There is currently a need for compact actuators capable of producing large deflections, large forces, and broad frequency bandwidth. In all existing transducer materials, large force and broadband responses are obtained at small displacements and methods for transmitting very short transducer element motion to large deformations need to be developed. This paper addresses the development of a hybrid actuator which provides virtually unlimited deflections and large forces through magnetorheological (MR) flow control and rectification of the resonant mechanical vibrations produced by a magnetostrictive Terfenol-D pump. The device is a compact, self-contained unit which produces large work output concurrently with stiffness and damping control and is self-locking when unpowered. To increase the output force, hydraulic advantage is created by implementing a driven piston diameter that is larger than the drive piston. Since the pump operates at high speeds in the low kHz range, a fast-acting MR fluid valve is required. The paper presents a four-port MR fluid valve in which the fluid controls its own flow while carrying the full transducer load. A multi-domain systems model for the coupled dynamics of the valve is presented. A four-port valve was constructed and tested for purposes of proof-of-the-concept validation, model verification and system parameter identification. The combined experimental and model results demonstrate the feasibility of the proposed transducer concept.

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