Method for controlling a steer-by-wire steering system of a road vehicle having a garage mode

Abstract

A method for controlling a steer-by-wire steering system (1) of a road vehicle having a feedback actuator (7), a road wheel actuator (5) and a control unit for controlling (7) and (5), the method comprising the steps of: - upon an external request to the control unit (8), providing a garage mode of the steer-by-wire steering system: a) switching off the feedback actuator (9); b) depending on the external request, moving the road wheel actuator to a predefined position or moving the road wheel actuator from one end position to another end position or fixing the position of the road wheel actuator in the previous position or in the central position; - After exiting garage mode, return (1) to its original position before entering garage mode and switch (7) on.

Description

Technical Field

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

Background Art

[0002] Steer-by-wire steering systems have no mechanical connection between the steering wheel and the road wheels. They include a feedback actuator for applying a feedback torque to the steering wheel and a road wheel actuator for changing the direction of the steerable road wheels.

[0003] The steering of a vehicle traditionally consists of adjusting the toe angle of the vehicle wheels during vehicle maintenance. In this case, steer-by-wire offers new possibilities. However, steer-by-wire also has difficulties, for example, with regard to calibration and towing.

Summary of the Invention

[0004] It is an object of the present invention to provide a method for controlling a steer-by-wire steering system of a road vehicle that enables handling of the above-described situation.

[0005] This object is achieved by a method for controlling a steer-by-wire steering system of a road vehicle having the features of claim 1.

[0006] Accordingly, there is provided a method for controlling a steer-by-wire steering system of a road vehicle having a feedback actuator, a road wheel actuator, and a control unit for controlling the feedback actuator and the road wheel actuator, the method including the following steps: - Providing a garage mode of the steer-by-wire steering system by an external request to the control unit: a) Switch off the feedback actuator; b) Depending on an external requirement, move the load wheel actuator to a predefined position, or move the load wheel actuator from one end position to another end position, or fix the position of the load wheel actuator to the previous position or the central position; - After the garage mode has ended, return the load wheel actuator to its original position before the steer-by-wire steering system entered the garage mode, and switch on the feedback actuator.

[0007] The garage mode enables handling maintenance or other special situations such as calibration and towing.

[0008] Preferably, the external requirement is transmitted by vehicle communication.

[0009] The external requirement can be sent from an external device outside the vehicle or from another control unit within the vehicle.

[0010] In one embodiment, the external requirement includes a requirement for toe angle adjustment, and in step b), the load wheel actuator is fixed at the central position.

[0011] The external requirement includes a requirement for the load wheel actuator position, and in step b), the load wheel actuator can be moved from one end position to another end position and returned to the original position.

[0012] Furthermore, the external requirement includes a requirement for towing, and in step b), the load wheel actuator position can be fixed to the previous position or the central position.

[0013] Furthermore, a steer-by-wire steering system is provided having a controller installed to implement the above-described method.

Brief Description of the Drawings

[0014] Preferred embodiments of the present invention will be described with reference to the drawings.

Figure 1

Figure 2

DETAILED DESCRIPTION OF THE INVENTION

[0015] FIG. 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 road wheel 4. The road wheel actuator 5 operates a rack 6 by means of a recirculating ball gear 7.

[0016] When the driver operates the steering wheel 3, the steering shaft 2 is rotated, which is detected by a shaft sensor (not shown in the figure). The control unit calculates an operating signal for the road wheel actuator 5 from the signal detected by the shaft sensor. By operating the rack 6 with the operating signal, the road wheel 4 is steered. At the same time, the force introduced from the road wheel 4 to the rack 6 is recognized by another sensor (not shown in the figure), and a feedback signal is calculated, which is applied to the steering shaft 2 by a steering wheel actuator 7, also referred to as a feedback actuator, so that the driver can recognize the feedback at the steering wheel 3.

[0017] According to the present invention, the steer-by-wire steering system 1 has a garage mode for maintenance and / or special use cases. The special use cases can be, for example, toe angle adjustment, end-lock position calibration of the road wheel actuator, towing, etc.

[0018] As shown in FIG. 2, there is an external garage mode request 8 sent to the control unit of the steering system. The external request can be transmitted through vehicle communication, such as OBD, CAN, Flexray, Ethernet, etc. The external request can be sent from an external device outside the vehicle or from another control unit within the vehicle. In response to the request, the feedback actuator 7 is switched off 9. The load wheel actuator 5 maintains its full functionality 10.

[0019] The garage mode enables toe angle adjustment. When the load wheel actuator is in the neutral position, the vehicle should move straight forward. However, during axle assembly or during the vehicle's lifetime, the left and right wheels may be oriented in a direction that is not straight forward. This can lead to skidding.

[0020] For toe angle adjustment, the load wheel actuator is fixed in the central position.

[0021] Furthermore, the garage mode enables position calibration of the load wheel actuator, and the load wheel actuator is moved from one end position to another end position and then returned to its original position. The end positions are preferably defined by the end positions of the load wheel actuator.

[0022] For other special use cases such as towing, the garage mode enables the load wheel actuator position to be fixed at the previous position or the central position according to an external request sent to the control unit. If the load wheel actuator is required to change its position, this is done after the target position by the request message.

[0023] After the garage mode ends, the load wheel actuator is gradually returned to its original position before the system entered this special mode, and the feedback actuator is switched on.

Claims

1. A method for controlling a steer-by-wire steering system (1) of 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), characterized in that the method comprises the following steps: - Giving a garage mode of the steer-by-wire steering system by an external request (8) to the control unit: a) Switch off the feedback actuator (9); b) Depending on the external request, move the road wheel actuator to a predetermined position, or move the road wheel actuator from one end position to another end position, or fix the position of the road wheel actuator to the position before entering the garage mode or the central position; - After the garage mode ends, if the position of the road wheel actuator (5) is moved in step b), return the road wheel actuator (5) to the original position before the steer-by-wire steering system (1) enters the garage mode, switch on the feedback actuator (7), while if the position of the road wheel actuator (5) is fixed in step b), keep the position of the road wheel actuator (5) as it is and switch on the feedback actuator (7).

2. The method according to claim 1, characterized in that the external request is transmitted by vehicle communication.

3. The method according to claim 1 or 2, characterized in that the external request is sent from an external device outside the vehicle or from another control unit within the vehicle.

4. The method according to claim 1, characterized in that the external request includes a request for toe angle adjustment, and in step b) the road wheel actuator (5) is fixed at the central position.

5. The method according to claim 1, characterized in that the external request includes a request for the road wheel actuator position, and in step b) the road wheel actuator (5) is moved from one end position to another end position and returned to the original position.

6. The method according to claim 1, characterized in that the external requirement includes a requirement for traction and that in step b) the load wheel actuator position is fixed to the immediately preceding position or the central position.

7. A steer-by-wire steering system (1) for a road vehicle having the control unit installed to carry out the method according to claim 1.

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