A step and settle positioning algorithm for electro-mechanical systems with damping

An algorithm for rapid step and settle positioning of electro-mechanical systems with damping is developed and applied. The controller combines a sub-optimal bang-bang trajectory with a smooth transition to a linear state feedback controller. This work follows from existing proximate time optimal control methods and extends the applicability of such methods by including damping in the plant model and relaxing a restriction on the allowable state feedback gains. By considering damping in the design, a trajectory profile that allows higher velocities is possible; the improvement in moving times is most apparent in systems with significant damping and for long moves. The controller is applied to a direct drive positioning table used in microelectronics manufacturing. Implementation issues are discussed and experimental results show the effectiveness of the technique.