A torque sensor using magnetostrictive sleeve attached to the shaft by shrink-fit

The torque sensor is one of the most important sensors for the control of the mechanical system. When the applied torque twists the shaft, the magnetic anisotropy can be induced in the surface of the magnetostrictive shaft such as a steel shaft. By using magnetostrictive sleeve attached to the shaft, mechanical property of the shaft and the magnetic property of the sleeve can be optimized independently, thus giving more flexibility to the sensor design. Several methods for detecting torque exerted on the rotating shaft have been developed based on various uses of the interaction between the magnetic anisotropy and the magnetization process. The authors' group have developed a planar pickup coil system to make the Dahle type torque sensor compact in which two figure-of-eight coils are orthogonally coupled and the mutual inductance is made sensitive to the applied torque. In this paper, the shaft part of the torque sensor is investigated, in which a magnetostrictive sleeve is attached to the shaft by shrink-fit.