Research On Neural Network Sliding Mode Control Of Virtual Axis Machine Tool

As a new configuration of machine tools,virtual axis machine tool forms a complementary relationship with traditional CNC machine tools.Virtual axis machine tool adopts parallel mechanism,and it has the character of short transmission chain, stiffness,light weight and high efficiency.Although the theory of its research and its practical applications have made some achievement,the virtual axis machine tool kinematics,dynamics,singular form,trajectory planning and motion control and other areas still have some unresolved issues.In this paper,the kinematics and control strategies of the virtual axis machine tools are studied.Firstly,based on the mechanical structure of 6-DOF virtual axis machine tool what has been analyzed,and listing the basic knowledge of its kinematics,the inverse kinematics solution of 6-DOF VAMT is deduced.Then it gives the trajectory planning method of VAMT,and plans out the system trajectory under set tasks.Secondly,based on the kinematic analysis and modeling of parallel mechanism,two kinds of control method are introduced,then the position tracking of the two kinds of control method and the control input variable are analyzed. Simulation results indicates that NNSMC method has quick tracking speed,high tracking precision,and can effectively eliminate system chatter which exsit in general sliding mode control.Thirdly,PC and PMAC motor control card are used to construct the hardware of control system of the virtual axis machine tool.Based on decentralized control strategy,the system is mainly composed by six parallel setted control channels,and each control channel is made up of one servo amplifier and one AC servo motor.It is a kind of distributed collaborative control system which is based on multiple independent controllers.Finally,a functional software control program is created by VC.And the paper gives the results of AC motor drive VAMT control experiment.The experiment uses the idea of multithreaded programming.The main thread is user interface thread.It is used for receiving user’s input.The auxiliary thread calculates the complex algorithm and transmits the control variable to the motor control card.The control card send control signal and then the VAMT can complete the given trajectory in the workspace. The results demonstrate that the control scheme designed is feasible and effective.