Hydraulic Seal Friction Coefficient Determination
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Solution Overview
Problem
Existing systems for determining the coefficients of friction in hydraulic cylinders, particularly those involving seals, face inaccuracies due to the variability of seal friction with pressure, which affects payload estimation and control in machines using hydraulic cylinders.
Innovation Solution
A system comprising a linkage member, a hydraulic cylinder, a force sensor, and a controller that moves the linkage member in both directions to measure force signals, calculates friction forces, and determines the hydraulic seal coefficient of friction based on these measurements, accounting for differences in force signals when engaging loads in both directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If seal friction is not accounted for in payload estimation, then the payload estimation system is simpler, but the measurement precision of payload is reduced
Solution Approach 1:
The patent extracts seal friction as a separate measurable quantity from the total hydraulic cylinder force. By using bidirectional force measurements, the system isolates friction force as a distinct component that can be calculated and removed from payload calculations, thereby improving measurement precision without requiring complex additional hardware
Solution Approach 2:
The system implements feedback by continuously measuring friction forces during hydraulic cylinder operation and using this information to compensate for friction effects in real-time payload estimation. The controller adjusts payload calculations based on measured friction data, improving accuracy while using existing system components
2Reliability
If friction forces are not separated from cylinder force measurements, then the measurement system is simpler, but the reliability of force measurements for payload control is reduced
Solution Approach 1:
The system uses the hydraulic cylinder's own operation to generate friction measurement data. By measuring forces during extension and retraction cycles, the system self-determines friction characteristics without requiring external testing equipment, thereby improving reliability while maintaining simplicity
Solution Approach 2:
Instead of trying to directly measure friction separately, the system measures total forces in both directions and inverts the calculation approach to derive friction as the difference between bidirectional measurements. This indirect method improves reliability by using readily available force sensor data
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 provides accurate determination of hydraulic seal coefficients, enhancing the precision of payload estimation and control in machines by isolating and quantifying seal friction, thereby improving operational accuracy and reliability.
Implementation Method 1
a force sensor configured to provide a force signal indicative of a force of the cylinder
Implementation Method 2
a hydraulic cylinder operatively connected to the linkage member for moving the linkage member along a path
Implementation Method 3
The friction associated with the hydraulic cylinder is generally composed of three components, namely Coulomb friction, viscous friction, and friction from the seals within the hydraulic cylinder
Data Source
AI summary
A system for determining a hydraulic seal coefficient of friction of a hydraulic cylinder includes a force sensor to provide a force signal indicative of a force of the cylinder. A controller is configured to receive a plurality of first force signals at a first load and determine a first friction force and receive a plurality of second force signals at a second load and determine a second friction force. A hydraulic seal coefficient of friction is determined based at least in part upon the first friction force and the second friction force. A method is also disclosed.