Rotational Angle Sensor with Sine-Wave Target and Asymmetric Coils
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Solution Overview
Problem
Existing rotational angle sensors face challenges with increased cost due to circuit pattern formation on rotary plates and high power consumption from numerous coils, leading to uneven magnetic field distribution and reduced accuracy.
Innovation Solution
A rotational angle sensor design featuring a metal annular rotary plate with a sine-wave shaped edge and a printed circuit board containing a primary coil and a secondary coil group, where the primary coil overlaps with the rotary plate and the secondary coils are arranged in a circular-arc shape with varying turns, optimizing magnetic field reception and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a circuit pattern such as a coil is formed in the rotary plate, then magnetic field generation is achieved, but manufacturing cost increases
Solution Approach 1:
The patent extracts the coil structure from the rotary plate and relocates it to the stationary detection head. The rotary plate is simplified to only contain the target pattern, eliminating the need for expensive circuit pattern formation on the rotating component while maintaining magnetic field generation capability through the stationary coil.
Solution Approach 2:
The patent inverts the traditional sensor configuration by placing the coil in the stationary detection head rather than on the rotating plate. This inversion allows the coil to remain fixed while the target pattern on the rotary plate rotates, achieving the same detection function with simplified manufacturing.
2Area of stationary object
If a large number of coils for generating magnetic fields are used, then magnetic field coverage is improved, but power consumption increases
Solution Approach 1:
The patent segments the detection function into two parts: a single primary coil for generating the magnetic field and multiple secondary coils for receiving the signal. This segmentation allows one coil to generate the magnetic field covering the entire rotary plate area while multiple smaller coils efficiently capture the modulated signal from different angular positions.
Solution Approach 2:
The patent combines multiple secondary coils into a unified detection system where their outputs are processed together. This merging allows the system to achieve comprehensive angular coverage through signal combination rather than requiring each coil to independently cover the entire area, reducing overall power consumption.
3Ease of manufacture
If coils are made small to reduce power consumption, then manufacturing is simplified, but magnetic field distribution becomes uneven and detection accuracy reduces
Solution Approach 1:
The patent applies local quality by positioning secondary coils at specific locations where they optimally detect the modulated magnetic field from the sine-wave target pattern. Each small coil is strategically placed to capture signals from specific angular regions, and the combination of locally optimized coil positions achieves uniform overall detection accuracy.
Solution Approach 2:
The patent transitions from requiring large coils in a single plane to using multiple small coils arranged in a spatial configuration. By utilizing the spatial dimension and arranging coils at different positions around the rotary plate, the system achieves uniform magnetic field detection coverage without requiring individually large coils.
4Measurement precision
If the number of secondary coils is increased to improve signal reception, then detection sensitivity increases, but device complexity increases
Solution Approach 1:
The patent employs asymmetric arrangement of secondary coils with different numbers of turns, positioned at specific angular intervals rather than uniformly distributed. This asymmetric configuration optimizes signal reception from the sine-wave target pattern while maintaining a manageable number of coils, balancing detection sensitivity with device simplicity.
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 configuration enhances detection accuracy and reduces manufacturing costs while improving sensitivity and signal-to-noise ratio, enabling precise rotational angle detection.
Implementation Method 1
a primary coil supplied with high-frequency current... By an alternating magnetic field generated by the excitation coil, induced current (eddy current) is generated in the closed circuit pattern of the rotor
Implementation Method 2
a secondary coil group outputting induced current to a detection IC detecting the induced current... fluctuation in magnetic field generated by the induced current is received by the reception coil
Data Source
AI summary
A rotational angle sensor includes a rotary plate and a printed circuit board in which a primary coil and a secondary coil group are arranged. Loops of the primary coil and the secondary coil group are along a surface of the printed circuit board. The rotary plate includes a target portion whose outer circumferential edge portion has a sine-wave shape. The primary coil overlaps with the target portion, and has a circular-arc shape along a rotational direction of the rotary plate. The secondary coil group includes 4n (n is a natural number) secondary coils arranged in a line along the rotational direction, on an inner circumferential side of the primary coil. The number of turns of a secondary coil on an end side in a line is smaller than that of a secondary coil on an inner side in the line.