Magnetostrictive Torque Sensor with Differential Amplifier
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Solution Overview
Problem
Conventional magnetostrictive torque sensors suffer from reduced detection sensitivity due to the presence of resistors or capacitors in the hold circuit, which also make them susceptible to disturbances like static electricity and radio transmissions.
Innovation Solution
A magnetostrictive torque sensor design that employs a magnetostrictive film, a detection coil, a current direction switching device, and an inversion device to detect torque based on constant voltage signals without a hold circuit, allowing for the omission of high impedance states and thus reducing sensitivity loss and susceptibility to disturbances, while also enabling the application of a bias magnetic field to counteract earth magnetism effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a hold circuit with resistor or capacitor is used to suppress disturbances, then disturbance suppression is improved, but detection sensitivity deteriorates due to voltage level reduction
Solution Approach 1:
The invention introduces a differential amplifier as an intermediary device between the detection coil and the output. This differential amplifier maintains constant voltage output without requiring high-impedance hold circuits, thus preserving detection sensitivity while still providing disturbance rejection through differential signaling
2Measurement precision
If the output side of the hold circuit is set to high impedance state to maintain detection sensitivity, then detection sensitivity is improved, but susceptibility to disturbances worsens
Solution Approach 1:
The differential amplifier serves as an intermediary that provides low-impedance constant voltage output without the high-impedance state. This intermediary device maintains detection sensitivity through proper signal conditioning while presenting a low-impedance output that is inherently more resistant to external disturbances
3Reliability
If a current direction switching device with unequal periods is used, then bias magnetic field application is improved, but device complexity worsens
Solution Approach 1:
The invention changes the time period parameters of the switching device to create unequal ON and OFF durations. By adjusting the duty cycle of the periodic switching, a DC current component is generated that produces the required bias magnetic field. This parameter modification allows reliable bias field application while using a relatively simple switching mechanism
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
This design enhances detection reliability by maintaining sensitivity and reducing the impact of disturbances, allowing for accurate torque detection even in environments with varying earth magnetism orientations.
Implementation Method 1
a magnetostrictive film for which magnetic properties change in response to a magnitude of a torque acted to a shaft
Implementation Method 2
a detection coil which detects variation of the magnetic properties of the magnetostrictive film
Data Source
AI summary
A magnetostrictive torque sensor of the present invention is provided with: a magnetostrictive film; a detection coil; a current direction switching device; and an inversion device, wherein: when the current flows in a direction from one side to another side of the detection coil by the current direction switching device, the torque reacted to the shaft is detected based on the input signal of the inversion device; and when the current flows in a inverse direction from another side to one side of the detection coil by the current direction switching device, the torque reacted to the shaft is detected based on the output signal of the inversion device.