A dynamic model of a hydraulic actuator/spool valve combination is developed using the bond graph method. Feedback linearization is used to develop a force controller for the system using hydraulic pressure in each chamber of the actuator along with piston position and velocity as feedback. The use of a feedforward term to compensate for the seal friction within the actuator provides for a stable and accurate controller. Velocity control is achieved through calculation of the reference force required to overcome the seal friction and produce the acceleration required to reach the desired velocity. It is shown that the use of such a force controller allows for an acceptable transition from velocity to force control when the piston comes in contact with an external surface.
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