A command shaping approach to enhance the dynamic performance and longevity of contact switches

The performance and longevity of contact type electromechanical switches and relays are traditionally major concerns in many electrical power and communication applications. The contact impact between a switch and its corresponding substrate due to applied voltage or current may reduce the fatigue life of such devices. Thus a conflict exists between the response bandwidth and the reliability of a device. In this article, using energy conservation and force equilibrium, a novel command shaping scheme for generating a desired input sequence to reduce the impact level while preserving the dynamic performance is proposed and developed. Through simulation and experimental characterization, it is demonstrated that the proposed shaping scheme can effectively reduce the impact and the settling time without sacrificing the bandwidth of the actuators. The robustness of the proposed shaper is explored from the standpoint of uncertainties from system parameters such as modal damping, modal stiffness, and air gaps, showing that the proposed shaper can handle the parameter variation up to a certain extent. For a system with significant parameter variations or containing moderate damping, a modified command design scheme and an on-line tuning scheme is proposed and demonstrated to allow further performance optimization.