| The friction of cylinder is the most important influence factors for accuracy of pneumatic servo system. The traditional cylinder uses the rubber ring to seal. This kind of contact sealing causes larger friction between piston and wall of the cylinder, and decreases the positioning accuracy and stability of servo system.The metal seal cylinder adopts the principle of gap seal, which decrease the friction of cylinder. The friction researches on metal seal cylinder haven't carried out yet, so it is necessary to gain the basic data of the friction characteristics by test experiment, to provide technical reference for practical application. In addition, because of the low friction property, it will be significant for the improvement of the pneumatic servo system's precision and stability by using the metal seal cylinder to compose a position servo system and researching the system's location property.Firstly, according to the extremely low friction characteristic of the metal seal cylinder, the primary factors impacting the measuring accuracy are analyzed. The measurement methods of its static and dynamic friction are proposed. The experimental platform is conducted, comprising appropriate measuring instruments which experiment desired. A number of test experiments for two series of cylinders are carried out in different conditions. The numerical range of static friction is obtained by the theory of error analysis. In addition, the dynamic friction of each cylinder was measured under the various velocities. And the dynamic friction curve was plotted with piecewise fitting.Secondly, the pneumatic position servo system is composed, which use metal seal cylinder as the Actuator and new electro-pneumatic proportional pressure valve as the control unit. The property of the proportional pressure valve has been researched by experiment, and the basic property of the system has been recognized by theoretical modeling, providing the reference to the next experiment research on position control.Then, the position location property of metal seal cylinder has been researched by PID control algorithm. Several methods of pressure control have been researched according to the property of pressure. After analyzing the influence by different control methods, a strategy for rapid positioning is proposed. For low steady state accuracy of the system, a variable parameter PID control algorithm is proposed which can improve the speed and accuracy of the system location by modifying the control parameters. And then, the single neuron PID controller is proposed for position location, the results show that the accuracy of system is higher. Lastly, the comparing experiments between metal seal cylinder and normal rubber seal cylinder has been done in the same experimental conditions. The results of experiments show that the metal seal cylinder can obtain a better effect of location. The accuracy and stability of the position servo system are improved significantly because of low friction. |
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