Active wheel damping

1. A vehicle suspension for controlling motion of a sprung and unsprung mass comprising:

a force source which is capable of applying a force in response to a control signal and without a physical stimulus, the force source coupling a vehicle unsprung mass and a vehicle sprung mass:

a sensor for detecting vertical motion of the sprung mass or a quantity from which vertical motion of the sprung mass can be derived;

an unsprung mass sensor for detecting vertical motion of the unsprung mass or a quantity from which vertical motion of the unsprung mass can be derived; and

control circuitry;

responsive to the sprung mass sensor for determining a force to reduce the vertical motion of the sprung mass in a first frequency range; and

responsive to the unsprung mass sensor for determining a force to reduce the vertical motion of the unsprung mass in a second frequency range;

wherein the first frequency range includes frequencies above and below the second frequency range and wherein the first frequency range does not include the second frequency range.

2. The vehicle suspension system of claim 1 , wherein the control circuitry comprises an anti causal filter.

3. The vehicle suspension system of claim 2 , further comprising circuitry for detecting vertical disturbances in the road ahead of a wheel that is a component of the unsprung mass.

4. The vehicle suspension system of claim 3 , wherein the wheel is a rear wheel and wherein the circuitry for detecting vertical disturbances in the road is associated with a front wheel.

5. The vehicle suspension system of claim 4 , wherein the anti-causal filter

determines, prior to the wheel's encountering the road disturbance, an estimated response of the vehicle suspension to the disturbance;

reverses with respect to time the estimated response to provide an anti causal response;

and

causes the controllable force source to apply the anti causal response prior to the wheel encountering the road disturbance.

6. The vehicle suspension system of claim 4 , wherein the anti causal filter scales the anti causal response to provide a scaled anti causal response and causes the controllable force source to apply the scaled anti causal response prior to the wheel encountering the road disturbance.

7. The vehicle suspension of claim 4 , wherein the estimated response is calculated over a first period of time, and wherein the scaled anti causal response is applied over a second period of time, shorter than the first period of time.

8. The vehicle suspension system of claim 4 , wherein the anti causal filter calculates a force to a road disturbance and wherein the force source commences applying the force to reduce the vertical displacement of the rear wheel before the rear wheel encounters the road disturbance.

9. The vehicle suspension system of claim 1 , further comprising a bandpass filter of eighth order or greater for filtering a signal representative of the vertical motion of the unsprung mass.

10. The vehicle suspension system of claim 1 , wherein the second frequency range includes a resonance frequency of a resonant system comprising the compliance of a tire and a mass of unsprung vehicle components.

11. The vehicle suspension system of claim 1 , the control circuitry comprising a nonlinear filter for filtering the force to reduce the vertical motion of the sprung mass or for filtering the force to reduce the vertical motion of the unsprung mass or both.

12. The vehicle suspension system of claim 11 , wherein the nonlinear filter is a deadband filter.

13. The vehicle suspension system of claim 11 , wherein the nonlinear filter is a clipper.

14. A method for controlling motion of a sprung and unsprung mass of a vehicle, where the unsprung mass incorporates a wheel with a tire and the unsprung mass resonates with a compliance of the tire at a resonance frequency, comprising:

a first detecting, of vertical motion of an unsprung mass of a vehicle or a quantity from which vertical motion of the unsprung mass of the vehicle can be derived or both;

in a first frequency band and responsive to the first detecting, determining a force to reduce the vertical motion of the unsprung mass;

a second detecting, of vertical motion of a sprung mass or a quantity from which vertical motion of the sprung mass can be derived or both;

in a second frequency band not including the resonance frequency of the unsprung mass, and responsive to the second detecting, determining a force to reduce the vertical motion of the sprung mass;

applying, in the first frequency range, by a force source which is capable of exerting a force in response to a control signal and without a physical stimulus and which couples the sprung mass and the unsprung mass, the force to reduce the vertical motion of the unsprung mass; and

applying, in the second frequency range, by the force source, the a force to reduce vertical motion of the sprung mass.

