Research on control methods of planar motors based on the modal forces

There is tight electromagnetic and mechanical coupling among planar motor (PM) 6- degree of freedom (DOF) motions for photolithography in semiconductor manufacturing. For the purpose of achieving decoupled control of the 6-DOF motions, this paper presents the current-controlled model of linear motor (LM) as the actuators, the concept of the actuator forces and the modal forces, and the decoupled dynamics model based on the modal forces. Under some reasonable assumptions on the prototype motor kinematics and structure parameters, the modal forces method successfully decouples the 6-DOF dynamics models and all the dynamics models become simple 2nd order linear systems which can be controlled with multiform linear controller. For the prototype motor, the transformation matrices between the modal forces and the actuator forces are derived and the current-controlled block diagram is presented.