Method and device for controlling a steering system

Abstract

The invention relates to a device and a method for controlling a steering system, wherein a target wheel steering angle speed (232) is determined on the basis of a target value (206) specified at a handle (104) of the steering system by a driver, in particular a force applied to the handle by the driver or a torque applied to the handle by the driver, and a wheel adjuster (106) for adjusting the wheel steering angle of steered wheels is controlled on the basis of the target wheel steering angle speed (232).

Description

[0001] Description

[0002] title

[0003] Method and device for controlling a

[0004] State of the art

[0005] The invention relates to a method and a device for controlling a steering system.

[0006] In an electric power steering system (EPS), a servo unit of the EPS is controlled by a controller in which, depending on the operating torque of a driver measured on a steering wheel of the EPS, in particular on a torsion bar of the EPS, a previously applied assistance torque is applied by the servo unit and the required steering forces of the driver are thereby reduced to comfortable values.

[0007] In a steering system with actively controlled steering feel, the torque is adjusted on the torsion bar, providing the driver with a previously applied steering feel. A steering angle specified by the driver on a steering wheel of the steering system is transmitted mechanically, for example, via a steering column and a steering pinion of the steering system to a steering rack and thus to the wheels.

[0008] A steer-by-wire (SbW) steering system based on this also detects a steering angle specified by the driver on the steering wheel and adjusts a desired torque on the torsion bar as feedback to the driver. The desired steering angle is transmitted to the wheels via a wheel actuator in the SbW steering system.

[0009] A self-steering steering system eliminates the mechanical coupling between the torsion bar and the wheel actuator. This provides new freedom in steering ratio design and the possibility of using a control element other than the steering wheel.

[0010] Instead of the steering wheel, a joystick or a joystick for each hand or other suitable steering input media can be used as an alternative control element.

[0011] These other controls make the steering wheel superfluous and offer new freedom in interior design.

[0012] For example, a handling angle specified by the driver is detected on the control element and a target wheel steering angle is calculated from the handling angle specified by the driver.

[0013] Due to the lack of a mechanical connection to the wheel actuator and thus to the wheels, a ratio (VSR - Variable Steering Ratio) between the control element and the wheel can be freely designed.

[0014] This design freedom can be used, for example, to make the steering ratio more direct. This reduces the steering angle required at the control element, increasing comfort for the driver.

[0015] Alternative control elements, such as a joystick, are very straightforward in design.

[0016] The resulting very direct transmission from the control element, i.e., the handle, to the steered wheels can sometimes result in a very dynamic and undesirably strong vehicle reaction. The selected transmission ratio (VSR) therefore represents only a compromise between the maximum steerable handle angle and the tolerable vehicle reaction.

[0017] If the VSR is set too directly, or if it is designed to be very direct with alternative control elements installed, even small dynamic steering inputs from the driver will result in violent vehicle reactions. This strong vehicle reaction significantly reduces the comfort level for both driver and passengers.

[0018] Disclosure of the invention

[0019] The method and device according to the independent claims implement a so-called force-based approach, in which the driver does not directly specify the steering angle, and the steering feel or torque is not adjusted as feedback for the driver. Instead, a target wheel steering angular velocity is determined from the force applied by the driver or the torque applied to the handle. As a result, the vehicle steers faster, the greater the force applied by the driver or the torque applied to the handle. This vehicle response represents a significantly increased sense of comfort for the driver and passengers.

[0020] The method for controlling a steering system provides that a target wheel steering angle speed is determined depending on a target value specified by a driver on a handle of the steering system, in particular a force applied by the driver to the handle or a moment applied by the driver to the handle, wherein a wheel actuator for setting a wheel steering angle of steered wheels is controlled depending on the target wheel steering angle speed.

