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Position-pose Control of a Pneumatic 3-UPU Robot Based on Immersion and Invariance

Yu Liu, Xiaodong Wang, Guoxin Zhao*, and Shuchao Ma
International Journal of Control, Automation, and Systems, vol. 20, no. 3, pp.956-967, 2022

Abstract : For pneumatic servo systems, the piston movement, time-varying parameters, and modeling uncertainties make high-precision position control difficult. A third-order mathematical model was established for a pneumatic 3-UPU (universal-prismatic-universal) robot system to provide a roughly accurate reference model for the control algorithm. Subsequently, a high-precision position-pose control algorithm based on immersion and invariance (I&I) was developed, where the leakage flow in the cylinder was incorporated as an interference term in the state equation, and the state equation was expanded. In addition, through a reasonable design of the compensation function and adaptive rate, the invariance and attraction of the error flow pattern were realized. The disturbance error was estimated in real time based on the adaptive law. Through the sliding surface, the control rate was designed, and the position-pose control of the robot was realized. The results showed that the I&I controller exhibits a strong robustness with a steady-state control accuracy of approximately 0.3 mm and a dynamic (0.2 Hz) tracking mean-squared error less than 6.4 mm.

Keyword : Immersion and invariance, modeling, pneumatic system, position-pose control, 3-UPU robot.

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