Stair descent control for powered lower limb devices

A non-transitory computer-readable medium comprising a plurality of instructions for causing a controller device for a lower limb device to perform the method comprising:

• selecting one of a plurality of states of a finite state model defining a stair descent controller to yield a current state;
• operating a motor of a powered knee joint of the lower limb device and a motor of a powered ankle joint of the lower limb device according to the current state;
• based on real-time sensor information for the lower limb device from a plurality of sensors and a transition trigger for the current state, transitioning from a current state to a subsequent state in the finite state model, wherein the real-time sensor information for the lower limb device and comprises an inertial measurement unit and a position sensor for angle measurements of the powered knee joint;
• computing an estimate of an orientation with respect to gravity of a thigh associated with the powered knee joint based on the real-time sensor information from the at least one inertial measurement unit;
• and
• repeating the operating, the transitioning, and the computing until a criteria for exiting the stair descent controller is met, wherein the criteria is met when the estimate indicates an absence of thigh flexion for a period of time.

The non-transitory computer-readable medium of claim 23,

• wherein the finite state model comprises a swing extension phase, a forefoot strike phase, a stance knee flexion phase, and a swing flexion phase and wherein the plurality of sensors further comprises a load sensor,
• wherein the transition trigger from the swing extension phase to the forefoot strike phase is detecting, by the load sensor, that a load on the lower limb device exceeds a threshold,
• wherein the transition trigger from the forefoot strike phase to the stance knee flexion phase is detecting that an angle of the powered ankle joint meets a threshold phase,
• wherein the transition trigger from the stance knee flexion phase to the swing flexion phase is detecting, by the load sensor, that the load on the lower limb device falls below the threshold, and
• wherein the transition trigger from the swing flexion phase to the swing extension phase is detecting that an angular velocity for the powered knee joint inflects.

The non-transitory computer-readable medium of claim 23, wherein the estimate is further based on at least one of:

• an estimation of a location of a segment of the lower limb device or a user through the at least one inertial measurement unit;
• a joint angle or angular velocity measurements from at least one of the plurality of sensors;
• a measurement of a degree of load or moment bearing in the lower limb device from a load sensor in the plurality of sensors, wherein the measurement of a degree of load is provided by a load sensor;
• or
• input received from a sensor.