Design and control of a fast tool servo used in noncircular piston turning process

Noncircular pistons are becoming more and more popular in the automotive industry. The challenge of machining this kind of pistons (e.g., middle-convex and varying ellipse piston (MCVEP)), lies in the rigorous demand of the cutting feed mechanism for large force generation, high stiffness, fast response, long stroke and high accuracy. The conventional processing methods cannot meet the challenge so a new piezoelectric actuator (PEA) based fast tool servo (FTS) mechanism was developed to incorporate additional functions to a general CNC system that will facilitate the execution of MCVEP turning. Since the desired tool trajectories are approximately periodic signals in MCVEP turning, and the repetitive control can achieve asymptotic tracking and disturbance rejection of periodic signals, a plug-in repetitive control is designed to be added on the conventional PID controller. In the experiments, the designed prototype was used to machine a MCVEP for the gasoline engine, which was equipped with the PEA-based FTS system, as well as the plug-in repetitive controller. The machining test validated the effective of the designed noncircular turning system.

► Fast tool servo is developed to cut the middle-convex and varying ellipse piston.
► Fast tool servo is based on a piezoelectric actuator and a flexure hinge.
► Fast tool servo can be used as a supplementation to the general CNC lathe.
► Plug-in repetitive controller is added on the conventional PID controller.
► Machining test has validated the system features for practical application.