Fuzzy Pid Control Of The Milling Process

The metal-milling manufacturing system is a time-varying nonlinear dynamic system. As the improvement of machining technology and production automation, the robust performance requirements of automatic control of manufacturing system are higher and higher. The conventional control algorithms based on accurate mathematical models are not competent for controlling the complicated dynamic systems. Therefore, intelligent control, which is not based on accurate mathematical model, will provide a new approach for those complicated dynamic systems. In this paper, fuzzy control is imported to the milling process control system, combined with PID, for controlling the manufacturing process.In the thesis, the uncertainty of closed loop milling control system is discussed in detail. Principle of PID control is discussed, and the effect of PID parameters on the performance of PID controller is analysised. And then, PID control for machining process is proposed. And then Fuzzy Controller (FC) for machining process is proposed to make cutting force reach the set desired value rapidly, steadily, and without error. The mechanism and peculiarity of FC is analyzed deeply, and fuzzy controller for milling process is designed. By assuming variation of the Depth of cutting, uncertainty of milling process is simulated, and simulation of both of the two way of control for the milling process is excuted with personal computer(PC), and results is analysised deeply.Basing on the work above, fuzzy PID controller for milling process is proposed. By presupposition of the variety of work situation, using Matlab to simulate the three controllers aboved for uncertain milling process. At the end, an experiment based on these controllers is progressed, with a closed loop milling control system by milling machine XK5140.It is indicated, from the results of the simulations and the experiments, that the response speed of FC for milling process is rapid, but a little steady-state error exists; to PID, the result is steady but overshoot is much larger; fuzzy PID has strongpoints but not defect, comparing with FC and conventional PID. In a word, it is advisable to import fuzzy mechanism to setting the parameters of PID for uncertain milling process.