Diagnosis Method for Valve-Controlled Hydraulic Cylinder Leakage Based on Subspace Identification

This paper proposes a fault diagnosis method based on subspace identification for the leakage fault detection of valve-controlled hydraulic cylinders. Firstly, the state-space model for the system is established, in which the external force on the piston of the hydraulic cylinder is selected as input signal, and the pressure of the two chambers, displacement and velocity of piston rod are chosen as state variables. Then, the estimation value of specific elements of the system matrix can be obtained in terms of the subspace identification theory. On this basis, the existence, type and level of the leakage fault are determined. Finally, the numerical simulation is conducted through MATLAB-Simulink to verify the proposed method. The results demonstrate that the proposed method is effective and has high accuracy.