[0021] Preferably, a centering angular velocity is determined as a function of the target value, the actual wheel steering angle and / or an actual wheel steering angular velocity determined as a function of the actual wheel steering angle and / or as a function of a rack force which is measured, determined based on a model or calculated from steering-internal measured variables, with which the steering system returns to an actual wheel steering angle for straight-ahead travel, wherein the target wheel steering angular velocity is reduced by the centering angular velocity.

[0022] Preferably, a vehicle speed of a vehicle steered by the steering system is detected, wherein the centering angular velocity is determined as a function of the vehicle speed. Preferably, the method for controlling the steering system with two handles provides that an actual value is detected for each handle, and the actual value for determining the target wheel steering angular velocity is determined as a function of the sum of the actual values ​​detected for each handle.

[0023] Preferably, the target wheel steering angle speed is integrated into a target wheel steering angle, wherein the wheel actuator is controlled to set the target wheel steering angle of the steered wheels.

[0024] Preferably, a target handling angle is determined as a function of an actual wheel steering angle and a transmission characteristic curve, wherein the actual wheel steering angle is detected by a sensor or determined by integrating the target wheel steering angular speed, wherein a target motor torque for an actuator on the handle is determined as a function of the actual handling angle and the target handling angle.

[0025] Preferably, the transmission characteristic curve assigns increasingly disproportionate values ​​of the target handling angle to the actual wheel steering angle in a first range, which starts from the actual wheel steering angle for straight-ahead driving or cornering with large curve radii, with increasing deflection from straight-ahead driving.

[0026] Preferably, the transmission characteristic curve assigns disproportionate values ​​of the target handling angle to the actual wheel steering angle in a second range, which starts from cornering with small to very small curve radii and ends with the maximum actual wheel steering angle, with further increasing deflection from straight-ahead driving.

[0027] Preferably, a vehicle speed of a vehicle steered by the steering system is detected, wherein the gear ratio is determined from a characteristic map that assigns the value of the target handling angle to the value of the actual wheel steering angle depending on the vehicle speed.

[0028] Preferably, a vehicle speed of a vehicle steered by the steering system is detected, wherein the target steering angle is determined from a characteristic map that assigns the value of the target steering angle to the value of the actual wheel steering angle depending on the vehicle speed. Preferably, the target wheel steering angular speed is determined depending on a steering feel torque, wherein the steering feel torque is determined depending on a vehicle speed, a force applied by the wheel actuator, a torque applied by the driver to the steering handle, and a wheel steering angle set by the wheel actuator.

[0029] Preferably, a wheel steering angular velocity is determined iteratively as a function of the sum of the torque applied by the driver and the steering feel torque, in particular wherein the sum of the torque applied by the driver and the steering feel torque and the vehicle speed are mapped to the wheel steering angular velocity using a characteristic map, and the steering feel torque is determined as a function of the wheel steering angular velocity. This means that the wheel steering angular velocity is used to determine the steering feel torque.

[0030] The device for controlling a steering system provides that the device is designed to detect an actual value specified by a driver on a handle of the steering system, in particular a force applied by the driver to the handle or a moment applied by the driver to the handle, and to control a wheel actuator for setting a wheel steering angle of steered wheels using the method for controlling the steering system.

[0031] A vehicle comprising the steering system and the device may also be provided.

[0032] Further advantageous embodiments can be found in the following description and the drawing. The drawing shows:

[0033] Fig. 1 shows a vehicle with a steering system and a device for controlling the steering system,

[0034] Fig. 2 is a block diagram of parts of a first controller for the steering system, Fig. 3 is a block diagram of parts of a second controller for the steering system, Fig. 4 is a block diagram of parts of a third controller for the steering system, Fig. 5 is a block diagram of parts of a fourth controller for the steering system, Fig. 6 is a block diagram of a first part of the controller for determining a target wheel steering angular speed for the steering system,

[0035] Fig. 7 is a block diagram of a second part of the controller for determining a target torque for the steering system,

[0036] Fig. 8 shows a characteristic curve for a transmission ratio,

[0037] Fig. 9 is a flowchart showing steps of a method for controlling the steering system.

