Hybrid terrain-adaptive lower-extremity systems
Hybrid terrain-adaptive lower-extremity apparatus and methods that perform in a variety of different situations by detecting the terrain that is being traversed, and adapting to the detected terrain. In some embodiments, the ability to control the apparatus for each of these situations builds upon five basic capabilities: (1) determining the activity being performed; (2) dynamically controlling the characteristics of the apparatus based on the activity that is being performed; (3) dynamically driving the apparatus based on the activity that is being performed; (4) determining terrain texture irregularities (e.g., how sticky is the terrain, how slippery is the terrain, is the terrain coarse or smooth, does the terrain have any obstructions, such as rocks) and (5) a mechanical design of the apparatus that can respond to the dynamic control and dynamic drive.
1. A lower-extremity prosthesis, comprising:
a foot member;
a lower leg member;
an ankle joint for connecting the foot member to the lower leg member;
an actuator for applying a positive torque feedback response to at least one of the lower leg member and the ankle joint to rotate the foot member with respect to the lower leg member;
a structural element coupled to the lower leg member and at least one of a strain gauge and displacement sensing apparatus for measuring the torque applied to the at least one of the lower leg member and the ankle joint; and
a controller configured to modulate the positive torque feedback response of the actuator during gait based on the measured torque, wherein the positive torque feedback response involves amplification of the torque applied to the at least one of the lower leg member and the ankle joint, wherein only the measured torque applied to the at least one of the lower leg member and the ankle joint is required for the amplification.
2. The prosthesis of claim 1 , comprising an inertial measurement unit from which a component of an inertial pose of at least one of the lower leg member, the ankle joint and the foot member, can be determined.
3. The prosthesis of claim 2 , wherein the inertial measurement unit is coupled to the lower leg member.
4. The prosthesis of claim 2 , wherein the inertial measurement unit is coupled to the foot member.
5. The prosthesis of claim 1 , wherein the controller is configured to calculate a component of ground reaction force and zero moment pivot coordinates imparted by an underlying surface onto the foot member based on a component of an inertial pose of the lower leg member, the torque applied to the lower leg member by the actuator, the axial force applied to the lower leg member, and an angle between the foot member and lower leg member.
6. The prosthesis of claim 5 , wherein the controller is coupled to the actuator and is configured to control the actuator for modulating at least one of an impedance, position or torque of the prosthesis throughout a walking cycle of the prosthesis based on the inertial pose trajectory of the lower leg member, the angle between the foot member and lower leg member, and the ground reaction force and the zero moment pivot coordinates.
7. The prosthesis of claim 5 , wherein the controller is coupled to the actuator and is configured to control the actuator as the wearer stands up from a seated position or sits down from a standing position based on a component of the inertial pose of the lower leg member, the angle between the foot member and lower leg member, and a component of the ground reaction force and the zero moment pivot coordinates.
8. The prosthesis of claim 1 , wherein the displacement sensing apparatus comprises a plurality of sensors and the displacement sensing apparatus measures the distance between each sensor and a surface of the structural element.
9. The prosthesis of claim 8 , wherein the sensors are selected from the group consisting of contact displacement sensors, non-contact displacement sensors, inductive coils, optical sensors, force-sensitive resistors, piezoelectric sensors, and strain sensors.
10. The prosthesis of claim 8 , wherein the plurality of sensors comprise a plurality of inductive coils on a circuit board.
11. The prosthesis of claim 10 , wherein changes in inductance of the inductive coils relative to a surface of the structural element are used to determine the displacement of the structural element.
12. The apparatus of claim 1 , wherein the at least one of a strain gauge and displacement sensing apparatus is configured to measure an axial force applied to the lower leg member.
13. The apparatus of claim 1 , wherein the positive torque feedback response of the actuator is represented by the following relationships:
Γ=−( k (θ−θ 0 )+ b{dot over (θ)}+j {umlaut over (θ)})+Γ reflex (α)
Γ reflex (α)=Γ Torque reflex (α)+Γ Velocity reflex
where Γ=torque applied, k=joint impedance, θ 0 =joint equilibrium, b=joint damping, j=joint intertia, θ reflex (α)=ankle reflex response, Γ Torque reflex (α)=positive torque feedback response, Γ Velocity reflex (α)=positive velocity feedback response, and α=one or more parameters that defines a torque response.
14. The apparatus of claim 13 , wherein a comprises an exponential parameter such that the positive torque feedback response relates exponentially to a measured torque, and the positive velocity feedback response relates exponentially to an angular velocity.