Device and method for controlling a rack position of a steering system

Abstract

The invention relates to a device (114) and a method for controlling a rack position (x Ra ) of a steering system (100), wherein the steering system (100) has a rack (104) and a motor (106) for moving the rack (104), wherein a rack position of the rack (104) is detected by a sensor (110) and a rotor position of a rotor of the motor (106) is provided, wherein a target motor torque for the motor (106) is determined, in particular by a controller, depending on the detected rack position and depending on the rotational speed, and the motor (106) is actuated with the target motor torque.

Description

[0001] Description

[0002] title

[0003] Device and method for controlling a rack position of a

[0004] State of the art

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

[0006] Conventional rack position control methods use a control error based on an estimate of rack position errors. The quality of this estimate can vary depending on the internal friction behavior of the steering system, as the friction level depends on aging and environmental conditions.

[0007] Due to production variations, the system properties of the steering system can change and exhibit fluctuations. In particular, the friction properties of the steering system change over time (aging), for example, due to wear (thrust piece position). The resulting changes in the properties of the steering system impair the control of the steering system.

[0008] For example, in a steering system motor used to adjust the rack position, movements of the motor's rotor occur that do not cause the rack to move due to internal steering friction. In a control system that regulates the rotor's movement as a function of the rotor's speed, the rotor's movement is transmitted completely to the controller. Rotor movements that do not result in the rack moving can cause undesirable motor torque oscillations in the closed control loop. Disclosure of the Invention

[0009] The method and device according to the independent claims avoid undesirable behavior of the closed control loop.

[0010] For example, unwanted motor torque oscillations are avoided, which could otherwise occur due to movements of the rotor that do not lead to movements of the rack position.

[0011] The method and device result in a better correlation between the evaluations from driving tests (the human perception of the system behavior in the vehicle) and the calculated controller error. The method and device allow road feedback information to be acquired more quickly.

[0012] The method for controlling a rack position of a steering system provides that the steering system has a rack and a motor for moving the rack, wherein a rack position of the rack is detected with a sensor and a rotor position of a rotor of the motor is provided. A target motor torque for the motor is determined, in particular with a controller, as a function of the detected rack position and as a function of the rotational speed, and the motor is controlled with the target motor torque. The calculation of the manipulated variable, i.e., the target motor torque, takes into account both the dynamics of the rotor and the dynamics of the rack.

[0013] The rotor position is detected, for example, with a sensor on the rotor.

[0014] The following measures will improve the performance of the control system.

[0015] It can be provided that a rack position deviation is determined depending on the target position and the detected rack position, and the target motor torque is determined depending on the rack position deviation. It can be provided that rotor oscillations are determined during control and used to determine the target motor torque.

[0016] It can be planned to determine friction losses during control and use them to determine the target motor torque. With the detected rack position, internal system friction can be determined much more easily, for example, estimated.

[0017] It may be provided that a time delay between a signal of the sensor that detects the rotor position and a rack position signal of the sensor that detects the rack position is detected and used to determine the target motor torque.

[0018] The device for controlling a rack position of a steering system is designed to detect a rack position of the rack with a sensor and to provide a rotor position of a rotor of the motor, to determine a target motor torque for the motor, in particular with a controller, depending on the detected rack position and depending on the speed, and to control the motor with the target motor torque.

[0019] For example, the device is designed to detect the rotor position with a sensor on the rotor.

[0020] It can be provided that the device is designed to determine a rack position deviation depending on the target position and the detected rack position, and to determine the target motor torque depending on the rack position deviation.

[0021] It can be provided that the device is designed to determine rotor oscillations during control and to use them to determine the target motor torque.

[0022] The device can be configured to determine friction losses during control and to use them to determine the target motor torque. The device can be configured to detect a time delay between a signal from the sensor that detects the rotor position and a rack position signal from the sensor that detects the rack position, and to use this time delay to determine the target motor torque.

[0023] A vehicle may be provided which comprises the steering system (100) and the device.

[0024] Further advantageous embodiments can be found in the following description and the drawing. The drawing shows:

[0025] Fig. 1 is a schematic representation of a steering system,

[0026] Fig. 2 is a flowchart showing steps of a method for controlling a rack position of the steering system.

[0027] Figure 1 shows a schematic diagram of a steering system 100.

[0028] In the example, a vehicle axle 102 is steered with the steering system 100.

[0029] The steering system 100 includes a rack 104 configured to steer the wheels of the steered vehicle axle 102.

[0030] The steering system 100 includes a motor 106 configured to move the rack 104 via a gear 108.

[0031] The steering system 100 comprises a sensor 110 which is designed to detect a rack position x Ra the rack 104.

[0032] The steering system 100 includes a sensor 112 configured to detect a rotor position w mo of the rotor of the motor 106.

[0033] A device 114 is designed to control the motor 106. The device 114 is designed to control the motor 106 depending on the rack position x detected by the sensor 110. Ra the rack 104.

[0034] The device 114 is designed to control the motor 106 depending on a rotor position w mo a rotor of the motor 106.

[0035] The device 114 is designed to move the motor 106 depending on a target position Rackpos req to control the rack 104.

[0036] The device 114 is designed to drive the motor 106 with a target motor torque T mo to control.

[0037] In the example, the device 114 comprises a controller which is designed to determine the target engine torque T mo for the motor 106 depending on the detected rack position x Ra and depending on the rotor position w mo to determine.

