Semi-actuated transfemoral prosthetic knee
Inventors
Fairbanks, Dylan Miller • Zoss, Adam Brian • Pillai, Minerva Vasudevan • Schwartz, Miclas • Harding, Nathan • Rosa, Matthew • Lambrecht, Bram Gilbert Antoon • Kruse, Sebastian • Kazerooni, Homayoon
Assignees
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Publication Number
US-8231688-B2
Publication Date
2012-07-31
Expiration Date
Abstract
A semi-actuated above knee prosthetic system, which is mostly passive in nature and includes a shank link coupled to an artificial foot, a knee mechanism connected to the shank link and a thigh link attached to an above-knee remaining lower limb of an amputee, is operable in either an actuated mode or an un-actuated mode controlled by a signal processor linked to various prosthetic mounted sensors which may include combinations of knee angle, stance, thigh angle and shank angle sensors. Power is delivered through an electric motor connected to a battery source and employed to drive a hydraulic pump which is part of an overall hydraulic power unit including the torque generator. A signal processor selects a swing state from at least forward, combination forward and descent, combination forward and ascent, reverse, combination reverse and descent, and combination reverse and ascent swing states.
Core Innovation
The invention describes a prosthetic knee device for an amputee with an above-knee remaining lower limb having a trunk. The device includes an artificial foot having a toe and a heel, a shank link coupled to the artificial foot, and a thigh link configured to be attached to the above-knee remaining lower limb. A knee mechanism interconnects the thigh link and the shank link to allow flexion and extension movements, and a torque generator is configured to generate torque between the shank link and the thigh link.
The invention uses a knee angle sensor creating a knee angle signal representing an angle between the shank link and the thigh link, and a stance sensor identifying which part of the artificial foot is in contact with ground. A signal processor receives signals from the knee and stance sensors, determines an estimated location of the artificial foot with respect to the trunk of the amputee, and, when the artificial foot leaves the ground, selects a type of swing state. The selectable swing state types include forward swing state, forward and descent swing state, forward and ascent swing state, reverse swing state, reverse and descent swing state, and reverse and ascent swing state.
The signal processor, when the leg is in a swing state, controls an angle between the shank link and the thigh link through the torque generator as a function of a thigh angle signal from a thigh angle sensor or from calculations based on signals received using a combination of a shank angle sensor in conjunction with the knee angle sensor. This control causes the artificial foot to follow a predetermined trajectory, including a trajectory generally parallel to the ground.
Claims Coverage
The partial content includes two independent claims. Across these claims, the inventive coverage centers on sensor-based estimation of the artificial foot location relative to the amputee trunk and swing-state selection upon foot lift, and swing-state control that drives the shank-thigh angle using thigh-angle or derived signals so the artificial foot follows a predetermined trajectory.
Trunk-relative estimated foot location and swing-state selection
A signal processor receives signals from the knee angle sensor and the stance sensor, determines an estimated location of the artificial foot with respect to the trunk of the amputee, and based on the estimated location when the artificial foot leaves the ground selects a type of swing state from forward swing state, forward and descent swing state, forward and ascent swing state, reverse swing state, reverse and descent swing state, and reverse and ascent swing state.
Swing control of shank-thigh angle for predetermined foot trajectory
When the leg is in a swing state, a signal processor controls the angle between the shank link and the thigh link through the torque generator as a function of a thigh angle signal from a thigh angle sensor or calculations based on signals received from a combination of a shank angle sensor in conjunction with the knee angle sensor such that the artificial foot follows a predetermined trajectory.
The independent claims collectively define a prosthetic knee device that uses knee-angle and stance sensing to estimate artificial foot location relative to the trunk for selecting among multiple swing-state types at foot-off, and that uses thigh-angle or derived signals to control the shank-thigh angle via the torque generator so the artificial foot follows a predetermined trajectory, including one generally parallel to the ground.
Stated Advantages
Reduced electric power compared to fully powered knees.
Smaller size.
Reduced hip torque and reduced hip power demand.
Increased mobility via synchronized control.
Documented Applications
Use as a prosthetic knee device coupled to an above-knee remaining lower limb of an amputee having a trunk.
Use as a prosthetic knee device coupled to the lower limb of a person.
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