel (4) based on the active reset.

Description

[0001] The invention relates to a control unit, a steer-by-wire steering system and a method for generating a counter torque on a steering wheel of a steer-by-wire steering system according to the respective preamble of the independent claims.

[0002] Electromechanical steering systems (EPS Electric Power Steering) have been known and used for a long time.

[0003] Steer-by-wire steering systems lack the mechanical connection between a steering column and a rack that deflects the wheels. To still provide the driver with haptic feedback about the steering forces acting on the road, at least one actuator is provided on the steering column, which generates a counter-torque on the steering wheel of the steer-by-wire steering system. This actuator is typically an electric motor, connected to the steering column via a gearbox, for example. This is also referred to as a force feedback actuator. The resulting counter-torque that is applied has a component for actively returning the steering wheel and a component due to feedback from the road. The resulting counter-torque is calculated using a steering wheel angle, a steering wheel angular velocity, a hand torque, a vehicle speed, and a rack force, with the hand torque being a measured torque on the steering wheel.It should be noted that the steering wheel is generally understood here as a steering handle.

[0004] Such a control unit for calculating a resulting counter-torque or such a generic steer-by-wire steering system is known, for example, from DE 10 2018 132 865 A1.

[0005] From DE 10 2017 105 370 A1 a method for estimating a rack force in a steer-by-wire steering system is known.

[0006] One problem is adjusting the resulting counter-torque on the steering wheel so that the driver feels a familiar haptic sensation on the steering wheel.

[0007] A generic control unit for a steer-by-wire steering system is known from DE 10 2021 214 452 B3.

[0008] The invention is therefore based on the technical problem of creating a control unit for an actuator for generating a counter-torque on a steering wheel of a steer-by-wire steering system, by means of which a steering feel can be adjusted in an improved manner. A further technical problem is the creation of a corresponding steer-by-wire steering system and the provision of a corresponding method for calculating the resulting counter-torque.

[0009] The solution to the technical problem is provided by a control device having the features of claim 1, a steer-by-wire steering system having the features of claim 3 and a method having the features of claim 4. Further advantageous embodiments of the invention emerge from the subclaims.

[0010] The control unit for an actuator for generating a countertorque on a steering wheel of a steer-by-wire steering system is configured to calculate a resulting countertorque from a steering wheel angle, a steering wheel angular velocity, a manual torque on the steering wheel, a vehicle speed, and a rack force. The resulting countertorque includes a component for active return and a component due to road feedback. The control unit includes a module configured to calculate a rack force based on the active return from the vehicle speed, the steering wheel angle, the steering wheel angular velocity, and the manual torque. The control unit has at least one adder that adds the rack force and the rack force due to the active return to form a total rack force.The advantage of determining rack force based on active return is that well-tuned models of EPS systems exist, so they can be used. It should be noted that the rack force can be measured or estimated.

[0011] The control unit has a further module, wherein the further module is designed to calculate the resulting counter torque from the total rack force and the vehicle speed.

[0012] Alternatively, the module is designed to additionally calculate a counter torque on the steering wheel based on the active return.

[0013] Preferably, the control unit then has a further module, wherein the further module is configured to calculate a counter-torque based on the rack force from the total rack force and the vehicle speed. The control unit has a further adder that adds the counter-torque on the steering wheel due to the active return and the counter-torque due to the rack force to produce a resulting counter-torque. This embodiment is somewhat more complex, but allows for the somewhat simpler consideration of additional influencing variables.

[0014] In general, it should be noted that in addition to the steering wheel angular velocity, a steering wheel angular acceleration can also be taken into account in the calculation.

[0015] With regard to the configurations of the steer-by-wire steering system and the method for generating a counter-torque on a steering wheel of a steer-by-wire steering system, reference is made in full to the preceding explanations.

[0016] The invention is explained in more detail below using preferred embodiments. The figures show: Fig. 1 a schematic block diagram of a steer-by-wire steering system, Fig. 2 a schematic block diagram of a control unit in a first embodiment, Fig. 3 a schematic block diagram of a control unit in a second embodiment and Fig. 4 a schematic block diagram of a control unit according to the prior art.

