Improving the Accuracy of Battery-Free Multiturn Absolute Magnetic Encoders by Using a Self-Referencing Lookup Table Algorithm
Ha Xuan Nguyen, Thuong Ngoc-Cong Tran, Jae Wan Park, Nhan Van Phan Tran, Jae Wook Jeon · IEEE Transactions on Instrumentation and Measurement · 2019
This article presents a self-referencing lookup table (LUT) algorithm to enhance the multiturn accuracy of a battery-free multiturn absolute magnetic encoder. The encoder consists of a single-turn angle for the measurement of the degree of rotation within 2π using a multipolar magnet to achieve high resolution and a multiturn counter to monitor the total number of revolutions made by the encoder's shaft through the different angles of the four bipolar magnets (BPMs) based on four-shaft gears. However, the signals from the BPMs are affected by factors, such as amplitude mismatch, dc offsets, random noises, and harmonic components that are as a result of electrical and mechanical distortions. To solve this problem, this article suggested a method derived from the single-turn angle and the raw signals from the BPMs to generate the LUTs for multiturn angles. These angles eliminate the effects of the disturbances. Additionally, a multiturn compensation algorithm is suggested to compensate for the number of revolutions made by the encoder. The proposed methods are simulated in MATLAB software and implemented in ARM STM32F407ZG. The effectiveness of the proposed method is demonstrated by the obtained results.