A simple and cost-effective electrostatic levitator for disk-shaped objects

Summary form only given. A new method for contactless electrostatic suspension of disk-shaped objects is proposed which is based on a switched-voltage control scheme. It operates according to a relay feedback control and deploys only a single high-voltage power supply capable of delivering a dc voltage of positive and/or negative polarity. In addition to the unique feature that no high-voltage amplifiers are needed, this method provides a remarkable simplification in the hardware realization relative to previously reported methods. It is shown analytically and experimentally that despite the inherent limit cycle property of the relay feedback based control, an excellent performance in vibration suppression is attained due to the presence of a relatively large squeeze film damping originating from the air between the electrodes and levitated object. In this paper, the functional principle of the switched-voltage control scheme, numerical analysis, stator electrode design, and a nonlinear dynamic model of the suspension system are described. Experimental results will be presented for a 4-inch silicon wafer that clearly reveal the capability of the proposed control structure to suspend the wafer stably with airgap variations decreasing down to less than 1 /spl mu/m at an airgap of 50 /spl mu/m.