[0017] In the Fig. Figure 1 shows a highly schematic block diagram of a steer-by-wire steering system 1. The steer-by-wire steering system 1 has a steering column module 2 and a steering gear module 3. The steering column module 2 has a steering handle in the form of a steering wheel 4, which is connected to a steering column 5. Arranged on the steering column 5 are a rotation angle sensor 6, a torque sensor 7, and an actuator 8, which is designed as an electric motor. The electric motor is mechanically coupled to the steering column 5, for example, via a gear (not shown). The actuator 8 is controlled by a control unit 9 in order to transmit counter-torques via the steering column 5 to the steering wheel 4, which generate haptic feedback for the driver.

[0018] The steering gear module 3 has at least one steering control unit 10, power electronics 11, a stator 12, and a rotor 13, wherein the rotor 13 is connected to a rack 14 via a gear (not shown). A rotor position sensor 15 is arranged on the rotor 13. The steering control unit 10, the power electronics 11, and the stator 12 are preferably redundant. The steering column module 2 and the steering gear module 3 are only connected for data purposes. The steering gear module 3 transmits a rack force F Z to the control unit 9. It is shown that the rack force F Z is estimated from the data of the rotor position sensor 15. However, it is also possible to calculate the rack force F Z directly. It is also possible that additional parameters are included in the estimation of the rack force F Z Various prior art methods are known to those skilled in the art.

[0019] Control unit 9 receives a steering wheel rotation angle φ as input and additionally generates a steering wheel rotation angle velocity φ̇. Further input variables are a vehicle speed V, a manual torque M H and the rack force F Z . The control unit 9 uses these input variables to determine a counter torque, which is then used up by the actuator 8.

[0020] Before the invention is explained in more detail, it will first be explained with reference to Fig. 4 the state of the art is explained.

[0021] The control unit 9 receives the aforementioned input variables and has a first module 16 and a second module 17. The first module 16 calculates, based on the input variables, steering wheel angle φ, steering wheel rotational speed ̇̇φ̇, manual torque M H and vehicle speed V a counter torque M ARdue to the active return of the steering wheel 4. In the second module 17, the vehicle speed V and the rack force F Z a counter-moment M FZ due to the rack force F Z calculated, whereby the two counter moments M AR and M FZ are added in an adder 18. The resulting counter torque M is then available at the output. R to.

[0022] In the Fig. Figure 2 shows a first embodiment of a control unit 9 according to the invention. The control unit 9 has a first module 20 and a further module 21. In the first module 20, the input variables vehicle speed V, steering wheel angle φ, steering wheel angle speed ̇φ̇ and manual torque M H a rack force F ZARfor active return. For this purpose, the familiar calculation rules for EPS steering systems can be used, where a return torque is calculated from a rack force. Accordingly, the calculation rules only need to be inverted. The rack force F ZAR Due to the active reset, the rack force F is then added to an adder 22. Z added. The result is then a total rack force F Zges . In the further module 21, the total rack force F Zges and the vehicle speed V the resulting counter torque M R This allows a very natural steering feel to be set on the steering wheel 4, drawing on many years of experience with EPS steering systems.

[0023] In the Fig.3 shows a further embodiment of the control unit 9, wherein the first module 20 additionally also has a counter torque M AR is calculated based on the active return. In a further module 23, the total rack force F Zges and the vehicle speed V a counter torque M ZF due to the total rack force F Zges which is then added in an adder 24 with the counter torque M AR due to the active return to the resulting counter torque M R is added. This embodiment is somewhat more complex, but offers more customization options. List of reference symbols 1 steer-by-wire steering system 2 steering column module 3. Steering gear module 4 steering wheel 5 Steering column 6 Angle sensor 7 Torque sensor 8 Actuator 9 Control unit 10 Steering control unit 11 Power electronics 12 Stator 13 Rotor 14 Rack 15 Rotor position sensor 16 Module 17 Module 18 adders 20 Module 21 Module 22 adders 23 Module 24 adders V Vehicle speed φ steering wheel angle φ̇ steering wheel rotational speed M H Hand torque F Z Rack force M FZ Counter torque due to the rack force M ZF Counter torque due to the total rack force F ZAR Rack force due to active return M R resulting counter torque M AR Counter torque due to active reset F Zges Total rack force

