Envelope-Level Resolver Nonorthogonal Error Calibration Considering Inductive Harmonics

Resolvers are widely adopted as angle sensors in electric transportation propulsion systems due to their high reliability. However, their outputs are often affected by systematic errors, notably non-orthogonal errors and inductive envelope harmonics, which are difficult to eliminate through manufacturing processes and harmful to the stability of electric transportation system. In particular, the presence of inductive harmonics severely impairs the calibration of non-orthogonal errors. To solve this, an envelope-level non-orthogonal error calibration system is proposed in this paper considering the inductive harmonics. The non-orthogonal error is directly observed from the envelopes of resolver outputs without the coupling of angle observer. And the arc-cosine and sigmoid functions are used to compensate the envelope, eliminating the model imprecision from the inductive harmonics. By the hardware-in-the-loop evaluation, the proposed system-level non-orthogonal error calibration method can eliminate 87% angle error under third-order inductive harmonics.