Adaptive robust control of direct drive proportional servo valves considering friction compensation and asymmetric state constraints

Le résumé fourni par la source

For the direct drive proportional servo valves system with parameter uncertainty, time-varying interference, nonlinear friction, and asymmetric state constraints, an adaptive robust control method is proposed. A novel state constraint strategy using a nonlinear transition function overcomes the limitations on the feasibility conditions of the virtual control law in the traditional Barrier Lyapunov function method. An improved LuGre friction model based on the tanh function is built, a dual friction observer is used to estimate and compensate the unmeasurable internal friction state. A nonlinear adaptive term is designed to handle time-varying uncertain parameters and disturbances, which not only avoids the coupling of parameters and disturbances, but also simplifies the tuning process. Nonlinear filtering of the virtual control input solves the differential explosion problem. Finally, stability analysis indicates that all closed-loop signals are bounded and ensures the asymptotic tracking performance of the system. Besides, simulations comparing three algorithms verify the proposed one’s feasibility and superiority.

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