Research On The Control Technology Of Middle-convex And Varying Ellipse Piston Turning

Noncircular section turning plays an important rule in mechanical manufacturing, especially in the piston machining. Addressing the machining of the pistons which are noncircular in cross-section and/or which are barreled along their length, the technical aspects related middle-convex and varying ellipse piston turning are discussed in this dissertation, especially for anti-disturbance performance of the servo tool holder. It includes such contents as follows:1. Based on synthetic analysis of the technical characteristics of traditional micro-feedmechanism for middle-convex and varying ellipse piston turning, the technological step to realize micro-feed with high frequency response and large travel was concluded. A middle-convex and varying ellipse piston numerical control turning system, with a moving coil type linear motor actuator driven tool holder has been built.2. Addressing the high-speed servo technology for the middle-convex and varying ellipsepiston numerical control turning machining, the numerical control system for middle-convex and varying ellipse piston numerical control turning was configured. In the respect of software, a new interpolation method was put forward. As for the hardware, a PC-based host-slave control system, with a digital signal processor (DSP) as the slave controller was developed in the need of high-speed servo.3. High frequency response and large travel driven tool holder is the most key part in theprocess of middle-convex and varying ellipse piston turning. A linear motor actuator driven tool holder and related mechanism was designed, and its model was given in the view of system dynamics. Based on the model, one controller only with the velocity feedback and the other with both position and velocity feedback closed loop were developed, their performances and its influence on the quality of the machined parts were also discussed.4. Repetitive action is needed by linear servo drive system in the process of middle-convexand varying ellipse piston machining. The input is periodic signal or command, the output is required to stably trace this kind of periodic input signal without static error.Repetitive control has good trace effect and disturbance restraint for periodic signal and/or periodic disturbance. The essence of repetitive control is revealed by thoroughly analyzing the stability of repetitive control system.5. Anti-disturbance performance is a key problem in the process of middle-convex and varying ellipse piston machining. To improve the tracking performance of the system and the ability for the servo tool holder to reject periodic cutting force, 3 new control methods have been discussed, and they were analyzed by theoretical analysis and computer simulation respectively. The simulation results show that the performance of tracking and disturbance restraint for piston lathe linear servo drive system has been improved effectively by the three methods. Good performances have been achieved and have a certain theoretical instruction sense.