Method for controlling a steer-by-wire steering system of a road vehicle having position calibration of a feedback actuator.

Abstract

The present invention relates to a method for calibrating the position of a feedback actuator (7) of a steer-by-wire steering system (1) of a road vehicle, the method comprising the following steps: Move the feedback actuator (7) to a first end stop position of the feedback actuator (7) and from there to a second end stop position; record the two end stop positions and determine a new defined center position based thereon; move the feedback actuator (7) to the new defined center position (9); store the new defined center position in memory as an offset value for the absolute steering wheel angle.

Description

Technical Field

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[0001] The present invention relates to a method for calibrating the position of a feedback actuator of a steer-by-wire steering system for a road vehicle as recited in the preamble of claim 1, and to a steer-by-wire steering system for a road vehicle having a feedback actuator.

Background Art

[0002] In a steer-by-wire steering system, there is no direct mechanical connection between the steering wheel and the steering linkage, and the vehicle wheels are directly driven by an electric motor. Therefore, the maximum steering wheel angle is no longer defined by a mechanical stop position in the steering gear. However, the maximum steering angle of the wheel is still limited in a steer-by-wire steering system. Therefore, the driver must be informed when the maximum steering angle is reached. The feedback actuator is located on the steering wheel or the steering column and imparts a steering feel to the steering wheel, but the feedback actuator is used to limit the maximum steering wheel angle to a specific angle (or a predefined number of rotations).

[0003] The absolute position of the feedback actuator must be calibrated before it is first used, for example, in the manufacturing cycle department or in a repair shop, if the system is replaced within the vehicle. Furthermore, the end stop position may change during the lifetime. Probably in most cases, the end stop position changes to a larger steering wheel angle during the lifetime of the steering system, but a change to a smaller steering wheel angle can also occur.

Summary of the Invention

[0004] Therefore, an object of the present invention is to provide a method for calibrating the position of a feedback actuator of a steer-by-wire steering system for a road vehicle that enables calibration of the absolute position of the feedback actuator.

[0005] This objective is achieved by a method for calibrating the position of a feedback actuator in a steer-by-wire steering system for a road vehicle having the features of claim 1, and a steer-by-wire steering system for a road vehicle having a feedback actuator having the features of claim 8.

[0006] Accordingly, a method for calibrating the position of a feedback actuator in a steer-by-wire steering system of a road vehicle is provided, characterized by including the following steps: - Move the feedback actuator to its first end stop position, and then move it from there to its second end stop position; - Record the two terminal stopping positions and determine the newly defined central position based on them; - Move the feedback actuator to the newly defined central position; - The newly defined center position is stored in memory as the offset value for the absolute steering angle.

[0007] This method makes it easy to perform and enable system calibration during maintenance or operation.

[0008] Preferably, this method includes the following additional steps: - If the end stop positions change during the lifespan of the steering system, the changed end stop positions are recorded, and any functions in the steering system that use the end stop positions are set to the changed end stop positions.

[0009] This allows for adaptation to changes in the feedback actuator, making the steering system more reliable. If the actual position of the feedback actuator is at a steering angle greater than the stored position, it is advantageous for the stored feedback actuator end stop position to be updated when the feedback actuator is operated. Furthermore, if the algorithm detects the mechanical end stop position at a steering angle smaller than previously stored, the stored feedback actuator end stop position can be updated when the feedback actuator is operated. In a preferred embodiment, the mechanical end stop position detection algorithm is based on the estimated motor torque, the direction of the estimated motor torque, and / or a combination of the position and movement of the feedback actuator.

[0010] The updated feedback actuator end stop position can be used for feedback actuator position-related functions for torque requests and / or for adjusting position requests sent to the load wheel actuator.

[0011] Furthermore, a steer-by-wire steering system for a road vehicle is provided, comprising a feedback actuator, a road wheel actuator, and a control unit for controlling the feedback actuator and the road wheel actuator, wherein the control unit is configured to carry out the above method. [Brief explanation of the drawing]

[0012] Preferred embodiments of the present invention will be described with reference to the drawings. [Figure 1] Figure 1 is a schematic diagram of a steer-by-wire steering system. [Figure 2] Figure 2 is a block diagram showing the calibration of the end stop position of the feedback actuator. [Figure 3]Figure 3 is a block diagram illustrating the adaptation of the steering system to the final stopping position. [Modes for carrying out the invention]

[0013] Figure 1 is a schematic diagram of a steer-by-wire steering system 1 having a steering shaft 2 connected to a steering wheel 3. There is no mechanical connection between the steering wheel 3 and the load wheel 4. A load wheel actuator 5 acts on a gear rack 6 by a recirculating ball gear.

[0014] When the driver operates the steering wheel 3, the steering shaft 2 rotates, which is detected by a shaft sensor (not shown in the diagram). The control unit calculates an actuation signal for the load wheel actuator 5 from the signal detected by the shaft sensor. By acting on the gear rack 6 with the actuation signal, the load wheel 4 is changed direction. At the same time, the force introduced from the load wheel 4 to the gear rack 6 is recognized by another sensor (not shown in the diagram), and a feedback signal is calculated, which is applied to the steering shaft 2 by the steering wheel actuator 7, also called the feedback actuator, so that the driver can perceive feedback in the steering wheel 3.

[0015] As shown in Figure 2, the position of the feedback actuator can be calibrated automatically after a certain period of time or at a repair shop while the vehicle is in operation.8

[0016] In the first step of the calibration process, the feedback actuator moves, for example, in position control, to a first end stop position, and from there to a second end stop position. Both end stop positions are mechanically defined. The two end stop positions are recorded. Using the recorded information, the feedback actuator is moved to a newly defined center position and remains there.9 The newly defined center position is stored in memory as an offset value of the absolute handle angle.

[0017] Feedback actuator torque and / or position actuation can be used for this calibration procedure.

[0018] If the end stop position changes during the lifespan of the steering system, the changed end stop position must be recorded, and the functions in the system must be set to the changed end stop position (see Figure 3).

[0019] In detail, the stored feedback actuator end stop position is updated during operation if the following conditions are met: - The actual position of the feedback actuator is at a handle angle greater than the stored position; and - The algorithm detects the mechanical end stop position at a smaller handle angle than previously stored. The mechanical end stop position detection algorithm can be based on an estimated motor torque, the direction of the estimated motor torque, and / or a combination of the position and movement of the feedback actuator.

[0020] The updated feedback actuator end stop position is then used for feedback actuator position-related functions for torque requirements (e.g., end stop position feeling conditions).

[0021] Furthermore, it is possible to adjust the position request (virtual gear ratio) sent to the load wheel actuator to the updated feedback actuator end stop position.

Claims

1. A method for calibrating the center position of a feedback actuator (7) stored in memory in a steer-by-wire steering system (1) for a road vehicle, comprising the following steps: - A step of moving the feedback actuator (7) to a mechanical first end stop position, and then moving it from there to a mechanical second end stop position, and detecting and recording the mechanical first end stop position and the mechanical second end stop position; - A step of determining a new central position based on the recorded mechanical first end stop position and the mechanical second end stop position; - A step of moving the feedback actuator (7) to a newly defined central position (9); - A process of storing the newly defined central position in memory.

2. A steer-by-wire steering system (1) for a road vehicle having a feedback actuator (7), a road wheel actuator (5), and a control unit for controlling the feedback actuator (7) and the road wheel actuator (5), wherein the control unit is configured to carry out the method described in claim 1.

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