INTRODUCTION
Recent advances in mobile technology have introduced powerful sensing capabilities in consumer devices, including depth sensing based on time-of-flight (ToF) LiDAR integrated into Apple’s iPhone 13 Pro and similar models. This study investigates the feasibility and limitations of such LiDAR systems in capturing structural vibrations for modal analysis, a critical tool in structural health monitoring. By employing a flexible vibrating target and comparing data against a high-precision laser displacement transducer, the study assesses the mobile LiDAR system’s accuracy and utility. The overarching goal is to evaluate whether consumer-grade mobile devices can be effectively employed for non-contact vibration measurement in academic and field-based research settings.
CHARACTERIZATION OF LIDAR SENSOR PERFORMANCE
To assess the LiDAR's effectiveness in capturing vibration data, the system was tested on a flexible steel cantilever setup. Noise levels, frequency response, and sensing range were systematically evaluated. One significant finding was that although the device camera operates at 60 Hz, the actual LiDAR depth map updates at only 15 Hz. This discrepancy has implications for frequency-domain analyses and requires downsampling of raw data to avoid aliasing errors. Despite inherent noise and distortion, LiDAR data demonstrated a high degree of correlation with laser displacement transducer results, validating the sensor's potential for modal identification under controlled conditions.
IMPACT OF MEASUREMENT CONDITIONS
The influence of environmental and setup parameters, such as the phone-to-target distance and lighting conditions, was studied to understand their impact on measurement quality. It was found that optimal sensing performance occurs when the device is positioned between 0.30 m and 2.00 m from the target. Lighting conditions had less influence on depth sensing performance due to the infrared nature of ToF LiDAR. These findings highlight the importance of appropriate positioning and environmental awareness in experimental setups using mobile LiDAR for structural analysis.
DATA PROCESSING AND MODAL IDENTIFICATION
Data acquired from the mobile LiDAR were processed using Stochastic Subspace Identification (SSI) in a Monte Carlo framework to extract stochastic modal parameters. This approach helped to account for sensor noise and improve reliability through repeated sampling. The analysis successfully identified natural frequencies with a mean deviation of just 1.9% from reference measurements, showcasing the potential of mobile LiDAR systems for modal analysis. The robustness of the method lies in combining sophisticated data processing techniques with prior structural knowledge to compensate for the lower sampling rate and higher noise.
COMPARATIVE ANALYSIS WITH HIGH-PRECISION SENSORS
Benchmarking against a laser displacement transducer provided crucial validation for the mobile LiDAR approach. Despite limitations in temporal resolution and increased noise, the iPhone-based LiDAR captured mode shapes and natural frequencies that closely matched those from high-precision sensors. While not a replacement for laboratory-grade equipment, the mobile solution offers a highly accessible, scalable alternative, especially suitable for preliminary diagnostics or environments where traditional setups are impractical or impossible to deploy.
APPLICATION POTENTIAL IN STRUCTURAL MONITORING
The study concludes that mobile LiDAR sensors, when correctly utilized, hold significant promise for structural health monitoring and diagnostic applications. Their portability, cost-efficiency, and non-contact operation make them ideal for scenarios such as scaled lab models, inaccessible field structures, or rapid inspections. Future work can explore integrating machine learning for automated diagnostics and expanding use in civil infrastructure systems. With further development, mobile LiDAR may redefine the boundaries of structural monitoring, democratizing access to advanced sensing technologies.
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