Hydraulic Motor End of Stroke Detection via Pressure Rate
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Solution Overview
Problem
Existing methods face challenges in accurately detecting the end of piston stroke in reciprocating piston hydraulic motors, particularly in low pressure systems where pressure fluctuations are not distinct, leading to inefficiencies and reduced detection accuracy.
Innovation Solution
A method and apparatus that utilize a hydraulic fluid pressure sensor and controller to detect the end of piston stroke by determining the magnitude of the rate of change of hydraulic fluid pressure and noise in the signal, distinguishing between compression and suction strokes, and determining when a predetermined percentage of the stroke has occurred, thereby improving detection accuracy and reducing processing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure sensor is used to detect pressure drop for end of stroke detection, then detection capability is provided, but in low pressure systems the pressure fluctuations are not distinct enough for accurate detection
Solution Approach 1:
The patent changes the detection parameter from absolute pressure drop magnitude to the rate of change of pressure (dp/dt). By detecting the instantaneous rate of pressure change rather than the pressure drop itself, the system can identify end of stroke events even when absolute pressure fluctuations are small in low pressure systems, thereby maintaining detection accuracy across different pressure conditions.
2Ease of operation
If shuttle valve is opened to reverse piston movement, then piston reversal is achieved, but pressure drop occurs that is difficult to distinguish from compression pressure in low pressure systems
Solution Approach 1:
The patent transforms the detection approach by monitoring the rate of pressure change (dp/dt) rather than pressure magnitude. When the shuttle valve opens, it creates a characteristic rapid pressure change regardless of the absolute pressure level. This allows the control system to reliably detect the valve opening event and trigger piston reversal even when the pressure drop is small and indistinguishable from compression pressures in low pressure systems.
3Productivity
If end of stroke detection is improved in low pressure systems, then pump efficiency increases, but more complex detection algorithms are required
Solution Approach 1:
The patent simplifies the detection algorithm by changing the measured parameter to the rate of pressure change. Instead of requiring complex analysis of pressure magnitude and fluctuation patterns, the system only needs to detect when dp/dt exceeds a threshold value. This parameter transformation maintains high pump efficiency through accurate end of stroke detection while avoiding the need for complex detection algorithms.
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 detection accuracy of piston stroke endings, improving the efficiency and delivery capacity of hydraulically actuated reciprocating piston pumps by up to 10%, effectively addressing the limitations of previous techniques in low pressure systems.
Implementation Method 1
detecting end of piston stroke when a magnitude of a rate of change of hydraulic fluid pressure is substantially greater than a magnitude of a mean rate of change of hydraulic fluid pressure
Data Source
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AI summary
It is challenging to detect end of stroke for hydraulically actuated, reciprocating piston pumps for a variety of reasons. When the pump pressurizes a process fluid to a 10 relatively low pressure the magnitude of hydraulic fluid pressure is not as distinct compared to the magnitude of a pressure drop across a shuttle valve employed to detect end of stroke, which makes detecting the end of stroke event difficult. A method is disclosed for detecting end of a piston stroke in a hydraulic motor comprising a reciprocating piston with a shuttle valve. The method comprises 1 detecting end of piston stroke when a magnitude of a rate of change of hydraulic fluid pressure is substantially greater than a magnitude of a mean rate of change of hydraulic fluid pressure over said piston stroke; and noise in a hydraulic fluid pressure signal is substantially negligible.