Rotary Encoder Absolute Position Detection Using Pulse Counting
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Solution Overview
Problem
Existing magnetic rotary encoders require significant processing time and computational load to detect absolute angular positions due to the need for A/D conversion and arctangent calculations for each output of multiple magnetosensitive elements.
Innovation Solution
A rotary encoder design featuring a first sensor unit with a pair of N and S poles and a second sensor unit with alternately magnetized N and S poles, utilizing pulse counting from the second sensor unit to determine the absolute angular position without the need for continuous A/D conversion and arctangent calculations, allowing for faster and more efficient angle position calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetosensitive elements are used to detect absolute angular position with high resolution, then measurement precision is improved, but processing time increases due to required A/D conversion and arctangent calculations
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correspondence between pulse counts and angular positions in a lookup table during system initialization. When angular position detection is needed, the system simply performs a table lookup based on the current pulse count, eliminating the need for real-time A/D conversion and arctangent calculations. This pre-computation approach significantly reduces processing time while maintaining high measurement precision.
Solution Approach 2:
The patent replaces the computational mechanism (A/D conversion and arctangent calculations) with a simpler lookup mechanism. Instead of performing complex mathematical operations in real-time, the system substitutes these calculations with a pre-computed table that maps pulse counts directly to angular positions, thereby reducing processing time while preserving measurement accuracy.
2Measurement precision
If multiple magnetosensitive elements are used to detect absolute angular position with high resolution, then measurement precision is improved, but computational load increases due to required A/D conversion and arctangent calculations
Solution Approach 1:
The patent reduces computational load by performing all complex calculations (A/D conversion and arctangent operations) in advance during system initialization and storing the results in a lookup table. During normal operation, the system only needs to perform simple table lookups based on pulse counts, dramatically reducing the computational processing load while maintaining high measurement precision.
Solution Approach 2:
The patent substitutes the complex computational system (requiring A/D conversion and arctangent calculations) with a simpler system based on pulse counting and table lookup. This substitution eliminates the need for continuous complex mathematical operations, significantly reducing computational processing load while preserving the ability to detect angular positions with high resolution.
3Productivity
If pulse counting method is used instead of continuous A/D conversion and arctangent calculation, then productivity is improved, but measurement precision may be compromised
Solution Approach 1:
The patent resolves this contradiction by pre-calculating the relationship between pulse counts and angular positions during system initialization and storing this correspondence in a lookup table. The pulse counting method itself is enhanced by using the pre-computed table to translate simple pulse counts into accurate angular positions, thereby maintaining high measurement precision while achieving fast calculation speeds.
Solution Approach 2:
The patent replaces the continuous A/D conversion and arctangent calculation system with a pulse counting system augmented by a pre-computed lookup table. This substitution maintains measurement precision by using the table to accurately map pulse counts to angular positions, while simultaneously improving productivity through the elimination of continuous complex calculations.
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 approach significantly reduces processing time and computational load, enabling faster and more accurate detection of absolute angular positions with improved resolution by using pulse counting and initial value calculations.
Implementation Method 1
a magnetic field generated by the magnet is detected by a magnetosensitive element (magnetic sensor) provided close to the rotating body
Implementation Method 2
in the case of using an element, like a Hall element, capable of detecting the intensity of the magnetic field including the direction of the magnetic field
Data Source
AI summary
A rotary encoder may include a first sensor unit including a first magnet, and a first magnetosensitive unit facing the first magnet; a second sensor unit including a second magnet with a plurality of pairs of N poles and S poles alternately magnetized, and a second magnetosensitive unit facing the second magnet; a circuit to generate pulses for counting from an output of the second sensor unit; and a counter to count the pulses. During activation, an angle position of the rotating body is calculated based on outputs of a first and second sensor unit, and after activation, pulse counting is counted by a counter.