Motor Drives

TMS320F240 DSP Solution for Obtaining Resolver Angular Position and Speed (Rev. A)

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This application report first presents a TMS320F240 DSP solution and then another unique approach using PGA411-Q1 for obtaining the angular position and speed of a resolver. A resolver is an absolute mechanical position sensor used, for example, in servo applications. It is basically a rotating transformer. The sinusoidal input reference is amplitude modulated with the sine and cosine of the mechanical angle, respectively. These two output signals have to be decoded to obtain the angular position. For decoding the resolver output signals, a basic method is introduced. It uses undersampling and an inverse tangent function. To achieve a higher angular resolution an improved method, which adds oversampling techniques is used. Due to an integral invariant filter, which is a combination of an IIR and FIR filter, the digitized angular position does not suffer any velocity lag.