Hydraulic Drive System Dynamic Pressure Threshold Control
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Solution Overview
Problem
Hydraulic drive systems with variable pump speeds face challenges in controlling and diagnosing operational conditions, particularly in determining when a storage tank is empty or if there is insufficient material being processed, due to factors influencing peak hydraulic system pressure such as process fluid pressure and kinetic friction, leading to inefficiencies and potential damage from short stroking.
Innovation Solution
A method that measures hydraulic fluid pressure and adjusts the pressure threshold values based on resistance from machinery and pump speed, calculates mechanical work done by the hydraulic drive unit, and warns operators or limits flow when expected mechanical work is not met, using formulas or look-up tables to correct for various influencing factors, thereby improving diagnostic control and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydraulic pump speed is increased to improve productivity, then the processing rate increases, but the peak hydraulic system pressure varies making diagnosis more difficult
Solution Approach 1:
The patent applies dynamics by making the pressure threshold dynamic rather than static. The threshold adjusts automatically with changes in hydraulic pump speed, allowing the system to maintain diagnostic accuracy across a range of operating speeds. This dynamic adaptation resolves the contradiction between high productivity (variable speeds) and reliable diagnosis (consistent pressure interpretation).
Solution Approach 2:
The system changes the pressure threshold parameter based on pump speed variations. When pump speed increases or decreases, the threshold is相应ly adjusted to maintain its effectiveness as a diagnostic criterion, thereby decoupling the relationship between speed variations and diagnostic reliability.
2Device complexity
If fixed pressure threshold is used for controlling hydraulic drive unit, then the control logic is simple, but the system reliability deteriorates due to short stroking and incomplete piston strokes
Solution Approach 1:
The patent changes the pressure threshold from a fixed value to a dynamic value that adapts to operating conditions. This adjustment prevents short stroking and incomplete piston strokes by ensuring the threshold remains appropriate across different pump speeds and process fluid pressures, thereby improving system reliability without adding significant complexity.
Solution Approach 2:
The system performs preliminary action by pre-establishing the relationship between pump speed, process fluid pressure, and appropriate pressure thresholds. This allows the control system to proactively adjust thresholds before problematic conditions occur, preventing short stroking and improving reliability rather than reacting to failures after they happen.
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 enhances the accuracy of diagnosing operational conditions, reduces idle time between piston strokes, and prevents damage by precisely determining the end of piston strokes and detecting abnormal operating conditions, leading to improved system efficiency and reliability.
Implementation Method 1
hydraulic pump delivers hydraulic fluid to a hydraulic drive unit
Implementation Method 2
convert hydraulic fluid pressure to mechanical movements in machinery that is coupled to and driven by the hydraulic drive unit
Implementation Method 3
measuring hydraulic fluid pressure to determine when the storage tank is empty
Data Source
AI summary
A method and apparatus are provided for hydraulic fluid supply between a hydraulic pump and a hydraulic drive unit, switching hydraulic fluid flow direction to the hydraulic drive unit or stopping hydraulic fluid flow to the hydraulic drive unit when measured hydraulic fluid pressure crosses a predetermined pressure threshold value. The method further comprises calculating an amount of mechanical work done by the hydraulic drive unit and warning an operator or limiting hydraulic fluid flow rate to the hydraulic drive unit when the calculated mechanical work for the drive cycle is less than an expected amount of mechanical work. The apparatus for practicing the method further includes a pressure sensor associated with a hydraulic fluid supply conduit between the pump and the drive unit, and an electronic controller programmed to operate the drive system according to the method.