Modeling and control of a 6-DOF contactless electromagnetic suspension system with passive gravity compensation

A contactless Electro-Magnetic Isolator (EMI) is designed for gravity compensation of a heavy payload by passive Permanent Magnetic (PM) force and control by active Lorentz force. The theoretically calculated PM force and torque produced by this EMI are presented. To characterize the EMI and to evaluate the vibration isolation performance, the Single EMI System (SEMIS) is designed by adding three horizontal and three vertical Lorentz actuators for control. It is a six Degrees-of-Freedom (DOF) contactless electromagnetic suspension system possessing the properties of inherent instability, nonlinearity, no mechanical contact, passive gravity compensation. The physical SEMIS model is developed based on reasonable assumptions and approximations. It is subsequently linearized for control design. The vibration isolation performance of the two control strategies, decoupled control and decentralized control, are simulated and compared. The results show that decentralized control has more significant coupling than the decoupled control for only two DOF-pairs.