Abstract:
Catapult ankles and related methods are disclosed. An example ankle prosthesis for operation in a swing phase and in a stance phase includes a motor, wherein the motor is configured to store energy with a first spring during the swing phase and plantarflex the ankle prosthesis during a push off portion of the stance phase.

Description:
RELATED APPLICATIONS 
       [0001]    This patent claims priority to U.S. Provisional Patent Application Ser. No. 62/241,489, filed on Oct. 14, 2015, entitled “Catapult Ankle and Related Methods.” The entirety of U.S. Provisional Patent Application Ser. No. 62/241,489 is incorporated herein by reference. 
     
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    [Not Applicable] 
       MICROFICHE/COPYRIGHT REFERENCE 
       [0003]    [Not Applicable] 
       BACKGROUND 
       [0004]    Lower limb loss causes severe mobility deficits that affect many other aspects of lives of amputees, including decreased community involvement and depression. One major cause for these mobility challenges is the lack of small, lightweight leg prostheses that can provide power like the human neuromuscular system. A person&#39;s walking or other ambulation gait can be cyclical, with a stance phase and a swing phase. Stance phase is the part of the gait cycle when weight is borne by the leg. Swing phase is the part of the gait cycle when the foot is in the air and weight is borne by the opposite leg. 
         [0005]    The human ankle is important for walking because it provides over half of the energy required to move the body forward. The ankle produces energy during part of the gait cycle known as “push off” or “powered plantarflexion.” During push off, the calf muscle contracts and propels the body into the next step. During the remainder of the gait cycle, the ankle produces little to no power. 
       COMPONENT LIST 
       [0000]    
       
           5  ankle system 
           10  motor 
           20  transmission 
           21  gear stage one 
           22  gear 
           23  gear stage  2   
           24  gear 
           25  output from gear  24   
           26  charging disk 
           27  chassis 
           28  spring pegs on the charging disk 
           29  spring pegs on the chassis 
           50  springs latex springs between each of  28  and  29   
           30  bearing blocks 
           31  gas spring. One end connected to chassis  27 , other end connected to foot  32   
           32  foot 
           33  ankle axle (ankle joint) 
           34  clutch. 
           35  microcontroller 
           36  clutch motor 
           37  sensor 
           38  sensor 
           39  pyramid to connect to pylon 
           40  axle 
       
