Time delay effects on performance and stability of a low cost electrostatic suspension system

To expand the potential industrial applications of electrostatic suspension systems, a low cost suspension system with high-voltage supplies instead of high-voltage amplifiers has already been implemented. In that system, the performance and stability are strongly affected by the time delay inherent in the system. It is therefore important to understand the sensitivity of stability and performance in relation to the time delay. In this paper a low cost electrostatic suspension system based on a delay controller is presented. The effect of time delay on the characteristics of the suspension system will be investigated. The critical time delay of the suspension system, defined as the maximum time delay that can be accepted by the system in order to ensure the system stability, will be derived in terms of bias voltage. The recoverable set whose domain depends on time delay will be found as well. The simulation and experimental results will show the effectiveness of the proposed method. In the experiments, a 3.5-inch aluminium disk was suspended without any mechanical contact at a reference gap length of about 300 μm in both atmospheric and vacuum environments.