Encoder Harmonic Cancellation via N-Phase Signal Processing
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Solution Overview
Problem
Existing optical encoders face challenges in efficiently removing high-order harmonics while following variations, as previous techniques either incompletely suppress harmonics or require complex computations leading to delays and inability to track harmonic changes.
Innovation Solution
An encoder configuration that generates N-phase sinusoidal signals with distinct phases, where N is greater than or equal to 5, and uses a computing part with specific amplifiers and subtractors to derive two-phase sinusoidal signals, effectively canceling third-order harmonics and noise by performing specific computations on the N-phase signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical filtering is used to suppress harmonics, then the influence of high-order harmonics is reduced, but the influence of third-order harmonics remains to some extent
Solution Approach 1:
The patent converts the harmful third-order harmonic components into beneficial cancellation signals by utilizing the symmetry properties of N-phase signals (where N≥5). The computing circuit processes multiple phase signals to generate output signals where third-order harmonics from different phases cancel each other out, while fundamental wave components are reinforced. This transforms the harmful harmonic interference into a useful cancellation mechanism.
Solution Approach 2:
The patent changes the parameter of phase number from conventional 2-phase or 4-phase to N-phase (N≥5). This parameter change enables the system to inherently suppress third-order harmonics through the mathematical properties of N-phase sinusoidal signals, where the harmonics from different phases cancel out during computation. This parameter modification fundamentally alters the harmonic suppression capability without requiring additional filtering components.
2Measurement precision
If geometric analysis and computation is used to remove harmonics, then third-order harmonics can be removed, but complicated computation is required and delay is caused
Solution Approach 1:
The patent segments the signal processing into distinct computational paths for different harmonic orders. The computing circuit is designed to process N-phase signals through specific mathematical operations that separately handle fundamental wave components and harmonic components. By segmenting the computation to focus only on the necessary operations for third-order harmonic cancellation, the system achieves efficient processing without requiring complex general-purpose harmonic analysis.
Solution Approach 2:
The patent replaces complex mechanical or computational harmonic analysis systems with a streamlined computing circuit that directly computes the necessary signal combinations. Instead of using sophisticated algorithms requiring extensive computation, the invention uses a dedicated circuit implementation that performs specific trigonometric operations in hardware, eliminating software computation delays and enabling real-time harmonic suppression.
3Device complexity
If conventional 2-phase or 4-phase encoding is used, then the system is simple, but harmonics of the third order or more cannot be efficiently removed
Solution Approach 1:
The patent creates a universal N-phase encoding system (N≥5) that simultaneously achieves multiple functions: maintaining relative simplicity in structure while providing inherent third-order harmonic suppression capability. The N-phase signal generation and processing circuit can be extended to different values of N, making the system universally applicable for various precision requirements without fundamentally changing the core harmonic cancellation mechanism.
Solution Approach 2:
The patent transitions from 2-phase or 4-phase signal systems to N-phase (N≥5) signal systems, adding an extra dimension to the phase space. This dimensional expansion provides additional degrees of freedom in signal processing, enabling the system to cancel third-order harmonics through the geometric and algebraic properties of N-phase sinusoidal signals while maintaining a relatively simple overall structure.
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 allows for efficient removal of third-order harmonics and noise, enabling accurate position detection without the need for complex computations, thus providing a simple and effective solution for harmonic suppression.
Implementation Method 1
a detector configured to read a signal from a scale and output N-phase sinusoidal signals
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An encoder includes a light receiving part and a computing part. The light receiving part 101 receives reflected light from a scale 10 and outputs N-phase sinusoidal signals in which respective phases of fundamental waves differ by 2π/N (N is an integer more than or equal to 5). The computing part 102 outputs a two-phase sinusoidal signal including an A phase and a B phase according to each of the N-phase sinusoidal signals. The A phase is expressed by a real part of sum of multiplier of N-phase sinusoidal waves and a member including the N. The B phase is expressed by an imaginary part of the sum of the multiplier of the N-phase sinusoidal waves and a member including the N.