Design and Testing of a Fluid-Cable Transmission

—This paper describes the principles, design, and testing of a novel transmission that combines the advantages of fluid and cable elements. The cable and fluid run concentrically inside a single flexible hose to connect a master piston to a remote slave piston. Together, the fluid and cable transmit bidirectional forces and motions. Since fluid acts on only one side of each piston, low-friction, leak-proof rolling diaphragms may be used instead of o-rings. The fluid-cable transmission eliminates the need for antagonistic cables and overcomes the friction and force limitations of conventional push-pull cables. It may be used as a low-friction remote actuation system in medical devices, assistive technology, and robotic manipulators. We analyze its transmission stiffness, describe its design and manufacture, and report on progress towards comparative testing.