TECHNICAL PAPER Nonlinear controller design for a magnetic levitation device

Abstract Various applications of micro-robotic tech-nology suggest the use of new actuator systems which allow motions to be realized with micrometer accuracy. Conventional actuation techniques such as hydraulic or pneumatic systems are no longer capable of fulfilling the demands of hi-tech micro-scale areas such as min-iaturized biomedical devices and MEMS production equipment. These applications pose significantly dif-ferent problems from actuation on a large scale. In particular, large scale manipulation systems typically deal with sizable friction, whereas micro manipulation systems must minimize friction to achieve submicron precision and avoid generation of static electric fields. Recently, the magnetic levitation technique has been shown to be a feasible actuation method for micro-scale applications. In this paper, a magnetic levitation device is recalled from the authors ’ previous work and a control approach is presented to achieve precise motion control of a magnetically levitated object with sub-micron positioning accuracy. The stability of the controller is discussed through the Lyapunov method. Experiments are conducted and showed that the pro-posed control technique is capable of performing a positioning operation with rms accuracy of 16 lm over a travel range of 30 mm. The nonlinear control strategy proposed in this paper showed a significant improve-ment in comparison with the conventional control strategies for large gap magnetic levitation systems