Abstract: A semi-active control method for a controllable fluid damper used in seat supports. The present method filters a relative displacement signal phase shifting the relative displacement sine wave by an angle from greater than 0.degree. through an angle less than 90.degree. to get a relative rate. The sign of the relative rate is compared to that of an absolute velocity curve obtained by integrating the absolute acceleration value obtained by an accelerometer attached to the controlled seat. If the signs are the same, the output to the damper is set to a minimum; if the signs are different, the value is set at the absolute velocity multiplied by an input gain. Endstop limits can be implemented with this control method.