A MODELING AND SIMULATION OF POSITION CONTROL OF ELECTROSTATIC SUSPENSION SYSTEM WITH UNCERTAIN FRINGING FIELD

The electrostatic suspension allows various materials such as conductor, semiconductor and dielectric materials to be suspended. Several electrostatic suspension systems have been proposed and shown to be effective for contactless transportation. Almost all of these systems work with very narrow aspect ratio in which the fringing field effect can be negligible. Increasing the aspect ratio in electrostatic suspension will introduce uncertainties into the modeling and control of the system due to the fringing field effect but large aspect ratio is required for increment of the potential application of the suspension system in practice. The existing approximate analytical expression for fringing field effect often results in complicated mathematical models from which it is difficult to design the controller for suspension system. This paper proposes a new modeling of a single-degree-of-freedom electrostatic suspension system working with large aspect ratio in which the fringing field is uncertain. Based on the model, an adaptive sliding mode control for position of the object is constructed. Robustness and global stability of the controller are proven by computer simulations of contactless suspension