Trajectory Control of MEMS Lateral Comb Resonators Under Faulty Conditions

Electrostatic force generation in MEMS Lateral Comb Resonators is not a function of the distance of the stationary and the moving plate (shuttle) in the direction of the movement. However, manufacturing imperfections and sometimes faulty conditions make the device operate asymmetrically which cause the rotational movement, orthogonal to the conventional direction of movement and put the device in unstable region of operation. In this case, the rotated lateral moving plate experiences an extra force generated which pulls the device into the region of instability. This paper illustrates the application of variable structure controllers to correct such behavior and to compensate the uncertainties exist in the microsystem parameters. The controller is composed of a self-tuning parameter estimation block and is designed to control Lateral Comb Resonators under healthy and faulty conditions. The controller utilizes through wafer optical monitoring techniques to provide position feedback signal. The controller is implemented in the real-time control board and is experimentally tested to demonstrate the effectiveness of the control under different operating conditions.