[0038] Figure 1 schematically illustrates a vehicle 100 with a steering system 102.

[0039] The steering system 102 comprises a handle 104 and a wheel actuator 106.

[0040] The vehicle 100 includes steered wheels 108. The vehicle 100 includes a device 110 for controlling the steering system 102. In the example, the steering system 102 includes the device 110.

[0041] The wheel adjuster 106 is designed to adjust a wheel steering angle on the steered wheels 108 of the vehicle 100.

[0042] The steering system 102 includes a sensor 112 for the wheel steering angle. It may be provided that the wheel steering angle is determined from another sensor signal, such as the rack position or the motor angle. In the example, the steering system 102 includes a sensor 114 for the force with which the wheel actuator 106 steers the steered wheels 108. It may be provided that the force is calculated.

[0043] The device 110 comprises a controller for controlling the steering system 102.

[0044] Examples of the controller are described below.

[0045] The exemplary controllers are designed differently in the examples depending on the type of handle 104 or the type of wheel actuator 106. Figure 2 shows a block diagram of parts of a first controller for the steering system 102.

[0046] The first controller is configured to receive a vehicle speed 202 from a vehicle communication bus 204.

[0047] The first controller is configured to receive a torque 206 applied by a driver to the handle 104 from a torque sensor 208. The torque 206 applied by the driver to the handle 104 is an example of a measured value of the driver's command for the first controller. The driver's command can also be the measured value of a force applied by the driver to the handle.

[0048] The first controller is designed to receive the actual steering angle 210 currently present at the handle 104 from a steering angle sensor 212.

[0049] The first controller is designed to output a desired motor torque 214 for controlling an actuator 216 for the handle 104.

[0050] The first controller is designed to control the wheel actuator 106 with a target engine torque 218, which is set with an actuator 220 for the wheel actuator 106.

[0051] The first controller is configured to receive a force 222 provided by the wheel actuator 106 from the force sensor 114. The force 222 can also be calculated using a model or based on other variables.

[0052] The first controller is configured to receive a wheel steering angle 224 set by the wheel actuator 106 from the wheel steering angle sensor 112.

[0053] Optionally, the sensor 112 is designed to output a set wheel steering angular velocity 225.

[0054] The first controller comprises a block 226 for determining a target torque 228. The first controller comprises a block 230 for determining a target wheel steering angular velocity 232 and a wheel steering angular velocity 233.

[0055] The first controller comprises a block 234 for determining the target engine torque 218. The block 234 for determining the target engine torque 218 is designed to determine the target engine torque 218 depending on the set wheel steering angular speed 225 and depending on the target wheel steering angular speed 232.

[0056] The first controller comprises a block 236 for determining a target handling angle 238. The block 236 for determining the target handling angle 238 is designed to determine the target handling angle 238 as a function of the set wheel steering angle 224 and as a function of the vehicle speed 202. To avoid the influence of an actual wheel steering angle signal corrupted by measurement noise or other disturbances, it can be provided to integrate the target wheel steering angular speed 232 to form a target wheel steering angle and to use this target wheel steering angle instead of the set wheel steering angle 224. When integrating the target wheel steering angular speed 232 to form the target wheel steering angle, care is taken to ensure correct initialization and to limit the internal integrator state to a maximum possible wheel steering angle.

[0057] With an offset-affected torque sensor 208 and a resulting target wheel steering angle speed 232 that is different from zero, drifting of the resulting target wheel steering angle signal 232 is prevented in the stationary state.

[0058] The first controller comprises a block 240 for determining the target engine torque 214. The block 240 for determining the target engine torque 214 is designed to determine the target engine torque 214 as a function of the target handling angle 238 and as a function of the currently set actual handling angle 210. The block 240 comprises, for example, an angle controller designed to output the target engine torque 214 to provide feedback on the target handling angle 238. The block 226 for determining the steering feel torque 228 is designed to determine the steering feel torque 228 as a function of the vehicle speed 202, the force 222, the torque 206 applied by the driver to the handle 104, the set wheel steering angle 224, and the wheel steering angular speed 233.

