Artificial Ankle-Foot System with Spring, Variable-Damping, and Series-Elastic Actuator Components

Abstract

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 . An artificial ankle comprising, in combination:
 a shin member;   a foot and ankle structure coupled for rotation with respect to said shin member at an ankle joint, said foot and ankle structure comprising:
 a curved flexible elastic foot member that defines a heel extremity and a toe extremity; and 
 a flexible elastic ankle member that connects said foot member to said ankle joint; and 
   a variable damper element for arresting the motion of said foot and ankle structure with respect to said shin member under predetermined conditions.   
     
     
         2 . An artificial ankle as set forth in  claim 1 , further comprising a motor for applying torque to said ankle joint to rotate said foot and ankle structure with respect to said shin member. 
     
     
         3 . An artificial ankle as set forth in  claim 2 , further including an elastic member operatively connected in series with said motor between said shin member and said foot and ankle structure to store energy when the relative motion of said foot and ankle structure and said shin member is being arrested by said variable damper and to thereafter apply an additional torque to said ankle joint when the relative motion of said foot and ankle structure with respect to said shin member is no longer arrested by said controllable variable damping element. 
     
     
         4 . An artificial ankle as set forth in  claim 3 , further including a controller for operating said motor to store energy in said elastic member when the relative motion of said foot and ankle structure and said shin member is being arrested by said variable damper. 
     
     
         5 . An artificial ankle as set forth in  claim 2 , wherein said variable damper includes a stop mechanism for preventing said ankle and foot structure from rotating beyond a maximum limiting rotational position. 
     
     
         6 . An artificial ankle as set forth in  claim 2 , wherein said motor adjusts the position of said foot and ankle structure relative to said shin member when said foot and ankle member is not in contact with a support surface. 
     
     
         7 . An artificial ankle as set forth in  claim 6 , further comprising a inertial sensing means for determining the relative elevation of said foot and angle structure and for actuating said motor in response to changes in said relative elevation. 
     
     
         8 . An artificial ankle as set forth in  claim 1 , further including an elastic member operatively connected in series with said motor between said shin member and said foot and ankle structure to store energy when the relative motion of said foot and ankle structure and said shin member is being arrested by said controllable variable damping element and to thereafter apply an additional torque to said ankle joint when the relative motion of said foot and ankle structure with respect to said shin member is no longer arrested by said controllable variable damping element. 
     
     
         9 . An artificial ankle as set forth in  claim 8 , wherein said variable damper includes a stop mechanism for preventing said ankle and foot structure from rotating beyond a maximum limiting rotational position. 
     
     
         10 . An artificial ankle as set forth in  claim 1 , wherein said variable damper includes a stop mechanism for preventing said ankle and foot structure from rotating beyond a maximum limiting rotational position. 
     
     
         11 . An artificial ankle as set forth in  claim 10 , wherein said variable damper further includes a controllable damping element for arresting the motion of said foot and ankle structure with respect to said shin member when said foot and ankle structure is storing and releasing energy. 
     
     
         12 . An artificial ankle as set forth in  claim 1 , wherein said variable damper element includes a controllable variable damper and a controller for actuating said controllable variable damper to arrest the motion of said foot and ankle structure with respect to said shin member under predetermined conditions. 
     
     
         13 . An artificial ankle as set forth in  claim 12 , wherein said controller actuates said controllable variable damper to arrest the motion of said foot and ankle structure when said foot and ankle structure is storing and releasing energy. 
     
     
         14 . An artificial ankle as set forth in  claim 13 , further comprising a motor for applying torque to said ankle joint to rotate said foot and ankle structure with respect to said shin and wherein said motor adjusts the position of said foot and ankle structure relative to said shin member when said foot and ankle member is not in contact with a support surface. 
     
     
         15 . An artificial ankle comprising, in combination:
 a shin member;   a foot and ankle structure coupled for rotation with respect to said shin member at an ankle joint, said foot and ankle structure comprising:
 a flexible elastic foot member that defines a heel extremity and a toe extremity; and 
 a flexible elastic ankle member comprising a unidirectional elastic element that engages at a small dorsiflexion angle; and 
   a motor connected for applying torque to said ankle joint to rotate said foot and ankle structure with respect to said shin member at controllable times.   
     
     
         16 . An artificial ankle as set forth in  claim 15 , further including an elastic member operatively connected in series with said motor between said shin member and said foot and ankle structure. 
     
     
         17 . An artificial ankle as set forth in  claim 15 , further including a stop mechanism for preventing said ankle and foot structure from rotating beyond a maximum limiting rotational position. 
     
     
         18 . An artificial ankle as set forth in  claim 16 , further including a controller for operating said motor to store energy in said elastic member. 
     
