What is a human-in-the-loop system in rehabilitation robotics?

• A. A system where the user actively participates in control or supervision; safety depends on user input as well as device autonomy.
• B. A system where the device operates completely autonomously with no user input.
• C. A system that only logs user data but does not participate in control.
• D. A system with external supervision only.

Answer: (A)

In rehabilitation robotics, a human-in-the-loop system means the user actively participates in control or supervision, and safety and effectiveness rely on a partnership between the person and the device. The robot responds to the user's intent—often detected through signals like muscle activity, motion, or other sensors—and provides appropriate assistance or resistance in real time, while safeguards and the option for the user to override keep control with the human participant. This collaborative approach lets the device adapt to the user's abilities and rehabilitation goals, rather than running without input or only passively collecting data. A system that operates completely on its own has no user input to guide movement, a setup that merely logs data is passive, and a system with only external supervision lacks in-the-moment user control.