Method for operating a steer-by-wire steering system of a non-track-bound vehicle, steer-by-wire steering system, and vehicle having a steer-by-wire steering system

Abstract

The invention relates to a method for operating a steer-by-wire steering system of a non-track-bound vehicle, wherein a steering request, produced by an actuation of a steering handle by means of a vehicle occupant, is detected and, on the basis of the actuation of the steering handle, a wheel angle is set on at least one vehicle wheel via a toothed rack of a steering gear. The method has the following steps: - detecting an at least temporarily specified lane, - determining whether a correction of the wheel angle of the vehicle wheel is necessary in order to stay on the detected lane, and - if it is determined that a correction of the wheel angle is necessary in order to stay on the lane, adjusting the wheel angle, independently of the actuation of the steering handle, in order to stay on the lane.

Description

[0001] Description

[0002] Method for operating a steer-by-wire steering system of a non-track-bound vehicle, steer-by-wire steering system and vehicle with a steer-by-wire steering system

[0003] The invention relates to a method for operating a steer-by-wire steering system of a non-track-bound vehicle according to claim 1, as well as a steer-by-wire steering system for carrying out the method according to dependent claim 7, and a vehicle with a steer-by-wire steering system according to dependent claim 8. For the prior art, reference is made, by way of example, to DE 102014 211 815 A1.

[0004] So-called steer-by-wire steering systems for vehicles are already known in various forms from the prior art. One such steer-by-wire steering system is shown, for example, in DE 102014211 815 A1.

[0005] Such a system differs from conventional steering systems in that the steering of the wheels is completely decoupled from the driver's mechanical steering movements, or rather, is transmitted solely through an electronic system. The conventional mechanical transmission devices are eliminated; instead, the driver generates data through their steering movements at the steering handle or steering wheel, which is then fed into an electronic control unit. This control module evaluates the data and translates it into corresponding steering commands. This, in turn, controls the steering gear, which executes the desired steering movement through a rack and pinion motion. If no such active control of the steering gear occurs, there is no rack movement – ​​meaning the rack remains stationary in all other cases. This means that the rack position, and thus the wheel position, is determined exclusively by the steering handle's action.The wheel position, and thus the wheel angle, is thereby fixed. Forces applied to the wheel or the rack do not lead to any change in the wheel position. The object of the invention is to demonstrate a method for operating a steer-by-wire steering system of a non-track-bound vehicle, which represents an improvement in terms of driving comfort and potential malfunctions.

[0006] The solution to the problem is achieved by a method for operating a steer-by-wire steering system of a non-track-bound vehicle with the features of claim 1, as well as by a steer-by-wire steering system for carrying out the method with the features of dependent claim 7 and a vehicle with a steer-by-wire steering system with the features of dependent claim 8. Advantageous embodiments and further developments are the subject of the dependent claims.

[0007] To implement the procedure, a steer-by-wire steering system is proposed, in which, as already explained in the introductory part, the steering request of a vehicle occupant is detected by actuating a steering handle and a wheel angle (also referred to as wheel steering angle) is set at a vehicle wheel via a rack and pinion of a steering gear depending on the actuating of the steering handle.

[0008] When the steering handle is operated, a hand torque is preferably applied, the magnitude or force of which is detected by appropriate sensors, or a steering wheel angle or steering handle angle is specified and detected by appropriate sensors. The steering command is then derived from this.

[0009] In an autonomously steering vehicle, the operation of the steering controls (steering wheel angle and / or hand torque) is specified by a driver assistance system.

[0010] In both cases, the wheel position and thus the wheel angle of the vehicle wheel is fixed by the driver assistance system or by the operation of the steering handle.

[0011] The steering of the wheels, or at least one of the vehicle wheels, is completely mechanically decoupled from the steering movement of the steering handle.

[0012] The vehicle in question is therefore fundamentally a non-track-bound vehicle, meaning that its directional control is not predetermined and can be freely selected by actively adjusting the wheel angles. Preferably, it is a motor vehicle, in particular a passenger car, truck, or the like.

