Method and control device for determining a controller output variable using a controller for a controlled system, in particular for a rack-and-pinion actuator of a steer-by-wire steering system, steering system comprising the control device, and vehicle comprising the steering system

Abstract

The invention relates to a method and control device (100) for determining a controller output variable (104) using a controller (102) for a controlled system (200), in particular for a rack-and-pinion actuator of a steer-by-wire steering system, comprising: detecting a first characteristic variable (106) which characterizes a force (4) which acts on the controlled system (200) and in particular influences a dynamic behaviour of the controlled system (200); detecting a second characteristic variable (108) which characterizes a manipulated variable of an actuator (202) of the controlled system (200); determining the controller output variable (104) on the basis of the first characteristic variable (106), the second characteristic variable (108) and a target value (2) by means of the controller (100). The invention further relates to a steering system comprising the control device (100) and to a vehicle comprising the steering system.

Description

[0001] R.412712 - 1 -Description Title Method and control device for determining a controller output variable with a controller for a controlled system, in particular for a rack and pinion actuator of a steer-by-wire steering system, a steering system comprising the control device, and a vehicle comprising the steering system. Prior art The present invention relates to a method and a control device for determining a controller output variable with a controller for a controlled system, in particular for a rack and pinion actuator of a steer-by-wire steering system, a steering system comprising the control device, and a vehicle comprising the steering system. In a steer-by-wire steering system of a vehicle, the wheels of the vehicle and, for example, a steering device are connected by electrical signals. A torque exerted on the steering device, for example by a driver, therefore has no direct mechanical influence on the wheels.The steer-by-wire steering system comprises, in particular, two subcomponents: a first subcomponent that receives the driver's input via the control unit, and a second subcomponent that translates this input into a steering movement. The second subcomponent is mechanically connected to the wheels, with an electrical connection between the first and second subcomponents. This electrical connection transmits a directional command from the driver to the second subcomponent. The second subcomponent is responsible for lateral movements, for example, of the vehicle's front axle. The second subcomponent can, for example, be designed as a rack and pinion actuator. R.412712 -. 2 -To achieve a good driving experience, the vehicle's response should accurately reflect the driver's steering input. Therefore, for example, the time lag between a movement of the steering mechanism and the movement of the wheels should exhibit a defined behavior, or rather, a guiding behavior. The movement of the wheels is caused by a lateral movement of the rack. In all possible driving situations, the steering system should maintain a certain degree of accuracy in the rack position. To control the rack's position, a controller generates motor torque for an actuator that drives the rack. The actuator's rotor movement is influenced, for example, by internal gearing phenomena and inertia. In known steering system designs, the rack's position is estimated from the rotor position and a gear ratio.Due to variations in the steering system's properties, for example, due to aging and wear, reliable steering behavior cannot be guaranteed by this estimation. For example, rotor movements are conceivable that, due to internal steering system friction, do not cause any movement of the rack. Nevertheless, this motion information is transmitted to the controller via the estimation of the rack's position, which can lead to undesirable oscillations of the actuator. Therefore, it is desirable to provide a control method for a steering system that is robust against disturbances and variable system properties. Disclosure of the Invention: This is achieved by a method, a control device, a steering system, and a vehicle according to the independent claims.The method for determining a controller output variable with a controller for a controlled system, in particular for a rack and pinion actuator of a steer-by-wire steering system, comprises: acquiring a first characteristic variable that is based on the R.412712 -. 3 -The first parameter characterizes the force acting on the controlled system, which particularly influences the dynamic behavior of the controlled system; a second parameter is acquired, characterizing the manipulated variable of an actuator within the controlled system; the controller output is determined based on the first parameter, the second parameter, and a setpoint. By determining the controller output based on the first parameter, friction phenomena within the controlled system, such as those of the steering system, can be implicitly represented without requiring specific modeling or estimation of these phenomena. The first and second parameters allow for the extraction and consideration of friction phenomena, such as those occurring during force transmission between the actuator and a rack in the steering system, when determining the controller output.This enables a robust determination of the controller output variable, resistant to disturbances and varying system properties of the controlled system. The method may include the acquisition of a third parameter, which is influenced by the second and / or first parameter, for example, an output variable of the controlled system to be controlled, where the controller output variable is determined as a function of the first, second, and third parameters. In this context, the third parameter represents a parameter that has a functional relationship with the first and / or second parameter. This functional relationship causes the dynamics of the third parameter and / or the third parameter itself to vary depending on the first and / or second parameter. This functional relationship could, for example, be an axle of a vehicle or the gearing of a rack and pinion actuator.By determining the controller output variable as a function of the third parameter, the method becomes more dynamic, as relationships between the controlled output variable of the controlled system and the first and / or second parameter can be taken into account. It can be provided that the controller output variable is determined for a rack and pinion actuator, where the first parameter is a force acting on a rack of the rack and pinion actuator and / or the second parameter is a position signal from an R.412712- driving the rack and pinion actuator. 