Trajectory control of pneumatic servo table with air bearing

Trajectory control design for a pneumatic servo table system considering pipeline and servo valve dynamics is studied. The table is mainly composed by a pneumatic actuator, a high-performance pneumatic servo valve and pipelines. The pneumatic actuator utilizes a pneumatic cylinder with air bearings. The servo valve has high dynamics up to 300Hz and is connected to the pneumatic actuator by pipeline. The system is pneumatically driven, providing the advantages of low heat generation and non-magnetic, nature suited to precise positioning. To simulate the system, we designed a linear model considering pipeline and servo valve dynamics. Experiment results suggest that with 7^th order control model the system can be accurately given. The model´s complexity made it necessary to reduce the model´s order. There are two poles are much further compared with other five poles in the pole loci of the 7^th order model, so the model is reduced to a 5^th order. A comparison of simulation and experiment results showed that the 5^th order model matches with the real system well. Based on this result, a 5^th order feed-forward has been designed. When a curve which can derivate by five times is inputted, the experiment results using different pipelines and displacement show that the maximum trajectory error has been minimized by about 20μm with 100mm displacement and 10μm with 50mm displacement.