Joint Identification of Stepper Motor Parameters and of Initial Encoder Offset
Abstract
The paper presents a new procedure to identify at the same time the electrical parameters of a permanent magnet stepper motor (PMSM) and the initial offset of an incremental encoder. The model considers effects due to the permanent magnet and to variable reluctance, and the resulting theory is applicable to cases where both or only one of these terms is present. The standard DQ model of PMSM's assumes that the permanent magnet is lined up with a winding when the position is zero. When an incremental encoder is used, an initialization procedure is required to zero the initial offset. In contrast, this paper computes a transformed model that accounts for the initial offset. then develops a least-squares identification algorithm that estimates the machine's electrical parameters together with the offset angle. Experiments show that the estimation procedure and a closed-control method using the estimated offset perform similarly compared to when the offset is reset to zero using an initialization procedure.
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