Design and control of a new 3-PUU fast tool servo for complex microstructure machining

Ultra-precision fast tool servo (FTS) machining technology is an effective method for complex surface microstructure machining. However, as for a single degree-of-freedom FTS, it can only achieve a high-rate reciprocating movement in one direction; thus, it cannot realize ultra-precision machining for some complex microstructural surface. Therefore, a novel flexure-based fast tool servo device composed of two platforms and three branched chains is proposed in this work, which aims to realize a robotic ultra-precision machining with XYZ translational precision motion. Each of the branched chain is made up of a prismatic pair, two hook hinges, and a connecting rod. The FTS mechanism design and modeling are carried out firstly; then, the FTS device characterization in terms of statics analysis and modal analysis is conducted; in order to suppress the hysteresis nonlinearity and improve the positioning precision, a new repetitive-compensated PID controller combined with an inverted modified Prandtl-Ishlinskii model is proposed to handle this issue. It indicates that the displacement amplification ratio is 3.87; thus, the workspace can reach to [− 85, 85]∪[− 80,80]∪[0,120]μm3, and the closed-loop positioning precision is 600 nm, which will be considered to fulfill practical FTS machining tasks.