[0059] In the example, block 230 is configured to determine the target wheel steering angular speed 232 as a function of the vehicle speed 202, the torque 206 applied by the driver to the handle 104, the steering feel torque 228, and the set wheel steering angle 224. In the example, the vehicle speed 202, the torque 206 applied by the driver to the handle 104, the steering feel torque 228, and the set wheel steering angle 224 are mapped to the target wheel steering angular speed 232 using a characteristic map.

[0060] In the example, the block 234 for determining the desired engine torque 218 is arranged in a rack actuator 242, which comprises the wheel actuator 106, the sensor 112 for the wheel steering angle, the sensor 114 for the force and the actuator 220 for controlling the wheel actuator 106.

[0061] In the example, the other blocks, the handle 104, the torque sensor 208, the steering angle sensor 212, and the actuator 216 for the handle 104, are arranged in a steering wheel actuator 244. In the example, the steering wheel actuator 224 is configured to receive the vehicle speed 202 from the vehicle communication bus 204.

[0062] Figure 3 shows a block diagram of parts of a second controller for the steering system 102. The second controller is designed like the first controller, except for the following differences.

[0063] Instead of block 230 for determining the target wheel steering angular speed 232, the second controller comprises a block 302 for determining a target wheel steering angle 304. Instead of block 234 for determining the target engine torque 218 as a function of the target wheel steering speed 232, the second controller comprises a block 306 for determining the target engine torque 218 as a function of the target wheel steering angle 304.

[0064] Figure 4 shows a block diagram of parts of a third controller for the steering system 102. The third controller is designed like the first controller, except for the following differences.

[0065] The third controller is designed without angle feedback. The third controller uses neither the steering angle 210 set on the handle 104 nor the target engine torque 214. This means that the steering system 102 can be designed without the steering angle sensor 212 and actuator 216 for the handle 104.

[0066] The third controller includes neither the block 236 for determining the handling angle 238 nor the block 240 for determining the target engine torque 214.

[0067] Figure 5 shows a block diagram of parts of a fourth controller for the steering system 102. The fourth controller is designed like the first controller, except for the following differences.

[0068] The steering system 102 has two handles 104 with respective torque sensors 208, steering angle sensors 212 and actuators 216.

[0069] In the example, a torque 502 applied by the driver for each handle is added to the torque 206 applied by the driver.

[0070] For each handle 104, a block 240 is provided for determining a respective target engine torque 214 depending on the set steering angle 210 of the respective handle 104.

[0071] Figure 6 shows a block diagram of a first part of the controller for determining the desired wheel steering angular velocity 232 for the steering system 102. In the example, the block 230 for determining the desired wheel steering angular velocity 232 or the block 302 for determining the desired wheel steering angle 304 comprises the first part.

[0072] The first part comprises a block 602 for determining a wheel steering angular velocity 604. In the example, the wheel steering angular velocity 233 is the wheel steering angular velocity 604 determined by block 602. The block 602 for determining the wheel steering angular velocity 604 is designed to determine the wheel steering angular velocity 604 as a function of a sum of the torque 206 applied by the driver and the steering feel torque 228 and as a function of the vehicle speed 202. In the example, it is provided that the sum of the torque 206 applied by the driver and the steering feel torque 228 and the vehicle speed 202 are mapped to the wheel steering angular velocity 604 using a characteristic map.

[0073] The map is tuned, for example, so that the driver can achieve the maximum possible wheel steering angle speed with a steering torque that is just comfortable for him. A major advantage of this concept is that the driver cannot oversteer the wheel actuator 106 and thus cannot become out of phase, because this is prevented by the wheel steering angle feedback to the driver.

