A Study of an Electro-Hydraulic Servo Actuator Control System to Compensate for Badly Damped Vibrations

The purpose of this study is to develop an electro-hydraulic servo actuator (EHSA) control system to compensate for badly damped vibrations by a spring-damping device (SDD). The EHSA controls the extension and retraction of the telescopic boom of a hydraulic manipulator with three degrees of freedom (3-DoF), subjected to the cyclic impact force generated by a hydraulic breaker. A solution was applied, in which the actuator barrel was rigidly mounted on the manipulator’s main boom, and the actuator piston rod was flexibly connected to the manipulator’s telescopic boom by an SDD acting as a vibroisolator. A hydraulic breaker is mounted on the telescopic boom to crush large rocks (oversize) on a Blake jaw crusher conveyor. The purpose of the EHSA control system was to compensate for vibrations that were badly damped by SDD. The dynamic system of the EHSA-SDD based on the Hammerstein model was identified using a third-order polynomial function for the nonlinear static subsystem, and an autoregressive model with exogenous input (ARX) for the dynamic linear subsystem. A modified recursive least squares (RLS) method with variable estimation was used to identify the EHSA-SDD control system. Based on the estimated autoregressive variables, the quality index of the EHSA-SDD control system was minimized. A test stand was built, on which the designed EHSA-SDD control system excited by the cyclic excitation force generated by a hydraulic breaker was verified.