Implementation of a physiologically identified PD feedback controller for regulating the active ankle torque during...

Area of Science:

• Neuroscience
• Biomedical Engineering
• Control Systems

Background:

• Proportional and derivative (PD) feedback controllers can compensate for neurological time delays in balance control.
• Previous studies identified PD gain pairs for robust system behavior and dynamic responses in quiet standing.

Purpose of the Study:

• To experimentally verify if a previously identified PD controller can regulate ankle torque for balance.
• To confirm if the PD controller can generate system dynamics mimicking physiological quiet standing.

Main Methods:

• A real-time closed-loop feedback circuit with a center of mass position sensor and functional electrical stimulator was used.
• The system controlled upright stance in a subject with von Hippel-Lindau Syndrome (McCormick Grade III), who had de-afferentation and de-efferentation.
• A time delay was incorporated into the PD controller to simulate neurological delays.

Main Results:

• The PD controller and functional electrical stimulation system successfully regulated active ankle torque for quiet stance.
• The system generated body sway and motor command dynamics comparable to those of healthy individuals.
• The subject could not sufficiently regulate ankle torque due to sensory and motor deficits.

Conclusions:

• The proposed PD controller, with functional electrical stimulation, can regulate ankle torque and mimic healthy balance dynamics.
• These findings suggest the theoretical possibility of PD-like control strategies for balance regulation.
• The study highlights the potential of engineered control systems to aid individuals with neurological disorders affecting balance.