     
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0030]      FIG. 1  is a profile view of a prosthetic ankle system. 
           [0031]      FIG. 2  is an exploded view of the prosthetic ankle system shown in  FIG. 1 . 
           [0032]      FIG. 3  is a diagram illustrating the general positioning of the elements of the prosthetic ankle system shown in  FIG. 1   
           [0033]      FIG. 4  is a profile view of spring held in place by spring pegs for use in the prosthetic ankle system shown in  FIG. 1   
           [0034]      FIG. 5  is a side view of the prosthetic ankle system shown in  FIG. 1 . 
           [0035]      FIG. 6  is a side view of the prosthetic ankle system shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    In an embodiment, an ankle system stores energy in a spring or a plurality of springs over a longer duration than just the period of push-off (in one example, for the entire gait cycle), and releases the energy when needed (in one example, push off). This design permits the use of a small, low power motor, instead of a heavier high power motor. The substantially reduced weight may ease the burden for amputees wearing a robotic ankle. The robotic ankle may be manufactured using the design described herein, and its control may be implemented on a microcontroller programmed with a finite state machine or another algorithm. In an embodiment, the ankle system uses a catapult mechanism to propel the ankle system forward during plantarflexion. 
         [0037]      FIGS. 1 and 2  illustrate a profile view and an exploded view, respectively, of an embodiment of ankle system  5 . The ankle system  5  comprises a motor  10 , a charging disk  26 , a chassis  27 , springs  50 , spring  31 , a clutch  34 , and a foot  32 . As illustrated in  FIG. 2 , the springs  50  are connected between the charging disk  26  and the chassis  27 . The motor  10  may run throughout all of the gait cycle, in order to provide the most power available to the ankle system  5  during powered plantarflexion. 
         [0038]    During stance phase before push-off, the ankle system  5  stores energy in the spring  31 . During swing phase, the motor operates to store energy in the ankle system  5  in both the stance and swing springs. During push off of the ankle system  5 , the energy stored the ankle system is released. For example, a spring system may store energy in the ankle system  5  until it is released during push-off. The clutch may be used to disengage the motor  10  from the ankle joint while energy is stored in the spring  31 . The motor and springs may be selected based on their ability to facilitate the appropriate mechanical power and energy storage. 
         [0039]    During the swing phase and the stance phase from toe-strike to mid-stance, the motor  10  runs to store energy in one or more of the springs  50  and the spring  31 . Energy in the springs  50  is stored by the charging disk  26  rotating about an axle  40  in relation to the chassis  27 , which is fixed. Energy in the spring  21  is stored when dorsiflexion of the foot  32  caused by running of the motor  10  and the ground reaction forces created when the foot  32  strikes the ground causes the spring  21  to compress. During powered plantarflexion, the motor  10  reverses its operation, and the energy from the motor  10 , the springs  50 , and the spring  31  all operate in the same direction to provide an increased torque to assist the user plantarflex the ankle system  5 . 
         [0040]    As illustrated in  FIGS. 1 and 2 , the motor  10  is coupled to a transmission  20 , which turns a first gear stage and a second gear stage. The first gear stage comprises gear  21  and gear  22 , where the rotation of gear  21  causes an opposite rotation of gear  22 . The gear  22  has a link  22   a  attached at the center of the gear  22  and extending therefrom. The link  22   a  connects to gear  23  (also illustrated in  FIG. 6 , a side view of the catapult ankle system). The second gear stage comprises gear  23 , gear  24 , and output member  25 , where rotation of gear  23  causes an opposite rotation of gear  24 . Gear  24  is connected to output member  25 , which may be positioned through bearing block  30 . Output member  25  has a sprocket  25   a  that interfaces with the teeth of the charging disk  26 , so that rotation of the output member  25  causes the charging disk  26  to rotate about the axle  40 . In the embodiment shown in  FIG. 2 , sensor  37  and sensor  38  may be used to determine the position of each of the gas spring  31 , chassis  27 , charging disk  26 , ankle axle  33 , and clutch  34 . As illustrated in  FIG. 2 , the gas spring  31  may be connected, on one end, to chassis  27 , and on the other end, to foot  32 . 
         [0041]    Spring pegs  28  attached to the charging disk  26  and spring pegs  29  attached to the chassis  27  hold the springs  30  in place. Springs  50  may be latex springs. In an embodiment, each spring  50  is a circular latex spring.  FIG. 4  shows a side profile illustration of an embodiment of a spring  50  held in place by spring pegs  28  and  29 . 
         [0042]    Various clutch configurations may be used in various embodiments of an ankle system. As illustrated in  FIGS. 5 and 6 , side views of the catapult ankle system, in an embodiment, the clutch  34  may be shaped so that when the clutch  34  is adjusted upwards towards the ankle system  5 , the teeth of the clutch  34  engage against the charging disk  26  to prevent the charging disk from rotating in a first direction. When the clutch is adjusted upwards towards the ankle system  5  in the opposite direction, the teeth of the clutch  34  engage against the charging disk  26  to prevent the charging disk  26  from rotating in a direction opposite the first direction. The clutch  34  may have its own motor, which may be coupled to an actuator to move the clutch  34  upwards towards the ankle system. 
         [0043]    During the swing phase of the ankle system  5 , the clutch  34  is engaged and the foot is dorsiflexed, which causes energy to be stored in spring  31  and springs  50 . During the early to mid-stance phase of the ankle system  5 , the clutch  34  disengages when the user&#39;s own ground reaction opposes the spring  31  and springs  50 . Once the clutch  34  has disengaged, the motor  10  stores energy in the springs  50 , and the user&#39;s force on the ankle system  5  stores energy in the spring  31 . At push off of the ankle system  5 , the clutch  34  engages again, and the motor  10 , the springs  50 , and the spring  31  operate together to provide energy in the same direction to assist in plantarflexion. The clutch  34  is only not engaged between early/mid-stance and push off. In the ankle system  5 , energy is stored in the springs  50  when the charging disk  26  rotates in a first direction with respect to the chassis  27 , which stretches the springs  50 . 
         [0044]    Motor  10  may be a brushless motor operated by a controller  35 . In an embodiment, the controller  35  may control the motor  10  and also may control the motor of the clutch  34 . The controller  35  may be coupled to sensors  37  and  38  (which may be linear potentiometers) attached to the ankle system  5 , which can detect the kinematics of the ankle system  5 . The controller  35 , the sensors, and the clutch  34  may be coupled together using appropriate communication busses, other electronics (such as FET switches) and power sources (such as a 12V LiPo battery). 
         [0045]    In an embodiment, the controller  35  determines that the ankle system  5  is in swing phase by using information from the sensors to determine the angle threshold of the ankle system  5 , which indicates whether the ankle is plantarflexed. The controller  35  sends an instruction to the motor  10  to dorsiflex the foot  32  to a sufficient dorsiflexion angle at the start of swing. The controller  35  then waits to receive information from the sensors that indicate start of stance (for instance, by an identification of heel contact). As the user begins to put his or her body weight on the ankle system  5 , the weight of the user counteracts the other torque on the clutch  34  and the clutch disengages. As the ankle system  5  transitions from mid-phase, the ankle system  5  rolls over, then stops from rolling over just before plantarflexion. The ankle speed just before plantarflexion is equal to 0. The sensors indicate to the controller  35  that the ankle speed is equal to 0, causing the controller  35  to cause the clutch  34  to engage, causing the motor  10 , the springs  50 , and the gas spring  31  to release their energy to plantarflex the ankle system  5 . 
         [0046]    The controller may be programmed with a control system based on a finite state control system architecture. This architecture employs a set of concatenated states with specific mechanical behaviors. During operation, the machine cycles through the states, which provide the behavior needed for walking. There are two parts to the finite state machine—the state behaviors and the state transitions. Based on the desired operation of the ankle, there may be four states. 
         [0047]      FIG. 3  illustrates a diagram that shows the general positioning of elements of an embodiment of an ankle system. One possible use of the ankle system is briefly described. During swing phase, the motor stores energy in both the stance and swing springs by compressing the stance spring and the swing spring towards system ground. During the early to mid-stance phase, the clutch disengages and the motor stores energy in the stance spring and the user&#39;s force on the system stores energy in the swing spring. At push off of the ankle system, the clutch engages and the motor, the stance spring, and the swing spring operate so that the energy stored in both springs is released to the wearer with high power. The clutch is used to disengage the motor from the ankle joint while energy is stored in the stance spring. The motor and springs may be selected based on their ability to facilitate the appropriate mechanical power and energy storage.