Designing method of permanent magnetic synchronous motor expansion state flux linkage sliding mode observer

The invention provides a designing method of a permanent magnetic synchronous motor expansion state flux linkage sliding mode observer. The method comprises following steps of establishing a four-stage expansion mode of a permanent magnetic synchronous motor on an alpha beta axis by taking stator current and rotor flux linkage as state variables; constructing a permanent magnetic synchronous motorexpansion state flux linkage sliding mode observer; according to estimation errors of stator resistance R, stator equivalent inductance L and rotor electric angular speed omega of the knownpermanent magnetic synchronous motor, acquiring the stator current error equation of a stator current observation part and a rotor flux linkage error equation of a rotor flux linkage observation part; according to the stator current error equation, obtaining a sliding mode control law; according to the rotor flux linkage error equation, obtaining a feedback matrix; and through the rotor flux linkage error equation, carrying out fil