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. An apparatus comprising:
a foot member;
a lower leg member worn by a wearer;
an ankle joint for connecting the foot member to the lower leg member;
an inertial measurement unit comprising a gyroscope for measuring an angular rate and an accelerometer for measuring acceleration, the inertial measurement unit disposed on the lower leg member to collocate a measurement of angular rate and acceleration for each of at least two axes of the lower leg member in a coordinate system; and
a hardware controller configured to:
track a trajectory of a point on the lower leg member over underlying terrain by the inertial measurement unit, the trajectory being tracked within a cycle defined by the wearer taking a single step with the lower extremity apparatus;
determine that the tracked trajectory matches an activity type selected from among a group of predefined activity types, or that the tracked trajectory does not match any of the predefined activity types, and
when the tracked trajectory matches the activity type, determining a mode of control based on the predefined activity type, and controlling the lower extremity apparatus according to the determined mode, or when the tracked trajectory does not match any predefined activity type, performing a predefined unclassified control operation.
2. The apparatus of claim 1 , wherein the inertial measurement unit is located on a forward face at a top of the lower leg member.
3. The apparatus of claim 1 , wherein the apparatus forms a system comprising a kinematic chain, and the inertial measurement unit is centrally located along the kinematic chain.
4. The apparatus of claim 1 , wherein the inertial measurement unit is configured to compute an orientation of the ankle joint, a position of the ankle joint in the coordinate system, and a velocity of the ankle joint.
5. The apparatus of claim 1 , wherein the point is at a virtual center of rotation of the ankle joint.
6. The apparatus of claim 1 , wherein the trajectory is determined based on an inertial pose of the lower leg member and an angle of the ankle joint defined by an angle between the foot member and the lower leg member.
7. The apparatus of claim 1 , the activity type being further determined based on the velocity of an angle of attack of the ankle joint.
8. The apparatus of claim 1 , wherein controller is configured to match the trajectory against the group of predefined activity types based on Bayesian pattern classification, a neural net, fuzzy logic, or a hierarchical temporal memory.
9. The apparatus of claim 1 , wherein the predefined unclassified control operation comprises one or more of:
performing a stochastic control to minimize a negative impact of foot strike forces and maximize a positive impact of reflex-induced ground forces on an energy of the apparatus; or
applying fuzzy logic or one or more ad hoc controls based upon a likelihood that an underlying terrain matches one of the predefined activity types.
10. The apparatus of claim 1 , wherein the activity type is selected from the group consisting of: moving on flat terrain, moving up stairs, moving down stairs, moving up a slope, and moving down a slope.
11. The apparatus of claim 1 , wherein the parameter is selected from the group consisting of joint position equilibrium, joint impedance, and joint torque.
12. The apparatus of claim 1 , wherein the trajectory is further tracked throughout a walking cycle of the lower extremity apparatus.