Research on Principal Technology of Contour Motion Control Systems
|Course||Detection Technology and Automation|
|Keywords||contour motion control computerized numerical control system multi-axis coordinated control position tracking control fuzzy control cross coupled control iterative learning control zero phase error tacking controller disturbance observer|
Contouring motion control is one of the important topics in motion control research, which has been widely applied in motion control tasks in manufacturing and other automation systems. As higher contour precision in modern automation systems is demanded, research on advanced contouring control strategies are very meaningful in theory and application.This dissertation focuses on two control methods, i.e., tracking control and contouring control. Based on mathematic modeling and distinguishing feature of each independent tracking control axis, two errors, that is, the circular arc radius error due to the finite bandwidth of the servo system and the elliptic error due to performance mismatch between motion axes, have been analyzed respectively. Several major factors affecting the contouring motion precision in CNC feeding servo systems have been studied via simulation. Typical error distribution curves have been thus obtained for contouring motion under the influence of different factors. To enhance the tracking performance, in this dissertation, the zero phase error tracking control (ZPETC) algorithm for discrete-time systems and the disturbance observer (DOB) have been investigated with a proposal to combine ZPETC and DOB for improved tracking performance. Moreover, the DOB filter design method is also discussed.If without any special treatment, any multi-axis tracking control contouring motion system is in nature an open-loop system in contour loop. In fact, in many applications such as CNC systems, contouring error is more important than tracking error. Therefore, this dissertation focused on contour error estimation algorithm and closed-loop contouring control based on the so-called“cross-coupling control”(CCC). A fuzzy logic approach has been proposed to handle the uncertainties in the system with an on-line fuzzy automatic parameter setting strategy in CCC.In many motion control tasks, it is usually required to follow a trajectory repeatedly. Conventional control algorithms do not take advantage of the repetitiveness. The basic idea of iterative learning control (ILC) is to construct a compensation signal based on the tracking error in each repetition so as to reduce the tracking error in the next repetition. In this dissertation, an optimal ILC algorithm for discrete time linear systems has been discussed and an integrated control strategy combined ILC algorithm and CCC was proposed. Also, this dissertation established a sufficient condition for ILC convergence of a class of uncertain nonlinear time varying systems with a discussion on the convergence speed. Furthermore, for a class of linear systems, frequency-domain convergence analysis has been provided for a closed-loop type ILC algorithm with a convergence speed comparison with the conventional Arimoto-type open-loop ILC algorithm.Finally, this dissertation introduces the research achievements in typical contouring control system–computerized numerical control (CNC) system for machine tool and technological characteristics of the developed CNC system.