Claims

[1] Control unit (9) for an actuator (8) for generating a counter torque (M R ) on a steering wheel (4) of a steer-by-wire steering system (1), wherein the control unit (9) is designed to determine from a steering wheel angle (φ), a steering wheel angular speed (φ̇), a manual torque (M H ) on the steering wheel (4), a vehicle speed (V) and a rack force (F Z ) a resulting counter moment (M R ), whereby the resulting counter moment (M R ) contains a component for an active reset and a component due to the feedback from the road, wherein the control unit (9) contains a module (20) which is designed to calculate the steering angle (φ), the steering wheel angular speed (φ̇) and the manual torque (M H ) a rack force (F ZAR) based on the active return, wherein the control unit (9) has at least one adder (22) which calculates the rack force (F Z ) and the rack force (F ZAR ) due to the active return to a total rack force (F Zges ) is added, characterized by that the control unit (9) has a further module (21), wherein the further module (21) is designed in such a way that from the total rack force (F Zges ) and the vehicle speed (V) the resulting counter torque (M R ), or the module (20) is designed to additionally generate a counter moment (M AR ) on the steering wheel (4) based on the active reset. [2] Control device according to claim 1, characterized by that the control unit (9) has a further module (23), wherein the further module (23) is designed in such a way that from the total rack force (F Zges ) and the vehicle speed (V) a counter torque (MZF ) due to the rack force (F Z ), wherein the control unit (9) has a further adder (24) which calculates the counter torque (M AR ) on the steering wheel (4) due to the active return and the counter torque (M ZF ) due to the rack force (F Z ) to a resulting counter moment (M R ) is added. [3] Steer-by-wire steering system (1), comprising at least one actuator (8) for generating a resulting counter-torque (M R ) on a steering wheel (4) and a control unit (9) for calculating the resulting counter-torque (M R ), wherein the control unit (9) is designed in such a way that from a steering wheel angle (φ), a steering wheel angular speed (φ̇), a manual torque (M H ) on the steering wheel (4), a vehicle speed (V) and a rack force (F Z ) the resulting counter moment (M R ), whereby the resulting counter moment (M R) contains a component for an active reset and a component due to the feedback from the road, wherein the control unit (9) contains a module (20) which is designed to calculate the steering angle (φ), the steering wheel angular speed (φ̇) and the manual torque (M H ) a rack force (F ZAR ) based on the active return, wherein the control unit (9) has at least one adder (22) which calculates the rack force (F Z ) and the rack force (F ZAR ) due to the active return to a total rack force (F Zges ) added characterized by that the control unit (9) has a further module (21), wherein the further module (21) is designed in such a way that from the total rack force (F Zges ) and the vehicle speed (V) the resulting counter torque (M R ), or the module (20) is designed to additionally generate a counter moment (MAR ) on the steering wheel (4) based on the active reset. [4] Method for generating a counter torque (M R ) by an actuator (8) on a steering wheel (4) of a steer-by-wire system (1), by means of at least one control unit (9) and an actuator (8) which is connected to the steering wheel (4) via a steering column (5), wherein the control unit (9) is based on a steering wheel angle (φ), a steering wheel angular speed (φ̇), a manual torque (M H ) on the steering wheel (4), a vehicle speed (V) and a rack force (F Z ) a resulting counter moment (M R ), where the resulting counter moment (M R ) contains a component for an active reset and a component due to feedback from the road, whereby the calculated resulting counter torque (M R) is implemented by the actuator (8), wherein the control unit (9) determines the vehicle speed (V), the steering wheel angle (φ), the steering wheel angular speed (φ̇) and the manual torque (M H ) a rack force (F ZAR ) is calculated based on the active return, which is calculated with the rack force (F Z ) to a total rack force (F Zges ) is added, characterized by that the control unit (9) calculates the total rack force (F Zges ) and the vehicle speed (V) the resulting counter torque (M R ) or additionally a counter moment (M AR ) on the steering wheel (4) is calculated based on the active reset.

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