Patent ID: 7076340

Claim:
A sensorless control method for a synchronous motor, comprising the steps of: taking a magnetic axis of the synchronous moto as a â€œÎ´â€ axis and taking an axis leading the Î´ axis by 90Â° C. as a â€œâ€axis; taking a coordinate Î³-Î´ axis rotating at a synchronous motor rotation speed iÎ´k and a specified magnetic axis of the synchronous electric motor as Î³, and taking an axis leading Î³by 90Â° C. as Î´, thereby setting a Î³-Î´ axis rotation at a synchronous motor rotation instruction speed Ï‰ rm taking a Î´-axis direction current instruction iÎ³(k) and Î´-axis direction current instruction iÎ´(k) as positive, thereby inducing torque for constraining maxnetic axis â€œÎ´â€at an angle leading the Î³axis; deriving a Î´-axis direction current instruction by means of feedback control for multiplying, by gain, a variation between the synchronous motor rotation instruction speed Ï‰ rm and an estimated speed Ï‰ rm derived through disturbance observation, which observation is prepared by a Î´-axis current formula and is taken as a synchronous motor induced voltage disturbance, adding, to the Î´-axis direction current instruction, a variation angle correction instruction iÎ´(k) derived from an external observation by way of a proportional integration controller, the observation being prepared by a Î³-axis current formula and being taken as a synchronous motor induced voltage disturbance; and aligning a Î³axis rotating at instruction speed Ï‰ rm with a real magnetic axis â€œd.â€