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 method for determining a change in traction between a foot member of an orthotic, prosthetic or exoskeleton apparatus and an underlying surface, the apparatus comprising a foot member, a lower leg member, an ankle joint for connecting the foot member to the lower leg member and a first actuator for applying torque to the ankle joint to rotate the foot member with respect to the lower leg member, the method comprising:
calculating ground reaction force and the zero moment pivot imparted by an underlying surface onto the foot member based on an inertial pose of the lower leg member, the torque applied to the lower leg member by the actuator, axial force applied to the lower leg member, and an angle between the foot member and lower leg member; and
calculating velocity of the foot member zero moment pivot based on the 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 the angle between the foot member and lower leg member.
2. The method of claim 1 , further comprising determining that the foot member is slipping or sinking if the velocity of the foot member zero moment pivot decreases during a portion of a gait cycle of the wearer between a foot-flat and toe-off condition.
3. The method of claim 2 , further comprising reducing torque applied to the lower leg member in response to determining that the foot member is slipping or sinking.
4. The method of claim 3 , further comprising reducing the torque applied to the lower leg member by an attenuation factor.
5. The method of claim 4 , wherein the attenuation factor is a predetermined attenuation factor.
6. The method of claim 4 , wherein the attenuation factor is determined based on the zero moment pivot velocity.
7. The method of claim 2 , further comprising reducing the torque applied to the lower leg member in response to the zero moment pivot velocity being below a predetermined threshold.
8. An orthotic, prosthetic or exoskeleton apparatus comprising:
a foot member,
a lower leg member,
an ankle joint for connecting the foot member to the lower leg member,
a first actuator for applying torque to the ankle joint to rotate the foot member with respect to the lower leg member, and
a controller configured to determine a change in traction between the foot member and an underlying surface, the determining comprising:
calculating ground reaction force and the zero moment pivot imparted by an underlying surface onto the foot member based on an inertial pose of the lower leg member, the torque applied to the lower leg member by the actuator, axial force applied to the lower leg member, and an angle between the foot member and lower leg member; and
calculating velocity of the foot member zero moment pivot based on the 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 the angle between the foot member and lower leg member.
9. The apparatus of claim 8 , wherein the controller is further configured to determine that the foot member is slipping or sinking if the velocity of the foot member zero moment pivot decreases during a portion of a gait cycle of the wearer between a foot-flat and toe-off condition.
10. The apparatus of claim 9 , wherein the controller is further configured to reduce torque applied to the lower leg member in response to determining that the foot member is slipping or sinking.
11. The apparatus of claim 10 , wherein the torque applied to the lower leg member is reduced by an attenuation factor.
12. The apparatus of claim 11 , wherein the attenuation factor is a predetermined attenuation factor.
13. The apparatus of claim 11 , wherein the attenuation factor is determined based on the zero moment pivot velocity.
14. The apparatus of claim 9 , wherein the controller is further configured to reduce the torque applied to the lower leg member in response to the zero moment pivot velocity being below a predetermined threshold.