Patent ID: 7314220

Claim:
A variable suspension system for use with a wheelchair having a forward end and a rear end, a frame, and at least one wheel coupled to at least one end of the frame for movement relative to the frame, the wheelchair further having a drive assembly operably coupled to the wheel to move the wheel toward or away from a supporting surface upon which the wheelchair is supported in response to moments generated by the drive assembly, the suspension system comprising: at least one sensor for sensing the vertical position of the wheel relative to the frame and generating a control input signal indicative of the wheel position; a controller operatively coupled to the sensor and responsive to the control input signal for generating a control output signal; and a controllable damper having a variable stiffness, operably coupled to the controller, the wheel, and the frame to provide a variable resistive force capable of being varied to any of multiple levels of force within a continuous range between upper and lower limits in response to the control output signal and resistive to the movement of the wheel, the resistive force being varied based at least in part upon the vertical position of the wheel.