Identification of Linear Hydraulic Actuator using Self-excited Oscillations

Identification of the dynamic properties of the linear hydraulic actuator using the self-excited oscillations is the main topic of the paper. The linear hydraulic actuators which consist of the hydraulic cylinder controlled by the flow control valve using the closed-loop control system with the position feedback have a lot of applications in the industry. The dynamic behaviour of hydraulic actuators depends on the dimensioning of the cylinder and control valve, working conditions such as system pressure, moving mass etc. Although the hydraulic drives are non-linear systems for the controller design the linearized models are used and the linear hydraulic cylinder is described by the second order system characterized by the low damping and eigenfrequency depending on the cylinder parameters. Experimental identification of the eigenfrequency and damping ratio of the actuator can be done by the simple experiment using the nonlinear element in the feedback and evaluation of the self-excited oscillations. The identification method, its application on the linear hydraulic actuator and results from the experiment on the laboratory test rig are introduced in the paper.