Magnetic Coupling for Multi-Turn Sensor Backlash Elimination
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Solution Overview
Problem
Existing position sensing devices face challenges in accurately determining the angular position and turn number of rotating objects over multiple turns due to mechanical backlash and hysteresis, limiting their resolution and reliability.
Innovation Solution
A position sensing device comprising a shaft with a magnet and a magnetic sensor for angular position measurement, and a non-magnetic sensor for turn-number measurement, which includes a wirewound resistive element and a sliding contact to minimize mechanical backlash, allowing for high-resolution angular position determination throughout multiple turns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mechanical coupling is used between the shaft and magnet to transmit rotational motion, then the angular position can be determined, but mechanical backlash occurs between the shaft and magnet leading to reduced measurement precision
Solution Approach 1:
The patent replaces the mechanical coupling between the shaft and magnet with a magnetic coupling system. The magnet is magnetically coupled to the shaft without direct mechanical contact, eliminating mechanical backlash while maintaining accurate angular position transmission. The magnetic field couples the rotational position from the shaft to the magnet, providing reliable and precise measurement without mechanical wear or backlash.
2Measurement precision
If a single sensor assembly is used for angular position measurement, then the angular resolution is high within one turn, but the resolution degrades over multiple turns due to mechanical wear and backlash
Solution Approach 1:
The patent eliminates mechanical contact between the shaft and magnet by using magnetic coupling, which prevents wear and maintains consistent measurement precision over the device's entire operational life. The magnetic coupling does not degrade like mechanical couplings, ensuring that angular resolution remains stable across multiple turns and throughout the device's service life.
Solution Approach 2:
The patent extracts the magnet from direct mechanical contact with the shaft, allowing it to be magnetically coupled instead. This separation removes the source of mechanical wear and backlash, enabling the device to maintain high angular resolution over extended periods and multiple turns without degradation from mechanical friction or backlash.
3Measurement precision
If a magnetic sensor is used for angular position measurement, then high resolution is achieved, but the sensor is sensitive to external magnetic fields and mechanical vibrations
Solution Approach 1:
The patent introduces a magnet as an intermediary between the shaft and the magnetic sensor. The magnet is magnetically coupled to the shaft and creates a controlled magnetic field that the sensor detects. This intermediary isolates the sensor from direct exposure to external magnetic fields and mechanical vibrations, while still accurately transmitting the angular position information through the magnetic coupling.
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 device achieves high-resolution position sensing with reduced hysteresis and mechanical backlash, maintaining angular resolution over multiple turns, and extending the life expectancy of the sensing device by reducing the impact of mechanical components on output degradation.
Implementation Method 1
a magnet and a magnetic sensor. The magnet is coupled to the shaft, and the magnetic sensor is positioned relative to the magnet such that the first sensor assembly allows measurement of an angular position of the magnet relative to the magnetic sensor
Implementation Method 2
The magnetic sensor can include a plurality of Hall-effect sensors
Implementation Method 3
a plurality of sine-cosine magneto-resistive (MR) sensors
Implementation Method 4
a plurality of giant magnetic resistive (GMR) sensors
Implementation Method 5
The electrical sensor can include a wirewound resistive element having first and second ends, a wiper assembly that includes the sliding contact, with the wiper assembly being configured to allow the sliding contact to move along the wirewound resistive element as the shaft is turned
Data Source
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AI summary
Devices and methods related to high-resolution multi-turn sensors. In some embodiments, a position sensing device can include a shaft having a longitudinal axis, and a first sensor having a magnet and a magnetic sensor. The magnet can be coupled to the shaft, and the magnetic sensor can be positioned relative to the magnet such that the first sensor allows measurement of an angular position of the magnet relative to the magnetic sensor to thereby allow determination of the corresponding angular position of the shaft within a given turn of the shaft. The position sensing device can further include a second sensor coupled to the shaft and configured to allow measurement of a turn-number of the shaft. The second sensor can include one or more of different types sensing functionalities to yield an output representative of the turn-number of the shaft.