Robot-assisted rehabilitation: Collaborating a smart avatar with an AAN controller

Despite advances in robot-assisted rehabilitation, existing control strategies often lack real-time personalization to account for subject-specific physiological capabilities, limiting the effectiveness of assist-as-needed interventions. Moreover, there is a further need to account for the patient's physiological functional capacity (PFC) in the design of such assistive technology. Here, an attempt has been made to create an Assist-as-Needed (AAN) Controller that works in collaboration with a Smart Avatar. The Smart Avatar mimics the patient's capabilities by learning in real-time and informing the controller. To efficiently predict the subject's level of involvement, a Reinforcement Learning (RL) based Inverse Dynamics model has been designed. Additionally, the controller for the Avatar has been appended with an Energy Map for modifying the reference trajectories and making the system energy efficient. The human torque estimated by the Smart Avatar assists the Assist-as-Needed (AAN) controller in providing the optimum robot torque to guide the subject's wrist along the modified trajectories. The developed algorithm was validated on five healthy participants. The system achieved trajectory tracking errors in the range of 0.01-0.04 rad across wrist motions. Subject- and axis-dependent differences in interaction torque were examined using descriptive statistics and torque profiles, supporting the feasibility of adaptive assistance under the tested conditions.