4 -The actuator is, for example, an electric motor. A rack and pinion actuator is used, for instance, to control the direction of travel of a vehicle, with the rack and pinion actuator moving the vehicle's wheels via an axle. By determining the controller output variable as a function of the force acting on the rack, friction phenomena and varying system properties of the rack and pinion actuator can be taken into account without having to model them explicitly. Internal friction phenomena and system stiffnesses of the rack and pinion actuator therefore do not need to be explicitly observed, but are implicitly considered in the control algorithm. The method becomes more robust against variations in driving conditions and axle stiffness, since the force is directly considered in the control algorithm. As a result, the efficiency of the method is independent of, for example, the properties of the axle that is operatively connected to the rack and pinion actuator.Integrating the force, in the form of the first parameter, into the process allows the controller to better represent the existing conditions and system properties of the rack and pinion actuator and to react more quickly to changes. This leads to more precise and reliable control, especially in demanding driving situations. The third parameter can be a position signal of the rack and pinion actuator. This position signal characterizes the position of the rack. The position directly influences the axle and the wheels of the vehicle. Conversely, forces acting on the wheels influence the position, or rather the dynamics, of the rack's position. By using the position signal in the process, faster responses to changes are possible, making the process more dynamic.It can be provided that the controller output characterizes a drive signal of the rack actuator, in particular a drive torque of the rack actuator. It can be provided that the setpoint characterizes a predetermined position of the rack of the rack actuator. The setpoint is, for example, dependent on a direction input from a driver of the R.412712. 5 -The vehicle's direction is determined. The driver can specify this direction using a control device. It is possible for the direction to be provided by a driver assistance system, for example, in autonomous driving mode. The controller can include a model of the controlled system, with the controller output determined based on this model. This allows for efficient controller implementation and accounts for the dynamics of the controlled system with a predefined level of accuracy. This makes the method more robust and reliable.The control device, which is configured to determine a controller output variable for a controlled system, in particular for a rack and pinion position control of a steer-by-wire steering system, by means of a method according to the above description, wherein the control device comprises a first sensor device 105, which is configured to detect the first characteristic value, and optionally a second sensor device, which is configured to detect the third characteristic value. The steering system, in particular a steer-by-wire steering system, comprises a control device according to the above description. The vehicle comprises a steering system according to the above description. Further embodiments are described in the drawing and the following description.The drawing shows: Figure 1 a block diagram of a control device for determining a controller output variable; Figure 2 a block diagram of an embodiment of the control device; Figure 3a a flowchart of a method for determining a controller output variable; Figure 3b a flowchart of an embodiment of the method; R.412712 -. 6 -Figure 4 shows a schematic representation of a section of a vehicle comprising a steering system and the control unit. Figure 1 shows a block diagram of a control unit 100. The control unit 100 is configured to determine a controller output variable 104 with a controller 102 for a controlled system 200, in particular for a rack and pinion actuator of a steer-by-wire steering system. The control unit 100 is configured to detect a first characteristic variable 106 by means of a first sensor device 105, which characterizes a force 4 acting on the controlled system 200. The force 4 particularly influences a dynamic behavior of the controlled system 200. The control unit 100 is configured to detect a second characteristic variable 108, which characterizes a manipulated variable of an actuator 202 of the controlled system 200. The actuator 202 serves, for example, to influence or set a controlled variable of the controlled system 200.The control device 100 is configured to determine the controller output variable 104 based on the first parameter 106, the second parameter 108, and a setpoint 2. The setpoint 2 is, for example, a predetermined value of the controlled variable of the controlled system 200. Figure 2 shows a block diagram of an embodiment of the control device 100. It can be provided that the control device 100 is configured to detect a third parameter 110 by means of a second sensor device 109, which is influenced by the second parameter 108 and / or the first parameter 106, for example, a controlled output variable of the controlled system 200. The control device 100 is configured to determine the controller output variable 104 based on the first parameter 106, the second parameter 108, and the third parameter 110.It may be provided that the third parameter 110 characterizes or is the controlled output variable of the controlled system 200. It may be provided that the controller output variable 104 is determined for a rack and pinion actuator 200 of a steering system 500 (Fig. 4), wherein the first parameter 106 is a force 4 acting on a rack 204 of the rack and pinion actuator 200 and / or the second parameter R.412712 -. 