Research On Kinematic Control Of Virtual Axis Machine Tool With 6 Degrees Of Freedom

Virtual Axis Machine Tool (VAMT) is characterized by the simple structure, high rigidity, large load handling capacity, and non-accumulation of position error. As the supplement of Series Machine Tool (SMT), VAMT has become the focus of research in machine tool, and plentiful research achievements have been acquired in mechanics, kinematics, dynamics, but few in kinematic control. However, difficulty in control of VAMT, brought by the simplification of its mechanical structure, has baffled its development, and has been a matter of great urgency. In this dissertation, based on the 6 hexaglide and Stewart platform VAMT, the kinematics control strategies were researched, in order to find the practical and accepted solutions.In this dissertation, the development survey, research actualities and application prospect of VAMT are introduced at first, and the models of kinematics, dynamics and linear motor servo are analyzed then. Currently the dynamics model is complex or established mechanically, which restricts the study of control theories. Thus this dissertation present a simple and easy-realized control idea, namely, the fore and torque of every leg determined by the inverse-solution of mechanics are regarded as changeable load force (disturbance) applied in motor, the elongation of the leg or displacement of sliding is regarded as the output of linear servo system. Then the position close-loop is constituted and trajectory track control is realized.On the base of model, considering the disturbance from the other 5 legs and variating load, we design an H-inf controller integrated with IP controller, which makes the system with the advantage of both H-inf control and IP control, and restrains the bad effect from variating disturbance. The simulation shows that this stradgy enhances the system robustness.In another solution, the coupling and load disturbances are regarded as the parameter variations of motor model, and the variation is observed, thus, the coupled dynamics of VAMTis decoupled to 6 single motor systems. For single loop system, the position and speed controllers are realized by neural network, the output of network is determined by the electric current related with the desired acceleration, and the acceleration tracking control is realized indirectly, which improves the trajectory tracking performance of the mobile platform. The initial weights of the neural network can be given according to the material meaning, which expedites the network convergence.This dissertation presents the conceiving of DSP-based V AMT control system. Developing software for brushless direct current electrical motor will benefit the practical development of DSP-based VAMT control system.Finally, we forecast the future control strategies and control system from different aspects.