EFFECT OF SERVOVALVE / ACTUATOR DYNAMICS ON DISPLACEMENT CONTROLLED TESTING

This paper presents a study of the use of servo-hydraulic actuators in the implementation of dynamic testing techniques in displacement control. Mathematical models for a displacement-controlled test system are presented and used to investigate the influences of the servo-system on the overall system. The influence investigated includes response amplitude reduction, system stability and controller gain setting, system response delay, and nonlinearities in servo-systems. Linear system analysis and computer simulation were conducted to explain and predict the system response. While the emphasis throughout is on the development of an understanding of the influences, a simple first-order phase-lead network was used to compensate for the amplitude reduction and response delay for tests with small hydraulic demands. The results indicated that the influences can be predicted and compensation schemes can be developed with the presented models.