Design and Positioning Control of a Flexure-Based Nano-positioning Stage Driven by Halbach Array Voice Coil Actuator

A long-stroke nano-positioning stage driven by voice coil actuator (VCA) and supported by flexure guide is designed in this paper. The Halbach permanent magnet array is implemented in the VCA to improve the air-gap flux density with the magnetic concentration effect. The air-gap magnetic field is modeled with an equivalent magnetic structure and verified by finite element analysis. The proposed equivalent magnetic structure reduces the number of boundary condition equations and hence simplifies the analysis procedure. Besides, a novel spring-damping tuning method is proposed based on the equivalent dynamic model of the closed-loop system. This tuning method regards P control and D control as a virtual spring and a virtual damper. The controller parameters are tuned in an intuitive way. Experimental results show that the positioning stage is capable of achieving a resolution of 40 nm within a stroke of 0.8 mm with high repeatability. The spring-damping tuning method ensures better control performance compared to Ziegler Nichols (Z–N) tuning method where overshoot and settling time are decreased.