This paper presents an inductive based sensor for angular displacement measurement. Its structure is basically similar to a resolver, but it is able to provide high precision measurement by use of an online self-calibration method which is also presented in this paper. The sensor consists of a ferromagnetic stator, a ferromagnetic rotor and four groups of coils. Two groups of coils in the rotor are supplied with quadrature Alternating Current (AC) signals to generate quadrature magnetic fields both in temporal and spatial domains. The other two groups of coils in the stator receive magnetic fields to produce two sine signals whose phases are proportional to the displacement of the rotor. However, the phase of one sine signal changes faster than that of the other one with the changing of the displacement. Different phase changing causes different measurement errors. The paper provides an online self-calibration method using the relation of the errors and finally improves the accuracy of the sensor. Simulations of sensor models have been implemented to verify the feasibility of working principles of the sensor.
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