Linear Actuator Displacement Sensing via External Vibration Analysis
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Solution Overview
Problem
Existing position measuring systems for piston position in cylinder-piston units require structural modifications and are sensitive to contamination and environmental factors, making them unsuitable for retrofitting and accurate measurement.
Innovation Solution
A non-invasive position measuring system that uses mechanical vibration excitation and detection to determine piston position through frequency analysis, allowing for external installation without altering the cylinder-piston unit's design and minimizing sensitivity to contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a displacement measuring system is integrated into the cylinder-piston assembly, then piston position can be determined, but structural modifications are required which increase manufacturing complexity
Solution Approach 1:
The patent replaces traditional mechanical displacement measuring systems (which require physical integration into the cylinder-piston assembly) with an acoustic vibration-based measurement system. The excitation element generates mechanical vibrations that propagate through the cylinder-piston assembly, and the detector captures these vibrations externally. This substitution eliminates the need for hollow bores, integrated sensors, or structural modifications to the piston rod, thereby resolving the contradiction between achieving precise position measurement and maintaining ease of manufacture.
Solution Approach 2:
The patent introduces acoustic vibrations as an intermediary medium to transfer information about piston position from the internal cylinder-piston assembly to external detectors. Instead of directly measuring position through physical contact or internal sensors, the system uses vibration waves that naturally propagate through the assembly's structure. This intermediary approach allows external measurement without requiring the measuring system to be integrated inside the cylinder, thus reducing manufacturing complexity while maintaining measurement capability.
2Measurement precision
If electromagnetic radio signals are used for displacement measurement, then piston position can be determined, but the system requires installation inside the cylinder which increases integration effort and is sensitive to contamination
Solution Approach 1:
The patent substitutes electromagnetic radio signal-based measurement with acoustic vibration-based measurement. Instead of using electromagnetic waves that require coupling into the cylinder and are sensitive to hydraulic fluid contamination and air bubbles, the system uses mechanical vibrations that propagate through the solid structure of the cylinder-piston assembly. This substitution eliminates sensitivity to fluid contamination while maintaining position measurement capability, and allows external placement of excitation and detection elements.
Solution Approach 2:
The patent extracts the measurement function from the internal hydraulic environment and relocates it to the external structural environment. By taking out the excitation element and detector from inside the cylinder and placing them on the outer surface, the system removes the measurement process from the contamination-prone hydraulic fluid environment. The vibrations are generated and detected externally, interacting with the cylinder wall structure rather than the hydraulic fluid, thus eliminating sensitivity to contamination while preserving position determination capability.
3Measurement precision
If structural modifications are made to the cylinder for measurement integration, then position measurement is enabled, but retrofitting existing assemblies becomes impossible
Solution Approach 1:
The patent replaces integration-based measurement with external excitation and detection. Instead of requiring hollow bores, embedded sensors, or modified piston rods, the system uses an excitation element that generates vibrations through contact with the outer cylinder surface and a detector that captures vibrations externally. This mechanical substitution enables the measurement system to function entirely from the outside, making it compatible with any existing cylinder-piston assembly regardless of its original design, thus achieving full retrofitting capability while maintaining position measurement precision.
Solution Approach 2:
The patent creates a universal measurement system that can be applied to any cylinder-piston assembly without requiring specific structural features. The excitation element and detector are designed to interface with the outer surface of the cylinder, which is a common feature across all such assemblies. This universal approach allows the same measurement system to be retrofitted onto existing assemblies with different designs, sizes, and applications, eliminating the need for custom modifications and enabling broad adaptability and versatility.
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 accurate piston position determination with reduced integration effort and improved robustness against environmental influences, facilitating retrofitting and enhancing measurement accuracy.
Implementation Method 1
The excitation element is configured to excite the cylinder-piston assembly to mechanical vibration by means of a pulsed or multi-frequency excitation
Implementation Method 2
The detector is configured to detect mechanical vibrations of the cylinder-piston assembly and convert them into measurement signals
Implementation Method 3
The detector is configured to detect mechanical vibrations of the cylinder-piston assembly and convert them into measurement signals
Implementation Method 4
The evaluation unit is configured to assign the measurement signals to a piston position based on a frequency spectrum and/or one or more characteristic frequencies
Data Source
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AI summary
A displacement measuring system (1) for determining a piston position in a cylinder-piston assembly (2) is proposed, comprising an excitation element (8), a detector (9) and an evaluation unit (14) connected to the detector (9), wherein the excitation element (8) is configured to excite the cylinder-piston assembly (2) to mechanical vibration by means of an impulse or an oscillating excitation, in particular multi-frequency excitation, and the detector (9) is configured to detect mechanical vibrations of the cylinder-piston assembly (2) and convert them into measurement signals, and wherein the evaluation unit (14) is configured to assign the measurement signals to a piston position on the basis of a frequency spectrum and/or one or more characteristic frequencies (R1, R2).