Systems and method for volitional control of jointed mechanical device based on surface electromyography
Systems and methods for controlling a weight bearing member having at least one powered joint are provided. A system includes a velocity reference module for receiving myoelectric control signals from a user during a non-weight bearing mode for the powered joint and generating a velocity reference for the powered joint based on the myoelectric control signals. The system further includes a volitional impedance module for generating a torque control signal for actuating the powered joint based at least on the velocity reference.
1. A controller for controlling a plurality of powered joints in a leg prosthesis, comprising:
a processor; and
a computer-readable medium, having stored thereon a plurality of instructions for causing the processor to perform the steps of:
receiving, from a plurality of electromyogram (EMG) electrodes associated with a plurality of different muscle groups of a user, EMG signals for the user during a non-weight bearing mode of operation for at least one powered joint in the plurality of powered joints;
determining an intent of the user based on a discriminant analysis of the EMG signals;
determining, based on the received EMG signals, movement characteristics for the at least one powered joint, the movement characteristics comprising an angular velocity, a joint stiffness, and a damping;
generating a velocity reference for the at least one powered joint based on the EMG signals and the intent of the user; and
transmitting, to a motor unit for the at least one powered joint, a torque control signal for actuating the at least one powered joint, the torque control signal comprising the determined movement characteristics and based at least on the velocity reference and the intent of the user.
2. The controller of claim 1 , wherein the torque control signal is generated using a model based on the behavior of a spring and dashpot element.
3. The controller of claim 1 , wherein the discriminant analysis is quadratic discriminant analysis of the EMG signals.
4. The controller of claim 1 , wherein the velocity reference is generated based on a principal component analysis of the EMG signals.
5. The controller of claim 1 , wherein the torque control signal is generated based on an equilibrium point derived from the velocity reference.
6. The controller of claim 5 , further comprising determining the equilibrium point based on the velocity reference and an initial angle of the at least one powered joint.
7. The controller of claim 1 , wherein the at least one at least one powered joint comprises a plurality of powered joints, and further comprising selecting an active one of the plurality of powered joints based on determining that the EMG signals indicate a co-contraction.
8. The controller of claim 1 , wherein the discriminant analysis is linear discriminant analysis of the EMG signals.
9. A method performed in a controller for controlling a plurality of powered joints in a leg prosthesis, comprising:
receiving, at the controller from a plurality of electromyogram (EMG) electrodes associated with a plurality of different muscle groups of a user, EMG signals for the user during a non-weight bearing mode of operation for at least one powered joint in the plurality of powered joints;
determining an intent of the user based on a discriminant analysis of the EMG signals;
determining, based on the received EMG signals, movement characteristics for the at least one powered joint, the movement characteristics comprising an angular velocity, a joint stiffness, and a damping;
generating, at the controller, a velocity reference for the at least one powered joint based on the EMG signals and the intent of the user; and
transmitting, from the controller to a motor unit for the at least one powered joint, a torque control signal for operating the motor unit and actuating the at least one powered joint, the torque control signal comprising the determined movement characteristics and generated based at least on the velocity reference and the intent of the user.
10. The method of claim 9 , wherein the torque control signal is generated using a model based on the behavior of a spring and dashpot element.
11. The method of claim 9 , wherein the discriminant analysis is quadratic discriminant analysis of the EMG signals.
12. The method of claim 9 , wherein the velocity reference is generated based on a principal component analysis of the EMG signals.
13. The method of claim 9 , wherein the torque control signal is generated based on an equilibrium point derived from the velocity reference.
14. The method of claim 9 , wherein the torque control signal is generated based on an equilibrium point derived from the velocity reference and an initial angle of the at least one powered joint.
15. The method of claim 9 , wherein the at least one at least one powered joint comprises a plurality of powered joints, and further comprising alternating an active one of the plurality of powered joints when the EMG signals indicate a co-contraction.
16. The method of claim 9 , wherein ascertaining the intent of the user comprises classifying the EMG signals as corresponding to one of flexion or extension.
17. The method of claim 9 , wherein the discriminant analysis is linear discriminant analysis of the EMG signals.