[0038] A rack force F acts on the steering system 100 from the vehicle axle 102 Ra . The dynamics of the steering system 100 are described in the example by the following equation (1) for the dynamics of the rotor of the motor 106 and equation (2) for the dynamics of the rack 104:

[0039] The exact rack position x Ra allows, by comparing the rotor position w mo and the rack position x Ra Friction losses between rotor position w mo and the rack position x Ra to approximate.

[0040] For example, the controller is designed to determine the target engine torque T mo depending on the friction losses.

[0041] The device 114 can be designed to detect a rack position deviation depending on the target position Rackpos req and the detected rack position x Ra and the target engine torque T modepending on the rack position deviation.

[0042] For example, the controller is designed to determine rack position deviation and the target motor torque T mo depending on the rack position deviation.

[0043] The device 114 can be designed to detect rotor oscillations during control and to determine the target motor torque T mo to use.

[0044] For example, the controller is designed to detect rotor oscillations during control and to determine the target motor torque T mo to use.

[0045] There may be a time delay between a signal from sensor 112 indicating the rotor position w mo detected, and a rack position signal from sensor 110, which detects the rack position x Ra recorded, occur.

[0046] The device 114 can be designed to detect the time delay and to determine the target engine torque T mo to use.

[0047] For example, the controller is designed to detect the time delay and to determine the target engine torque T mo to use.

[0048] The device 114 can be designed to determine the friction losses depending on the rotor position w mo and the rack position x Ra and the target engine torque T mo depending on the friction losses.

[0049] The device 114 is configured to execute a method for controlling the rack position of the steering system 100. Figure 2 shows a flowchart with steps of the method.

[0050] In the example, the steering system 100 is a steer-by-wire steering system of a vehicle 116. The device 114 and the method can also be used for steering systems other than the steer-by-wire steering system of a vehicle. The method includes a step 202.

[0051] In step 202, the rack position x Ra detected by the sensor 110 and the rotor position w mo provided.

[0052] The rotor position w mo is detected, for example, with a sensor on the rotor.

[0053] By using the sensor 110, the exact rack position x Ra the rack 104 is determined.

[0054] Subsequently, a step 204 is executed.

[0055] In step 204, the target engine torque T mo for the motor 106 depending on the detected rack position x Ra and depending on the speed w mo certainly.

[0056] In the example, the target engine torque T mo for the motor 106 with the controller depending on the detected rack position x Ra and depending on the rotor position w mo too determined.

[0057] In an example, a rack position deviation is determined depending on the target position Rackpos req and the detected rack position x Ra determined, and the target engine torque T mo depending on the rack position deviation.

[0058] It can be provided that the rotor oscillations are also determined during the control and used to determine the target motor torque T mo be used.

[0059] It can be provided that the friction losses are also determined during the control and used to determine the target engine torque T mo be used.

[0060] It can be provided that the time delay is detected and used to determine the target engine torque T mois used.

[0061] Subsequently, a step 206 is executed. In step 206, the motor 106 is driven with the target motor torque T mo controlled.

[0062] Step 202 is then executed.

Claims

Claims 1. Method for controlling a rack position of a steering system (100), characterized in that the steering system (100) has a rack (104) and a motor (106) for moving the rack (104), wherein a rack position of the rack (104) is detected with a sensor (110) and a rotor position of a rotor of the motor (106) is provided (202), wherein a target motor torque for the motor (106) is determined, in particular with a controller, depending on the detected rack position and depending on the speed (204), and the motor (106) is controlled with the target motor torque (206).

2. Method according to claim 1, characterized in that the rotor position is detected (202) with a sensor (112) on the rotor.

3. Method according to one of the preceding claims, characterized in that a rack position deviation is determined as a function of the desired position and the detected rack position, and the desired engine torque is determined as a function of the rack position deviation (204).

4. Method according to one of the preceding claims, characterized in that rotor oscillations are determined during the control and used to determine the desired motor torque (204).

5. Method according to one of the preceding claims, characterized in that friction losses are determined during the control and used to determine the target engine torque (204).

6. Method according to one of the preceding claims, characterized in that a time delay between a signal of the sensor (112) which detects the rotor position and a rack position signal of the Sensor (110) which detects the rack position, detects it and uses it to determine the target engine torque (204).

7. Device (114) for controlling a rack position of a steering system (100), characterized in that the steering system (100) has a rack (104) and a motor (106) for moving the rack (104), wherein the device (114) is designed to detect a rack position of the rack (104) with a sensor (110) and to provide a rotor position of a rotor of the motor (106), to determine a target motor torque for the motor (106), in particular with a controller, depending on the detected rack position and depending on the speed, and to control the motor (106) with the target motor torque.

8. Device (114) according to claim 7, characterized in that the device (114) is designed to detect the rotor position with a sensor (112) on the rotor.

9. Device (114) according to claim 7 or 8, characterized in that the device (114) is designed to determine a rack position deviation depending on the desired position and the detected rack position, and to determine the desired motor torque depending on the rack position deviation.

10. Device (114) according to one of claims 7 to 9, characterized in that the device (114) is designed to determine rotor oscillations during the control, and to determine the target motor torque (T mo ) to use.

11. Device (114) according to one of claims 7 to 10, characterized in that the device (114) is designed to determine friction losses during the control, and to determine the target engine torque (T mo ) to use.

12. Device (114) according to one of claims 7 to 11, characterized in that the device (114) is designed to have a Detect a time delay between a signal from the sensor (112) detecting the rotor position and a rack position signal from the sensor (110) detecting the rack position and use it to determine the target motor torque.

13. Vehicle (116), characterized in that the vehicle (116) comprises a steering system (100) and the device (114) according to one of claims 7 to 12.

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