Integrating fluxgate for magnetostrictive torque sensors

Abstract

A torque sensing apparatus for picking up a magnetic field of a magnetostrictive material disposed on a shaft, comprising: a first integrating ring; a second integrating ring; a first fluxgate return strip and a second fluxgate return strip each being connected to the first integrating ring at one end and the second integrating ring at the other end; an excitation coil; and a feedback coil; wherein the first integrating ring and the second integrating ring are configured to be positioned to pick up flux signals along the entire periphery of the ends of the magnetostrictive material.

1 . A torque sensing apparatus for picking up a magnetic field of a magnetostrictive material disposed on a shaft, comprising: 
 a first integrating ring;    a second integrating ring;    a first fluxgate return strip and a second fluxgate return strip each being connected to said first integrating ring at one end and said second integrating ring at the other end;    an excitation coil comprising a first coil and a second coil, said first coil being wound about said first fluxgate return strip and said second coil being wound about said second fluxgate return strip and said first and said second coil are connected in series to provide a measurement flux; and    a feedback coil wound about said excitation coil;    wherein said first integrating ring, said second integrating ring, said first fluxgate return strip and said second fluxgate return strip provide a low reluctance closed loop flux path and are disposed on a cylindrical member being configured to allow said shaft to be rotatable received therein.    
   
   
       2 . The torque sensing apparatus as in  claim 1 , wherein said first integrating ring, said second integrating ring, said first fluxgate return strip and said second fluxgate return strip are constructed out of a high-permeable material.  
   
   
       3 . The torque sensing apparatus as in  claim 1 , wherein said first integrating ring and said second integrating ring are configured to pick up magnetic flux along the periphery of the magnetostrictive material.  
   
   
       4 . (canceled)  
   
   
       5 . (canceled)  
   
   
       6 . (canceled)  
   
   
       7 . The torque sensing apparatus as in  claim 1 , wherein said first integrating ring and said second integrating ring are configured to be positioned to pick up flux signals along the entire periphery of the ends of the magnetostrictive material.  
   
   
       8 . The torque sensing apparatus as in  claim 1 , wherein said first integrating ring, said second integrating ring, said first fluxgate return strip and said second fluxgate return strip are constructed out of a high-permeable material and said first integrating ring and said second integrating ring are configured to pick up magnetic flux along the periphery of the magnetostrictive material and the torque sensing apparatus further comprises a pickup coil.  
   
   
       9 . The torque sensing apparatus as in  claim 8 , wherein the application of a torque to the shaft will provide an induced voltage in the pickup coil, the induced voltage contains a 2 nd  harmonic component which is extracted by a means of a lock-in amplifier and rectified and fed, as current, to the feedback coil via a voltage to current converter to nullify the 2 nd  harmonic component, wherein the 2 nd  harmonic voltage is proportional to the torque to the shaft.