[0074] The first part comprises a block 606 for determining a centering angular velocity 608. The block 606 for determining the centering angular velocity 608 is designed to determine the centering angular velocity 608 as a function of the torque 206 applied by the driver, as a function of the vehicle speed 202, the force 222, the set wheel steering angle 224, and a set wheel steering angular velocity 610. In the example, the wheel steering angular velocity 225 output by the sensor 112 is used as the set wheel steering angular velocity 610. It can be provided to derive the set wheel steering angle 224 from the wheel steering angular velocity 610. In the example, it is provided that the torque 206 applied by the driver, the vehicle speed 202, the set wheel steering angle 224, and the set wheel steering angular velocity 610 are mapped to the centering angular velocity 608 using a characteristic map.Determining the centering angular velocity 608 from the wheel steering angular velocity 610 and the force 222 has the advantage of obtaining a more natural return behavior, which also takes into account, for example, different vehicle loads, tires and road friction coefficients.

[0075] The characteristic map for the centering angular velocity 608 is set, for example, so that the driver does not have to actively steer back to straight-ahead driving, and the current wheel steering angle is not maintained when the handle 104 is released. This prevents the vehicle from entering a stationary circular motion. During operation with the handle 104 gripped by the driver, the driver feels a counter-torque that attempts to move the handle 104 back to the center position. With a suitable application, this can already provide a simple steering feel.

[0076] In addition to the first part, block 302 for determining the desired wheel steering angle 304 includes an integrator 612 that integrates the desired wheel steering angular velocity 232 into the desired wheel steering angle 304. Optionally, the desired wheel steering angle 304 is determined as a function of the set wheel steering angle 224 and the desired wheel steering angular velocity 232.

[0077] Figure 7 shows a block diagram of a second part of the controller for determining the steering feel torque 228 for the steering system 102.

[0078] The second part allows for the adjustment of many aspects that are taken into account when tuning for good steering feel. The following application functions make it possible to specifically map aspects relevant to steering feel, such as friction, damping, inertia, and the lateral forces on the steered wheels 108, into the steering feel torque 228.

[0079] The second part comprises a block 702 for determining a first component 704 of the steering feel torque 228 depending on the force 222 applied by the wheel actuator 106 and the torque 206 applied by the driver. The block 702 for determining the first component 704 comprises, for example, a set of characteristic curves from which a characteristic curve is selected depending on the vehicle speed 202. The characteristic curves from the set of characteristic curves are designed to map the applied force 222 to the first component 704. This represents force feedback of the controller.

[0080] The second part comprises a block 706 for determining a second component 708 of the steering feel torque 228 as a function of the torque 206 applied by the driver and the vehicle speed 202. The block 706 for determining the second component 708 comprises a friction coefficient modeling that is dependent on the vehicle speed 202 and the torque 206 applied by the driver, which models the second component 708 as a function of the respective vehicle speed 202 and the respective torque 206.

[0081] The second part comprises a block 710 for determining a third component 712 of the steering feel torque 228 as a function of the torque 206 applied by the driver, the vehicle speed 202 and the wheel steering angular velocity 610. The block 710 for determining the third component 712 comprises a damping modeling that is dependent on the vehicle speed 202, the torque 206 applied by the driver and the wheel steering angular velocity 610, which models the third component 712 as a function of the respective vehicle speed 202 and the respective torque 206 and the respective wheel steering angular velocity 610.

[0082] The second part comprises a block 714 for determining a fourth component 716 of the steering feel torque 228 as a function of the torque 206 applied by the driver, the vehicle speed 202 and the wheel steering angular velocity 610. The block 714 for determining the fourth component 716 comprises an inertial modeling dependent on the vehicle speed 202, the torque 206 applied by the driver and the wheel steering angular velocity 610, which models the fourth component 716 as a function of the respective vehicle speed 202 and the respective torque 206 and the respective wheel steering angular velocity 610.

