The Control of a Long-Range Single-Axis Nanometer Positioning System

Abstract

This paper is focusing on the control strategy design of a long-range single-axis positioning system [1], which has a travel range of 100 mm. The positioning system was constructed by a linear guide, a feeding mechanism and three stacked piezoelectric actuators. The stacked piezoelectric actuators were used to drive the feeding mechanism with a circular movement, which will feed the linear guide by friction force. Through continuous feeding, an unlimited travel range positioning system can be achieved. Two-stage control strategy was introduced for the positioning control, i.e. coarse motion control and fine motion control. At coarse motion stage, impact-drive motion combined with fuzzy control was used to accelerate the linear guide to approach the target position. At fine motion stage, stick-drive motion combined with classical feedback–feedforward control can provide a nanometer positioning accuracy. The control algorithm was implemented on TMS320F240 DSP-based control board, and the experimental results show that the proposed feeding mechanism system with two-stage control strategy can achieve a travel range more than 90 mm with maximum velocity of 5.8 mm/s, average velocity 1 mm/s, steady state error is less than 20 nm, positioning bias is less than 0.5 nm and standard deviation is less than 7 nm.