In the active probing approach, an idle phase is injected with low amplitude diagnostic signal to obtain the phase inductance. The inductance of a stator phase winding varies significantly between aligned and unaligned condition of the rotor and stator poles. The rotor position can therefore be determined from the phase inductance information. The methods that fall under this category are the flux linkage method [6], phase current waveform methods [7], [8], [9], modulation method [10], [11], and neural network method [12]. The effect of the magnetic saturation can be ignored under the active probing approach if a low amplitude diagnostic signal is injected to the phase winding which avoids magnetic saturation.
