AN INTEGRATED SENSOR HEAD IN SILICON FOR CONTACTLESS DETECTION OF TORQUE AND FORCE

An integrated micromachined torque sensor head in silicon for contactless detection of torque and force is described. It is based on a magnetic yoke with an exciting and a receiving coil that detects the change of permeability of a rotating shaft and an amorphous ribbon with strong magnetostrictive properties, respectively. The designed sensor head determines directly the change of permeability mu by measuring the magnetic flux density in the air gap between the yoke and the amorphous ribbon (shaft). The problem arising with this kind of torque measurement is the variation of the air gap when the shaft is rotating, and especially when a torque is applied. The sensor presented here allows the influence of the air-gap variation to be eliminated by differential measurement of the magnetic flux density. 3-D simulations of the magnetic circuit show the magnetic properties of the sensor head. The development of the complete integrated sensor head starts with components like an NiFe yoke shaped by KOH etched membranes, coils with a large cross-sectional area and CMOS MAGFETs.