[0083] The use of the wheel steering angular velocity 610 as input of the steering feel functions in block 710 for damping modeling and in block 716 for inertia modeling has the great advantage that the inertia and the damping do not influence the centering angular velocity and thus centering behavior when the control element is not held can be applied independently of the inertia and damping feel for the behavior when the control element is held.

[0084] In the example, the first part 704, the second part 708, the third part 712 and the fourth part 716 are added to the target torque 228.

[0085] Figure 8 shows a transmission characteristic curve with which the target handling angle 800, normalized to the maximum handling angle, can be determined depending on the actual wheel steering angle 224. Multiplying the normalized target handling angle 800 by the currently applied maximum handling angle results in the target handling angle 238.

[0086] A value 802 of the actual wheel steering angle 224 for straight-ahead travel, in the example 0°, is assigned a value of the standardized target handling angle 800 for straight-ahead travel, in the example 0.

[0087] A value 804 of the actual wheel steering angle 224 for a maximum steering angle of the steering system 102, in the example 31°, is assigned a value of the standardized target handling angle 800 of 1.

[0088] The exemplary transmission characteristic curve 806 assigns a value of the actual wheel steering angle 224, between the value 802 of the actual wheel steering angle 224 for straight-ahead travel and the value 804 of the actual wheel steering angle 224 for the maximum steering angle, a value of the standardized desired handling angle 800, which is disproportionately large compared to the standardized desired handling angle resulting from the proportional transmission characteristic curve 812.

[0089] In the example, the transmission characteristic curve 806 assigns increasingly disproportionate values ​​of the standardized target handling angle 800 to the actual wheel steering angle 224 in a first range 808, which is based on the actual wheel steering angle for straight-ahead travel or cornering with large curve radii, with increasing deflection from straight-ahead travel.

[0090] The exemplary transmission characteristic curve 806 assigns to the actual wheel steering angle 224 in a second range 810, which starts from cornering with small to very small curve radii and ends with the maximum actual wheel steering angle, decreasing disproportionate values ​​of the standardized target handling angle 800 with increasing deflection from straight-ahead driving.

[0091] An alternative implementation provides for the target handling angle 238 to be determined directly from the actual wheel steering angle 224 using the transmission characteristic curve 806 instead of the standardized target handling angle 800.

[0092] A dashed transmission curve 812 is a transmission ratio that is constant over the actual wheel steering angle 224.

[0093] The advantage of the disproportionate gear ratio according to gear ratio characteristic curve 806 is the possibility of selecting an indirect gear ratio for the normal driving range (small wheel steering angles) and a significantly more direct gear ratio when steering and near the end stop. This allows for significantly reduced vehicle reaction in the normal driving range while still maintaining a very small steering angle range at the handle 104.

[0094] A special application variant of the transmission is when the standardized target steering angle is applied to 0 across the entire actual wheel steering angle 224. This means that the actual wheel steering angle 224 is not reported back to the control element. Rather, the handle 104 is blocked. The driver then always feels a blocked control element, and by pressing the handle 104, e.g., to the right or left, the driver steers the vehicle. This means that no actuator or angle sensor is required on the handle 104. This has cost and packaging advantages.

[0095] A preferred implementation of this variant without actively controlled handle angle, i.e., without an electromechanical actuator and without a handle angle sensor, is a passive, mechanical mount or guide for the handle with a suitably constant or variable stiffness, which allows a relatively small angle of rotation of the handle depending on the force applied by the driver. For improved steering feel and hands-off behavior, the mount features a pleasant friction and damping torque. It is important that the spring stiffness is large enough to transfer the handle to the position for straight-ahead travel after the handle is released, despite friction and damping. The torque sensor for the force or torque applied by the driver is integrated into this mount.

[0096] Figure 9 shows a flowchart with steps of a method for controlling the steering system.

[0097] The method includes a step 902.

