Aiming at the problem of large speed fluctuation caused by parameter time-varying and load disturbance in the speed control of surface-mounted permanent magnet synchronous motor(SPMSM)

a model-free predictive direct speed control(MFPDSC) method based on third-order extended state observer(ESO) is proposed to improve the steady-state performance based on obtaining the fast speed response of the servo system. First

the second-order mathematical model of the motor speed is reconstructed

and the speed disturbance is equivalent to the lumped disturbance of the current

which enhances the system's response speed to the load disturbance and strengthens the constraint control of the speed. Second

the control subset is designed in the rotating coordinate system to improve the multi-objective optimization's cost function constraint performance. Then

a third-order ESO is designed to observe the lumped disturbance of the motor's second-order model

simplifying the control structure of the model-free direct speed prediction control. Using frequency domain analysis

the suppression effect of the third-order ESO on the system disturbance is proved

and the stability of the control system is demonstrated by using the root locus. Finally

by building a drive system of SPMSM

the advantages of the proposed control strategy in the response speed and parameter time-varying disturbance suppression are verified.