Artificial ankle-foot system with spring, variable-damping, and series-elastic actuator components

Abstract

An artificial foot and ankle joint consisting of a curved leaf spring foot member that defines a heel extremity and a toe extremity, and a flexible elastic ankle member that connects said 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, and a controllable damper is employed to lock the ankle joint or to absorb mechanical energy as needed. The controller and a 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 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 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 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.  
   
   
       17 . An artificial ankle as set forth in  claim 16  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 when the relative motion of said foot and ankle structure and said shin member is being arrested by said variable damper.  
   
   
       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 ankle and foot structure for storing energy during a dorsiflexion period as the weight of said wearer displaces said elastic ankle and foot structure and for releasing energy during a powered plantarflexion period as said elastic foot and ankle structure urges said wearer in a forward direction with respect to said support surface,    a shin member,    an ankle joint for connecting said ankle and shin structure for rotational motion with respect to said shin member,    a motor for applying a torque to said ankle joint tending to move said ankle and foot structure with respect to said shin member,    a stop mechanism coupled between said ankle and foot structure and said shin member for preventing the rotation of said ankle and foot structure with respect to said shin member beyond a limiting position,    a controllable variable damper coupled to said ankle joint for arresting the motion of said ankle and foot structure with respect to said shin member under predetermined conditions,    and a controller connected to operate said motor and said controllable variable damper at predetermined times relative to said dorsiflexion period and said plantarflexion period.    
   
   
       20 . An artificial ankle and foot system as set forth in  claim 19  wherein said controller operates said controllable variable damper to arrest the motion of said ankle and 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 and ankle structure with respect to said shin member when said ankle and 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 and ankle structure with respect to said shin member when said ankle and 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.