Online digital compensation method for AMR sensors

Anisotropic Magnetoresistance (AMR) sensors are magnetic sensors often used for angle measurements. The sensor outputs should be two perfect sinusoidal signals that depend on the angle to be measured. However due to non-ideal properties of the sensor, the actual outputs include undesired parameters as offset voltage, amplitude imbalance and harmonics. All of them generate errors in the angle calculation. Offset voltage and amplitude imbalance are the first and second largest sources of angle errors for which until now are the mainly compensated. The required compensation factors are usually estimated at the start of the sensor life and not updated during its lifetime. Although the sources of angle errors show variations due to wearing and aging effects, so far it is considered that these variations are not significant to affect the sensor accuracy. However, this will change in the future, especially in safety-critical applications that will demand higher accuracy. Then it will be necessary to update the compensation factors during the sensor lifetime. This paper proposes an online compensation method to reduce the offset voltage, the amplitude imbalance and hence the angle error in AMR sensors. It was verified using simulated data as well as real measurements, showing a good performance in all the cases. Unlike most of the compensation methods proposed until now, our method is suitable to be used during the sensor lifetime.