Multi-turn Rotation Angle Detection Using Magnetic Field Sensing
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Solution Overview
Problem
Existing rotation angle detection devices face issues with precision, resolution, zero drift, nonlinearity, and reliability, especially for multi-turn rotations, due to errors introduced by relative gear movements and limited pulse distribution, leading to low resolution and incorrect direction detection.
Innovation Solution
A device with a main gear and driven gears featuring a two-stage speed reduction mechanism and magnetically sensitive angle sensing chips, which provides high resolution and stability by maintaining the relative position of gears and using magnetic field direction changes to calculate absolute rotation angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a relative relation detection method using two driven gears externally meshed with the main gear is used, then the rotation angle can be detected through calculation, but errors of the driven gears are introduced during calculation leading to serious fluctuation of precision, resolution, zero drift and nonlinearity
Solution Approach 1:
The patent replaces the mechanical calculation method (using gear ratios and relative position calculations) with a magnetic field-based absolute detection method. Angle sensing chips directly sense the magnetic field direction to obtain absolute rotation angles without mechanical calculation, thereby eliminating error accumulation and improving both precision and reliability.
Solution Approach 2:
The patent introduces magnets as intermediaries between the rotating shaft and the angle sensing chips. The magnets create a magnetic field that rotates with the shaft, allowing the angle sensing chips to directly detect the absolute rotation angle without mechanical gear calculations, thus improving measurement reliability.
2Ease of operation
If two pulse signals are output using optoelectronics or Hall principle, then the rotation angle can be obtained from pulse phase relation, but the zero position cannot be marked and recorded requiring re-identification each power-on
Solution Approach 1:
The patent performs preliminary action by pre-establishing the zero position relationship between the magnets and the rotating shaft during assembly. The angle sensing chips directly detect this absolute position from power-on, eliminating the need for re-identification and ensuring consistent zero position reference.
3Measurement precision
If the number of holes or teeth corresponding to each pulse is limited within 360 degrees, then the pulse signals can be generated, but the highest resolution of the detection device may only reach up to 0.5 degrees due to limited space
Solution Approach 1:
The patent replaces the mechanical pulse generation method (using physical holes or teeth on gears) with a magnetic field-based detection method. The magnets and angle sensing chips enable continuous absolute angle detection without discrete pulses, achieving 0.007 degrees resolution without increasing installation space.
4Reliability
If the rotation direction is determined by the sequence of two pulses, then the rotation angle can be detected, but the rotation direction cannot be identified when signals are missed
Solution Approach 1:
The patent replaces the pulse sequence-based direction detection with a magnetic field vector-based method. The angle sensing chips directly detect the magnetic field direction to determine both angle and rotation direction continuously, eliminating signal loss issues and improving reliability.
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 achieves high precision and reliability in multi-turn rotation angle detection, with a resolution of up to 0.007 degrees, and maintains accurate zero position detection without power-off storage, enhancing system stability and fault-proofing.
Implementation Method 1
When the magnets rotate, the magnetic field direction above the surfaces thereof also rotates. The angle sensing chips located above the magnets output an angle value indicating the change of the magnetic field direction when sensing the change of the magnetic field direction
Implementation Method 2
Both the driven gears and the circle-number gear are provided with bearings, the bearings have magnets fixed therein
Data Source
AI summary
A device and method for detecting an absolute multi-turn rotation angle. The device includes a housing, a cover plate and a rotating shaft. The rotating shaft is fixed with a main gear, which is meshed with driven gears including a large driven gear and a small driven gear. The main gear is externally meshed with the large driven gear. The driven gears are connected with a two-stage speed reduction device which enables the rotating shaft to rotate multiple circles to slow down to a circle-number gear and enables the circle-number gear to rotate one circle only. Both driven gears and the circle-number gear are provided with bearings. The bearings have magnets therein, and the two magnets are relatively fixed with the driven gears and the circle-number gear, respectively. The top edges of the bearings fit with a printed circuit board, angle sensing chips which are fixed on the printed circuit.