Optimal Design and Control of a Voice Coil Motor Driven Flexure Hinge for AFM Actuator

Abstract

A systemic design procedure of general VCM (Voice Coil Motor) to fine z-axis AFM (Atomic Force Mi- croscopy) actuator is introduced for fast and precision actu- ation. Design parameters are selected based on the dynamic model of VCM and flexure hinge, and design process is proceeded in point of fast and precision actuation performances. To verify the performance of the designed actuator, frequency response of the actuator and contact type AFM image of a standard grid sample are performed. I. INTRODUCTION In recent nano-technology, surface measurement and anal- ysis using AFM (Atomic Force Microscopy), are widely uased(1). The application of the AFM is wide spreading to many field such as scanning probe lithograph, high density data storage device technology, etc(2)(3). For these applications, fast and accurate image acquisition is the most important performance. Above all, the fine z-axis actuator mainly affects to the image acquisition performance. Conventionally, PZT with a flexure hinge motion guide mechanism has been used for the fine z-axis actuator of AFMs. However, the PZT actuator has the disadvantages of hysteresis, creep, and unsymmetrical actuation. To overcome these disadvantages of PZT actuator mechanism, a fine z-axis actuator driven by VCM with flexure hinge was proposed.(4) VCM has almost the same push/pull force and symmetrical actuation without hysteresis and creep problems(5). There- fore, the VCM with the flexure hinge for fine z-axis actuator of AFM guarantees the linear motion and nonlinearity free AFM image acquisition. In this research, a systemic design procedure of the fine z-axis AFM actuator is introduced using the VCM and the flexure hinge for fast and precision actuation. To present the systemic design procedure, firstly, the required specifications for the fast and precision actuation of the fine z-axis AFM ac- tuator are defined. Secondly, the final design parameters are selected from the electric, mechanic, and magnetic modeling of the VCM and flexure hinge system. Using these design parameters, optimal design is proceeded to optimize values of design parameters for the required specifications. To verify the performance of designed actuator, the frequency response