Electro-rheological (ER) gel is a relatively new type of functional material that has been developed. ER gel has a shear stress characteristic on the surface, which increases according to the applied electric field. Introducing the gel into the interface elements of a force transmission system facilitates the realization of functional clutches and brakes. This study aims to develop a linear actuator which is safe, can operate in reverse and can generate a large force using such a functional clutch. Applying an ER gel clutch in a force transmission system results in a decrease of inertia and the mechanical limits of the maximum speed not obstructing high controllability. This contributes to high safety. This paper reports, in particular, on stabilizing the output of the linear actuator.