Steering device and method for operating the steering device

Abstract

Method for operating a steering device (102), steering device (102) and vehicle (100) comprising the steering device (102), wherein the steering device (102) comprises a rack (106), an electric motor (108) for adjusting a position of the rack (106), a first controller (110) for controlling the electric motor (108) depending on a deviation (116) of an actual position (118) of the rack (106) from a desired position (120) of the rack (106), a second controller (112) for controlling the electric motor (108) depending on the deviation (116) of the actual position (118) from the desired position (120), and a device (114) for switching from the control of the electric motor (108) by the first controller (110) to the control of the electric motor (108) by the second controller (112), wherein the device (114) is designeddepending on a deviation of an actual value from a target value, to switch from the control of the electric motor (108) by the first controller (110) to the control of the electric motor (108) by the second controller (112), wherein the actual value is the actual position (118) of the rack (106) and the target value is the target position (120) of the rack (106), or wherein the actual value is a derivative of an actual position (118) of the rack (106) and the target value is determined depending on a difference between the actual position and a target position (120) of the rack (106).

Description

State of the art

[0001] The invention relates to a steering device and a method for operating the steering device. Disclosure of the invention

[0002] The steering device and method according to the independent claims prevent a failure of the steering device. This fulfills increased requirements for controller accuracy and ASIL D requirements.

[0003] The steering device comprises a rack, an electric motor for adjusting a position of the rack, a first controller for controlling the electric motor depending on a deviation of an actual position of the rack from a desired position of the rack, a second controller for controlling the electric motor depending on the deviation of the desired position from the actual position, and a device for switching from the control of the electric motor by the first controller to the control of the electric motor by the second controller, wherein the device is designed to switch from the control of the electric motor by the first controller to the control of the electric motor by the second controller depending on a deviation of an actual value from a desired value, wherein the actual value is the actual position of the rack and the desired value is the desired position of the rack,or wherein the actual value is a derivative of an actual position of the rack and the target value is determined depending on a difference between the actual position and a target position of the rack.,

[0004] It can be provided that the device is designed to monitor the deviation of the actual value from the target value and, depending on the deviation of the actual value from the target value, to switch from the control of the electric motor by the first controller to the control of the electric motor by the second controller.

[0005] It can be provided that the device is configured to compare the deviation of the actual value from the target value with a limit value and to switch from controlling the electric motor by the first controller to controlling the electric motor by the second controller if the deviation of the actual value from the target value is greater than the limit value. This means that the device is configured to particularly well detect the need for switching.

[0006] The device can be configured to determine the limit value depending on the deviation of the actual value from the target value. This means that the device is configured to adapt the limit value to the deviation of the actual value from the target value.

[0007] The device can be configured to determine an increasingly narrow limit value as the deviation of the actual value from the target value increases. This means that the device is configured to set the limit value more sensitively as the deviation of the actual value from the target value increases.

[0008] The device can be configured to determine both the limit value for a positive deviation of the actual value from the target value and the limit value for a negative deviation of the actual value from the target value. The limit values ​​can be the same or different from one another. This means that the device is configured to set asymmetric limit values.

[0009] A vehicle may be provided which includes the steering device.

[0010] The method for operating a steering device provides that the steering device has a rack, an electric motor for adjusting a position of the rack, a first controller for controlling the electric motor depending on a deviation of an actual position of the rack from a target position of the rack, a second controller for controlling the electric motor depending on the deviation of the actual position from the target position of the rack, wherein depending on a deviation of an actual value from a target value, switching is carried out from the control of the electric motor by the first controller to the control of the electric motor by the second controller, wherein the actual value is the actual position of the rack and the target value is the target position of the rack, or wherein the actual value is a derivative of an actual position of the rack and the target value is determined depending on a difference between the actual position and a target position of the rack.

[0011] The method may monitor the deviation of the actual value from the target value, and depending on the deviation of the actual value from the target value, the system switches from controlling the electric motor by the first controller to controlling the electric motor by the second controller. This allows for particularly accurate detection of the need for switching.

[0012] It can be provided that the method provides that the deviation of the actual value from the target value is compared with a limit value, and that a switch is made from the control of the electric motor by the first controller to the control of the electric motor by the second controller if the deviation of the actual value from the target value is greater than the limit value.

[0013] The method may provide for the limit value to be determined based on the deviation of the actual value from the target value. This adjusts the limit value to the deviation of the actual value from the target value.

[0014] The method can be designed to determine an increasingly narrow limit value as the deviation of the actual value from the target value increases. This means that the limit value is set more sensitively as the deviation of the actual value from the target value increases.

