Hydraulic Machine Diagnosis via Torque Fluctuation Analysis
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Solution Overview
Problem
Current methods for diagnosing failures in hydraulic machines, particularly in cylinder units, are complex and costly due to the need for multiple pressure sensors, and often struggle to differentiate between failures caused by cylinder unit issues and other factors, leading to potential damage from stuck valves or pistons.
Innovation Solution
A method that detects torque fluctuations in a no-load state using standard deviation and specific frequency analysis to diagnose sticking failures in high-pressure and low-pressure valves, and pistons, without requiring in-cylinder pressure sensors, thereby simplifying the configuration and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure sensors are disposed in each cylinder to diagnose failure of a cylinder unit, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the diagnostic function from individual cylinder-level measurements to system-level torque measurements. By removing the need for in-cylinder pressure sensors and using only torque sensor data, the system achieves failure diagnosis without the complexity of multiple distributed sensors while maintaining diagnostic capability through alternative measurement approaches.
Solution Approach 2:
The torque sensor serves multiple functions: it measures overall system performance and simultaneously enables detection of individual cylinder unit failures through frequency analysis. This multi-functional use of a single sensor type replaces the need for specialized in-cylinder pressure sensors, reducing device complexity while maintaining diagnostic precision.
2Device complexity
If discharge pressure sensor output is used to diagnose failure, then device complexity is reduced, but measurement precision deteriorates due to inability to differentiate failure causes
Solution Approach 1:
The patent applies preliminary signal processing actions to torque measurement data by performing frequency analysis before diagnosis. This preliminary action of decomposing torque signals into frequency components enables the system to identify specific failure modes (high-pressure valve sticking, low-pressure valve sticking, piston sticking) that would otherwise be indistinguishable, thereby improving measurement precision while maintaining simple device configuration.
Solution Approach 2:
The patent focuses on analyzing specific frequency components (ω×m where m≥2) rather than attempting to interpret the entire torque signal spectrum. This partial action approach concentrates diagnostic effort on the most informative frequency bands that correspond to cylinder unit failures, achieving precise failure identification without requiring complex analysis of all possible signal variations.
3Measurement precision
If torque fluctuation analysis is performed to detect cylinder unit failure, then measurement precision is improved for failure detection, but device complexity increases due to additional processing requirements
Solution Approach 1:
The patent replaces complex mechanical diagnostic systems (multiple pressure sensors, mechanical indicators) with electronic signal processing of torque data. By substituting physical measurement complexity with computational analysis of existing torque signals, the system achieves high measurement precision for failure detection while avoiding the physical complexity of additional sensors and mechanical diagnostic apparatus.
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 approach allows for accurate and cost-effective failure diagnosis in hydraulic machines by isolating cylinder unit issues from other factors, preventing damage and ensuring early detection of potential malfunctions.
Implementation Method 1
a torque sensor for obtaining a torque of the rotation shaft
Data Source
Figure 1
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AI summary
A method is for diagnosing a hydraulic machine including a rotation shaft, a high-pressure line, a low-pressure line, cylinders, pistons guided by the respective cylinders, a cam configured to reciprocate the pistons in conjunction with rotation of the rotation shaft, high-pressure valves provided for respective working chambers formed by the cylinders and the pistons, for switching a communication state between the high-pressure line and the respective working chambers, and low-pressure valves provided for the respective working chambers, for switching a communication state between the low-pressure line and the respective working chambers. The method includes a step of detecting a failure of the hydraulic machine, the failure including at least one of sticking of the high-pressure valves in an open state, sticking of the low-pressure valves in a closed state, or sticking of the pistons, on the basis of at least one of a standard deviation of a torque of the rotation shaft in a no-load state of the hydraulic machine, or a fluctuation component of a specific frequency from among a torque fluctuation of the rotation shaft, a pressure fluctuation in the high-pressure line, and an output fluctuation of the hydraulic machine, the specific frequency being determined by a rotation speed ω of the rotation shaft and a cam-lobe number m of the cam.