     
         19 . An artificial ankle and foot system for supporting a human wearer as said wearer walks on a support surface comprising, in combination:
 an elastic foot structure for storing energy during a dorsiflexion period as the weight of said wearer displaces said elastic foot structure and for releasing energy during a powered plantarflexion period as said elastic foot structure urges said wearer in a forward direction with respect to said support surface;   a shin member;   an ankle joint for connecting said foot structure for rotational motion with respect to said shin member, the ankle joint further comprising a stop mechanism for preventing the rotation of said foot structure with respect to said shin member beyond a limiting position;   a motor for applying a torque to said ankle joint tending to move said ankle and foot structure with respect to said shin member; and   a controller connected to operate said motor at predetermined times relative to said dorsiflexion period and said plantarflexion period.   
     
     
         20 . An artificial ankle and foot system as set forth in  claim 26 , wherein said controller operates said controllable variable damper to arrest the motion of said foot structure with respect to said shin member during said powered plantarflexion period. 
     
     
         21 . An artificial ankle and foot system as set forth in  claim 20 , wherein said controller operates said motor to reorient said foot structure with respect to said shin member when said foot structure is not in contact with said support surface. 
     
     
         22 . An artificial ankle and foot system as set forth in  claim 21 , further including an additional elastic member for storing energy from said electric motor prior to each powered plantarflexion period and for releasing energy during said powered plantarflexion period. 
     
     
         23 . An artificial ankle and foot system as set forth in  claim 19 , wherein said controller operates said motor to reorient said foot structure with respect to said shin member when said foot structure is not in contact with said support surface. 
     
     
         24 . An artificial ankle and foot system as set forth in  claim 23 , further including an additional elastic member for storing energy from said electric motor prior to each powered plantarflexion period and for releasing energy during said powered plantarflexion period. 
     
     
         25 . An artificial ankle and foot system as set forth in  claim 19 , further including an additional elastic member for storing energy from said electric motor prior to each powered plantarflexion period and for releasing energy during said powered plantarflexion period. 
     
     
         26 . An artificial ankle and foot system as set forth in  claim 19 , further comprising a controllable variable damper coupled to said ankle joint for arresting the motion of said foot structure with respect to said shin member under predetermined conditions. 
     
     
         27 . An artificial ankle and foot system as set forth in  claim 22 , the additional elastic member comprising a unidirectional elastic element that engages at a small dorsiflexion angle. 
     
     
         28 . An artificial ankle and foot system as set forth in  claim 24 , the additional elastic member comprising a unidirectional elastic element that engages at a small dorsiflexion angle. 
     
     
         29 . An artificial ankle and foot system as set forth in  claim 19 , further comprising a flexible elastic element operatively connected in series with the motor. 
     
     
         30 . An artificial ankle comprising, in combination:
 a shin member;   a foot and ankle structure coupled for rotation with respect to the shin member at an ankle joint, the foot and ankle structure comprising a flexible elastic foot member that defines a heel extremity and a toe extremity;   a motor connected for applying torque to the ankle joint to rotate the foot and ankle structure with respect to the shin member at controllable times; and   a flexible elastic element operatively connected in series with the motor between the shin member and the foot and ankle structure.   
     
     
         31 . The artificial ankle of  claim 30 , the foot and ankle structure further comprising a flexible elastic ankle component that stores energy during dorsiflexion. 
     
     
         32 . The artificial ankle of  claim 31 , the flexible elastic ankle component comprising a unidirectional elastic element that engages at a small dorsiflexion angle. 
     
     
         33 . The artificial ankle of  claim 30 , further comprising a variable damper element for arresting the motion of the foot and ankle structure with respect to said the member under predetermined conditions. 
     
     
         34 . The artificial ankle of  claim 30 , wherein the motor adjusts the position of the foot and ankle structure relative to the shin member when the foot and ankle structure is not in contact with a support surface. 
     
     
         35 . The artificial ankle of  claim 30 , further comprising an inertial sensing means for determining the relative elevation of the foot and ankle structure and for actuating the motor in response to changes in said relative elevation. 
     
     
         36 . The artificial ankle of  claim 30 , further comprising a stop mechanism for preventing the ankle and foot structure from rotating beyond a maximum limiting rotational position. 
     
     
         37 . The artificial ankle of  claim 15 , further comprising a variable damper element for arresting the motion of the foot and ankle structure with respect to said the member under predetermined conditions. 
     
     
         38 . The artificial ankle of  claim 15 , wherein the motor adjusts the position of the foot and ankle structure relative to the shin member when the foot and ankle member is not in contact with a support surface. 
     
     
         39 . The artificial ankle of  claim 15 , further comprising an inertial sensing means for determining the relative elevation of the foot and ankle structure and for actuating the motor in response to changes in said relative elevation.