Research On Compliant Pneumatic Control System Of The Micro-Polishing-Robot

Nowadays, as Chinese economic taking off and the rapid development of manufacturing industries, higher and higher requirements are made for quality and efficiency in machining die and mould with free-curved surfaces. And the requirements on low cost, high efficiency and high flexibility of the precision machining equipment increased rapidly. But at present, processes of precision machining die and mould with free-curved surface still depends mainly on the handwork of skilled workman. Because the handwork is not only low efficiency and unstably machining quality, but also requires the operators having higher skills. If the operators make a slight mistake, the machined surface would be caused fatal injury, even cause the mode entire scrapped. Such limitations have become bound mold cavity surface's modern production bottlenecks. Therefore, it is inevitable to study the theory and technology of automatic precision machining for free-form surfaces. The subject present a new technology idea that use the small finishing equipment for the processing of large free-form surface, the surface free from the research and development of micro-positioning polishing robot free surface geometry based on its own information and information technology in road surfaces free of large-scale self-lapping and polishing. It is the first that set the robot position / profile / pressure / velocity control integration at home and abroad.This Micro-Polishing-Robot is mainly composed of the main body organization, (including the terminal implementing agencies), the power systems, the sensor systems, the control systems and other components, and its mechanical structure as shown in Figure 1. The mobile instruction of the Micro-Polishing-Robot adopts four uniform distribution wheels, among them the front wheel and the back wheel are driving wheels. The two wheels are driven by two Maxon DC servo motors which hold optical encoder. They can compose to be semi-closed loop control in the way of speed feedback. The other two wheels are driven wheels. They are linked with the upper body of the Micro-Polishing-Robot by suspension system, always ensure that the four wheels of the Micro-Polishing-Robot are in close contact with the ground.In this paper, I have designed a pneumatic control system to control the Micro-Polishing-Robot polishing pressure. The pneumatic control system is mainly composed of pneumatic parts and electric control parts. The pneumatic parts is mainly composed of Short-Stroke Cylinder, proportional pressure valve, pressure sensors, gas source (air compressor), pneumatic triple pieces (tapping gas filter, valve, fuel-air), the trip switch, a one-way throttle, the two three solenoid valve, muffler etc. And the electric control parts. is mainly composed of IPC, drives, amplifiers and A / D, D / A conversion device etc.The process of free surface polishing is very complex. There are many factors affecting the processing result, especially the polishing pressure Fn . For this reason the polishing pressure model of the micro-polishing-robot is set up:The pneumatic control system's Mathematical model was established under this condition: Fn = F: In order to ensure that the Mathematical model is right and to do further research on the dynamic characteristics of the pneumatic control system, we used Matlab software on the model dynamic simulation analysis. Prepare M function file on Matlab platform to perform analysis on the basic characteristics of the system. Figure. 2 is the open-loop bode Figure without PID regulator of the control system. Figure. 3 is the closed-loop step-response curve flat without PID regulator of the control system. From the stability margin of the closed-loop system and the step-response curve we can see that the system is unstable. Furthermore, the rise and adjust time is too long and it did not meet the requirement of the control system. Therefore, we used conventional PID controller to regulate the dynamic characteristics of the control system. Selecting appropriate adjustment parameters make the performance of the control system have a large degree of improvement. This can be shown in the Figure 4and Figure5..