Device, vehicle and method for optimizing road feedback at a motor-movable control element of a steering system of a vehicle with a wheel steering angle actuator

Abstract

Device, vehicle and method for optimizing road feedback at a control element (106) of a steering system (104) of a vehicle (100) with a wheel steering angle actuator (108) that is movable by a motor (110), wherein an operating parameter of the steering system (104) is detected which characterizes an externally acting force or torque and / or acceleration at the wheel steering angle actuator (108), wherein a reference for the operating parameter, in particular an expected operating parameter or an expected dynamic of the operating parameter, is specified, wherein it is determined that the operating parameter deviates from the reference, wherein a motor torque for moving the control element (106) is determined depending on the operating parameter, and wherein the motor (110) is controlled depending on the motor torque when it is determined that the operating parameter deviates from the reference.

Description

State of the art

[0001] The invention relates to a device, a vehicle and a method for optimizing road feedback on a control element of a steering system of a vehicle with a wheel steering angle adjuster that can be moved by a motor.

[0002] In conventional steering systems such as electronically assisted steering systems or steer-by-wire systems, a driver of a vehicle on a level road is given a steering feel via the control element, which provides the driver with information about the steering and vehicle movement. Disclosure of the invention

[0003] The device, the vehicle and the method according to the independent claims provide a driver with feedback on high-frequency excitations at the wheel steering angle adjuster caused by the road surface, regardless of the steering feel on a level road surface.

[0004] The method for optimizing road surface feedback on a control element of a steering system of a vehicle with a wheel steering angle adjuster that can be moved by a motor provides that an operating variable of the steering system is detected that characterizes an externally acting force or an externally acting torque and / or an acceleration on the wheel steering angle adjuster, wherein a reference for the operating variable, in particular an expected operating variable or an expected dynamics of the operating variable, is specified, wherein it is determined that the operating variable deviates from the reference, wherein a motor torque for moving the control element is determined depending on the operating variable, and wherein the motor is controlled depending on the motor torque if it is determined that the operating variable deviates from the reference.

[0005] Preferably, a target movement of the steering system is specified, with the reference being determined based on the target movement and a vehicle movement. This provides feedback on deviations from the target movement caused by the road surface.

[0006] Preferably, it is provided that a check is carried out to determine whether a driver specifies a desired steering movement, with the engine torque being specified even if the driver does not specify a desired steering movement, or that the dynamics with which a driver specifies a desired steering movement are checked, with the engine torque being specified even if the driver does not specify any dynamics for the desired steering movement. This provides feedback even when the driver is not actively steering.

[0007] Preferably, it is determined that the operating variable is greater than the reference, and the engine torque is specified when it is determined that the operating variable is greater than the reference. This provides feedback at a larger operating variable than would be expected based on a steering movement by the driver.

[0008] Preferably, the operating variable characterizes an externally acting force or torque, or an acceleration of a motor of the wheel steering angle actuator. This provides feedback at a greater force dynamic or acceleration than would be expected based on the driver's steering movement.

[0009] It is preferably provided that a deviation of the operating variable of the steering system from the reference is mapped onto the engine torque with a factor or with a characteristic curve, in particular amplified or attenuated, or wherein the operating variable of the steering system is mapped onto the engine torque with a characteristic map depending on a further operating variable of the steering system, in particular a desired additional torque, or depending on an operating variable of the vehicle, in particular a vehicle speed or a vehicle lateral acceleration, in particular amplified or attenuated.

[0010] The reference for the expected dynamic response of the operating variable is preferably a cutoff frequency. A high-pass filter having the cutoff frequency is used to determine whether the operating variable deviates from the reference, and the engine torque is determined based on a portion of the operating variable passing through the high-pass filter. For example, a dynamic response greater than the reference frequency of, say, 5 Hz is reported back to the driver.

[0011] The reference for the expected dynamics can be an expected dynamics of the externally acting force or the externally acting moment, in particular an expected dynamics which is determined on the basis of a desired steering movement and other vehicle variables, in particular a vehicle speed or a lateral acceleration, or an expected dynamics of a steering movement with respect to an expected acceleration.