[0015] The method may specify that, for the deviation of the actual value from the target value, both the limit value for a positive deviation of the actual value from the target value and the limit value for a negative deviation of the actual value from the target value are determined. The limit values ​​can be the same or different. This results in asymmetric limit values.

[0016] Further advantageous embodiments can be found in the following description and the drawing. The drawing shows: Fig. 1 a schematic representation of a vehicle with a steering device, Fig. 2 an exemplary first controller of the steering device, Fig. 3 an exemplary second controller of the steering device, Fig. 4 a flowchart with steps of a method for operating the steering device.

[0017] In Fig. 1 schematically shows a vehicle 100 with a steering device 102. The steering device 102 is configured to steer steered wheels 104 of the vehicle 100.

[0018] The steering device 102 comprises a rack 106 which is designed to steer the steered wheels 104.

[0019] The steering device 102 includes an electric motor 108 for adjusting a position of the rack 106.

[0020] The steering device 102 comprises a first controller 110 for controlling the electric motor 108. The steering device 102 comprises a second controller 112 for controlling the electric motor 108. The steering device 102 comprises a device 114 for switching from the control of the electric motor 108 by the first controller 110 to the control of the electric motor 108 by the second controller 112.

[0021] The first controller 110 is designed to control the electric motor 108 depending on a deviation 116 of an actual position 118 of the rack 106 from a desired position 120 of the rack.

[0022] The second controller 112 is designed to control the electric motor 108 depending on the deviation 116 of the actual position 118 of the rack 106 from the desired position 120 of the rack 106.

[0023] The device 114 is designed to switch from the control of the electric motor 108 by the first controller 110 to the control of the electric motor 108 by the second controller 112 depending on a deviation 116' of an actual value from a target value.

[0024] In one example, the actual value is the actual position 118 of the rack 106 and the target value is the target position 120 of the rack 106.

[0025] In one example, the actual value is a derivative of the actual position 118 of the rack 106 and the target value is determined depending on a difference between the actual position 118 and the target position 120.

[0026] In the example, the steering device 102 comprises a computing device 122 which is designed to determine the deviation 116 of the actual position 118 from the desired position 120.

[0027] In one example, the computing device 122 is configured to determine the deviation 116 of the actual position 118 from the target position 120 by forming a difference between the actual position 118 and the target position 120.

[0028] In one example, the computing device 122 is configured to determine the deviation 116' of the actual value from the target value.

[0029] In one example, the actual value is the actual position 118 of the rack 106 and the target value is the target position 120 of the rack 106.

[0030] In one example, the actual value is a derivative of the actual position 118 of the rack 106 and the target value is determined depending on a difference between the actual position and a target position 120 of the rack 106.

[0031] The device 114 is designed to monitor the deviation 116' of the actual value from the target value and, depending on the deviation 116', to switch from the control of the electric motor 108 by the first controller 110 to the control of the electric motor 108 by the second controller 112.

[0032] In the example, the device 114 comprises a switch 124 which is designed to switch, depending on a switching signal 126, from the control of the electric motor 108 by the first controller 110 to the control of the electric motor 108 by the second controller 112.

[0033] In the example, the device 114 comprises a monitoring device 128 which is designed to monitor the deviation 116' of the actual value from the target value and to determine the switching signal 126 for switching from the control of the electric motor 108 by the first controller 110 to the control of the electric motor 108 by the second controller 112 depending on the deviation 116.

[0034] It can be provided that the device 114, in the example the monitoring device 128, is designed to compare the deviation 116' of the actual value from the target value with a limit value and to switch from the control of the electric motor 108 by the first controller 110 to the control of the electric motor 108 by the second controller 112 if the deviation 116' of the actual value from the target value is greater than the limit value.

[0035] It can be provided that the device 114, in the example the monitoring device 128, is designed to determine the limit value depending on the deviation 116' of the actual value from the target value.

[0036] It can be provided that the device 114, in the example the monitoring device 128, is designed to determine the limit value depending on the difference between the actual position 118 and the target position 120 determined by the computing device 122.

[0037] It can be provided that the device 114, in the example the monitoring device 128, is designed to determine an increasingly narrower limit value with increasing deviation 116' of the actual value from the target value.

[0038] It can be provided that the device 114, in the example the monitoring device 128, is designed to determine both the limit value for a positive deviation 116' of the actual value from the target value and to determine a negative deviation 116' of the actual value from the target value for the deviation 116' of the actual value from the target value.