[0098] In step 902, an actual value 206 specified by a driver on a handle 104 of the steering system 102 is measured.

[0099] The actual value 206 is, for example, the force applied by the driver to the handle 104 or the moment applied by the driver to the handle 104.

[0100] In a steering system 102 with two handles 104 for the right and left hand, the actual value 206 is, for example, the sum of the individual actual values ​​502, ie, for example, the sum of the force applied by the driver with both hands or the sum of the moment applied by the driver with both hands.

[0101] The method includes a step 904.

[0102] In step 904, the target wheel steering angular velocity 232 is determined.

[0103] In the example, the target wheel steering angular velocity 232 is determined depending on the steering feel torque 228. The steering feel torque 228 is determined, for example, depending on the vehicle speed 202, the force 222, the torque 206 applied by the driver to the handle 104, and the set wheel steering angle 224.

[0104] In the example, the target wheel steering angular velocity 232 is reduced by the centering angular velocity.

[0105] The centering angular velocity is determined, for example, depending on the actual value 206, the actual wheel steering angle 224 and / or depending on the actual wheel steering angular velocity, which is determined depending on the actual wheel steering angle 224. It can also be provided that the centering angular velocity is determined depending on the vehicle speed 202.

[0106] The method includes a step 906.

[0107] In step 906, the wheel actuator 106 is controlled to set a wheel steering angle of steered wheels 108 depending on the desired wheel steering angular speed 232.

[0108] It can be provided that the wheel actuator 106 is controlled to adjust a wheel steering angle of steered wheels 108 depending on the desired wheel steering angle 304, which is integrated depending on the desired wheel steering angular speed 232.

[0109] If feedback to the driver is provided, the procedure may include additional steps to determine this feedback and report it back to the driver.

[0110] The method optionally includes a step 908.

[0111] In step 908, a desired handling angle 238 is determined depending on the actual wheel steering angle 224 and the transmission characteristic curve 806.

[0112] The actual wheel steering angle 224 is detected, for example, by the wheel steering angle sensor 112. Alternatively, the actual wheel steering angle 224 is determined, for example, by integrating the desired wheel steering angular velocity 232.

[0113] With the ratio characteristic curve 806, for example, a value of the standardized target handling angle 800 is assigned to the value of the actual wheel steering angle 224 between the value 802 of the actual wheel steering angle 224 for straight-ahead travel and the value 804 of the actual wheel steering angle 224 for the maximum steering angle of the steering system 102, which is disproportionately large compared to a value proportional to the actual wheel steering angle 224. For example, the ratio characteristic curve 806 assigns increasingly disproportionate values ​​of the standardized target handling angle 800 to the actual wheel steering angle 224 in the first range 808 with increasing deflection from straight-ahead travel.

[0114] For example, the transmission characteristic curve 806 assigns decreasingly disproportionate values ​​of the standardized desired handling angle 238 to the actual wheel steering angle 224 in the second range 810 with further increasing deflection from straight-ahead travel.

[0115] It can also be provided that the transmission characteristic curve is determined from a characteristic map which additionally assigns the value of the standardized target handling angle 800 to the value of the actual wheel steering angle 224 depending on the vehicle speed 202.

[0116] The target handling angle 238 is determined from the standardized target handling angle and the currently valid maximum handling angle.

[0117] The method optionally includes a step 910.

[0118] In step 910, the target motor torque 214 for the actuator on the handle 104 is determined depending on the actual handle angle 210 and the target handle angle 238.

Claims

Claims 1. A method for controlling a steering system (102), comprising determining (904) a target wheel steering angle speed (232) as a function of an actual value (206) specified (902) by a driver on a handle (104) of the steering system (102), in particular a force applied by the driver to the handle or a moment applied by the driver to the handle, wherein a wheel actuator (106) is controlled (906) to set a wheel steering angle of the steered wheels (108) as a function of the target wheel steering angle speed (232).