[0012] Preferably, the deviation of the operating variable or the motor torque is delayed by a dead-time element and / or filtered by a low-pass filter and / or limited by a limit value and / or a gradient of the operating variable or the motor torque is limited. The dead-time element and the low-pass filter prevent feedback due to noise. The limit value prevents excessive feedback.

[0013] The motor of the control element is preferably controlled or regulated depending on the engine torque.

[0014] The device for optimizing the road feedback on the control element of the steering system of the vehicle with the wheel steering angle adjuster, which control element can be moved by the motor, provides that the device comprises a device for detecting an operating variable of the steering system, which characterizes an externally acting force / torque and / or an acceleration on the wheel steering angle adjuster, and a device for regulating or controlling the motor, which is designed to control the motor with the method.

[0015] Further advantageous embodiments can be seen from the following description and the drawing. The drawing shows Fig. 1 a vehicle with a device for optimising road feedback, Fig. 2 steps in a process to optimize road feedback.

[0016] In Fig. 1, a vehicle 100 with a device 102 for optimizing road feedback is shown schematically.

[0017] The vehicle 100 includes a steering system 104.

[0018] The steering system 104 comprises an operating element 106, a wheel steering angle adjuster 108 and a motor 110 for moving the operating element 106.

[0019] In the example, the control element 106 is a steering wheel. Another control element, such as a joystick, may be provided.

[0020] The steering system 104 is, for example, an electronic power steering (EPS) or steer-by-wire (SbW) system. In the case of the SbW system, the wheel steering angle actuator 108 can be a central actuator, meaning the left and right wheels are mechanically connected to one or more motors. In the case of the SbW system, the wheel steering angle actuator 108 can be an individual wheel actuator, meaning the left and right wheels are not connected, with one motor per wheel or multiple motors per wheel. Depending on the design, the procedure is carried out individually for each axle or wheel.

[0021] The device 102 comprises a device 112 for detecting an operating variable of the steering system 104, which characterizes an externally acting force or an externally acting moment and / or an acceleration at the wheel steering angle adjuster 108.

[0022] The device 112 is designed, for example, to detect a torque or an acceleration on a rotor of a servo motor of the wheel steering angle adjuster 108.

[0023] The operating variable is, for example, the torque or the acceleration.

[0024] The device 102 comprises a device 114 for regulating or controlling the motor 110, which is designed to control the motor 110 using a method which is described below with reference to Fig. 2 is described.

[0025] The method comprises a step 200.

[0026] In step 200, a desired movement of the steering system 104 is specified.

[0027] For example, the target movement is specified by the driver of the vehicle 100, in particular by a movement of the control element 106.

[0028] It may be provided that, in addition to or instead of the driver, a check is performed to determine whether or not the driver has specified a desired movement of the steering system. For example, the engine torque is specified if the driver does not specify a desired movement. If the driver specifies a desired movement, step 200 is executed in this case; otherwise, step 202 is executed.

[0029] The method includes a step 202.

[0030] In step 202, a reference for a company variable is specified. In step 200, the reference is idealized to 0.

[0031] The reference is determined depending on the target movement and vehicle variables such as vehicle speed.

[0032] In the example, the operating variable characterizes an externally acting force or an externally acting moment on the wheel steering angle actuator 108.

[0033] The reference specifies the expected farm size or an expected dynamic of the farm size.

[0034] For example, the reference for the externally acting force or moment or their dynamics is determined using a sensor on the rotor of the actuator or by a calculation using an estimator based on internal quantities.

[0035] The method is also applicable to moments or accelerations at the wheel steering angle adjuster 108.

[0036] In this case, the operating variable characterizes an acceleration at the wheel steering angle adjuster 108.

[0037] For example, in this case, the reference specifies the acceleration of the actuator's rotor or its dynamics.

[0038] The method includes a step 204.

[0039] In step 204, an operating variable of the steering system 104 is recorded.

