Compensation for Temperature Variation in Magnetostrictive Torque Sensor Using Perpendicularly Magnetizing Coils

A robust torque sensor with rapid response was constructed by forming magnetostrictive layers and mounting coils on a carbon steel shaft. A sensitive and reliable Fe40Ni56Cr4 magnetostrictive layer was formed using a low-pressure plasma spray method. A magnetic field perpendicular to the magnetostrictive layer plane is generated by a current flowing through the twin coils to magnetize the steel shaft in the radial direction (the hard axis direction). Linear characteristics of the sensor output with respect to the applied torque (between ¿40 and +40 N-m) were obtained using the twin coils at exciting frequencies of up to 600 kHz. Variations in the sensor output at zero stress and in the sensitivity to temperature variations of the steel shaft were compensated using newly constructed non-inductive coils to detect the temperature of the ¿-layers.