Artificial ankle-foot system with spring, variable-damping, and series-elastic actuator components
An artificial foot and ankle joint consists of a curved leaf spring foot member having a heel extremity and a toe extremity, and a flexible elastic ankle member that connects the foot member for rotation at the ankle joint. An actuator motor applies torque to the ankle joint to orient the foot when it is not in contact with the support surface and to store energy in a catapult spring that is released along with the energy stored in the leaf spring to propel the wearer forward. A ribbon clutch prevents the foot member from rotating in one direction beyond a predetermined limit position. A controllable damper is employed to lock the ankle joint or to absorb mechanical energy as needed. The controller and sensing mechanisms control both the actuator motor and the controllable damper at different times during the walking cycle for level walking, stair ascent, and stair descent.
1. A device comprising:
a) a mechanical ankle joint;
b) a controllable actuator to exert a torque about the joint, the actuator including a motor and
a spring that is operatively coupled with the motor;
c) an artificial sensory system comprising at least one sensor selected from the group consisting of a position sensor, a velocity sensor, a gyroscope, an accelerometer, and a force sensor; and
d) a control system configured to cause the motor to store elastic energy in the spring during controlled dorsiflexion based on information from the at least one sensor for later release of stored elastic energy from the spring during powered plantar flexion of the gait cycle, wherein the motor stores elastic energy during controlled dorsiflexion over a longer period of time than the amount of time to release energy from the spring during powered plantar flexion to augment power output of the joint.
2. The device of claim 1 , further comprising a stop adapted to prevent rotation of the joint beyond a predetermined limit.