[0040] In the example, this characterizes the external force acting on the wheel steering angle actuator 108.

[0041] The method includes a step 206.

[0042] In step 206, it is determined whether the operating variable deviates from the reference. The reference is, for example, a high-pass filtered force or a maximum dynamic force depending on, for example, the vehicle speed.

[0043] It may be provided that a determination is made as to whether the operating variable is greater than the reference or not. It may be provided that step 208 is executed if it is determined that the operating variable is greater than the reference or if there is a deviation from the reference.

[0044] If the operating variable deviates from the reference, step 208 is executed. Otherwise, step 200 is executed.

[0045] In step 208, a motor torque for moving the control element 106 is determined depending on the operating variable.

[0046] For example, the deviation of the operating variable of the steering system 104 from the reference is mapped to the engine torque using a factor or a characteristic curve.

[0047] The factor or the characteristic curve, for example, has a reinforcing effect, at least in sections.

[0048] The factor or the characteristic curve, for example, has a weakening effect, at least in sections.

[0049] The operating variable of the steering system 104 is mapped to the engine torque, for example, using a characteristic map depending on another operating variable of the steering system 104.

[0050] In one embodiment, the further operating variable is a desired additional torque of the steering system 104.

[0051] For example, the target additional torque and the force or acceleration difference are mapped to the engine torque using the characteristic map.

[0052] In one embodiment, an operating variable of the vehicle 100, in particular a vehicle speed or a vehicle lateral acceleration, is mapped to the engine torque using the characteristic map.

[0053] The characteristic map has a reinforcing effect, at least in sections.

[0054] The characteristic map, for example, has a weakening effect, at least in sections.

[0055] In one embodiment, the operating variable or the motor torque is changed by a dead zone.

[0056] In one embodiment, the operating variable or the motor torque is filtered by a low-pass filter.

[0057] In one embodiment, the operating variable or the motor torque is limited by a limit value.

[0058] In one embodiment, a gradient of the operating size or the engine moment is limited.

[0059] An example for calculating the motor torque involves mapping the operating variable to a force, which is then converted into the motor torque.

[0060] For example, the force is determined as a function of a quantity for describing a desired acceleration of the steering system 104, ie a rotor acceleration, on the basis of a rack position specification.

[0061] For example, the force is determined as a function of a quantity describing an actual acceleration of the steering system 104, ie a rotor acceleration. For example, the calculation includes the following functional parts:

[0062] Scaling of an acceleration difference, i.e., the deviation between the target acceleration, i.e., the reference, and the actual acceleration, i.e., the operating variable. Scaling is performed, for example, using a factor or a characteristic curve.

[0063] Calculation of a disturbance acceleration, ie, the acceleration to be generated by the motor torque at control element 106. The disturbance acceleration is, for example, the scaled acceleration difference.

[0064] Conversion of the disturbance acceleration to the motor torque. Optionally, saturation of the disturbance acceleration or the motor torque to the limit value can be provided. Instead of using the motor torque, a target manual torque can also be used, which is controlled by the motor 110.

[0065] It can be provided that a sign of the acceleration or force is changed in order to determine acceleration and motor torque correctly for further use.

[0066] A step 210 is then executed.

[0067] In step 210, the motor 110 is controlled depending on the motor torque.

[0068] This means that the motor 110 is controlled depending on the motor torque or the target manual torque if it is determined that the operating variable deviates from the reference.

[0069] The motor 110 is controlled, for example, depending on the motor torque or, in particular, controlled with a PID controller to adjust the desired manual torque.

[0070] By changing the engine torque, the driver receives feedback on control element 106.

[0071] It can be provided that the reference for the expected dynamics of the operating variable is a cutoff frequency. This cutoff frequency is specified as a reference, for example, in step 202. For example, in step 206, a high-pass filter having the cutoff frequency is used to determine that the operating variable deviates from the reference. In this case, the deviation is a portion of the operating variable that passes through the high-pass filter. For example, in step 210, the engine torque is determined as a function of the portion of the operating variable that passes through the high-pass filter.

