As an important component of a high-speed active magnetic bearing (AMB) system, a non-contact displacement sensor has important impacts on the overall performance of the system. A traditional inductive displacement sensor signal demodulation circuit which is composed of discrete components, has a high cost and a large space occupation. In order to develop a low-cost, high-integrated demodulation design of an inductive displacement sensor, this paper took the integrated synchronous demodulation chip as the core, performed tasks including the hardware design and manufacturing, software development and circuit debugging, built a test platform of the inductive displacement sensor and finished evaluation experiments for the integrated synchronous demodulation design. The experimental results shown that the linearity between the synchronous demodulation chip output signal and rotor displacement was 2.187%, the sensitivity was 2.9185 V/mm, the minimum resolution was up to 1 μm, and it could meet the displacement detection requirements of general AMB systems.

Inductive displacement sensors based on the integrated demodulation chip

Aim at the design of inductive displacement sensor,structural characteristic of coil and core is the key factor affecting the sensor performance. In order to improve the detection performance of the sensor,a model of the sensor coil and core was established based on Biot-Savart Law,corresponding model was constructed by finite element software. And then,by analyzing the situation of the changing parameters of the coil and core or the installation and processing errors,the relationship information between measurement performance with varying parameters and installation and processing errors was obtained. The relationship can be used to optimize the sensor. The results indicate that when the ratio of the coil length and the length of the core between 1.45 to 1.6,sensor can get a better relative change of inductance. Linearity is insensitive to the varying of the coil length and core length and radius. It is around at 0.5%, installation eccentric and inclined of the core has little effect on the sensor performance. Relative change of inductance will decrease with increasing of the core taper.

Liu Lv-lian

Papers

Characteristic optimization of structural for inductive displacement sensors