“…One of the early motivations on developing DOB was to design an online load toque observer in motor drives. Recently, disturbance observation techniques have been extensively investigated as load toque observation, for example, see DOB [23], [24], [32], [85]- [88], ESO [12], [33], [36], [89], generalized proportional integral observer (GPIO) [90], [91], sliding mode disturbance observer (SMDO) [92] and intelligent disturbance observer (IDO) [70], [93], [94] for PMSM ( [12], [23], [24], [32], [33], [36], [92]), IM ( [85], [86], [89]- [91], [93], [94]) and BLDCM ( [87], [88]), respectively.…”