Jittered Pole Magnet Ring for Rotary Position Tracking
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Solution Overview
Problem
Existing rotary joint devices face challenges in accurately determining the rotational position of components with rotating platforms, particularly in systems like RADARs and robotic systems, due to the lack of precise methods for tracking angular position over time.
Innovation Solution
A magnet ring with jittered poles is used, where the boundaries between neighboring poles are shifted relative to a uniform spacing, creating a characteristic shift pattern that can be measured by magnetic field sensors to determine the rotational position by correlating the measured magnetic field pattern with the known shift pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If uniform spacing of poles is used in the magnet ring, then manufacturing is simpler and more consistent, but rotational position measurement precision deteriorates due to inability to detect absolute position and resolve ambiguity
Solution Approach 1:
The patent applies asymmetry by intentionally introducing non-uniform spacing between magnetic poles in the magnet ring. Specifically, at least one pole is positioned at a different angular location than what would be expected in a perfectly uniform distribution. This asymmetric configuration creates a unique magnetic field signature that enables absolute rotational position determination, resolving the measurement ambiguity that plagues uniform pole arrangements while maintaining manufacturing feasibility.
2Adaptability or versatility
If multiple separate components (motor and encoder) are used, then functionality is more versatile, but device complexity and noise increase
Solution Approach 1:
The patent merges the motor and encoder functionalities into a single integrated magnet ring assembly. The magnet ring serves dual purposes: generating the magnetic field necessary for motor operation and simultaneously providing the magnetic pole positions required for encoder functionality. This consolidation eliminates the need for separate encoder components, reducing device complexity and minimizing noise from multiple interacting components while maintaining both motor and encoding capabilities.
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 solution allows for accurate determination of the rotational position of the magnet ring, enabling precise tracking of relative displacement and position control in rotary joint devices, while also combining the functionality of an electric motor and magnetic encoder, reducing noise and manufacturing variations.
Implementation Method 1
generating a first magnetic field that interacts with a second magnetic field generated by four or more poles of a magnet ring
Data Source
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AI summary
An apparatus includes a first platform and a second platform configured to rotate relative to the first platform about an axis. A magnet ring is mounted to the first platform and centered around the axis. The magnet ring includes four or more magnetized poles positioned such that each respective boundary between neighboring poles is shifted relative to a corresponding nominal boundary defined by a uniform spacing of boundaries of the poles around the magnet ring. Idle shifted boundaries of the poles define a characteristic shift pattern for the magnet ring. A magnetic field sensor is connected to the second platform. Circuitry is configured to (i) determine a magnetic field pattern generated by the poles based on data generated by the sensor and (ii) determine a rotational position of the first platform relative to the second platform by correlating the magnetic field pattern to the characteristic shift pattern.