Design Of MWEDM Servo Control System Driven By Piezoelectric Ceramics

Micro Wire Electrical Discharge Machining (MWEDM) is an important part of micro-fabrication technology, and it deals with micro complicated surface workpieces, especial the top and bottom different curve, which are made of conducting materials and difficult to machining. In this thesis, the research state of MWEDM and its servo technology both at home and aboard are summarized. Based on the demand of this project and the characteristic of a special MWEDM machine tool, the hardware and software design of four-axis MWEDM servo system is introduced. Experiments are done on the machine tool. The three research works are mainly included in this paper.Based on the structure of machine tool, the hardware structure of the control system is established, and the main function modules of the single-axis servo control card based on DSP, such as position control model, position detection model etc, are designed. The method of incomplete derivation closed loop PID control with adaptive dead-zone inverse compensate is applied to control the position of the piezoelectric ceramics motors. It not only can reduce the overshoot to improve the machining accuracy, but also can eliminate dead-zone caused by piezoelectric ceramics linear motor.On the demand analysis of servo control system software, a CNC system based on the Windows operating system of the MWEDM machine tool is developed. It adopts an easier and more feasible method of interpolation called simple linear arithmetic to enhance execution efficiency of the program. And the system can also emulate and track the locus of three-dimension workpieces in real time by using Direct3D.In addition, the characteristics of machining the top and bottom different curve are studied. According to the motion rules of four-axis wire cutting, the control parameters and control model of cutting the top and bottom different curve are established and an four-axis interpolation method is presented.