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

An integrated micromachined torque sensor head in silicon for contactl ess detection of torque and force is described. It is based on a magne tic yoke with an exciting and a receiving coil that detects the change of permeability of a rotating shaft and an amorphous ribbon with stro ng magnetostrictive properties, respectively. The designed sensor head determines directly the change of permeability mu by measuring the ma gnetic flux density in the air gap between the yoke and the amorphous ribbon (shaft). The problem arising with this kind of torque measureme nt is the variation of the air gap when the shaft is rotating, and esp ecially when a torque is applied. The sensor presented here allows the influence of the air-gap variation to be eliminated by differential m easurement of the magnetic flux density. 3-D simulations of the magnet ic circuit show the magnetic properties of the sensor head. The develo pment of the complete integrated sensor head starts with components li ke an NiFe yoke shaped by KOH etched membranes, coils with a large cro ss-sectional area and CMOS MAGFETs.