| Pneumatic systems have been used widely in industrial automation field such as chemical industry, medicine, textile, micro-electric and bioengineering for its advantages of simple in structure, anti-pollution, high performance to cost, easy to maintenance and anti-jamming. With the development of the pneumatic proportional system, pneumatic system control is extended from logical control to proportional/servo control area. However, the pneumatic systems have the disadvantages of inherent strong nonlinearity, low natural frequency and nonlinear influence of friction, it is difficult to obtain the satisfactory control performance, and its uses in industry area are limited. In this dissertation, the study on improving the positioning precision for the pneumatic proportional system is presented. The system friction nonlinear compensation and intelligent control method are developed based on the study of its dynamic Behaviors.In the paper, the features and development of pneumatic proportional system are presented, the friction compensation and the use of intelligent control technology in pneumatic are analyzed. Based on the study on working performance and features of the system, the friction mechanism is developed, the friction is overcome by adding chatter signal to the system, the intelligent hybrid controller is presented according to its nonlinear, the system tracking trajectory is realized.Theory on friction compensation based on high frequency low amplitude chatter signal is presented. To overcome the system steady-state error and scrawl under low velocity caused by friction, we usually improve the machining accuracy and lubricating of the move parts to reduce the system friction. However, in pneumatic proportional system, the nonlinear friction influence on the motion performance is reduced by improving the mechanical structure of the cylinder, or using high precision new cylinder, these methods will lead to high price, the nonlinear friction is not eliminated thoroughly, and the system positioning precision and low-velocity tracking precision are not improved finally. So it is necessary to combine modern control method with friction compensation to reduce the influence on movement precision of system nonlinear.Friction model of the pneumatic proportional system is developed based on the viscoelasticity method. Study on the system friction mechanism is developed, it is found that a part of static friction is turned into dynamic friction, the maximum static friction is reduced, the response speed is raised, and the stick-slip motion is transformed into a steady one by adding proper chatter signal. Based on the stability theory on the chatter signal added, it is found when the chatter frequency is 3.3times of the natural one, the positioning precision is the highest. And when the chatter frequency is equal to the system natural one, resonance happens. When the relationship between amplitude and load is A = 0.005F +1.0333 the hysteresis time is shorten from 0.17s to 0.02s.Intelligent hybrid control method is advanced to overcome the nonlinear of system. Intelligent control is a new automation technique which uses various intelligentized technology to realize the control of complicated system. The control purpose is to obtain good control performance by developing a controller which is suitable for the system Behaviors according to the controlled object. Influenced by the factors such as working load, pressure, flow and quiescent point, the moving pneumatic proportion system is nonlinear typically. So speaking strictly, there is no a control method which is suitable for the whole process of the controlled object, it is difficult to obtain famous control effect by use of conventional control method, and it is necessary to develop the most suitable control method according to different controlled-object.Based on the non-linearization of pneumatic system, the neural-fuzzy control is embedded in the expert control, a compositive real-time intelligent hybrid control method is produced. Not only has the controller ability of logical reasoning and advanced intelligent behavior of the expert control, but the instinct reasoning ability of the neural-fuzzy, the coupled control method realizes the parallel control and knowledge sharing. The experiments prove that the hybrid controller have the advantages of quick response, high control performance, it embodies both rapidity and flexibility, a high trajectory tracking precision and good robustness are obtained when the system work.The dynamic Behavior model of the pneumatic proportional valve-controlled cylinder system is developed, which describes the rules between positioning precision and dynamic parameters. Study on the main factors such as the pressure, flow and load which influence the system dynamic Behaviors is developed. The equation between positioning precision and dynamic parameters is provided by use of multiple nonlinear regression analysis, which describes the system positioning error under different working conditions.The system identification and stability analysis of the pneumatic proportional system is presented. To eliminate the errors caused by linearization and obtaining an accurate system model, the system identification process is designed, and the stablity study on system is done based on the identified model. Based on the model, study on the reliability is developed, the system is steady judged by Nyquist steady judgement.Finally, the control program and interface two-freedom pneumatic proportional system is presented, its high precision tracking trajectory is realized. The system positioning precision of point-to-point is within±0.100mm, and the continuous tracking trajectory control precision is within±0.274mm, it is expected to replace the expensive servo system.
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