Abstract
A high-accuracy demodulation algorithm is required to estimate angular position and angular velocity from resolver signals. In order to improve the estimation accuracy of conventional phase-locked loop (PLL) based demodulation method, a Chebyshev filter-based type III PLL method is proposed in this paper. The proposed method makes PLL become a system of type III tracking loop, which could greatly reduce the theoretical constant deviation in the estimation results of conventional type II PLL in case of variable speed. Meanwhile, the eigenvalues of type III PLL are placed to be the same position as those of a Chebyshev low-pass filter. In this way, demodulation parameters with stronger filter properties can be obtained to effectively suppress the high-frequency measurement noise in resolver signals. Thus, the proposed method can achieve higher demodulation precision compared with the conventional ones. Simulations and experiments are performed to validate the proposed demodulation method.
Highlights
Modern control algorithms for servomotors require accurate feedback information of both angular position and angular velocity
Filter of type III phase-locked loop (PLL) on the basis of Chebyshev low-pass filter, whose characteristic is closer to the ideal low-pass filter [24]
The resolver simulator takes a digital signal processor (DSP) TMS320F28335 (Texas Instruments Company, Dallas, TX, USA) as the core, and it can produce two envelope signals according to the preset value of angular position and velocity
Summary
Modern control algorithms for servomotors require accurate feedback information of both angular position and angular velocity. The angular position and velocity can be measured by shaft sensors, such as optical encoders, magnetic encoders, and resolvers. A resolver generates two amplitude-modulated analog signals with rotor position information. High-accuracy resolver-to-digital conversion (RDC) is required in order to extract rotor position and velocity from the resolver signals [4]. Filter of type III PLL on the basis of Chebyshev low-pass filter, whose characteristic is closer to the ideal low-pass filter [24]. III PLLfilter on the of Chebyshev low-pass filter, whose characteristic the nth-order. Chebyshev low-pass is basis as follows [25]. Characteristic is closer to the ideal low-pass filter [24]. The amplitude-frequency characteristic of the nth-order Chebyshev low-pass filter is as follows [25] 1 H ( ) = (10).
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