Hi, the AMCLIB_BemfObsrvDQ is not a sliding mode observer. It’s a Luenberger-type observer which estimates BEMF in a quasi-synchronous rotating coordinate γδ using angle of θγδ (angle between γ-axis and α-axis) for Park transformation. The BEMF in coordinate γδ reflects the angle error (θerror ) between γ-axis and the d-axis of the rotor. Then, a tracking observer (AMCLIB_TrackObsrv) is used to make θerror approach to 0, so that θγδ will be the real rotor position in the end. The observer is based on the mathematical model of the motor, thus the parameters of the observer are derived from the parameters of the motor. The AMMCLib User's Guide provides equations for calculating the observer parameters from the motor parameters.
