Design of an open-loop controlled auto- focusing VCM actuator without spring plates

The smart cell phone market has rapid growth in recent years and cell phone camera modules have strong requirement for capturing images and communication in our daily use. Accordingly, in the present study, a novel compact voice coil motor (VCM) actuator is proposed for auto-focusing (AF) of cell phone camera modules. Compared to conventional VCM actuators with open-loop position control mechanism, the proposed VCM actuator is featured with absence of spring plates. In the proposed approach, the magnetic restoring force is used to replace the restoring force of the spring plates in the open-loop control VCM actuators. The motivation of this study is to characterize the performance of the proposed VCM actuator using simulation methods and then evaluate experimentally this device using a laboratory-built prototype. The results show that the proposed VCM actuator has the sizes of 8.5 mm x 8.5 mm x 7.5 mm, the maximal input current of 40 mA, the maximal response time of 10 ms, and the average measured Lorentz force of 2200 mgw for the input current of 40 mA in its whole displacement (stroke of 0.4 mm), and it operates the AF function well.