Ultra precision motion control of a multiple degrees of freedom magnetic suspension stage

A general framework for ultra precision motion control of magnetic suspension actuation systems with large travel ranges in multiple degrees of freedom (DOF) is presented. It encompasses the development of nonlinear electromagnetic force model for 6-DOF actuation, and the design of the necessary control architecture for ultra precision motion control of magnetic suspension actuation systems. A 6-DOF magnetic suspension stage (MSS) was designed and fabricated to illustrate the developed framework. The MSS consists of multiple electromagnets that are located around the flotor and are utilized to suspend and modulate its position and orientation. The control architecture takes the six control parameters provided by a laser measuring system and intends to control the 6-DOF motion by regulating the current in the electromagnets. The developed robust nonlinear control architecture consists of three components: 1) feedback linearization; 2) force distribution; and 3) H_∞ robust controllers for each DOF of motion. Several experiments are designed to illustrate the desired characteristics of the developed system