A model-based impedance control of a 6-dof electrohydraulic stewart platform

In this paper, a model-based impedance controller for a six-degree-of-freedom (dof) electrohydraulic Stewart platform mechanism is developed. Rigid body and electro-hydraulic models, including servovalve models are employed and described by a set of integrated system equations. Friction and leakage of hydraulic elements are also included. The developed controller uses the system dynamic and hydraulic model to yield servovalve currents. The control law consists of two signals, a feedback and a feedforward signal. An impedance filter modifies the desired trajectory according to a specified behaviour. The modified trajectory is fed to the system model to reduce the effects of the nonlinear hydraulic dynamics. Simulations with typical desired trajectories are presented and a good performance of the controller is obtained.