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While there is a wide range of actuation technologies, none currently rivals the overall performance (power density, bandwidth, stress, stroke) of conventional hydraulic actuation . It is well known in the actuation community that the power-to-weight ratios and the power-to-volume ratios of hydraulic actuators are, respectively, around 5 times and 10 to 20 times larger than comparable electric motors. Due to fundamental limitations in the magnetic flux density in the supporting structures and limitations in the heat transfer out of electric actuators, significant changes in these ratios are not likely in the near future . Thermal limitations associated with electric motors do not apply to hydraulic actuators since the hydraulic fluid cools and lubricates the system. However, with all of these virtues, hydraulic actuators have serious practical implementation problems. Typically, servo-based hydraulic actuators are leaky and have generally poor energy efficiencies. This work addresses a new type of electric actuator that combines the best of both the electric and hydraulic mediums.