Improvement of a Force Transmission Between Wheel and Road

Abstract

A method for improving the force transmission between a wheel of a vehicle and the road is disclosed. The method has the following steps: determining target dynamics of a wheel; and, adjusting the dynamics of the wheel by a driving device of the vehicle by actively applying a torque to the wheel to set the target dynamics. A device, a vehicle, and a computer product are disclosed to execute the method.

Claims

1.-14. (canceled)

15. A method for improving a force transmission between a wheel of a vehicle and a road, the method comprising: determining target dynamics of a wheel; and applying a torque to the wheel to achieve the target dynamics.

16. The method of claim 15, wherein the torque is applied in response to actual dynamics of the wheel not matching the target dynamics.

17. The method of claim 15, wherein the torque is applied to maintain actual dynamics of the wheel matching the target dynamics.

18. The method of claim 15, wherein the torque is applied during or after an occurrence that causes actual dynamics of the wheel to deviate from the target dynamics.

19. The method of claim 15, wherein the torque is applied in response to the wheel exceeding a maximum traction utilization.

20. The method of claim 15, wherein the torque is applied during or after a brake intervention or an acceleration.

21. The method of claim 15, wherein the torque is applied by an electric driving engine.

22. The method of claim 15, wherein the target dynamics provide the wheel with optimum traction utilization.

23. The method of claim 15, wherein the target dynamics are determined based on a target value.

24. The method of claim 23, wherein the target value comprises a wheel target speed, a wheel target slip, a wheel target rotational speed, and/or a wheel target acceleration.

25. The method of claim 15, further comprising: applying a brake to the wheel to prevent the applied torque from overshooting the target dynamics.

26. The method of claim 15, wherein the wheel is one of a plurality of wheels, and wherein the torque is applied individually for each wheel or on an axle-by-axle basis.

27. A vehicle comprising: a wheel; and a data processing unit configured to: determine a target speed of the wheel that ensures a transmission capability of a braking force on a road by the wheel; apply break pressure to the wheel; determine an actual speed of the wheel; and in response to a difference between the target speed of the wheel and the actual speed of the wheel exceeding a threshold: release the brake pressure from the wheel; and apply an accelerating torque to the wheel.

28. The vehicle of claim 27, wherein the accelerating torque is applied after the brake pressure is released from the wheel.

29. The vehicle of claim 27, wherein the accelerating torque is applied before the brake pressure is released from the wheel.

30. The vehicle of claim 27, wherein the accelerating torque is applied directly from a driving device to the wheel.

31. The vehicle of claim 27, wherein the accelerating torque is applied indirectly from a driving device to the wheel via a gear.

32. The vehicle of claim 27, wherein the accelerating torque is applied by an electric engine.

33. The vehicle of claim 27, wherein the accelerating torque is applied to an axle of the wheel.

34. A vehicle comprising: a wheel; and means for applying an accelerating torque to the wheel to cause the wheel to reach a target speed, wherein the target speed is reached faster by applying the accelerating torque as compared to relying upon vehicle inertia to provide acceleration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows an exemplary influencing of a wheel of a vehicle by a braking with interventions of an antilocking system;

[0037] FIG. 2 shows a vehicle having an axle-by-axle drive; and

[0038] FIG. 3 shows a vehicle having an individual wheel drive.

DETAILED DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 shows an exemplary influencing of a wheel of a vehicle by a braking with interventions of an antilocking system.

[0040] A timeline is shown, which shows the lapse of time from left to right.

[0041] Thereover, the time courses of a vehicle reference speed v.sub.Ref, a wheel target speed v.sub.TargetWheel and a wheel speed v.sub.Wheel are shown.

[0042] The vehicle reference speed v.sub.Ref corresponds to the actual speed of the vehicle over ground. This is, for example, directly detected or determined by an estimation method.

[0043] The wheel target speed v.sub.TargetWheel describes target dynamics of the wheel, which are determined to ensure a desired transmission capability of the braking force on the road by the wheel. This is carried out by a comparison of the wheel target speed v.sub.TargetWheel with the vehicle reference speed v.sub.Ref. Thus, a desired wheel slip to be reached to support the braking force on the road may be set by the wheel target speed v.sub.TargetWheel.

[0044] The dynamics of the wheel are adjusted to the wheel target speed v.sub.TargetWheel during braking. The braking is thereby, for example, carried out by a friction brake, such as a disc or drum brake, or by an electrodynamic brake. In any event, a braking torque is applied to the wheel.

[0045] If the braking is too strong, a locking of the wheel occurs. This is recognizable by the dotted drops of the wheel speed v.sub.Wheel, at which the wheel speed v.sub.Wheel decreases with a steep gradient. When the deviation of the wheel speed v.sub.Wheel from the wheel target speed v.sub.TargetWheel is too large or when the deviation exceeds a predetermined threshold, respectively, the braking at such wheel is stopped or the braking force is reduced, respectively, such that the wheel is re-accelerated by the vehicle inertia and can be brought up to the wheel target speed v.sub.TargetWheel.

[0046] According to the invention, the time until the wheel re-establishes the wheel target speed v.sub.TargetWheel is shortened such that the wheel speed v.sub.Wheel is optimally set with respect to the vehicle reference speed v.sub.Ref.

[0047] Therefore, an accelerating torque is applied to the wheel by the driving device of the vehicle to accelerate it in addition to the effect of the vehicle inertia. A course of a wheel speed v.sub.Wheel′ resulting therefrom is represented by a corresponding solid line. Due to the accelerating effect of the torque of the driving device in comparison to a sole acceleration of the wheel by the inertia of the vehicle, it is achieved that the wheel speed v.sub.Wheel′ arrives more quickly at the wheel target speed w.sub.TargetWheel. The dynamics of the wheel are therefor returned more quickly to the optimum target dynamics, thus restoring the condition of optimum force transmission. In this way, the braking distance may be shortened.