[0039] For example, it is provided that the limit value for the positive deviation 116' of the actual value from the target value differs from the limit value for the negative deviation 116' of the actual value from the target value. In the example, the limit values ​​are specified such that the speed of the rack 106 remains within an accepted range as long as the deviation 116' of the actual value from the target value remains within the limit values. In the example, the limit values ​​are specified such that the device 114 is configured to switch when the speed of the rack 106 leaves the accepted range.

[0040] In the example, the first controller 110 is designed to determine a first target motor torque 130 for controlling the electric motor 108 depending on the deviation 116 of the actual position 118 from the target position 120.

[0041] In the example, the second controller 112 is designed to determine a second target motor torque 132 for controlling the electric motor 108 depending on the deviation 116 of the actual position 118 from the target position 120.

[0042] In the example, the electric motor 108 is controlled either with the first target motor torque 130 or the second target motor torque 132, depending on the position of the switch 124.

[0043] In Fig. 2 shows an exemplary first controller 110. The first controller 110 is configured, for example, to control the first target engine torque 130 depending on a deviation 202 of the actual value 134 from a target value 204 using a first torque controller 206. In the example, the first torque controller 206 is a PID controller. The first controller 110 and the second controller 112 are different. The first controller 110 and the second controller 112 preferably differ in such a way that the same error does not lead to an incorrect engine torque in both.

[0044] In the example, the first controller 110 is configured to determine the target value 204 depending on the deviation 116 of the actual position 118 from the target position 120. In the example, the first controller 110 is configured to determine the target value 204 from a characteristic curve 208 that assigns the target value 204 to the deviation 116. It may be configured that the characteristic curve 208 is selected from a set 210 of characteristic curves depending on the deviation 116 of the actual position 118 from the target position 120.

[0045] In Fig. Figure 3 shows an exemplary second controller 112. The second controller 112 is configured, for example, to control the second target motor torque 132 depending on the deviation 116 of the actual position 118 from the target position 120 using a second torque controller 302. In the example, the second torque controller 302 is a PID controller.

[0046] In Fig.4 shows steps of a method for operating the steering device 102.

[0047] The method includes a step 402.

[0048] In step 402, the electric motor 108 is controlled by the first controller 110 depending on the deviation 116 of the actual position 118 from the target position 120.

[0049] The method includes a step 404.

[0050] In step 404, it is determined whether or not to switch from the control of the electric motor 108 by the first controller 110 to the control 408 of the electric motor 108 by the second controller 112.

[0051] If it is determined that the switch should be made from the control of the electric motor 108 by the first controller 110 to the control 408 of the electric motor 108 by the second controller 112, step 406 is executed. Otherwise, step 402 is executed.

[0052] For example, the deviation 116' of the actual value from the target value is monitored.

[0053] For example, the deviation 116' of the actual value from the target value is compared with a limit value and it is determined that the control of the electric motor 108 by the first controller 110 should be switched to the control 408 of the electric motor 108 by the second controller 112 if the deviation 116' of the actual value from the target value is greater than the limit value.

[0054] It can be provided that the limit value is determined depending on the deviation 116' of the actual value from the target value. It can be provided that an increasingly narrower limit value is determined as the deviation 116' of the actual value from the target value increases.

[0055] It can be provided that the limit value is determined depending on the deviation 116 of the actual position 118 of the rack 106 from the target position 120 of the rack 106. It can be provided that an increasingly narrower limit value is determined as the deviation 116 of the actual position 118 of the rack 106 from the target position 120 of the rack 106 increases.

[0056] In one example, for the deviation 116' of the actual value from the target value, both the limit value for a positive deviation 116' of the actual value from the target value and a negative deviation 116' of the actual value from the target value are determined, with different limit values. This means that asymmetric limit values ​​are used.

[0057] In the example, the limit value is specified such that the speed of the rack 106 remains within an accepted range as long as the deviation 116' of the actual value from the target value remains within the limit values. This means that switching occurs when the speed of the rack 106 leaves the accepted range.

[0058] In step 406, the control of the electric motor 108 is switched from the control of the electric motor 108 by the first controller 110 to the control 408 of the electric motor 108 by the second controller 112.

[0059] This means that it can be provided that the deviation 116' of the actual value from the target value is monitored and the increasingly narrow limit value is determined depending on the deviation 116.

[0060] This means that it can be provided that the deviation 116' of the actual value from the target value is monitored and, depending on the deviation 116' of the actual value from the target value, the control of the electric motor 108 by the first controller 110 is switched to the control of the electric motor 108 by the second controller 112.