[0013] The vehicle preferably comprises at least two, and more preferably at least (or exactly) four wheels. In the case of exactly four wheels, two are located on a front axle and two on a rear axle of the vehicle. In particular, the wheels of the front axle are adjustable by means of a steer-by-wire steering system.

[0014] The proposed method captures, in a single step, a vehicle's at least temporarily predetermined lane. Such a lane represents a section of roadway designed in such a way that the vehicle's trajectory is essentially predetermined, at least for this section. This lane preferably includes a lane boundary on at least one side. For example, such a predetermined lane could be a rail-like track, such as those found in car washes, on ramps, or during a car or truck's journey on a ship or train, etc. The lane boundary could then be a raised section or step on at least one side, thus limiting the lane on at least one side.

[0015] The lane, which is at least temporarily defined, is preferably designed such that the steering angle of a standard vehicle (in particular a truck or a car) is at least substantially determined or restricted by the existing temporary lane marking. The lane marking preferably sets or substantially defines the steering angle.

[0016] In a proposed vehicle with a steer-by-wire steering system, such a temporarily predetermined track of the vehicle is preferably set by detecting an external rack force. For this purpose, an applied rack force or a load on the rack due to external influences (i.e., especially from the vehicle wheel) can be determined based on calculations, estimates, or measurements, possibly with appropriate sensors.

[0017] Alternatively or additionally, it is also possible to detect the at least temporarily defined lane using appropriate sensors or a vehicle navigation system. For example, an image recognition device, in particular a vehicle (exterior) camera used to capture the vehicle's surroundings, can detect such a at least temporarily defined lane. A vehicle navigation system can, for example, identify the vehicle's current location where such a at least temporarily defined lane is likely to be found. For instance, the vehicle may be programmed with information indicating that such a defined lane exists at or within a car wash.

[0018] In a further step, it is determined whether a correction of the wheel angle of at least one vehicle wheel is necessary to maintain the detected track (especially without contact).

[0019] The primary objective is to ensure that the vehicle remains within its lane without causing damage. In the context of this invention, "without causing damage" specifically refers to a vehicle wheel remaining undisturbed within its lane or lane markings.

[0020] The aim here is to avoid or prevent situations in which at least one vehicle wheel is pinched or damaged by a track boundary while driving or stationary, since the wheel angle does not change automatically due to the technical characteristics of the steer-by-wire steering system. This situation occurs particularly when a wheel angle is set on the track while driving or stationary, and this angle is so large that the wheel collides with the track or the track boundary, resulting in pinching or damage. It is also possible that the vehicle wheel could jump out of the track or the track boundary (e.g., a guide rail). This should be avoided.

[0021] When an external rack force (originating from the vehicle wheel), as explained above, is detected, it can be used, for example, based on the current vehicle speed, lateral acceleration, or tilt, etc., to determine whether this detected rack force is caused by wheel binding against the track gauge of the at least temporarily defined track. Alternatively or additionally, it is also possible to determine a potential need for wheel angle correction through appropriate calculations, estimates, or measurements. For example, suitable detection devices (sensors, distance meters, etc.) can be used to calculate or estimate whether the current wheel angle, in relation to the track gauge dimensions, leads to contact, or in particular, damage or binding of the vehicle wheel against the track or its gauge.

[0022] If a correction of the wheel angle is necessary to maintain the track, the wheel angle is adjusted or changed in a subsequent step to maintain the detected track, independently of the steering hand operation. The wheel angle is adjusted, in particular reduced or increased, to such an extent that contact, damage, or binding of the vehicle wheel by the track or track limiter is avoided or prevented.

[0023] In a preferred embodiment of the invention, the wheel angle is adjusted independently of the steering handle operation to maintain the vehicle's lane position only if the steering handle operation is below a predetermined maximum force. It is particularly preferred that the maximum hand torque at the steering handle (i.e., the predetermined maximum force) does not exceed approximately 2 Nm. This preferred setting serves as a switching criterion, providing additional plausibility for the aforementioned correction requirement. If the hand torque at the steering handle is too high (especially above 2 Nm), this indicates that the driver intentionally wants to steer the vehicle. In such cases, lane position is given less priority than the driver's actual steering input.

