Dynamic difficulty adjustment of rehabilitation tasks throughreal-time emotion feedback and performance

The decision of proper difficulty level for patients in robot-assisted rehabilitation while keeping them engaged is still an open challenge. We develop an adaptive robot-assisted rehabilitation therapy to challenge the subjects by changing the difficulty level of the rehabilitation task considering their performance (score) (Performance Feedback Based Adjustment (PFBA)), their emotions through physiological signals (skin conductance) (Physiological Feedback Based Adjustment (PHFBA)), and both performance and emotions at the same time (Performance and Physiological Feedback Based Adjustment (PPFBA)). The concept is evaluated in 20 healthy subjects performing the tasks with an upper-extremity exoskeleton RehabRoby. The system adapts difficulty levels of the tasks by maintaining the subject's performance, and skin conductance at a moderate level to balance the engagement, and challenge for each subject. The mean difficulty level distribution showed that PHFBA on the average suggests slightly easier difficulty levels (2.62±0.43, mean±std) to the subjects than PFBA (5.93±0.88, mean±std) and PPFBA (3.99±0.38, mean±std). Easier difficulty level adjustment resulted in less engaged subjects and correspondingly lower subjects' skin conductance response (SCR) (9.35±8.9, mean±std) and heart rate (HR) (89.27±9.35, mean±std) values in PHFBA compared to PFBA and PPFBA. Additionally, easier difficulty level adjustment resulted in lower valence value (5.7±0.95, mean±std), arousal (5.45±1.6, mean±std) and dominance (5.9±1.5, mean±std) subjective ratings in PHFBA compared to PFBA and PPFBA. It was also noted that the difficulty variance of PPFBA (4.97±2.06, mean±std) was higher than PFBA (1.48±0.49, mean±std) and PHFBA (3.52±1.41, mean±std) which meant that PPFBA offered wider levels to each subject. A wider variety of difficulty level suggestions might increase the amazement experienced by the subject, and the subject might become more engaged in the rehabilitation task, and consequently, Meantemp value in PPFBA (1.33±1.5, mean±std) was lower than the PFBA (2.39±1.78, mean±std) and PHFBA (2.03±1.58, mean±std).