[0048] Further, FIG. 1 shows the point in time, at which the driving device applies the torque for accelerating the wheel. As an example, the brake pressure p supplied to the brake is shown at the first drop of the wheel speed v.sub.Wheel. The brake pressure p is built up until a point in time t.sub.1. Subsequently, the antilocking system intervenes and the brake pressure p is released again. From a point in time t.sub.2, the brake pressure is reduced to such an extent that the vehicle inertia is sufficient to re-accelerate the wheel, as recognizable by the dotted course of the wheel speed v.sub.Wheel, since the reversal point of the wheel speed v.sub.Wheel is at t.sub.2. Furthermore, it can be seen from the course of v.sub.Wheel′ that the accelerating intervention of the driving device achieves that the reversal point is earlier, i.e. temporally before t.sub.2. In this example, it is assumed that the driving device applies the accelerating torque to the wheel, when the point in time t.sub.1 is exceeded, i.e. when the intervention by the antilocking system is carried out.

[0049] For further improvement of the method described here, it may also be provided that the accelerating torque by the driving device is already applied before the point in time t.sub.1, i.e. before the intervention of the antilocking system. In this way, the accelerating effect by the driving device may directly start from the point in time t.sub.1. If the applied torque is large enough, the accelerating effect may also overcompensate the braking force of the brake such that the accelerating effect already starts before the point in time t.sub.1.

[0050] According to another advantageous embodiment of the invention, it is provided that the torque by the driving device is applied such that the accelerating effect already occurs before the drop of the wheel speed v.sub.Wheel. In this way, by the interaction of brake and drive device, it may be achieved that a drop of the wheel speed v.sub.Wheel does not occur and, instead, the wheel speed v.sub.Wheel is held approximately permanently or exclusively permanently at the wheel target speed v.sub.TargetWheel. Thus, a further improvement of the force transmission between wheel and road may be achieved in comparison to the embodiment shown in FIG. 1.

[0051] FIG. 2 shows a vehicle having an axle-by-axle drive.

[0052] The shown vehicle comprises a non-driven axle 1. A second axle 2 of the vehicle is driven by the driving device M. Therefore, a gear G is provided that distributes the power of the driving device M to the wheels R.sub.1, R.sub.2 of the axle.

[0053] The vehicle is configured to adjust the dynamics of the wheels R.sub.1, R.sub.2 by the driving device M to predetermined target dynamics. The driving device M is therefore configured to provide a respective torque to the gear G, whereby it is distributed to the wheels R.sub.1, R.sub.2.

[0054] During braking, one of the wheels R.sub.1, R.sub.2 or both of the wheels R.sub.1, R.sub.2 may get locked or at least in a state, in which a deviation of the wheel speed v.sub.Wheel from the wheel target speed v.sub.TargetWheel exceeds a predetermined value, as previously described with respect to FIG. 1.

[0055] If such a state is present, the driving device M will apply a respective torque to the wheels R.sub.1, R.sub.2 via the gear G to adjust their wheel speed v.sub.Wheel to the wheel target speed v.sub.TargetWheel or to maintain the wheel target speed v.sub.TargetWheel. In such event, this may be carried out by applying an accelerating torque by the driving device M.

[0056] Even without a presence of a braking, the driving device may be used to adjust the dynamics of the wheel to the target dynamics.

[0057] When the vehicle accelerates and one of the wheels R.sub.1, R.sub.2 or both of the wheels R.sub.1, R.sub.2 start(s) to spin, a braking effect by a respective torque applied to the wheels R.sub.1, R.sub.2 by the driving device M and via the gear G may be applied to these such that they are braked again. This implies that the driving device M is configured to apply a respective torque. For example, this is the case when the driving device M comprises an electric driving engine (electric machine/motor).

[0058] This also applies for the case, in which the ground of the wheels R.sub.1, R.sub.2 changes, as mentioned at the beginning. That is, a deviation of the dynamics of the wheels R.sub.1, R.sub.2 from target dynamics may be provided during a constant drive, a braking or an acceleration, wherein then the target dynamics at the wheels R.sub.1, R.sub.2 may be set accordingly by the driving device M.

[0059] In the shown embodiment, the gear G has to be configured accordingly to distribute the torque of the driving device M to the wheels R.sub.1, R.sub.2 as required.

[0060] FIG. 3 shows a vehicle having an individual wheel drive.

[0061] In contrast to the embodiment of FIG. 2, a separate driving device M is assigned here to each wheel R.sub.1, R.sub.2 of the axle 2. Thus, influencing the dynamics individually for each wheel towards target dynamics is possible, whereas in the embodiment shown in FIG. 2, a torque for influencing by the drive device M must be directed to the wheel whose dynamics deviate from the target dynamics.

[0062] Otherwise, the operating principles of this embodiment correspond to the ones as shown in FIG. 2.

LIST OF REFERENCE SIGNS

[0063] 1 axle [0064] 2 axle [0065] G gear [0066] M driving device [0067] p brake cylinder pressure [0068] R.sub.1 wheel [0069] R.sub.2 wheel [0070] t time [0071] t.sub.1 point in time [0072] t.sub.2 point in time [0073] v.sub.Ref vehicle reference speed [0074] v.sub.TargetWheel wheel target speed [0075] v.sub.Wheel wheel speed [0076] v.sub.Wheel′ wheel speed