Angle Detection Methods for a CMOS Smart Rotary Encoder
Kazuhiro Nakano*, Toru Takahashi***, and Shoji Kawahito**
*Graduate School of Electronic Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8011, Japan
**Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8011, Japan
***R&D Center, NTN Corporation, 1578 Higashi-Kaizuka, Iwata, Shizuoka 438-8510, Japan
A CMOS smart magnetic rotary encoder is useful for compact equipment such as personal robots. In the proposed encoder, the geometrical angle of a magnet is detected with digital signal processing. The output signal of our proposed system is susceptible to sensor offsets caused by sensors mismatch and misalignment between sensor chip and magnet. The accuracy of angle detection method and the robustness to rotation axis misalignment depend greatly on the angle detection algorithm. This paper presents three types of angle detection and their performance in precision and compares rotation angle misalignment tolerance. Simulation results show that detecting two zero-crossing points in the signal profile, ZC method, is the most adequate for this system.
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