Motor Current Sideband Analysis for Conveyor Belt Stretch Detection
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Solution Overview
Problem
Existing systems for diagnosing power transmission mechanism abnormalities, such as stretch in belts or chains, face challenges in accurately detecting stretch without relying on mechanical parameters that change with time and are prone to erroneous diagnoses due to interference from other mechanical device frequencies.
Innovation Solution
A stretch detection system that converts motor current signals to the frequency domain, calculates integral values within specific frequency ranges, and diagnoses stretch based on these values, excluding frequencies that indicate other mechanical abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the length of the power transmission mechanism is used to calculate rotation frequency for abnormality diagnosis, then the diagnosis method can be implemented, but the measurement precision deteriorates because the length changes with time and cannot be accurately grasped
Solution Approach 1:
The patent replaces mechanical measurement methods (using physical length and rotation speed sensors) with electrical signal analysis. By analyzing the current signal from the motor driving the power transmission mechanism and transforming it to the frequency domain, the system extracts stretch information directly from electrical characteristics, eliminating the need for mechanical parameters that change over time.
2Adaptability or versatility
If a wide frequency range is observed to detect power transmission mechanism abnormalities, then more abnormality types can be detected, but the reliability deteriorates due to erroneous diagnosis from motor and other device frequencies being included
Solution Approach 1:
The patent segments the frequency spectrum into distinct regions: a first frequency region containing the fundamental rotation frequency and its harmonics (which may indicate motor or device abnormalities), and a second frequency region containing sideband frequencies (which specifically indicate power transmission mechanism stretch). By analyzing only the sideband region, the system achieves specific and reliable stretch detection without false positives from other sources.
Solution Approach 2:
The patent extracts and isolates the sideband frequency components from the overall current signal spectrum. By using Fast Fourier Transform to convert the time-domain current signal into the frequency domain, the system identifies and extracts only the sideband frequencies that are characteristic of power transmission mechanism stretch, separating them from the fundamental frequencies that indicate other types of abnormalities.
Data Source
AI summary
A stretch detection system of a power transmission mechanism is connectable to a conveyor system including a motor, a rotation mechanism driven by the motor, and the power transmission mechanism driven by rotation of the rotation mechanism. The stretch detection system converts a signal of a current of the motor into a frequency domain signal, and calculates an integral value by performing integration on the frequency domain signal obtained by the frequency domain signal conversion unit, by using, as an integration range, at least one of regions of a sideband wave having a frequency determined using a rotation frequency of the rotation mechanism. A stretch diagnosis unit diagnoses a state of stretch of the power transmission mechanism by using the integral value calculated by the integral value calculation unit. Further, an output unit outputs a diagnosis result of the stretch diagnosis unit.