Do you know the principle of resolver for servo motor?

A single channel angle measurement system can be constructed by using two identical sine and cosine resolvers. One resolver is a transmitter and the other is a control transformer. The transmitter is excited by AC power supply. The accuracy of resolver is 6', and the accuracy of single channel system is not less than 6'. In order to improve the control accuracy of the system, a dual-channel angle measuring system can be adopted. Four resolvers with the same structure, two XZ 1 and XZ2 constitute the coarse channel angle measurement system, and the other two XZ3 and XZ4 constitute the main channel angle measurement system. XZ 1 and XZ3, XZ2 and XZ4 are respectively connected by speed increasers, and the speed increase ratio is I (I = 15 ~ 30). When the spindle drives the XZ 1 rotation angle θ 1 of the coarse channel, the XZ3, which is proficient in the road, rotates the angle θ 1, and XZ2 is coaxial with the load. When its rotation angle is θ2, the rotation angle of XZ4 is θ 2. The coarse channel output voltage Uc 1=kUr sinδ, and the main channel XZ4 output voltage Uc2=kUrsiniδ, where δ = θ 1-θ 2. Their output voltages are processed by coarse and fine converters and driven by amplifiers. A dual-channel servo system can be formed by using a dual-channel angle measurement system. When the error angle δ is small, it is controlled by the main channel signal, and when the error angle δ is large, it is controlled by the coarse channel signal. Therefore, the highest control accuracy of the system can reach 3 ″ ~ 7 ″. In order to reduce the nonlinear error caused by the gear clearance of the reducer, an electric variable-speed dual-channel angle measuring system, that is, a multipole resolver, can be adopted. It is to install unipolar and multipolar resolver in a machine body, and use a shaft. The coarse channel system is composed of unipolar transformer and the main channel system is composed of multipolar resolver. This can not only improve the accuracy, but also simplify the structure.