7 - 108 is a position signal of an actuator 202 driving the rack actuator, for example, an electric motor. The rack actuator 200 is an exemplary embodiment of the control system 200. The dynamics of the rack actuator 200 can be described, for example, by the following equations: ^^̈^^ = ^(^^^^ , ^^̇^^ , ^^^^^ , ^̇^^^^ , ^^^) (1)^̈^^ = ^(^^^^ , ^^̇^^ , ^^^ , ^̇^^ , ^^^) (2) Where ^ describes ^^^ a rotor position of actuator 202, which can, for example, represent the second characteristic value. ^ ^ ̇ ^^describes a rotor speed of the actuator and ^ ^ ̈ ^^ a rotor acceleration. The variable ^ ^^ describes a position, ^ ^ ̇ ^ a speed and ^̈ ^^ an acceleration of the rack 204. By ^ ^^A drive torque of the actuator 202 is described, and the variable ^^^ describes the force 4 acting on the rack actuator 200, in particular on the rack 204. The force 4 ^^^ is, for example, an external steering signal caused by the axle that influences the dynamics of the rack actuator 200. It can be provided that the controller output variable 104 characterizes a drive signal of the rack actuator 200, in particular the drive torque ^^^ of the actuator 202 of the rack actuator 200. The drive torque ^^^ is used to control the position ^^^ of the rack 204. It can be provided that the third characteristic variable 110 is a position signal of the rack 204 of the rack actuator 200. The third characteristic variable 110 can, for example, determine the position ^ ^^characterize or be these. It can be provided that the controller 102 includes a model 112 of the controlled system 200, wherein the controller output variable 104 is determined depending on the model 112. The model 112 can, for example, be expressed in the form of the following dynamic equations. R.412712 - 8 - The parameter ^ ^ describes the stiffness of the system, for example the rack and pinion actuator 200, ^ ^ includes, for example, all damping phenomena that occur between the actuator 202 and the rack 204 and ^ ^^ describes internal friction phenomena of the actuator 202. These parameters can vary, for example, depending on the driving situation and the ambient temperature. The parameter ^ denotes a gear ratio that can be provided between the actuator 202 and the rack 204. The parameter ^^^ characterizes an inertia of the rotor of the actuator 202. The parameter ^^^ Describes a mass of the rack 204. Using the first parameter 106 in the form of the force ^^^, the second parameter 108 in the form of the rotor position ^^^^, and the third parameter 110 in the form of the position ^^^ of the rack 204, which are recorded and therefore known, the dynamic equation (3) can be simplified as shown below. ^^(^^^^ − ^^^^) + ^^(^^̇^^ − ^ ^̇^^) = ^^^ − ^^^^^̇^^ − ^^^^^̈^^ (5) Equation (5) can be substituted into the dynamic equation (4) as shown below. It may be intended that the setpoint 2 characterizes a predetermined position of the rack 204 of the rack actuator 200. It is conceivable that the setpoint represents the predetermined position ^ ^^^the rack 204. This can be determined, for example, based on a desired direction input from the driver of a vehicle that includes the rack actuator 200. Accordingly, it can be provided that the control device 100 is designed by means of the controller 102, within the framework of a control, to minimize the following relationship.^^ = ^^^^ − ^^^ (7) R.412712 - 9 - Starting from equation (6), for example, a sliding-mode controller can be determined which defines, for example, the following sliding surface ^:^ = ^^̈ + (^^ + ^^) ^^̇ + (^^^^ + 1)^^ (8) Within the framework of the known sliding-mode method, the following can be defined: ℎ = ((^^ + ^^)^^̇ + (^^^^ + 1)^^) (9) Using equations (9) and (8), the following relationship can be formulated starting from equation (6). Starting from equation (10) and the sliding-mode method, for example the following control algorithm can be formulated for the controller 102, where ^ ^^The controller output size is 104. This describes a parameter of the sliding-mode method. The first recorded parameter 106, in the form of the force 4 ^^^ acting on the rack 204, and the third recorded parameter 110, in the form of the position ^^^ of the rack 204, are directly incorporated into the described control algorithm. The stiffness of the rack actuator 200 does not need to be observed, and internal transmission losses of the rack actuator 200 do not need to be observed. External steering signals, such as road feedback information, are taken into account in the control algorithm (11) by the recorded force 4 ^^^. Alternatively, the control algorithm can be reformulated based on the dynamic equations (3) and (4) and the sliding-mode method, if R.412712 - 10 - for example, only the first parameter 106, in the form of the force 4 ^ ^^ , and the second parameter 108, in the form of the rotor position ^ ^^^is captured. This control algorithm can be defined, for example, as follows, where ^ ^^ The controller output size is 104. The target value 2 represents a desired rotor position. ^^^ of actuator 202 of rack and pinion actuator 200 is used. This is because the position ^ ^^Since the movement of the rack 204 is not directly incorporated into the control algorithm (12), rapid or high-frequency movements of the rack 204 are not immediately detected, making the control algorithm (12) more robust and less susceptible to disturbances. Figure 3a shows a flowchart of a method 300 for determining the controller output variable 104 with the controller 102 for the controlled system 200, in particular for the rack actuator 200 of a steer-by-wire steering system. The method 300 includes acquiring 302 the first parameter 106, which characterizes the force 4 acting on the controlled system 200, which in particular influences the dynamic behavior of the controlled system 200. Furthermore, the procedure 300 includes acquiring 304 the second parameter 108, which characterizes a manipulated variable of an actuator 202 of the controlled system 200, and determining 306 the controller output variable 104 depending on the first parameter 106, the second parameter 108 and the setpoint 2 by means of the controller 102.This can be done, for example, by means of a control algorithm according to equation (12). Figure 3b shows an embodiment of the method 300 in a flowchart. It can be provided that the method 300 comprises acquiring 308 the third parameter 110, which is influenced by the second parameter 108 and / or the first parameter 106, for example, an output parameter of the controlled system 200 to be controlled, wherein the controller output parameter 104 is determined depending on the first parameter 106, the second parameter 108, and the third parameter 110. This can be done, for example, by means of a control algorithm according to equation (11). R.412712 -. 11 -It can be provided that the control device 100 is configured to execute the method 300 to determine the controller output variable 204. Figure 4 shows a schematic representation of a section of a vehicle 400. In this section, a wheel 402 of the vehicle is shown, which is controlled by a steering system 500. The steering system 500 includes the control device 100 for this purpose. The wheel is coupled to the rack and pinion actuator 200 of the steering system 500 by means of an axle 404. The force 4 acting on the rack 204, for example, is transmitted via the axle 404. It can be provided that the vehicle 400 includes further wheels 402 which are controlled by the steering system 500 or further steering systems 500. In the example shown, the vehicle includes a control means 406 by means of which the driver of the vehicle 400 can specify a direction of travel.Based on this direction of travel or direction specification, the target value 2 for the control device 100 can be determined.

