3D Scanning Laser Vibrometer for Curved Surface Vibration Analysis
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Solution Overview
Problem
Current 3D laser vibrometer systems face challenges in efficiently measuring 3D vibrations of curved structures due to limitations in scan path consistency and the inability to monitor transient vibrations in real-time, especially when using single systems, which are not suitable for structures with complex surfaces.
Innovation Solution
A 3D continuously scanning laser vibrometer (CSLV) system comprising three laser heads with mirrors and a profile scanner to determine a 3D zig-zag scan trajectory, allowing for synchronized scanning of curved surfaces and enabling efficient measurement of 3D vibrations with high spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional LDV is used to measure vibration, then the measurement is non-contact, but it can only capture velocity response along a single axis
Solution Approach 1:
The system divides the measurement task into three separate LDVs, each measuring vibration along one of the three orthogonal axes. This segmentation allows each sensor to specialize in a single axis while collectively providing complete 3D vibration measurement capability, resolving the contradiction between non-contact measurement and multi-axis capability.
Solution Approach 2:
The invention transitions from single-axis measurement to three-dimensional measurement by adding spatial dimensions. Three LDVs are positioned to measure along the x, y, and z axes respectively, transforming the measurement capability from one-dimensional to three-dimensional through dimensional expansion.
2Measurement precision
If multiple triaxial accelerometers are used to capture 3D vibrations, then comprehensive vibration data is obtained, but mass loading effect and tethering problems occur
Solution Approach 1:
The invention replaces mechanical contact-type accelerometers with optical laser Doppler vibrometers. This substitution eliminates the mass loading effect and tethering problems associated with physical sensors while maintaining the capability to measure 3D vibrations, as the laser beams can penetrate the structure to measure vibrations on the back side.
3Measurement precision
If laser spots stay at one measurement point for enough time to conduct averages, then high frequency resolution is achieved, but measurement time increases significantly
Solution Approach 1:
The system implements continuous scanning measurement where laser spots continuously move across the structure surface while collecting vibration data. This continuous action allows simultaneous measurement of multiple points without stopping to average at each point, maintaining frequency resolution while dramatically reducing total measurement time compared to point-by-point averaging.
Solution Approach 2:
The system pre-positions three LDVs to cover different spatial locations and orientations before measurement begins. This preliminary arrangement enables parallel data collection from multiple viewpoints, allowing the system to achieve comprehensive 3D vibration coverage without sequential point-by-point measurement.
4Adaptability or versatility
If three LDVs are placed at three locations to extend to 3D measurement, then 3D vibration data is obtained, but calibration among laser beams becomes complex
Solution Approach 1:
The system uses a universal calibration approach where all three LDVs measure vibrations of the same reference structure (cantilever beam) under identical boundary conditions. This universal reference allows simultaneous calibration of all three sensors using the same known mode shapes and frequencies, simplifying the calibration process compared to individual calibration procedures.
Solution Approach 2:
The invention creates a digital copy or model of the reference structure's vibration characteristics through finite element analysis. This computational model serves as a reference for calibrating all three LDVs, allowing the system to compare measured data against predicted mode shapes and frequencies for accurate calibration without complex physical reference measurements.
5Device complexity
If a single CSLDV system is used for 3D vibration measurement, then the system is simpler, but scan path consistency cannot be ensured across curved surfaces
Solution Approach 1:
The system divides the curved surface measurement task into three separate measurement zones, each handled by one LDV positioned to optimize its viewing angle. This segmentation allows each sensor to focus on a specific region with consistent scan paths, avoiding the complexity of maintaining single scan path consistency across the entire curved surface from one location.
Solution Approach 2:
Each LDV is positioned and configured to optimize measurement quality for its specific viewing angle and target region on the curved surface. This local optimization ensures that each sensor achieves the best possible scan path consistency for its local measurement zone, accommodating the curvature variations that would be difficult to handle from a single position.
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
The system significantly reduces measurement time and increases efficiency, achieving high accuracy in determining operating deflection shapes and mode shapes of curved structures, with results comparable to commercial 3D SLDV systems while being more efficient in data acquisition.
Implementation Method 1
laser Doppler vibrometer (LDV) was developed to measure vibration of a structure in a non-contact way
Data Source
AI summary
3D continuously scanning laser vibrometer (CSLV) systems and methods for determining operating deflection shapes (ODSs) and mode shapes based on measured 3D vibrations of curved structure surfaces are disclosed. According to an aspect, a system includes first, second, and third laser heads with mirrors configured to be positioned for scanning a curved surface of a structure. The system includes a profile scanner configured to determine a 3D scan trajectory for the curved surface of a structure. Further, the system includes a computing device that controls the first, second, and third laser heads to scan the curved surface of the structure based on the determined 3D scan trajectory. Further, the computing device is configured to measure the 3D vibrations of the curved surface of the structure, and to determine operating deflection shapes and mode shapes of the structure based on the measured 3D vibrations of the curved surface of the structure.