Research On Low-speed Stick-slip Characteristics And Criterion Of Pneumatic Cylinder

Stick-slip sometimes takes place when a cylinder moves at low speed. It will affect the cylinder steady motion and severely it will also cause working error and equipment broken. It is impossible to eliminate stick-slip absolutely. It only can be avoid by predicting the working range of stick-slip and setting proper working parameters. But stick-slip is a complicated phenomenon in which many factors are involved. It is a problem that with what working parameters stick-slip will not occur and how to predict stick-slip in advance to keep away from the stick-slip range and find out the cylinder normal working range to make steady motion. This is a domestic and foreign problem not solved for long term in the process of designing and using cylinder.To the subject of cylinder stick-slip characteristic criterion in low-speed motion, an in-depth theoretical analysis and experimental study is made in this thesis. First the mechanism of stick-slip occurring and affecting factors on stick-slip is analyzed thoroughly. Taking the cylinder that is now commonly used in the industrial application as the tested object, the friction force model of cylinder, the metewand for judging stick-slip and the stick-slip criterion including many factors are studied.To build up the mathematic and simulation model exactly describing the cylinder stick-slip motion, some common used friction force models are compared and analyzed by fitting experimental data. Then the limit of the friction models describing the stick-slip motion now is found and the Stribeck exponential function model is selected as friction force model. Compared with other friction force models, the exponent function model is the best one to describe the friction force of cylinder when stick-slip occurs and it significantly improves accuracy of cylinder mechanics and motion model.It is found by experiment that the first velocity amplitude criterion used worldwide presently may make wrong judge. The second velocity amplitude criterion is presented based on the analysis and summarization of experiments on motion and stick-slip characteristics of the cylinder. When the second velocity amplitude is higher than half of cylinder average moving velocity, stick-slip will occur. This criterion will not make wrong...