The present disclosure relates to variable recruitment actuator systems and related methods. In one embodiment, a variable recruitment actuator system utilizes a central hydraulic pump, an accumulator, a plurality of variable recruitment actuators, and a pressurized reservoir of hydraulic fluid to provide highly efficient hydraulic regenerative energy harvesting in systems requiring both eccentric and concentric motion. In another embodiment, a powered prosthetic or orthotic device, or a legged robot, utilizes a system as previously described to capture energy from the eccentric motion of the knee joint to provide concentric motion of both the knee and ankle joints later on in a gait cycle.

The present disclosure pertains to prosthetic systems that encompass a prosthetic foot and a pump mechanism devised to eliminate fluid between a prosthetic socket and a residual limb or liner, thereby sustaining a hypobaric pressure chamber within a cavity of the prosthetic socket. The pump mechanism may incorporate a fluid chamber established between a membrane and the housing of the pump mechanism. Forces resulting from the user's gait during the compression and expansion of the prosthetic foot can be transmitted to an L-brace, which is configured to actuate the membrane of the pump mechanism, facilitating the influx and efflux of fluid into and from the fluid chamber.

A .[.prosthetic system includes a.]. prosthetic foot .[.defining an upper surface and having a flexible configuration and.]. .Iadd.including a movable member and .Iaddend.a pump .[.system attached to the prosthetic foot.]. .Iadd.mechanism.Iaddend.. The pump .[.system includes a pump.]. mechanism .[.defining.]. .Iadd.defines .Iaddend.a fluid chamber .[.having variable configuration and an actuating part.]. .Iadd.positioned between the member and the foot.Iaddend.. .[.The actuating part is arranged to selectively engage with and separate a distance from the upper surface of the foot plate to move the pump mechanism between a first position in which a volume of the fluid chamber is zero or near-zero and a second position in which the volume of the fluid chamber is expanded relative to the first position. The volume of the fluid chamber increases when the actuating part moves away from the upper surface of the foot plate..]. .Iadd.During heel strike, the member pulls the upper side of the pump forward to expand the fluid chamber; during stance or toe-off, the member pushes the pump backward to compress the fluid chamber. The member includes two non-pivotally joined pieces..Iaddend.