Planetary Gear Reducer Diagnosis Using Dual Vibration Speed Estimation
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Solution Overview
Problem
Existing abnormality diagnosis methods for planetary gear speed reducers in construction machines, particularly those coupled to hydraulic motors, face challenges due to the variability of input speed and the difficulty in measuring actual speed-of-rotation data, especially when direct acquisition from an inverter is not possible.
Innovation Solution
An abnormality diagnosis device equipped with first and second vibration sensors attached to the speed reducer housing and motor housing, respectively, and a processor that computes peak frequencies and characteristic frequencies from vibration data to determine gear abnormalities without direct speed measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a speed-of-rotation sensor is installed to measure actual rotation speed for accurate abnormality diagnosis, then measurement precision is improved, but device complexity and installation difficulty increase due to exposed rotation portions and environmental contamination
Solution Approach 1:
The patent uses vibration signals as an intermediary to indirectly obtain speed-of-rotation information. Instead of directly measuring rotation speed with a sensor on the exposed shaft, the system captures vibration signals from the speed reducer housing, extracts frequency components through spectral analysis, and derives rotation speed from the characteristic frequencies. This intermediary approach avoids direct contact with contaminated rotation portions while achieving accurate speed measurement.
Solution Approach 2:
The patent replaces the mechanical speed-sensing system (rotation sensor on shaft) with a vibration-based measurement system. By substituting direct mechanical measurement with vibration signal analysis, the system eliminates the need for physical sensor installation on exposed rotation portions, thereby reducing device complexity and installation difficulty while maintaining measurement capability.
2Measurement precision
If vibration sensing is performed near the planetary gear mechanism to diagnose gear abnormalities, then abnormality detection accuracy is improved, but the system cannot obtain speed-of-rotation data when driven by hydraulic motors
Solution Approach 1:
The patent implements a feedback mechanism where vibration signals are continuously monitored, spectral analysis is performed to extract characteristic frequencies, and the derived rotation speed information is fed back into the diagnosis algorithm. This closed-loop approach allows the system to compensate for the lack of direct speed data by using vibration-based speed estimation, thereby maintaining accurate gear abnormality detection even when driven by hydraulic motors without direct speed sensors.
3Measurement precision
If direct speed-of-rotation data is acquired from an inverter for electric motors, then measurement precision is improved, but this approach is not applicable to hydraulic motors where inverters are not used
Solution Approach 1:
The patent creates a universal speed measurement approach that works for both electric motors and hydraulic motors. By using vibration signal analysis as a common methodology, the system eliminates the need for motor-type-specific measurement approaches (inverter data for electric motors vs. direct sensing for hydraulic motors). The vibration-based method provides a multi-functional solution that adapts to different motor types and drive systems, thereby improving system versatility and adaptability.
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
Enables easy and accurate abnormality diagnosis of planetary gear speed reducers in construction machines driven by hydraulic motors, overcoming the challenge of variable input speed and difficult speed measurement.
Implementation Method 1
a first vibration sensor attached to a speed reducer housing that is a housing of the planetary gear speed reducer and configured to sense vibration of the speed reducer housing
Implementation Method 2
a second vibration sensor attached to a motor housing that is a housing of the hydraulic motor and configured to sense vibration of the motor housing
Implementation Method 3
compute characteristic frequencies corresponding to respective rotation periods of the plurality of gears on the basis of the speed of rotation of the hydraulic motor, the number of the plurality of gears, and the number of teeth of each of the plurality of gears
Implementation Method 4
extract an amplitude at a characteristic frequency, and, when the extracted value is higher than a threshold value, it is determined that the gear linked to the characteristic frequency is damaged
Data Source
AI summary
An abnormality diagnosis device for a planetary gear speed reducer includes a second vibration sensor attached to a housing of a hydraulic motor having an output shaft coupled to the planetary gear speed reducer. A controller computes a peak frequency Fm of the hydraulic motor and a speed of rotation of the hydraulic motor on the basis of second vibration data acquired through the second vibration sensor, compute, on the basis of the computed speed of rotation, the number of a plurality of gears included in the planetary gear speed reducer, and the number of teeth of each of the gears, characteristic frequencies fd of the plurality of gears, and determines presence or absence of abnormality in the plurality of gears on the basis of the peak frequency Fm of the hydraulic motor and amplitudes at the characteristic frequencies fd of first vibration data acquired through a first vibration sensor attached to the planetary gear speed reducer.