Unified controller for a powered knee prosthesis
Disclosed are prosthetic systems comprising a powered knee prosthesis and a volitional controller configured to provide control of the prosthesis to the user. The prosthetic system may be configured to enable a user to walk on smooth and/or uneven terrain and to ascend and/or descend stairs. The volitional controller may be configured in a contact state when the prosthesis is in contact with a ground surface and a no contact state when the prosthesis is lifted from the ground surface. When in the contact state, the controller may output a knee torque signal for controlling the powered knee of the prosthesis. The knee torque signal may be based on a target knee torque determined by the knee orientation and the torque measured at the ankle of a prosthetic foot. When in the no contact state, the controller may output a knee torque signal based on a desired knee position.
1 . A system for providing volitional control to a powered knee prosthesis, comprising:
a powered knee prosthesis comprising a powered knee joint; and
a volitional controller comprising one or more processors and one or more hardware storage devices having instructions stored thereon that are executable by the one or more processors to cause the controller to at least:
determine a knee orientation and an ankle torque;
determine a target knee torque based on the knee orientation and ankle torque, wherein the target knee torque is determined by summing
(i) a step-up torque calculated from measured knee orientation wherein the step-up torque increases from a lower knee orientation threshold to a maximum value and then decreases toward an upper knee orientation threshold, and
(ii) a biarticular torque defined as a knee flexion torque that is proportional to a measured ankle plantarflexion torque; and
output a knee torque signal to the powered knee joint of the powered knee prosthesis to adjust the powered knee joint toward the target knee torque,
wherein the controller does not classify ambulation activity or switch between activity-specific controllers according to walking, stair ascent, or stair descent activities.
2 . The system of claim 1 , wherein the instructions further cause the controller to determine a thigh orientation and a prosthetic knee velocity.
3 . The system of claim 1 , wherein the biarticular torque is further determined by multiplying the measured ankle plantarflexion torque with a biarticular knee gain and a biarticular thigh gain, wherein:
the biarticular knee gain has a value dependent on measured knee orientation, with a maximum value at or below a lower knee orientation threshold and a minimum value at or above an upper knee orientation threshold; and
the biarticular thigh gain has a value dependent on measured thigh orientation, with a minim value at or below a lower thigh orientation threshold and a maximum value at or above an upper thigh orientation threshold.
4 . The system of claim 1 , wherein the target knee torque is further determined by adding a damping torque.
5 . The system of claim 4 , wherein the damping torque is proportional to and opposite a prosthetic knee velocity.
6 . The system of claim 1 , wherein the instructions further cause the volitional controller to:
receive a ground state signal; and
configure the controller in a contact state or a no contact state;
wherein the knee torque signal is configured to adjust the powered knee joint toward the target knee joint when the controller is in the contact state.
7 . They system of claim 6 , wherein when the controller is in the no contact state the knee torque signal is configured to adjust the powered knee joint toward a desired knee orientation, the desired knee orientation being determined by summing a minimum jerk trajectory and an adaptive orientation, wherein:
the minimum jerk trajectory is a trajectory selected to minimize changes to angular acceleration of a shank of the powered knee prosthesis; and
the adaptive orientation is a product of a synergistic orientation angle and an adaptive gain, wherein
(i) the synergistic orientation angle is proportional to and opposite the knee orientation, and
(ii) the adaptive gain is based on a toe-off knee orientation measured at the transition from the contact state to the no contact state, the adaptive gain having a higher value at lower toe-off knee orientation and a lower value at higher toe-off knee orientation.
8 . The system of claim 1 , wherein the powered knee prosthesis comprises:
a shank having a proximal and a distal end;
a prosthetic foot connected to the distal end of the shank;
a powered knee joint connected to the proximal end of the shank; and
a socket configured to receive a residual limb of a user, wherein the socket is connected to the powered knee joint.
9 . The powered-kace-and-prosthetic log-system of claim 1 , wherein the powered knee prosthesis comprises a ground reaction force (GRF) sensor and an inertial measurement unit (IMU).
10 . The system of claim 1 , wherein the powered knee prosthesis is configured to enable a user to walk on even and/or inclined surfaces and to ascend and/or descend stairs.
11 . A method for controlling a powered knee prosthesis, comprising:
determining a knee orientation and an ankle torque;
determining a target knee torque based on the knee orientation and ankle torque, wherein the target knee torque is determined by summing
(i) a step-up torque that is related to knee orientation wherein the step-up torque increases from a lower knee orientation threshold to a maximum value and then decreases toward an upper knee orientation threshold, and
(ii) a biarticular torque defined as a knee flexion torque that is proportional to a measured ankle plantarflexion torque; and
outputting a knee torque signal to a powered knee joint of the powered knee prosthesis to adiost powered knee joint toward the target knee torque.
12 . The method of claim 11 , further comprising determining a thigh orientation and a prosthetic knee velocity.
13 . The method of claim 11 , further comprising configuring a volitional controller in a contact state or a no contact state and basing the knee torque signal on the target knee torque when the volitional controller is in the contact state.
14 . A system for providing volitional control to a powered knee prosthesis, comprising:
a powered knee prosthesis comprising a powered knee joint;
and a volitional controller comprising one or more processors and one or more hardware storage devices having instructions stored thereon that are executable by the one or more processors to cause the controller to at least:
receive a ground state signal indicating a transition from a contact state to a no contact state;
determine a toe-off knee orientation defined as the knee orientation measured at the transition from the contact state to the no contact state;
and output a knee torque signal to the powered knee joint of the powered knee prosthesis to adjust the powered knee joint toward a desired knee orientation, the desired knee orientation being determined by summing a minimum jerk trajectory and an adaptive orientation, wherein the minimum jerk trajectory is a trajectory selected to minimize changes to angular acceleration of a shank of the powered knee prosthesis, wherein the adaptive orientation is a product of a synergistic orientation angle and an adaptive gain,
wherein (i) the synergistic orientation angle is proportional to and opposite a current knee orientation, and
(ii) the adaptive gain is based on the toe-off knee orientation, with a higher value at lower toe-off knee orientation and a lower value at higher toe-off knee orientation.
15 . The system of claim 14 , wherein the controller does not classify ambulation activity or switch between activity-specific controllers according to walking, stair ascent, or stair descent activities.