Laser Micromachining System, Electrical Control System Design

In the self-developed laser micro-processing system, microfabrication is processed in this method that laser beam is fixed and the processing work piece is moving. Processing work piece has lots of moving modes and various given diagrams can be processed. Diameter of the laser beam is 10 m .Positioning error of this kinetic control system is required within Sum. This article analyses the mathematical model of this kinetic control and construction of the circuit. The circuit has been simulated and completed so its function is accomplished.The electric control system is a key part in this laser micro-processing system. The control system is composed of setting unit(host computer ), digital controller ,input channel (position detector)and output channel (actuating mechanism). Digital controller communicates with PC though serial interface. The setting value (processing track) and moving method are downloaded from PC to digital controller.Digital controller is the kernel of the electric control system and it is composed of minimum system based on AT89C52 ,serial interface ..control and driving circuit of step motor, processing unit of grating scale signal, keyboard and digital displayer interface .Digital controller ,in put channel and output channel compose the closed loop movement control system .2P Step motor ,the operator in the system ,is a device which has integral unit so this control system is a no static error system . Using arithmetic of PID with dead zone and minimum limit eO is limited by the resolution of operator or feedback unit.According to the control accuracy requirement , TSA100 - A 2D electric control table ,made by Zolix Instruments Co. is used as operator. Control and driving circuit of step motor is based on TA8435H which is a kind of special -purpose chip for driving bipolar step motor. It has characteristics of brief circuit, high stability and subdivision control. The resolution of the step motor is 1.25 m.Displacement feedback unit is chosen the grating scale with 4 m grating spacing of DONG SAN Co. [Korea] .The grating scale signal need to be 4 folds subdivided and directional discriminated. Using electronic subdivision technique, a FPGA single chip is realized the function of grating scale signal processing unit. The displacement feedback resolution is within 1 m. This design makes the area of PCB diminished and a brief circuit while control system runs safely and reliably.Controller receives the displacement feedback signal sent by grating scale, control the movement of actuating mechanism-step motor. Arithmetic of PID ensures the position error of moving control is within 2 m and moving control system can be operated in accordance with the designed targets .