Design and evaluation of prosthetic shoulder controller.

Area of Science:

• Biomedical Engineering
• Rehabilitation Engineering
• Human-Machine Interfaces

Background:

• Advanced prosthetic arms require intuitive control systems for users with shoulder disarticulation or high-level transhumeral amputation.
• Existing control methods for powered prostheses often lack the dexterity needed for natural movement.
• Development of novel sensing technologies is crucial for next-generation upper-limb prosthetics.

Purpose of the Study:

• To develop and evaluate a 2-degree-of-freedom (DOF) shoulder position transducer for controlling powered prosthetic arms.
• To assess the efficacy of different transducer designs (with and without resistance) and control schemes (position vs. velocity).
• To establish a robust evaluation protocol using Fitts' law for prosthetic performance assessment.

Main Methods:

• Development of a 2-DOF shoulder position transducer measuring protraction-retraction and elevation-depression.
• Implementation of position and velocity control schemes for prosthetic humerus DOFs.
• Design of an evaluation protocol based on Fitts' law to quantify task performance.

Main Results:

• Transducers providing resistance to shoulder movement demonstrated superior performance compared to those without resistance.
• A position control scheme, where prosthetic effector position is proportional to shoulder position, outperformed a velocity control scheme.
• The developed transducer successfully controlled two DOFs of a powered prosthetic humerus.

Conclusions:

• The 2-DOF shoulder position transducer offers a viable control solution for powered prosthetic arms, particularly for individuals with high-level amputations.
• Resistance in the transducer and a position-based control strategy enhance prosthetic functionality and user performance.
• The Fitts' law-based evaluation protocol provides a standardized method for assessing prosthetic device and control scheme performance.