Varying Pitch Encoder Scale for Absolute Position Detection
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Solution Overview
Problem
Industrial control systems face challenges in accurately determining the position of moving carts along tracks, especially when power is removed, as traditional encoder systems rely on incremental measurements and lack precise absolute position detection.
Innovation Solution
The implementation of a varying scale encoder system with successively increasing or decreasing pitch magnets and sensors, analogous to a Vernier principle, allows for absolute position determination by detecting phase differences between sensor readings, enabling immediate position availability upon power application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional magnetic sensors are used to determine cart position, then position measurement is possible when cart is near sensors, but position feedback is lost when cart is away from sensors or during power-up
Solution Approach 1:
The patent applies preliminary action by pre-configuring the encoder scale with varying magnet lengths before the cart moves or power is applied. The non-uniform magnet arrangement creates a unique magnetic field pattern that can be recognized by sensors immediately upon power-up, eliminating the need for incremental counting and providing absolute position knowledge from the start.
Solution Approach 2:
The patent changes the parameter of magnet lengths along the encoder scale from uniform to non-uniform (varying) lengths. This parameter change creates a distinctive magnetic field signature that enables absolute position determination. The varying magnet lengths produce characteristic peak patterns in the magnetic field that can be uniquely identified by sensors, providing both position measurement and feedback reliability.
2Ease of manufacture
If uniform encoder scales are used, then simple manufacturing is achieved, but position determination requires complex incremental counting and loses accuracy during power-up
Solution Approach 1:
The patent applies local quality by varying the magnet lengths at different locations along the encoder scale. Instead of using uniform magnets throughout, specific non-uniform magnet arrangements are placed at particular positions to create recognizable magnetic field patterns. This localized variation in magnet dimensions provides the necessary position information while maintaining overall manufacturing 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 solution provides a low-cost, high-resolution absolute encoder system capable of determining the position of moving elements with precise measurements, including direction, velocity, and acceleration, even when power is off, enhancing the accuracy and reliability of industrial control processes.
Implementation Method 1
the sensors can determine the absolute position of the cart by measuring the varying magnetic field strength or varying magnetic field angle from the magnetic encoder scale on the cart
Implementation Method 2
each sensor can detect successively increasing or decreasing properties (such as magnetic fields) from the scale in a uniquely identifiable pattern
Data Source
AI summary
By configuring an encoder scale as a varying scale with successively increasing or decreasing pitch, sensors in a travel path of the scale can detect a phase difference to determine an absolute position of the scale for use in an industrial control system. Due to the successively increasing or decreasing pitch, each sensor can detect successively increasing or decreasing properties (such as magnetic fields) from the scale in a uniquely identifiable pattern. By taking the difference between readings of adjacent sensors, each sensor detecting properties of the scale, an absolute position of the scale between the sensors can be determined. The principle for feedback for the encoder system is analogous to a Nonius or Vernier principle to determine absolute position.