Hello,
the equation AMCLIB_BemfObsrvDQ_Eq2 corresponds to the implemented observer structure which intentionally presumes that the phase error between the estimated quasi-synchronous frame gamma/delta and the synchronous rotor flux frame d/q is zero. If we assume that the feedback loop has converged to a steady state, the function will return zero angle theta_err, the term ed(n) in the AMCLIB_BemfObsrvDQ_Eq2 will be zero, and the term eq(n) will be proportional to the magnitude of the induced back-electromotive force. If, however, the two reference frames are not aligned (e.g. during a transient), the PI controllers will attempt to compensate the alignment error by increasing/decreasing ed(n)/eq(n) and the function will return non-zero value theta_err. The return value theta_err of the BEMF observer function is the only output that is needed for the feedback loop and can be used as an input for the angle tracking observer (AMCLIB_TrackObsrv). Outputs ed(n) and eq(n) (which are provided in the structure pEObsrv) can be used for debugging purposes or to detect fault states.
Function AMCLIB_BemfObsrvDQSetState is explained in the AMMCLib 1.1.31 User's Guide in the chapter 2.2.7.
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