Method for controlling a steer-by-wire steering system of a road vehicle with a feedback actuator that has an entry and exit mode.

Abstract

The invention relates to a method for controlling a steer-by-wire steering system (1) for a road vehicle, wherein the steer-by-wire steering system (1) comprises a steering means (3), a road wheel actuator (5) for actuating road wheels (4) and a feedback actuator (11) for applying a feedback torque to the steering means, wherein the following steps are provided: • When an entry situation is detected (12), the feedback actuator (11) is switched on and a resistance torque against the rotation of the steering device (3) is provided in an entry mode; • When the normal shutdown process of the steering system is completed, an exit mode of the feedback actuator (11) is activated and a resistance torque against the rotation of the steering device (3) is provided.

Description

[0001] The present invention relates to a method for controlling a steer-by-wire steering system of a road vehicle according to the preamble of claim 1 and to a steer-by-wire steering system for a road vehicle.

[0002] With steer-by-wire steering, the vehicle's steering wheel is decoupled from the steering mechanism. With this type of steering, there is no mechanical connection between the steering wheel and the steering gear. The steering movement is achieved by a steering actuator with an electric motor. The steering actuator operates based on the measured values ​​of various steering parameters, such as the steering wheel angle, vehicle speed, etc. The measured values ​​are transmitted electronically by sensors to the steering actuator, causing the electric motor to drive the steering rack and align the steerable wheels in the desired direction.

[0003] Although the mechanical connection between the steering wheel and the wheels is eliminated, a steer-by-wire steering system is expected to provide the same functionality and steering feel as a conventional mechanically coupled steering system. The forces generated by the movement of the wheels must be fed back to the steering wheel to provide the driver with information for directional control. This feedback also contributes to the steering feel, which is referred to as "steering feel." In steer-by-wire steering systems, the feedback, or steering feel, is generated by a feedback actuator connected to the steering wheel.

[0004] When the vehicle is parked, the steering shaft and steering mechanism rotate freely, as they are not connected to any mechanical resistance. However, many drivers are accustomed to using the steering mechanism as a handle when getting in and out. With conventional steering columns, they are used to the fact that the steering is difficult to steer, even when the vehicle is turned off, because it is mechanically connected to the wheels.

[0005] The aim of the present invention is to provide a method by which a steering means of a steer-by-wire steering system of a road vehicle can be used as a handle during entry and exit.

[0006] This purpose is achieved by a method having the features of claim 1 and by a steer-by-wire steering system for a road vehicle.

[0007] Accordingly, a method is provided for controlling a steer-by-wire steering system for a road vehicle, the steer-by-wire steering system comprising a steering means, a road wheel actuator for actuating road wheels, and a feedback actuator for applying a feedback torque to the steering handle, the method comprising the following steps: • When an entry situation is detected, the feedback actuator is switched on and a resistance torque against the rotation of the steering means is provided in an entry mode; • When the normal shutdown procedure of the steering system is completed, an exit mode of the feedback actuator is activated and a resistance torque against the rotation of the steering means is provided.

[0008] Even though steer-by-wire systems lack mechanical resistance, this method allows the steering device, preferably a steering wheel, to be used as a handle when getting in and out.

[0009] Preferably, the resistance torque is provided by a position control mode of the feedback actuator that maintains the initial position of the steering wheel and makes movement of the steering wheel difficult when the entry or exit mode is activated.

[0010] It is advantageous if the entry and / or exit mode is terminated based on at least one signal and / or after a specific time period has elapsed. The time period is preferably an adjustable parameter. The at least one signal can be the detection of a drop in the mains voltage below a specific value and / or a vehicle request signal.

[0011] Preferably, the feedback actuator is switched off when the exit mode is terminated.

[0012] Preferably, the normal operating mode of the feedback actuator is started or the feedback torque actuation for providing the resistance torque is switched off when the entry mode is ended.

[0013] Preferably, the boarding situation is recognized based on the following criteria - Signals from vehicle communication, - the steering angle signal, and / or - the steering torque signal and / or - other signals indicating hand detection (and the presence of the hands) on the steering device.

[0014] Furthermore, a steer-by-wire steering system for a road vehicle is provided, which is designed to carry out the method described above.

[0015] A preferred embodiment of the present invention will be described with reference to the drawings. Fig. 1: is a schematic representation of a steer-by-wire steering system of a motor vehicle, and Fig. 2: shows a block diagram of an entry and exit mode.

