Absolute Angle Calculation for Magnetic Encoder Based On Magnetic Flux Density Difference

Encoders are the most commonly used position measurement sensors in industrial machines and robots. Compared to potentiometers, encoders have advantages in terms of environmental resistance and cost, and their detection speed and resolution are comparable to those of potentiometers, so the use of encoders in the field of precision positioning continues to expand. Since the accuracy of motor control depends on the accuracy of angle and angular velocity obtained from the encoder, encoders with high reliability and high accuracy are required. The authors have developed a high-resolution and high-accuracy absolute rotary encoder that applies eccentric rotation. However, eccentric rotation causes vibration due to disproportionate force, which may lead to deterioration of accuracy and lifetime.In this paper, we proposed a new angle calculation method that calculates the absolute angle from the signal characterized by the use of magnets with different magnetic flux densities. With the proposed method, the absolute angle is obtained with the same accuracy as the conventional method.