Stair ascent and descent control for powered lower limb devices

A lower limb device comprising:

• a powered knee joint with a motor for providing an output torque at the powered knee joint;
• a powered ankle joint with a motor for providing an output torque at the powered ankle joint;
• a plurality of sensors for generating real-time sensor information for the lower limb device, wherein at least one of the plurality of sensors comprises an inertial measurement unit and a position sensor for angle measurements of the powered knee joint;
• at least one processor communicatively coupled to the plurality of sensors, the powered knee joint and the powered ankle joint;
• and
• a computer-readable medium comprising stored instructions for causing the at least one processor to perform the steps comprising:
• selecting one of a plurality of states of a finite state model defining a stair descent controller to yield a current state;
• operating the motor of the powered knee joint and the motor of the powered ankle joint according to the current state,
• based on the real-time sensor information for the lower limb device and a transition trigger for the current state, transitioning from a current state to a subsequent state in the finite state model,
• 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.