Modelling and optimum design of a fine actuator for optical heads

Abstract

In this paper, a new modelling of a fine actuator for optical pick-up has been proposed and multiobjective optimization of it has been performed. The fine actuator is constituted of the bobbin supported by wire suspension, the coils wound around the bobbin, and the magnets which cause the magnetic flux. If current flows in the coils, magnetic force is produced to position the bobbin. The magnetic force is not only balanced with spring force of wire, but also with the inertial and viscous force. In this model the transfer function from input voltage to output displacement of bobbin has been obtained so that we can describe this integrated system which have both electromagnetic and mechanical parts. Wire suspension is regarded as a continuous Euler beam, damper as distributed viscous damping, and bobbin as a rigid body which can make vertical motion only. According to the modelling, the high frequency dynamic characteristics of the fine actuator can be known and the effect of damping can be investigated while the conventional modelling cannot. In optimization, two objective function has been chosen to maximize the fundamental frequency and the sensitivity with respect to input voltage. These objective functions will satisfy the trends which will enhance the access speed and the actuator gain in the optical pick-up technology of next generation. (C) 1997 Published by Elsevier Science Ltd.