A new brushless synchro with look‐up table error compensation

Abstract

In synchros and resolvers, brushes, and slip-rings produce a lot of noise in the output signal. Compared to encoders, the application of such position sensors in precision control systems is restricted because of their low accuracy. In this paper, a novel scheme of a brushless synchro is introduced. In this scheme, the primary and secondary windings are mounted on the stator, and the stator magnetic flux passes a certain path in the rotor with inducing voltage in the secondary winding. In this paper, a software method based on simple look-up table is used to enhance accuracy and reliability of the output signal of the proposed synchro. The operation principle of the brushless synchro is clearly described in the paper using a finite element method (FEM). The number of turns for the stator coils is calculated by a method based on desired harmonic elimination to have a sinusoidal magneto motive force. Some prototypes have been fabricated, and two experiments have been implemented in order to verify the theoretical concepts and to evaluate the accuracy of the fabricated synchros. Results show the proposed brushless synchro has high accuracy. Figure 13. (a )Input line to line voltage and output signal at zero reference angle θ ref = 0. (b) Input line to line voltage and output signal at 90°difference will respect to zero reference angle θ ref = 0. (c) Input line to line voltage and output signal at 180°difference with respect to zero reference angle θ ref = 0. 586 M. GHAFARZADEH ET AL.