Design And Implementation Of Placement Machine's Double-Motor Synchronization Control System

The placement machine is used to mount tiny electronic components onto PCB (Printed Circuit Board) fast and accurately. It is mainly made up of two systems. One is the machine vision system whose function is to locate the components and PCB marks precisely. And the other one is the motion control system who controls the motion of placement head in the X-Y plane. This paper focuses on one important problem of the motion control system. This problem is that when one axis, say, the Y axis is driven by double motors, the two motors have to be synchronized. The multi-motor synchronization control system is widely used in industry. For example, numerical control machines and bilateral cut units in the rolling mill. So it is a significant problem to study.This paper chooses two DC motors as the driven device for the placement machine, build mathematical model according to the motors'parameters and do lots of research on the three-loop control system based on this model. Respective controllers are designed for the current loop, speed loop and position loop. And this model is simulated and validated. At the same time, this paper adopted the deviation coupling control strategy for the double-motor synchronization control system, so as to solve the shortages of traditional PID control strategy. This paper also designed the compensator based on the adaptive-fuzzy PID parameters'tuning algorithm. Simulation results show that the control strategy and algorithm adopted in this paper perform rather well to solve the synchronization problem.The hardware design for the synchronization system is the essence of the paper. TM320LF2407A DSP chip is used as the CPU. Gate drive and H-bridge circuits are designed to drive the motors based on the PWM'S pulse output function. The current loop is realized through the sampling to the motor armature's current by the sampling resistor. To realize the motors'synchronization control, speed and position'closed-loop control, both synchronization control board and communication board are designed. In the control board, PCM3362 is chosen as the control unit and CPLD acts as the decoding unit. And the communication board is designed based on ISA bus standard. The hardware system adopts the modular design method for the sake of convenience of debug, maintenance and expansibility. Based on this method, the control board and communication board are designed separately. The actual debug of the boards shows that the hardware system and algorithm can meet needs of synchronization demand of the motors. So ways are paved to test the advanced control algorithms in the actual machine.