Control positioning of torsional electrostatic actuators by current driving

In this paper, a novel charge control procedure of the moveable electrode of a torsional electrostatic actuator is presented It is demonstrated that pull-in charge limits the controllable range not only with parasitic capacitances but also without them. Charge is injected into the actuator by means of a switched current source. Current injection is controlled measuring voltage drop on a series capacitance, and a$@flop closing the loop provides the synchronous operation of the system. In fact, the control circuit is a current sigma-delta control.