Variable-mechanical-impedance artificial legs

Abstract

In one aspect, the invention provides methods and apparatus facilitating an adjustable-stiffness prosthesis or orthosis (including approximations to arbitrarily definable non-linear spring functions). Spring rates may be varied under no-load conditions during a walking gate cycle to minimize power consumption. In another aspect, the invention provides methods and apparatus for outputting positive power from a prosthesis or orthosis, facilitating high-performance artificial limbs. In one embodiment of the invention, the positive power is transferred from a functioning muscle to the prosthesis or orthosis, which mimics or assists a non-functioning or impaired muscle. In another embodiment of the invention, the positive power comes from an on-board power source in the prosthesis or orthosis.

Having described the invention, what is claimed is:  
     
         1 . A variable impedance prosthesis or orthosis, comprising: 
 a. A proximal end for interfacing to a user;    b. a distal end for interfacing to the environment;    c. a stiffness controller;    d. a controllable-spring-rate spring element.    
     
     
         2 . The apparatus of  claim 1 , wherein said controllable-stiffness spring element comprises multiple parallel interlockable spring elements.  
     
     
         3 . The apparatus of  claim 1 , wherein said controllable-stiffness spring element comprises a spring element with a variable mechanical advantage.  
     
     
         4 . The apparatus of  claim 1 , wherein said controllable-stiffness spring element comprises multiple parallel valved pneumatic spring elements.  
     
     
         5 . The apparatus of  claim 1 , wherein said controllable-stiffness spring element comprises a spring element and a parallel powered mechanical force source.  
     
     
         6 . The apparatus of  claim 1 , wherein said controllable-stiffness spring element comprises a spring element and a series powered mechanical displacement source.  
     
     
         7 . The apparatus of  claim 1 , wherein said controllable-spring-rate spring element further comprises: 
 a. a first spring element disposed between said proximal end and said distal end;    b. a mechanical energy storage element;    c. a controllable power source configured to store energy in said energy storage element;    d. a controllable coupling between said energy storage element and said first spring element;    e. a controller configured to control timing and rate of power output of said controllable mechanical power source, and coupling of controllable coupling.    
     
     
         8 . The apparatus of  claim 7 , wherein said controllable mechanical power source comprises a muscle and a controllable mechanical coupling between said muscle and said energy storage element  
     
     
         9 . A method for providing variable mechanical impedance in a prosthetic or orthotic, comprising varying the spring rate a controllable-spring-rate spring automatically with a spring-rate controller as a function of a repeated cycle of use of said prosthetic or orthotic.  
     
     
         10 . The method of  claim 9 , wherein said variable-spring-rate spring comprises multiple parallel interlockable spring elements, and said controller controls the interlocking of said elements.  
     
     
         11 . The method of  claim 9 , wherein said variable-spring-rate spring further comprises a first spring and an energy storage element, and further comprising: 
 a. storing energy from a power source in said energy storage element during a first span of time;    b. releasing energy from said energy storage element in the form of mechanical work displacing a proximal end of a prosthesis from a distal end of said prosthesis or orthosis during a second span of time.