Torque Sensor Magnetometer Dual Coil Cancellation
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Solution Overview
Problem
Existing magnetometers for torque sensors face challenges in accurately measuring torque due to manufacturing tolerances and external magnetic fields, such as the Earth's field, which cause incomplete cancellation of external magnetic effects and result in inconsistent readings.
Innovation Solution
A magnetometer design featuring dual coil assemblies with independent driving circuits and adjustable gain, allowing for precise cancellation of external magnetic fields by generating out-of-phase ripple currents that attenuate common mode signals, thereby accommodating manufacturing inconsistencies and external influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single coil assembly is used in the magnetometer, then the device complexity is reduced, but the ability to cancel external magnetic fields and reject common mode signals is insufficient
Solution Approach 1:
The magnetometer is divided into multiple independent coil assemblies (first and second coil assemblies) that can be driven by separate circuits. Each coil assembly operates independently with its own drive circuit, allowing differential signaling and common mode rejection. This segmentation enables the system to cancel external magnetic field effects while maintaining manageable complexity through modular design.
2Measurement precision
If manufacturing tolerances are strict, then the measurement precision is improved, but the ease of manufacture deteriorates
Solution Approach 1:
The invention introduces independently adjustable gain circuits for each coil assembly, allowing post-manufacturing calibration and adjustment. This parameter adjustment capability compensates for manufacturing tolerances and assembly variations, enabling high measurement precision without requiring extremely tight manufacturing tolerances. The gain adjustment mechanism allows the system to self-calibrate and maintain accuracy despite manufacturing variations.
3Reliability
If the coil assemblies are driven by a single circuit, then the device complexity is reduced, but the ability to independently adjust sensitivities and reject common mode signals is limited
Solution Approach 1:
The drive system is segmented into separate first and second drive circuits, each independently controlling a respective coil assembly. This segmentation enables differential signaling where the two circuits can be driven 180 degrees out of phase, allowing the system to reject common mode signals from external magnetic fields. The independent drive circuits provide the necessary degrees of freedom for common mode rejection while the differential nature of the system keeps the overall complexity manageable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively cancels external magnetic field effects, providing accurate torque measurements by independently adjusting the sensitivity of each flux gate section, thus improving the reliability of torque sensing in magnetometers.
Implementation Method 1
The alternating current provides for the periodic magnetic saturation of the magnetic elements. The magnetic field produced by the torque transducer shaft is superimposed on the periodic magnetic field generated by the coils. Changes in the inductance of the coils due to magnetic saturation results in a voltage that is induced to the coils.
Implementation Method 2
The torque transducer element typically includes a magnetoelastic material that responds to the application of torque by generating a corresponding magnetic field. The application of torque to the magnetoelastic material creates shear stresses within the magnetized regions causing the direction of the magnet field generated by the torque transducer element to shift from a substantially circumferential direction to a helical direction.
Implementation Method 3
Magnetically saturatable strips are disposed between the coil and the torque transducer element. These magnetic strips are magnetically saturated by the alternating current that is produced within the coils. The magnetic strips are magnetically saturated by the alternating current that is produced within the coils.
Data Source
AI summary
The magnetometer assembly according to this invention includes a first coil assembly and a second coil assembly for detecting separate magnetic fields along an axial portion of a torque transducer. The first and second coil assemblies are driven by independently adjustable circuits. Each of the circuits are independently adjustable to adjust the gain that is distributed to each of the first and second coils. This provides for an adjustment and precise alignment of a magnetic field generated by the first coil and the second coil assembly such that external magnetic fields can be cancelled providing increased accuracy and reduced hysteresis effects.