[0072] It can be provided that the reference for the expected dynamics is specified, whereby the force is limited by a gradient limitation and a disturbance is eliminated by forming the difference between the unlimited and limited force.

Claims

[1] Method for optimising road feedback on a control element (106) of a steering system (104) of a vehicle (100) with a wheel steering angle adjuster (108) which can be moved by a motor (110), characterized by that an operating variable of the steering system (104) is detected (204), which characterizes an externally acting force or an externally acting torque and / or an acceleration at the wheel steering angle adjuster (108), wherein a reference for the operating variable, in particular an expected operating variable or an expected dynamics of the operating variable, is specified (202), wherein it is determined (206) that the operating variable deviates from the reference, wherein a motor torque for moving the control element (106) is determined (208) depending on the operating variable, and wherein the motor (110) is controlled (210) depending on the motor torque if it is determined that the operating variable deviates from the reference. [2] Method according to claim 1, characterized bythat a desired movement of the steering system (104) is specified (200), wherein the reference is determined depending on the desired movement and a vehicle movement (202). [3] Method according to one of the preceding claims, characterized by that it is checked (200) whether a driver specifies a desired movement of the steering system or not, whereby the engine torque is also specified (210) if the driver does not specify a desired movement, or whereby it is checked with which dynamics a driver specifies a desired steering movement, whereby the engine torque is also specified if the driver does not specify any dynamics of the desired steering movement. [4] Method according to one of the preceding claims, characterized by that it is determined (206) that the operating variable is greater than the reference, wherein the engine torque is specified (210) if it is determined that the operating variable is greater than the reference. [5] Method according to one of the preceding claims, characterized bythat the operating variable characterizes an externally acting force or an externally acting moment or an acceleration of the wheel steering angle adjuster (106). [6] Method according to one of the preceding claims, characterized by that a deviation of the operating variable of the steering system (104) from the reference is mapped to the engine torque, in particular amplified or attenuated, with a factor or with a characteristic curve (208) or wherein the operating variable of the steering system (104) is mapped to the engine torque, in particular amplified or attenuated, with a characteristic map depending on a further operating variable of the steering system, in particular a desired additional torque, or depending on an operating variable of the vehicle (100), in particular a vehicle speed or a vehicle lateral acceleration. [7] Method according to one of the preceding claims, characterized bythat the reference for the expected dynamics of the operating variable is a cut-off frequency, wherein a high-pass filter having the cut-off frequency is used to determine (206) that the operating variable deviates from the reference, and wherein the engine torque is determined as a function of a portion of the operating variable passing through the high-pass filter (208). [8] Method according to one of the preceding claims, characterized by that the reference for the expected dynamics is an expected dynamics of the externally acting force or the externally acting moment, in particular an expected dynamics which is determined on the basis of a target steering movement and other vehicle variables, in particular a vehicle speed or a lateral acceleration, or an expected dynamics of a steering movement with respect to an expected acceleration. [9] Method according to one of the preceding claims, characterized bythat the operating variable or the engine torque is delayed by a dead-time element and / or filtered by a low-pass filter and / or limited by a limit value (208) and / or that a gradient of the operating variable or the engine torque is limited (208). [10] Method according to one of the preceding claims, characterized by that the motor (110) is controlled or regulated depending on the motor torque (210). [11] Device (102) for optimising road feedback on a control element (106) of a steering system (104) of a vehicle (100) with a wheel steering angle adjuster (108) which can be moved by a motor (110), characterized bythat the device (102) comprises a device (112) for detecting an operating variable of the steering system (104), which characterizes a force and / or an acceleration at the wheel steering angle adjuster (108), and a device (114) for regulating or controlling the motor (110), which is designed to control the motor (110) using the method according to one of claims 1 to 10. [12] Vehicle (100), characterized by that the vehicle (100) comprises the device (102) for optimizing road feedback on an operating element (106) of a steering system (104) of a vehicle (100) with a wheel steering angle adjuster (108) according to claim 11, which operating element can be moved by a motor (110).

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