Electronic Position Encoder Harmonic Error Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electronic position encoders are vulnerable to short-range measurement errors, particularly from higher harmonics such as fifth and seventh harmonics, and pitch compensation is challenging in compact read heads due to manufacturing limitations.
Innovation Solution
The electronic position encoder employs a detector portion with two sets of sensing elements arranged at equally spaced phases of the scale period, with one set offset by Ps/4 relative to the other, and a signal processing configuration that independently acquires and combines signals from both sets to determine the relative position, effectively suppressing errors from amplitude, phase mismatches, and higher harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional single-set sensing elements are used, then device complexity is reduced, but measurement precision deteriorates due to short-range errors from harmonics and amplitude/phase mismatches
Solution Approach 1:
The detector portion is segmented into multiple sets of sensing elements (first set, second set, third set, fourth set) positioned at different locations along the measuring axis. Each set independently measures spatial phase, and the measurements are combined to eliminate short-range errors. This segmentation allows the system to achieve high measurement precision without requiring complex pitch compensation mechanisms.
Solution Approach 2:
The patent applies preliminary action by pre-positioning multiple sets of sensing elements at specific locations before measurement occurs. The spatial phase measurements from these pre-positioned sets are combined to eliminate errors that would otherwise require complex real-time compensation. This approach simplifies the overall device while maintaining high measurement accuracy.
2Measurement precision
If pitch compensation is applied to reduce measurement errors, then measurement precision improves, but manufacturing precision requirements increase due to compact read head constraints
Solution Approach 1:
Instead of requiring high-precision pitch compensation in a compact read head, the patent segments the measurement function across multiple sensing element sets positioned at different locations. This distributes the measurement function and reduces the precision requirements for individual components, making manufacturing more feasible while maintaining overall measurement accuracy.
Solution Approach 2:
The patent transitions from a single-location measurement approach to a multi-location approach along the measuring axis. By distributing sensing elements across multiple positions (adding the dimension of spatial distribution), the system eliminates the need for complex pitch compensation mechanisms, thereby reducing manufacturing precision requirements.
3Measurement precision
If multiple sets of sensing elements are used, then measurement precision improves by suppressing harmonics and mismatches, but device complexity increases
Solution Approach 1:
The detector portion is divided into multiple independent sensing element sets, each performing simple spatial phase measurement. The segmentation allows each set to operate independently with simple processing, while the combination of their outputs achieves high measurement precision by suppressing harmonics and mismatches.
Solution Approach 2:
Each set of sensing elements serves itself by independently measuring spatial phase at its specific location. The multiple sets collectively self-correct for harmonics and amplitude/phase mismatches through their combined measurements, eliminating the need for complex external compensation circuitry.
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 reduces short-range errors, eliminating the need for pitch compensation and suppressing errors from amplitude mismatch, phase mismatch, fifth, and seventh harmonics, resulting in improved measurement accuracy with minimal residual errors.
Implementation Method 1
twisted magnetic flux coupling loops in an inductive encoder which reduce errors from signal offset and undesired even harmonics
Implementation Method 2
inductive sensors are known to be one of the sensor types that is most immune to contamination by particles, oil, water, and other fluids
Data Source
AI summary
An electronic position encoder comprises a scale including a periodic scale pattern along a measuring axis direction having a scale period Ps, and a detector portion comprising a first group of sensing elements, a second group of sensing elements, and a signal processing configuration. The second group of sensing elements is located at a group position which is equal to K2*Ps+PS/M relative to the first group of sensing elements along the measuring axis direction, where K2 and M are integers. The signal processing configuration independently acquires a first set of detector signals from the first group of sensing elements, and a second set of detector signals from the second group of sensing elements, and determines a relative position between the detector portion and the scale pattern based on the first set of detector signals and the second set of detector signals.