Claims

R.412712 - 12 -Claims 1. A method (300) for determining a controller output variable (104) with a controller (102) for a controlled system (200), in particular for a rack and pinion actuator of a steer-by-wire steering system, comprising: - acquiring (302) a first parameter (106) that characterizes a force (4) acting on the controlled system (200), which in particular influences a dynamic behavior of the controlled system (200); - acquiring (304) a second parameter (108) that characterizes a manipulated variable of an actuator (202) of the controlled system (200); - determining (306) the controller output variable (104) as a function of the first parameter (106), the second parameter (108) and a setpoint (2) by means of the controller (100). 2.The method (300) according to claim 1, comprising acquiring (308) a third parameter (110) which is influenced by the second parameter (108) and / or the first parameter (106), for example an output parameter of the controlled system (200) to be controlled, wherein the controller output parameter (104) is determined depending on the first parameter (106), the second parameter (108) and the third parameter (110). The method (300) according to one of the preceding claims, wherein the controller output variable (104) is determined for a rack actuator (200) of a steering system (500), wherein the first parameter (106) is a force (4) acting on a rack (204) of the rack actuator and / or the second parameter (108) is a position signal of an actuator (202), for example an electric motor, driving the rack actuator.

4. The method (300) according to claims 2 and 3, wherein the third parameter (110) is a position signal of the rack (204) of the rack actuator (200). R.412712 - 13 -5. The method (300) according to claim 3 or 4, wherein the controller output variable (104) characterizes a drive signal of the rack actuator (200), in particular a drive torque of the actuator (202) of the rack actuator (200).

6. The method (300) according to any one of claims 3 to 5, wherein the setpoint (2) characterizes a predetermined position of the rack (204) of the rack actuator.

7. The method (300) according to any one of the preceding claims, wherein the controller (102) comprises a model (112) of the controlled system (200), wherein the controller output variable (104) is determined (306) depending on the model (112). 8.Control device (100) configured to determine a controller output variable (102) for a controlled system (200), in particular for a rack and pinion actuator (200) of a steer-by-wire steering system, by means of a method (200) according to claims 1 to 7, wherein the control device (100) comprises a first sensor device 105 configured to detect the first characteristic variable (106) (302) and optionally a second sensor device (109) configured to detect the third characteristic variable (110) (308).

9. Steering system (500), in particular a steer-by-wire steering system, comprising a control device (100) according to claim 8.

10. Vehicle (400) comprising a steering system (500) according to claim 9.

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