[0016] Fig. Figure 1 is a schematic drawing of a steer-by-wire system 1 with a steering shaft 2 connected to a steering mechanism 3. There is no mechanical connection between the steering mechanism 3 and the wheels 4. A road wheel actuator 5 actuates a rack 6, which is part of a front wheel axle 8, via a rack and pinion gear 7. The front wheel axle 8 has two tie rods 9 for the road wheels 4, of which only one road wheel 4 is sketched.

[0017] When a driver operates the steering mechanism 3, the steering shaft 2 rotates, which is detected by a shaft sensor (not shown in the drawings). When the vehicle is switched on, a control unit 10 calculates an operating signal for the road wheel actuator 5 from the signal detected by the shaft sensor. By actuating the rack 6 with the actuation signal, the front wheel axle 8 is moved sideways and the road wheels 4 are rotated. At the same time, the forces introduced by the road wheels 4 into the wheel axle 8 are detected by another sensor (not shown in the drawings), and a feedback signal is calculated. This feedback signal is introduced into the steering shaft 2 by a feedback actuator 11, allowing the operator to detect the feedback in the steering mechanism 3.

[0018] Fig.Figure 2 shows a schematic block diagram of a method for controlling the steering system with an entry / exit mode. In a first step 12, the system detects an entry or exit situation.

[0019] An entry situation can be detected based on signals from the vehicle communication 13, e.g., door state, door lock state, release signal from the vehicle, wake-up signal based on the steering angle signal 14, e.g., when a change in the steering angle of the steering wheel exceeds a defined threshold, and / or based on other signals representing hand detection on the steering means 15, e.g., generated by a capacitive sensor implemented in the steering wheel. If an entry situation is detected, the feedback actuator is switched on in an entry mode and simulates a mechanical resistance that makes moving the steering wheel difficult, allowing the steering wheel to be used as a handle for entering the vehicle. This can be achieved by a position control mode of the feedback actuator 16, which maintains the initial position of the steering wheel when the feedback actuator is activated.To simulate high mechanical resistance, the feedback actuator exerts resistance against the rotation of the steering shaft.

[0020] Entry mode can be terminated based on signals, e.g., when the supply voltage drops below a certain value and / or due to a vehicle request and / or after a certain period of time, where the period is an adjustable parameter. After entry mode is terminated, the normal operating mode of the feedback actuator is started or the feedback torque control for providing a resistance torque is terminated.

[0021] The feedback actuator activates an exit mode 12 after the normal shutdown procedure of the steering system has ended. In exit mode, the feedback actuator simulates a high mechanical resistance, making it difficult to move the steering wheel so that it can be used as a handle for exiting the vehicle. This can be achieved by a position control mode of the feedback actuator 16, which maintains the initial position of the steering wheel when the feedback actuator is activated. The exit mode can be terminated based on signals, e.g., when the supply voltage drops below a certain value and / or due to a vehicle request and / or after a certain period of time has elapsed, where the period of time is an adjustable parameter. When the exit mode is ended, the feedback actuator is switched off.

Claims

[1] Method for controlling a steer-by-wire steering system (1) for a road vehicle, wherein the steer-by-wire steering system (1) comprises a steering means (3), a road wheel actuator (5) for actuating road wheels (4) and a feedback actuator (11) for applying a feedback torque to the steering means, characterized by that the following steps are planned: • When an entry situation is detected (12), the feedback actuator (11) is switched on and a resistance torque against the rotation of the steering means (3) is provided in an entry mode; • When the normal shutdown process of the steering system is completed, an exit mode of the feedback actuator (11) is activated and a resistance moment against the rotation of the steering means (3) is provided. [2] Method according to claim 1, characterized byin that the resistance moment is provided by a position control mode of the feedback actuator (16) which maintains the initial position of the steering wheel (3) and makes it difficult to move the steering wheel (3) when the entry or exit mode is activated. [3] Method according to claim 1 or 2, characterized by that the entry and / or exit mode is terminated due to at least one signal and / or after a certain period of time has elapsed. [4] Method according to claim 3, characterized by that the at least one signal is the detection of a mains voltage drop below a certain value and / or a vehicle request signal. [5] Method according to one of the preceding claims, characterized by that the feedback actuator (11) is switched off when the exit mode is ended. [6] Method according to one of the preceding claims, characterized bythat the normal operating mode of the feedback actuator (11) is started or the feedback torque request is terminated when the entry mode is terminated. [7] Method according to one of the preceding claims, characterized by that the entry situation is recognized (12) on the basis of - signals from vehicle communication (13), - a steering angle signal (14), and / or - a steering torque signal and / or - other signals representing hand detection on the steering device (15). [8] Steer-by-wire steering system (1) for a road vehicle for carrying out the method according to one of the preceding claims.

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