The effect of velocity feedback in position control of high performance servo hydraulic actuators

Fast responding linear servo-hydraulic actuators with precise motion control are required in applications like seismic shake table and material testing for qualification of components to be used in nuclear reactors. The achievable bandwidth of a servo-hydraulic actuator in position control mode is improved by adding a velocity feedback to it. A fifth order linear state space model of the servo hydraulic linear actuator was derived and validated with experiments. The step response and frequency response of a simple proportional position control and a proportional position control with velocity feedback was simulated and compared using this model. This paper illustrates the effect of velocity feedback in simple proportional position control in three different ways-pole zero map, Block diagram and Practical approach. All the simulations were supported by experimental results. The paper concludes that higher control bandwidth can be achieved using proportional position control with velocity feedback in linear servo hydraulic actuators.