[0061] This means that it can be provided that the deviation 116' of the actual value from the target value is monitored and that in the case of a positive deviation 116' of the actual value from the target value greater than the limit value for the positive deviation or in the case of a negative deviation 116' of the actual value from the target value greater than the limit value for the negative deviation 116' of the actual value from the target value.

[0062] Step 408 is then executed.

[0063] In step 408, the electric motor 108 is controlled by the second controller 112 depending on the deviation 116 of the actual position 118 from the target position 120.

Claims

[1] Steering device (102), characterized bythat the steering device (102) comprises a rack (106), an electric motor (108) for adjusting a position of the rack (106), a first controller (110) for controlling the electric motor (108) depending on a deviation (116) of an actual position (118) of the rack (106) from a desired position (120) of the rack (106), a second controller (112) for controlling the electric motor (108) depending on the deviation (116) of the desired position (118) from the actual position (120), and a device (114) for switching from the control of the electric motor (108) by the first controller (110) to the control of the electric motor (108) by the second controller (112), wherein the device (114) is designed to control the electric motor (108) depending on a deviation (116') of an actual value from a desired value of the electric motor (108) by the first controller (110) to the control of the electric motor (108) by the second controller (112),wherein the actual value is the actual position (118) of the rack (106) and the target value is the target position (120) of the rack (106), or wherein the actual value is a derivative of an actual position (118) of the rack (106) and the target value is determined as a function of a difference between the actual position and a target position (120) of the rack (106). [2] Steering device (102) according to claim 1, characterized by that the device (114) is designed to monitor the deviation (116') of the actual value from the target value and, depending on the deviation (116') of the actual value from the target value, to switch from the control of the electric motor (108) by the first controller (110) to the control of the electric motor (108) by the second controller (112). [3] Steering device (102) according to claim 2, characterized bythat the device (114) is designed to compare the deviation (116') of the actual value from the target value with a limit value, and to switch from the control of the electric motor (108) by the first controller (110) to the control of the electric motor (108) by the second controller (112) if the deviation (116') of the actual value from the target value is greater than the limit value. [4] Steering device (102) according to claim 3, characterized by that the device (114) is designed to determine the limit value depending on the deviation (116') of the actual value from the target value. [5] Steering device (102) according to claim 4, characterized by that the device (114) is designed to determine an increasingly narrower limit value with increasing deviation (116') of the actual value from the target value. [6] Steering device (102) according to one of claims 3 to 5, characterized bythat the device (114) is designed to determine both the limit value for a positive deviation (116') of the actual value from the target value and a negative deviation (116') of the actual value from the target value for the deviation (116') of the actual value from the target value. [7] Vehicle (100), characterized by that the vehicle (100) comprises the steering device (102) according to one of claims 1 to 6. [8] Method for operating a steering device (102), characterized bythat the steering device (102) has a rack (106), an electric motor (108) for adjusting a position of the rack (106), a first controller (110) for controlling the electric motor (108) depending on a deviation (116) of an actual position (118) of the rack (106) from a desired position (120) of the rack (106), a second controller (112) for controlling the electric motor (108) depending on the deviation (116) of the desired position (118) from the actual position (120), wherein depending on a deviation (116') of an actual value from a desired value, the control (402) of the electric motor (108) by the first controller (110) is switched over to the control (408) of the electric motor (108) by the second controller (112), wherein the actual value determines the actual position (118) of the rack (106) and the target value is the target position (120) of the rack (106),or wherein the actual value is a derivative of an actual position (118) of the rack (106) and the target value is determined as a function of a difference between the actual position and a target position (120) of the rack (106). [9] Method according to claim 8, characterized by that the deviation (116') of the actual value from the target value is monitored (404), and depending on the deviation (116') of the actual value from the target value, the control of the electric motor (108) by the first controller (110) is switched to the control of the electric motor (108) by the second controller (112) (406). [10] Method according to claim 9, characterized bythat the deviation (116') of the actual value from the target value is compared with a limit value (404), and switching is made (406) from the control of the electric motor (108) by the first controller (110) to the control of the electric motor (108) by the second controller (112) if the deviation (116') of the actual value from the target value is greater than the limit value. [11] Method according to claim 10, characterized by that the limit value is determined depending on the deviation (116') of the actual value from the target value (404). [12] Method according to claim 11, characterized by that with increasing deviation (116') of the actual value from the target value, an increasingly narrower limit value is determined (404). [13] Method according to one of claims 10 to 12, characterized by, for the deviation (116') of the actual value from the target value, both the limit value for a positive deviation (116') of the actual value from the target value and a negative deviation (116') of the actual value from the target value are determined (404).

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