Magnetoelastic Torque Sensor with Local Measurement of Ambient Magnetic Field

A torque sensor comprising:

• a shaft that receives an applied torque, the shaft comprising:
• a first null region, a second null region, and a third null region that each generate a negligible magnetic field;
• and
• a first magnetoelastic region and a second magnetoelastic region that each generate a non-negligible magnetic field responsive to the applied torque;
• a first null region sensor proximal the first null region and generating a first null region magnetic field measure corresponding to a magnitude of an ambient magnetic field;
• a second null region sensor proximal the second null region and generating a second null region magnetic field measure corresponding to the magnitude of the ambient magnetic field;
• a third null region sensor proximal the third null region and generating a third null region magnetic field measure corresponding to the magnitude of the ambient magnetic field;
• a first magnetoelastic region sensor proximal the first magnetoelastic region and generating a first magnetoelastic region magnetic field measure corresponding to the magnitude of the ambient magnetic field and a magnitude of the non-negligible magnetic field generated by the first magnetoelastic region responsive to the applied torque, wherein the first magnetoelastic region magnetic field measure is less than or equal to a first maximum magnetoelastic region magnetic field measure, the first maximum magnetoelastic region magnetic field measure defining a first detectable range of the first magnetoelastic region sensor;
• a second magnetoelastic region sensor proximal the second magnetoelastic region and generating a second magnetoelastic region magnetic field measure corresponding to the magnitude of the ambient magnetic field and a magnitude of the non-negligible magnetic field generated by the second magnetoelastic region responsive to the applied torque, wherein the second magnetoelastic region magnetic field measure is less than or equal to a second maximum magnetoelastic region magnetic field measure, the second maximum magnetoelastic region magnetic field measure defining a second detectable range of the second magnetoelastic region sensor;
• and
• a controller coupled to the first null region sensor, the second null region sensor, the third null region sensor, the first magnetoelastic region sensor, and the second magnetoelastic region sensor that:
• determines whether the first magnetoelastic region sensor has entered a magnetoelastic region sensor saturation condition by determining whether the first magnetoelastic region magnetic field measure has saturated the first detectable range;
• determines whether the second magnetoelastic region sensor has entered the magnetoelastic region sensor saturation condition by determining whether the second magnetoelastic region magnetic field measure has saturated the second detectable range;
• determines whether the first null region sensor has entered an intense ambient magnetic field condition by determining whether the first null region magnetic field measure is greater than a threshold ambient magnetic field measure;
• determines whether the second null region sensor has entered the intense ambient magnetic field condition by determining whether the second null region magnetic field measure is greater than the threshold ambient magnetic field measure;
• determines whether the third null region sensor has entered the intense ambient magnetic field condition by determining whether the third null region magnetic field measure is greater than the threshold ambient magnetic field measure;
• and
• calculates a magnitude of the applied torque based on the first null region magnetic field measure, the second null region magnetic field measure, the third null region magnetic field measure, the first magnetoelastic region magnetic field measure, and the second magnetoelastic region magnetic field measure.

A method of calculating a magnitude of an applied torque using a torque sensor, the torque sensor including a shaft that includes a plurality of null regions that each generate a negligible magnetic field and a magnetoelastic region that generates a non-negligible magnetic field responsive to the applied torque, a plurality of null region sensors each proximal one of the null regions, a magnetoelastic region sensor proximal the magnetoelastic region, and a controller coupled to the plurality of null region sensors and the magnetoelastic region sensor, the method comprising steps of:

• receiving, with the shaft, the applied torque;
• generating, with the magnetoelastic region, the non-negligible magnetic field responsive to the applied torque;
• generating, with each null region sensor, a null region magnetic field measure corresponding to an ambient magnetic field;
• generating, with the magnetoelastic region sensor, a magnetoelastic region magnetic field measure corresponding to the ambient magnetic field and the non-negligible magnetic field, wherein the magnetoelastic region magnetic field measure is less than or equal to a maximum magnetoelastic region magnetic field measure, the maximum magnetoelastic region magnetic field measure defining a detectable range of the magnetoelastic region sensor;
• determining, with the controller, whether the magnetoelastic region sensor has entered a magnetoelastic region sensor saturation condition by determining whether the magnetoelastic region magnetic field measure has saturated the detectable range;
• determining, with the controller, whether a null region sensor of the plurality of null region sensors has entered an intense ambient magnetic field condition by determining whether a null region magnetic field measure generated by a null region sensor of the plurality of null region sensors is greater than a threshold ambient magnetic field measure;
• and
• calculating, with the controller, the magnitude of the applied torque based on the null region magnetic field measures and the magnetoelastic region magnetic field measure.