Oversampling Synchronous Envelope Detection for Resolver-to-Digital Conversion

In software-based resolver-to-digital conversion, it is necessary to detect the sinusoidal and cosinusoidal envelopes from the amplitude-modulated resolver signals in advance. The synchronous peak sampling method is usually used. However, the sampling frequency is limited by the excitation frequency in this method, which may lead to large quantization errors in the detected envelopes. To solve this problem, an oversampling synchronous envelope detection method is proposed in this article. First, the resolver signals are sampled at multiple fixed phase angles within each excitation period by synchronous oversampling. Second, the oversampled resolver signals are divided into multiple envelope pairs for normalization and correction. Finally, the calibrated envelope pairs are integrated into a complete pair of sinusoidal and cosinusoidal envelopes of the angular position. Thus, the envelope detection of resolver signals is implemented. Compared with the synchronous peak sampling, the proposed method can effectively reduce the quantization errors of the detected envelopes and the measurement accuracy of the rotor angular position can be further improved. Simulation and experimental results demonstrate the effectiveness of the proposed method.