What is an impedance control strategy in rehabilitation robotics, and when is it used?

• A. A control approach that mimics mechanical impedance, used to interact safely with human users, adapt to varying stiffness, and provide compliant assistance.
• B. A strategy to maximize device speed regardless of patient safety.
• C. A method that disregards user interaction to simplify control.
• D. A fixed-stiffness controller that never adapts to the user.

Answer: (A)

Impedance control in rehabilitation robotics focuses on shaping the interaction forces between the person and the device by selecting a desired impedance—how the system responds to motion and applied forces. By mimicking mechanical impedance, the robot presents a compliant interface: it can resist more when the patient needs support and yield when the patient moves or applies varying forces. This enables safe collaboration, as contact forces stay within comfortable limits and the device can adapt to changes in user stiffness, motor ability, and task demands. Because of this adaptability and safety focus, impedance control provides compliant assistance rather than rigid guidance. It’s not about maximizing speed, it doesn’t disregard user input, and it isn’t fixed-stiffness—the approach adjusts to the user’s behavior and needs.