“…As mentioned previously, there are four different types of controllers that are commonly used in the closed-loop control of anesthesia: proportional-integral-derivative, model predictive, adaptive, and fuzzy-logic controllers. Besides these controllers, strategies such as observer-controllers [213], robust and robust deadbeat controllers [220], [263], [328], nonlinear H-infinity controllers [329], non-overshooting tracking controller [330], sliding mode controllers [331], [332], and other types of nonlinear controllers [333] have been studied for use in anesthesia. Some of these studies have employed performance metrics such as settling-time, overshoot, undershoot, lowest observed BIS value (BIS-NADIR), performance error (PE), median performance error (MDPE), median absolute performance error (MDAPE), total variation (TV), integrated absolute error (IAE), and WOBBLE (an index of response variations over time) to compare their results and controller effectiveness to other control strategies in attempts to demonstrate advantages over other schemes and find the most suitable class of controllers for anesthesia [272], [334]- [336].…”