Study On Kinetics And Cushion Performance Of High-speed Pneumatic Cylinder

Pneumatic technology is a new kind of mechanical transmission technologies, and after more than two hundred years of development, it has been widely applied in different fields of production automation. As the most widely used actuators in pneumatic system, cylinders are demanded to run in high speed to improve the production efficiency in industrial automation fields. However, vibration and shock in the end of stroke are prone to be caused when the cylinders running in high speed. Because of that, the life time of the cylinders is seriously shortened. Therefore, the cushion problem in the end of stroke of high-speed cylinder has become the key technical problem that restricts it’s the rapid development.The main research content of this thesis is to make a comprehensive analysis and research of the dynamic characteristics and cushion performance of the high-speed cylinders through the method that combining theory and experiment, and then put forward ways to improve the cushion performance of high-speed cylinders.Based on the theory of pneumodynamics and thermodynamics, the thesis establishes a dynamic theoretical model of different phases during the running process of the high-speed cylinder, including starting phase, accelerating phase, cushion decelerating phase and residual gas exhausting phase. A simulation model with friendly man-machine interactive interface is established based on the theoretical model using the software of SIMULINK and GUI in MATLAB. Then the thesis simulates the dynamic characteristics of the high-speed cylinder using the simulation model and analyze the simulation results in detail.Then, the thesis designs and builds up an experimental system for dynamic characteristics testing of cylinders, including design of pneumatic circuits, installation of components and programming of acquiring and controlling program, providing an experimental basis for the verification of the theoretical simulation model and the cushion performance researching of high-speed cylinders. Then the dynamic characteristics are tested during the running process of the high-speed cylinder using the experimental system. And the thesis contrastively analyze the simulation results and the experimental data to prove that the simulation model is correct.Base on the theoretical and experimental foundation built before, the thesis further analyze the cushion status of the high-speed cylinder and the cushion ability of traditional relief valve cushion structure, and points out the shortage of relief valve structure in adjusting performance according the experiment results. And then the genetic algorithm is used for the structural optimization of the relief valve. The simulation model is used to analyze the cushion performance before and after the structural optimization. The analysis result reveals that the cushion performance of the high-speed cylinder has been obviously improved.Finally, in order to improve the cushion performance of high-speed cylinders further, the thesis puts forward a new cushion structure of cushion pressure controlling type and finishes the design of related structures. Based on the structures designed, the thesis establishes a dynamic simulation model for the new cushion structure and makes simulation and analysis using this model. The analysis result reveals that the new type cushion structure can make the high-speed cylinder to acquire good cushion status in the end of stroke when running in high speed, and the cushion adjusting performance of the new cushion structure is better than the relief valve cushion structure.In summary, according to the research of this thesis, the cushion performance can be improved through structural optimization or using the new type cushion structure of cushion pressure controlling, and the feasibility of the two methods is analyzed using simulation models. The thesis provides a theoretical reference for design and development of cushion structure of high-speed cylinders in the future.