PROSTHESIS WITH POWERED ANKLE AND TOE JOINTS
Disclosed herein is a robotic ankle foot prosthesis that replicates the key biomechanical functions of the biological ankle and toe joints while matching the weight, size, and battery life of passive microprocessor-controlled prostheses. A single actuator powers the ankle and toe joints. The mechanism maximizes the mechanical energy regeneration during walking while imitating the physiological features of energy injection by way of the ankle joint and energy dissipation by way of the toe joint.
1 . A powered assistive ankle and foot device, comprising:
a shank assembly comprising an ankle joint and a shank pivot shaft offset from the ankle joint;
a tarsal assembly comprising a proximal section and a distal section, the proximal section being connected to the shank pivot shaft;
a toe assembly comprising a toe joint and a toe pivot shaft offset from the toe joint, the toe pivot shaft being connected to the distal section of the tarsal assembly; and
a linear actuator associated with the tarsal assembly, the linear actuator being configured as a linear series elastic actuator,
wherein the linear actuator is configured to adjust the distance between the shank pivot shaft and the toe pivot shaft to thereby provide simultaneous torque to both the ankle joint and the toe joint.
2 . The device of claim 1 , wherein the linear series elastic actuator comprises a screw, a nut, and a compliant element.
3 . The device of claim 2 , wherein the linear actuator comprises a ball screw assembly.
4 . The device of claim 2 , wherein the compliant element is mechanically connected to the nut and functions to move the nut toward a neutral position along the screw when the screw is not rotated.
5 . The device of claim 2 , wherein the compliant element is attached to and spans between a proximal anchor and a distal anchor, wherein the proximal anchor is connected to the nut and the distal anchor is connected to the toe pivot shaft.
6 . The device of claim 5 , wherein the proximal and distal anchors include bores sized to receive the screw.
7 . The device of claim 1 , wherein an offset distance between the ankle joint and the shank pivot shaft is greater than an offset distance between the toe joint and the toe pivot shaft.
8 . The device of claim 1 , wherein:
when a distance between the shank pivot shaft and the toe pivot shaft is lessened, the ankle joint moves in plantarflexion and the toe joint moves in toe flexion; and
when a distance between the shank pivot shaft and the toe pivot shaft is increased, the ankle joint moves in dorsiflexion and the toe joint moves in toe extension.
9 . The device of claim 1 , wherein the toe assembly includes a mechanical stop configured to prevent the toe assembly from moving past a neutral position.
10 . The device of claim 1 , further comprising a motor mechanically connected to the linear actuator to power the linear actuator.
11 . The device of claim 10 , wherein the motor is attached to or housed within the shank assembly.
12 . The device of claim 11 , wherein the motor does not rotate relative to a shank frame during ankle joint movement of the device.
13 . The device of claim 11 , wherein the motor is in direct contact with the shank frame.
14 . The device of claim 10 , wherein the motor is mechanically connected to the linear actuator via a power transmission assembly, wherein the power transmission assembly comprises multiple bevel gears.
15 . The device of claim 14 , wherein a first bevel gear is coaxial to an output gear, a second bevel gear is coaxial with the shank pivot shaft, and a third bevel gear is coaxial to an axis of rotation of screw of the ball screw assembly and functions to transfer power to the screw.
16 . The device of claim 1 , wherein the shank assembly comprises a pyramid adaptor, the pyramid adaptor comprising an integrated ground force sensor.
17 . The device of claim 1 , wherein the device is a prosthesis.
18 . A powered assistive ankle and foot device, comprising:
a shank assembly comprising an ankle joint;
a tarsal assembly comprising a proximal section and a distal section, the proximal section being connected to the shank assembly;
a toe assembly connected to the distal section of the tarsal assembly, the toe assembly comprising a toe joint; and
a linear actuator included in or associated with the tarsal assembly and configured to power movement of both the ankle joint and the toe joint, wherein the linear actuator comprises a screw, a nut, and a compliant element,
wherein the compliant element is connected to the nut and functions to move the nut toward a neutral position along the screw when the screw is not rotated.
19 . The device of claim 18 , wherein the compliant element is attached to and spans between a proximal anchor and a distal anchor, wherein the proximal anchor is connected to the nut and the distal anchor is connected to the toe pivot shaft, and wherein proximal and distal anchors include bores sized to receive the screw.
20 . The device of claim 18 , wherein the device is a prosthesis.