Research On The Servo Control System Of Common Pneumatic Cylinder And Its Application In Automatic Sample Loom

ABSTRACTDue to its cleanliness, simple structure, comparatively low cost, convenient operation and easily implemented automation, pneumatic system is becoming an essential way of automation increasingly. In recent several decades, the research on pneumatics is widely carried out by all of the countries in the world. Especially with the emergence of the electric-pneumatic-servo control technology, pneumatic system is extended from logical control to servo control. As a result, the application range of pneumatics is extended widely. But the pneumatic system in automatic sample loom is still based on the way of two points positioning restricted by mechanism. In order to improve the performance of automatic sample loom, the way of application of pneumatic servo control technology in automatic sample loom is put forward.According to the requirements of the automatic sample loom, a single-rod double-acting common pneumatic cylinder is selected as the actuator, but it's difficult to carry out servo control because of its serious nonlinear friction and unsymmetry. This paper designs high quality controllers to focus on both point-to-point positioning and continuous trajectory tracking control, so that it can reach the requirements of automatic sample loom. The main contents are shown as follows:Firstly, on the basis of analyzing the problems of the automatic sample loom in existence, the way of application of pneumatic servo control technology in automatic sample loom is put forward. The experimental test rig for servo control system of single cylinder is established on the basis of structure and principle analysis, and real-time control is carried out by hybird programming with Labview and Matlab. The nonlinear mathematic model of system is established and then linearized, this model shows that the system is high order and nonlinear. A mass of experiments are carried out for friction tests, the voltage of the proportional valve's middle position and system's acting deadband is also determined during the experiments; its I/O character is well mastered, and it is the basis of the controller design.Secondly, a PID controller is designed for the system, during the experiments of responding several kinds of input signals, it is found that there are some disadvantages of the PID controller in this nonlinear system. During the sine wave trajectory tracking control, a PID controller with friction feedforward is developed and some effects are obtained. But generally, the error is still big and the response is unstable; the PID controller can't completely eliminate the phenomena of slipping oscillation of step response or the instability of squarewave response.In order to solve these problems, a fuzzy controller is developed and a mass of experiments are carried out. The result shows that there is no slipping oscillation of step response, the squarewave response is stable, the precision of sine wave response in a certain frequency band is improved and its adaptive ability is enhanced. It reaches the applied requirements in the automatic sample loom basically. So the fuzzy controller is stable and effective.Finally, the work of this study is summarized, and some suggestions and expectations are put forward for further research.