Unobtrusive Yet Precise Velocity Perturbations During Voluntary Elbow Movement for Reliable Joint Dynamics...

Area of Science:

• Robotics
• Biomechanics
• Human-Robot Interaction

Background:

• Robotic systems assess joint dynamics via limb perturbations.
• Position perturbations limit voluntary motion, while force perturbations yield orientation-dependent responses.
• Existing methods face limitations in balancing voluntary movement and precise perturbation control.

Purpose of the Study:

• To develop and validate a novel robotic control strategy combining admittance control and position perturbations.
• To enable objective assessment of joint dynamics during continuous voluntary movement.
• To demonstrate the reliability, accuracy, and smoothness of the proposed method.

Main Methods:

• Implemented a hybrid control system integrating admittance control with precisely timed position perturbations.
• Utilized a minimum-jerk trajectory for smooth transitions between control modes.
• Conducted experiments with six healthy participants to evaluate the system's performance.

Main Results:

• All perturbations reliably reached target velocities within 1 ms of the acceleration time window.
• High accuracy was demonstrated with a Root Mean Square Error (RMSE) of 1.1 deg/s (0.55%) under demanding conditions.
• Smooth transitions were confirmed by a perturbation perceivability accuracy of 22.1%.

Conclusions:

• The developed controller reliably and accurately assesses joint dynamics during voluntary elbow movements.
• This approach facilitates objective joint property estimation during activities of daily living.
• The method offers a promising advancement for robotic-assisted biomechanical assessments.