2. Method according to claim 1, characterized in that a centering angular speed is determined as a function of the actual value (206), an actual wheel steering angle (224) and / or an actual wheel steering angular speed determined as a function of the actual wheel steering angle (224) and / or as a function of a rack force which is measured, determined based on a model or calculated from steering-internal measured variables, with which the steering system (102) returns to an actual wheel steering angle for straight-ahead travel, wherein the desired wheel steering angular speed (232) is reduced by the centering angular speed.

3. Method according to claim 2, characterized in that a vehicle speed (202) of a vehicle (100) steered by the steering system is detected, wherein the centering angular speed is determined as a function of the vehicle speed (202).

4. Method according to one of the preceding claims, characterized in that for controlling the steering system with two handles (104), an actual value (502) is recorded (902) for each handle (104) and the actual value (206) for determining the desired wheel steering angular speed (232) is determined (904) as a function of a sum (206) of the actual values ​​(502) recorded for each handle (104).

5. Method according to one of the preceding claims, characterized in that the desired wheel steering angle speed (232) is integrated to a desired wheel steering angle (304), wherein the wheel actuator (106) is controlled (906) to set the desired wheel steering angle (304) of the steered wheels (108).

6. Method according to one of the preceding claims, characterized in that a desired handling angle (238) is determined (908) as a function of an actual wheel steering angle (224) and a transmission characteristic curve (806), wherein the actual wheel steering angle (224) is detected by a sensor (112) or determined by integrating the desired wheel steering angular speed (232), wherein a desired motor torque (214) for an actuator (216) on the handle (104) is determined (910) as a function of the actual handling angle (210) and the desired handling angle (238).

7. Method according to claim 6, characterized in that the transmission characteristic curve (806) assigns increasingly disproportionate values ​​of the desired handling angle (238) to the actual wheel steering angle (224) in a first range (808), which starts from the actual wheel steering angle for straight-ahead travel or cornering with large curve radii, with increasing deflection from straight-ahead travel.

8. Method according to claim 6 or 7, characterized in that the transmission characteristic curve (806) assigns decreasingly disproportionate values ​​of the desired handling angle (238) to the actual wheel steering angle (224) in a second range (810), which starts from cornering with small to very small curve radii and ends with the maximum actual wheel steering angle, with further increasing deflection from straight-ahead travel.

9. Method according to one of claims 6 to 8, characterized in that a vehicle speed (202) of a vehicle (100) steered by the steering system (102) is detected, wherein the desired handling angle (238) is determined from a characteristic map which assigns the value of the desired handling angle (238) to the value of the actual wheel steering angle (224) as a function of the vehicle speed (202).

10. Method according to one of the preceding claims, characterized in that the desired wheel steering angular speed (232) is determined (904) as a function of a steering feel moment (228), wherein the steering feel moment (228) is determined as a function of a vehicle speed (202), a force (222) applied by the wheel actuator (106), a moment (206) applied by the driver to the handle (104), and a wheel steering angle (224) set by the wheel actuator (106).

11. The method according to claim 10, characterized in that a wheel steering angular speed (604) is determined iteratively as a function of a sum of the torque (206) applied by the driver and the steering feel torque (228), in particular wherein the sum of the torque (206) applied by the driver and the steering feel torque (228) and the vehicle speed (202) are mapped to the wheel steering angular speed (604) using a characteristic map, and the steering feel torque (228) is determined as a function of the wheel steering angular speed (604).

12. Device (110) for controlling a steering system (102), characterized in that the device (110) is designed to detect an actual value specified by a driver on a handle (104) of the steering system (102), in particular a force applied by the driver to the handle (104) or a moment applied by the driver to the handle (104), and to control a wheel actuator (106) for setting a wheel steering angle of steered wheels (108) using the method according to one of claims 1 to 11.

13. Vehicle (100), characterized in that the vehicle (100) comprises the steering system (102) and the device (110) according to claim 12.

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