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This paper presents a general vector control principle of surface-mounted permanent magnet (SPM) motors with arbitrary back-electromotive-force (back-EMF) waveform, then applies it to minimize the force pulsation of three-phase linear permanent magnet brushless dc motors (LPMBDCMs). The principle is derived from the force equation in the dot product form of the current vector and the permanent magnet (PM) flux linkage derivative vector. It indicates that the mutual force is proportional to the amplitude of current vector, and the ohmic loss is at the minimum when the current vector is aligned with the PM flux linkage derivative vector. Based on a d'q' asynchronously rotating reference frame considering the effects of PM flux linkage harmonic, a new id' = 0 vector control method with the cogging force compensation is proposed according to the principle. From the results of simulation with an accurate finite element (FE) based phase variable model, the validity of the proposed control method is verified compared with the conventional PWM current control for a LPMBDCM.
Date of Publication: March 2010