Nonlinear closed-loop control of an electrostatic torsional micro-mirror by means of differential actuation

Differential actuation for electrostatic torsional mirror control has the advantage of torque amplification and linearization of the actuation voltage curve. However, this is achieved at expense of a reduced stability range. Furthermore, the linearization is valid only for small deflections, when an open-loop control scheme is used. This work presents a nonlinear closed-loop control in order to obtain stable operations and linearized input-output responses in the whole range of deflection. It is also shown that differential actuation makes it possible to circumvent the uncontrollability of the system at the flat position, allowing the micro-mirror to swing through this point with continuous bounded control. The simulation results show the strength and the performance of the proposed control scheme.