An Optimal Actuator Placement Method for Direct-drive Stages to Maximize Control Bandwidth

This paper develops an optimal actuator placement method for direct-drive stages. Control bandwidth of rigid body motion, which is limited by flexible modes, is maximized. According to a reduced-order state-space model of stage dynamics, a dual-loop optimization method is proposed to optimize actuator locations. In the inner loop, a specific control scheme is employed to obtain the maximum control bandwidth, which is used to formulate a cost function. This control scheme is only for optimization, which does not limit the choices of control methods for an optimized stage. In the outer loop, Genetic Algorithm (GA) is employed to minimize the cost function such that the actuator locations are optimized. Compared with existing over-actuation methods, this method has low cost and complexity. Numerical simulations verify the effectiveness of the proposed method.