Multi-Turn Position Sensor Using Magnetic Flux Density
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Solution Overview
Problem
Existing angular sensors are limited to measuring one rotation (360 degrees) and face ambiguity when sensing multiple turns of a rotating device, making it difficult to accurately determine the rotational position of a shaft beyond a single turn.
Innovation Solution
A rotational position sensor system that includes a rotatable shaft with a movable carrier and a magnet, where the magnet's position is measured using a magnetic sensor circuit to determine the rotational position across multiple turns, with a programmable range and high resolution capabilities, and a shield to protect against external electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnet is moved along the longitudinal axis to enable multi-turn sensing, then the measurement range is improved, but the device complexity increases due to the need for a movable carrier and threaded coupling mechanism
Solution Approach 1:
The patent replaces complex mechanical multi-turn sensing mechanisms with a magnetic field-based sensing system. A magnet is coupled to the rotating shaft, and its position is tracked using magnetic sensor circuits that detect changes in magnetic flux density. This substitution eliminates the need for complex mechanical encoders or multi-turn potentiometers while achieving high-resolution multi-turn measurement.
Solution Approach 2:
The patent introduces a movable carrier as an intermediary element that translates rotational motion of the shaft into linear motion of the magnet along the longitudinal axis. This carrier uses a threaded coupling mechanism to convert rotation into precise linear displacement, allowing the magnet's position to serve as a proxy for measuring the shaft's rotational position across multiple turns.
2Ease of operation
If the magnet's position is measured using magnetic flux density, then non-contacting measurement is achieved, but measurement precision is reduced due to flux density ambiguity at certain positions
Solution Approach 1:
The patent resolves position ambiguity by measuring magnetic flux density in multiple dimensions. Instead of relying on a single flux density measurement that may be ambiguous, the system uses multiple magnetic sensor circuits positioned at different locations to detect flux density components along different axes. This multi-dimensional measurement approach allows unique identification of the magnet's position throughout its entire range of motion.
Solution Approach 2:
The patent divides the measurement task into multiple independent measurements by using several magnetic sensor circuits. Each sensor measures the magnetic flux density at its specific location, and the combined data from all sensors provides comprehensive information about the magnet's position. This segmentation of the sensing function eliminates blind spots and ambiguity that would exist with a single sensor.
3Measurement precision
If the range of linear motion of the magnet is increased to cover multi-turn rotation, then the measurement range is improved, but the device complexity increases due to larger sensor assembly and housing
Solution Approach 1:
The patent uses magnetic field sensing to replace mechanical measurement systems that would require physical contact and complex mechanical structures for multi-turn measurement. The magnetic sensor assembly can detect the magnet's position non-contacting, allowing for a more compact design compared to mechanical encoders or resolvers that would need corresponding physical structures for each turn.
Solution Approach 2:
The magnetic sensor circuit serves multiple functions: it detects the magnet's position along the longitudinal axis, determines the shaft's rotational position, and provides multi-turn measurement capability. This multi-functional approach eliminates the need for separate mechanical systems for each measurement function, reducing overall device complexity.
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
Enables accurate determination of rotational position beyond one turn with high resolution and reduced ambiguity, while shielding against external radiation and electromagnetic interference, providing a reliable and precise measurement of rotational position.
Implementation Method 1
a magnetic sensor circuit disposed relative to the magnet, and configured to measure a first flux density along the magnetization axis and a second flux density along a direction perpendicular to the magnetization axis
Data Source
Figure 1~3
Figure 4A~4B
Figure 4C~7B
AI summary
Disclosed are systems and methods for effectively sensing rotational position of an object. In certain embodiments, a rotational position sensor (100) can include a shaft (102) configured to couple with the rotating object. The shaft (102) can be configured to couple with a magnet carrier (104) such that rotation of the shaft (102) yields translational motion of the carrier (104). A magnet (106) mounted to the carrier (104) also moves longitudinally with respect to the axis of the shaft (102), and relative to a magnetic field sensor (108) configured to detect the magnet's longitudinal position. The detected longitudinal position can be in a range corresponding to a rotational range of the shaft, where the rotational range can be greater than one turn. In certain embodiments, the rotational position sensor can include a programmable capability to facilitate ease and flexibility in calibration and use in a wide range of applications.