Method for generating haptic feedback

Abstract

A method and a device generate haptic feedback for a vehicle driver, the haptic feedback being generated by applying an additional torque, which alternates about an average total steering torque, to a steering grip of a vehicle by way of an actuator. When the present haptic feedback is recognized and/or simultaneously when haptic feedback occurs, the actuator is actuated such that the magnitude of the average total steering torque is increased by a compensation torque.

Claims

1. A method for generating haptic feedback for a vehicle driver of a vehicle, comprising: generating the haptic feedback by applying an alternating torque by an actuator to an initial steering torque applied to a steering grip of a vehicle, wherein the haptic feedback is a vibration on the steering grip; and controlling the actuator, when the vibration on the steering grip is present and/or simultaneously when the vibration on the steering grip occurs, to provide a compensating torque to the steering grip such that a drop in the initial steering torque caused by the vibration on the steering grip is compensated for by the compensating torque and such that an effect of a lighter steering sensation associated with an increased dynamic friction on the steering grip during the vibration on the steering grip is compensated for by the compensating torque.

2. The method according to claim 1, wherein the compensating torque is maintained, at least in part, until the end of the haptic feedback.

3. The method according to claim 2, wherein the compensating torque decreases to the value 0 at least by the end of the haptic feedback.

4. The method according to claim 1, wherein the compensating torque decreases to the value 0 at least by the end of the haptic feedback.

5. The method according to claim 1, wherein the haptic feedback warns the vehicle driver of leaving a driving lane.

6. A steering system of a vehicle comprising a haptic feedback generator configured to execute: generating haptic feedback by applying an alternating torque by an actuator to an initial steering torque applied to a steering grip of a vehicle, wherein the haptic feedback is a vibration on the steering grip; and controlling the actuator, when the vibration on the steering grip is present and/or simultaneously when the vibration on the steering grip occurs, to provide a compensating torque to the steering grip such that a drop in the initial steering torque caused by the vibration on the steering grip is compensated for by the compensating torque and such that an effect of a lighter steering sensation associated with an increased dynamic friction on the steering grip during the vibration on the steering grip is compensated for by the compensating torque.

7. The steering system according to claim 6, wherein the actuator is one or both of a support motor and a servo motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graphical diagram illustrating the current problem as addressed by the prior art.

(2) FIG. 2 is a graphical diagram illustrating the method according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(3) FIG. 1 is a diagram showing the curve of the torque M on a steering wheel of a vehicle over time t. The diagram shows the situation when an alternating torque M.sub.X1 is activated by a support motor at time t.sub.1 in the steering system and the steering wheel is thus set into vibration. The driver feels these vibrations as a vibration of the steering wheel. Such a vibration due to the alternating torque M.sub.X1 of the support motor is a technically relatively easily implemented manner of generating haptic feedback for the driver in certain situations and thus of providing a driver assistance system.

(4) For example, a vibration of the steering wheel generated in such a way can warn or alert the driver of an unintended or accidental departure from a driving lane.

(5) However, in the systems which are known in the prior art (cf. FIG. 1), disadvantages still exist in the implementation or the method for warning the driver by means of a steering wheel vibration which is generated by a support motor. One such disadvantage is a drop in the steering torque or friction at the onset of the vibration of the steering wheel. This problem specification from the prior art will be explained in more detail in the following on the basis of the diagram of FIG. 1. The method according to the invention is then discussed in FIG. 2.

(6) In the diagram in FIG. 1, the curve of the torque M against time t shows the torque on a steering wheel of a vehicle which is sensed by a vehicle driver as haptic feedback. Depending on the driving situation, the support motor assists the driver in steering the vehicle.

(7) At this point it is assumed that this exemplary embodiment is a case of a lane maintenance system as described.

(8) If the vehicle then crosses the lane boundary at time t.sub.1, the driver assistance system warns the vehicle driver of this using haptic feedback. The steering wheel begins to vibrate due to the alternating torque applied by the support motor.

(9) However, at the time t.sub.1, namely at the onset of the vibration, a drop E is apparent in the initial steering torque or the original average total torque M.sub.0 to a significantly lower average torque M.sub.X1. This drop E of the steering torque is attributable to a low friction in the entire steering system, which is associated with a higher component of dynamic friction relative to static friction at the onset of the vibration. The mean or averaged torque M.sub.X1 which is present during the vibration (period t.sub.hr) is therefore much lower than the average total torque M.sub.0 expected by the driver.

(10) This drop E is noticeable to a driver as a lighter or smoother steering feel, and due to the sudden change can lead to involuntary steering maneuvers. This can negatively affect the driving comfort.

(11) After the vibration (i.e. after the period of time t.sub.hr at time t.sub.3) the feel of the steering is then the same as before the vibration again.

(12) The method according to the invention, which is now shown in the diagram in FIG. 2, is intended to eliminate the previously described problem of the drop in steering torque or friction identifiable in FIG. 1.

(13) FIG. 2 shows, like FIG. 1, a diagram with the profile of the torque M on the steering wheel over time t. This is also intended to illustrate again the situation of a steering wheel vibration as a warning to the vehicle driver of the vehicle departing from a lane.

(14) At the time t.sub.1, the alarm, i.e. the steering wheel vibration, occurs. However, unlike in the method known from the prior art (cf. FIG. 1 time t.sub.1), in this specific case at the time t.sub.1 of the commencement of the vibration, a compensating torque M.sub.FM is activated by the support motor. This compensating torque M.sub.FM compensates the drop E in the steering torque shown in FIG. 1 during a vibration of the steering wheel.

(15) The now averaged steering torque M.sub.x2 during the vibration is higher and more familiar to the driver than the averaged steering torque M.sub.x1 without the activation of a compensating torque M.sub.FM (see FIG. 1).

(16) In this specific case, the compensating torque M.sub.FM at the time t.sub.1 is activated simultaneously with the beginning of the steering wheel vibration.

(17) However, it is alternatively also possible to activate the compensating torque M.sub.FM (shortly) before the beginning of the steering wheel vibration.

(18) Furthermore, as indicated by the curve over the period t.sub.hR of the compensation torque M.sub.FM in FIG. 2, the compensation torque M.sub.FM remains at a constant level during the vibration until time t.sub.2, while it subsequently decreases and by the end of the vibration, i.e. at time t.sub.3, reaches the value 0 again. In this case, the curve or the profile k of the compensation torque M.sub.FM decreases linearly from time t.sub.2 down to the value zero (at time t.sub.3).

(19) The time t.sub.2 in this case describes a suitably selected time at which the compensating torque linearly decreases and which is determined by an electronic control unit as mentioned.

(20) Since the decrease over the temporal course of the vibration or haptic feedback is now barely noticeable to the driver in the feel of the steering, such a reduction in the compensation torque M.sub.FM is advantageous.

(21) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.