[0024] Furthermore, the following additional preferred switching criteria can be applied. It is preferably provided that the wheel angle is only adjusted independently of the steering hand operation to maintain the lane if the current vehicle speed is below a predetermined maximum speed, the lateral acceleration of the vehicle is below a predetermined maximum lateral acceleration, or the current wheel steering angle of the vehicle wheel is below a predetermined maximum wheel steering angle.

[0025] Damage or binding of the vehicle wheel, as described above, occurs particularly in situations at near-standstill speeds or even when the vehicle is stationary. For example, in a car wash or on a ramp. Therefore, the changeover criterion of a maximum speed also serves to validate the need for the aforementioned correction.

[0026] As mentioned several times above, it is preferable that the wheel steering angle is only adjusted independently of the steering handle operation to maintain the vehicle's alignment if it is determined that the currently set wheel angle is causing damage to or distortion of the vehicle wheel or a component of the steer-by-wire steering system. Therefore, if, for example, only a harmless contact of the vehicle wheel with the track or track limiter is detected, it is not necessarily required to change the wheel angle.

[0027] In addition to the aforementioned method, as already mentioned above, a steer-by-wire steering system for a non-track-bound vehicle is proposed for carrying out the method according to one of claims 1 to 6.

[0028] Furthermore, a vehicle with a steer-by-wire steering system configured to perform the method according to any one of claims 1 to 6 is proposed.

[0029] The steer-by-wire system includes a steering handle for the driver or a passenger to input a steering input. This input is then electronically transmitted to a steering gear (or a rack and pinion of the steering gear) to adjust the wheel angle. The steering of the wheels, or at least one wheel, is completely mechanically decoupled from the steering movement of the steering handle.

[0030] As described above, the vehicle includes at least one wheel with an adjustable wheel angle via the steer-by-wire steering system. Preferably, it is a passenger car or truck with at least two wheels steerable by the steer-by-wire system. The steering of the wheels, or of at least one wheel, is completely mechanically decoupled from the steering movement of the steering handle.

[0031] Furthermore, a control unit is provided which, in the event that a correction of the wheel angle is necessary, controls the steering gear or the rack of the steering gear independently of any action on the steering handle.

[0032] The proposed method thus enables damage-free driving or damage-free stay of the vehicle on the lane in certain situations, in particular where a temporary lane is specified for the vehicle.

Claims

Patent claims 1. Method for operating a steer-by-wire steering system of a non-track-bound vehicle, wherein the steering request of a vehicle occupant is detected by actuating a steering handle and a wheel angle is set at at least one vehicle wheel via a rack of a steering gear depending on the actuating of the steering handle, comprising the following steps: - Capturing a track that is at least temporarily predetermined, - Determine whether a correction of the wheel angle of the vehicle wheel is necessary to maintain the detected track; - If it is determined that a correction of the wheel angle is necessary to maintain the toe, the wheel angle is adjusted to maintain the detected toe independently of the steering hand operation. Method according to claim 1, wherein the wheel angle is adjusted independently of the steering hand operation to maintain the toe only if the steering hand operation is below a predetermined maximum force. Method according to claim 1 or 2, wherein the wheel angle is adjusted independently of the steering hand operation to maintain the toe only if the current vehicle speed is below a predetermined maximum speed and / or the lateral acceleration of the vehicle is below a predetermined maximum lateral acceleration and / or the current wheel steering angle of the vehicle wheel is below a predetermined maximum wheel steering angle.Method according to one of the preceding claims, wherein the wheel steering angle is adjusted independently of the operation of the steering handle to maintain the track only if it is determined that the currently set wheel angle leads to damage to the vehicle wheel and / or a component of the steer-by-wire steering system.

5. Method according to one of the preceding claims, wherein the at least temporarily predetermined track of the vehicle is detected by detecting an external rack force.

6. Method according to one of the preceding claims, wherein the at least temporarily predetermined lane of the vehicle is detected by sensors and / or by a vehicle navigation system. 7 Steer-by-wire steering system of a non-track-bound vehicle for carrying out the method according to one of claims 1 to 6. 8 Vehicle with a steer-by-wire steering system configured to perform the method according to any one of claims 1 to 6.