Stance controller and related methods
Systems and methods are disclosed for operating a joint of a prosthesis during a phase of stance. In an embodiment, a method for such operation comprises determining a joint angle of the joint, determining a walking speed of the prosthesis, retrieving a torque value from a lookup table stored in a memory, on the basis of the joint angle and the walking speed, and initiating a signal to apply a torque to the joint of the prosthesis in an amount based on the torque value.
1. A method for operating a joint of a prosthesis during a phase of stance, comprising:
a. determining a joint angle of the joint;
b. determining a walking speed magnitude of the prosthesis;
c. retrieving, using only the joint angle and the walking speed, a torque value from an intact leg's quasi-stiffness profile,
wherein the quasi-stiffness profile is representative of torque data for an able-bodied joint,
wherein the able-bodied joint corresponds to the joint of the prosthesis, and
wherein the intact leg's quasi-stiffness profile is encoded in a lookup table stored in a memory; and
d. initiating a signal to apply a torque to the joint of the prosthesis in an amount based on the torque value.
2. The method of claim 1 , further comprising operating the prosthesis on a ground; and determining an inclination of the ground at the position under the prosthesis; wherein the step of retrieving the torque value from the lookup table stored in the memory is based on the inclination of the ground.
3. The method of claim 1 , wherein the method is used to control the prosthesis during an early phase of stance, a mid-phase of stance, and a late phase of stance.
4. The method of claim 1 , wherein the joint of the prosthesis is the knee joint.
5. A method for operating a prosthesis comprising a knee joint and an ankle joint during a phase of stance, comprising performing the method of claim 1 for the knee joint and performing the method of claim 1 for the ankle joint.
6. The method of claim 1 , where the torque value is retrieved from the lookup table using interpolation.
7. The method of claim 1 , wherein the signal to apply the torque to the joint of the prosthesis is modified, based on a weight of the user of the prosthesis, to normalize the torque to apply.
8. The method of claim 1 , wherein the method is used to control the prosthesis during an early phase of stance, a mid-phase of stance, and a late phase of stance.
9. The method of claim 1 , wherein the joint of the prosthesis is the knee joint.
10. A method for operating a prosthesis comprising a knee joint and an ankle joint during a phase of stance, comprising performing the method of claim 1 for the knee joint and performing the method of claim 1 for the ankle joint.
11. The method of claim 1 , where the torque value is retrieved from the lookup table using interpolation.
12. The method of claim 1 , wherein the signal to apply the torque to the joint of the prosthesis is modified, based on a weight of the user of the prosthesis, to normalize the torque to apply.
13. The method of claim 1 , wherein the lookup table is selected from a plurality of lookup tables.
14. The method of claim 13 , wherein each lookup table in the plurality of lookup tables is associated with a distinct phase of stance.
15. The method of claim 1 , wherein the determining the walking speed magnitude of the prosthesis comprises measuring a shank orientation of a user of the prosthesis using a complementary filter.
16. A method for operating a joint of a prosthesis, comprising:
a. setting the prosthesis to a first stance phase and, while the prosthesis is in the first stance phase:
determining a first joint angle of the joint;
determining a first walking speed of the prosthesis;
retrieving, using only the first joint angle and the first walking speed, a first torque value from a first intact leg's quasi-stiffness profile,
wherein the quasi-stiffness profile is representative of torque data for an able-bodied joint,
wherein the able-bodied joint corresponds to the joint of the prosthesis in the first stance, and,
wherein the intact leg's quasi-stiffness profile is encoded in a first lookup table stored in a memory; and
initiating a first signal to apply a torque to the joint of the prosthesis in an amount based on the first torque value; and
b. setting the prosthesis to a second stance phase and, while the prosthesis is in the second stance phase:
determining a second joint angle of the joint;
determining a second walking speed of the prosthesis;
retrieving, using only the second joint angle and the second walking speed, a second torque value from a second intact leg's quasi-stiffness profile,
wherein the quasi-stiffness profile is representative of torque data for the able-bodied joint in the second stance,
and wherein the intact leg's quasi-stiffness profile is encoded in a second lookup table stored in a memory; and
initiating a second signal to apply a torque to the joint of the prosthesis in an amount based on the second torque value.
17. The method of claim 16 , further comprising smoothing the second signal after a transition from the first stance phase to the second stance phase.
18. The method of claim 17 , wherein the smoothing occurs during the 20 ms following the transition.
19. The method of claim 16 , wherein step (b) occurs when a movement of an ankle joint of the prosthesis inverts between dorsiflexion and plantarflexion.