15. The method of claim 14 , wherein the determining of the force to reduce the vertical motion of the unsprung mass is determined by an anti causal filter.

16. The method of claim 15 , wherein the first determining comprises detecting vertical disturbances in the road ahead of a wheel which is a component of the unsprung mass.

17. The method of claim 16 , wherein the wheel is a rear wheel and wherein the detecting vertical disturbances in the road ahead of the wheel is associated with a front wheel.

18. The method of claim 17 , wherein the applying of the force to reduce vertical motion of the unsprung mass is commenced before the rear wheel encounters the unsprung mass.

19. The method of claim 15 , further comprising:

determining an estimated response to the road disturbance of the unsprung mass prior to the rear wheel's encountering the road disturbance; and

reversing with respect to time the estimated response to provide an anti causal response.

20. The method of claim 19 , further comprising scaling the anti causal response to provide a scaled anti causal response; and

causing the controllable force source to apply the scaled anti causal response prior to the rear wheel encountering the road disturbance.

21. The method of claim 20 , wherein the determining of the estimated response to the road disturbance comprises determining the estimated response over a first period of time, and wherein the applying of the force to reduce vertical motion of the unsprung mass comprises applying the force to reduce the vertical motion of the unsprung mass over a second period of time, shorter than the first period of time.

22. The method of claim 14 , further comprising filtering by an eighth order filter a signal representative of the vertical motion of the unsprung mass so that the second frequency band does not include the first frequency band.

23. The method of claim 14 , further comprising:

filtering by a nonlinear filter the force to reduce the vertical motion of the unsprung mass or the force to reduce the vertical motion of the sprung mass or both.

24. The method of claim 23 , the filtering by a nonlinear filter comprising filtering with a deadband filter.

25. The method of claim 23 , the filtering by a nonlinear filter comprising filtering with a clipper.

26. Apparatus comprising:

a wheel hop damper, comprising

a sensor to detect vertical motion of an unsprung mass of a vehicle in a first frequency range;

a controller to determine a force for the force source to apply to reduce the vertical motion of the unsprung mass in the first frequency range; and

a force source which is capable of exerting a force between a sprung mass and an unsprung mass in response to a control signal and without a physical stimulus

wherein the wheel hop damper is free of a damping mass

wherein

the wheel hop damper is incorporated in a suspension system of a vehicle, the suspension system comprising

a sensor to detect vertical motion of a sprung mass of the vehicle in a second frequency range not including the first frequency range; and

a controller to determine a force for the force source to apply to reduce the vertical motion of the sprung mass in the second frequency range.

27. The apparatus of claim 26 , wherein the second frequency range includes frequencies above and below the first frequency range.

28. The apparatus of claim 26 , the suspension system further comprising an eighth order bandpass filter for filtering a signal representative of the vertical motion of the unsprung mass.

29. The apparatus of claim 26 , wherein the wheel hop damper controller comprises an anti causal filter.

30. The apparatus of claim 29 , wherein the anti causal filter calculates a response to a road disturbance and causes the response to commence before the wheel encounters the road disturbance.

31. The apparatus of claim 29 , wherein the anti-causal filter

determines, prior to the wheel's encountering the road disturbance, an estimated response of the vehicle suspension to the road disturbance;

reverses with respect to time the estimated response to provide an anti causal response;

and

causes the controllable force source to apply the anti causal response prior to the wheel encountering the road disturbance.

32. The apparatus of claim 31 , wherein the anti causal filter scales the anti causal response to provide a scaled anti causal response and causes the controllable force source to apply the scaled anti causal response prior to the wheel encountering the road disturbance.

33. The apparatus of claim 32 , wherein the estimated response is calculated over a first period of time, and wherein the scaled anti causal response is applied over a second period of time, shorter than the first period of time.

34. The apparatus of claim 26 , wherein the first frequency range includes a resonance frequency of a resonant system comprising the compliance of a tire and a mass of unsprung vehicle components.

35. The apparatus of claim 26 , further comprising a nonlinear filter for filtering the force to reduce the vertical motion of the unsprung mass.