A drone-based inspection system that can fly, hover, and navigate around structures to perform the inspection in an efficient/fast manner can considerably reduce inspection time. Active thermography is a well-known non-destructive testing method for inspection. However, using it on a drone is challenging due to the drone needing to carry an appropriate heat source, batteries or tethering system to power the heat source and to provide adequate flight time. This complicates the inspection process and can restrict the amount of thermal energy that can be applied to the inspected structure. Another challenge with drone-based active infrared thermography (DBAIT) is that, unlike traditional active thermography inspection in which, the source is either stationary or moving in a precisely controlled manner, the drone and the heat source are subjected to undesired dynamic motion. This paper presents the results of experiments performed to compare potential heat sources that can be retrofitted onboard a drone to conduct active thermographic inspection.
A drone-based inspection system that can move “freely” around an aircraft to perform the inspection of all the areas of interest in a fast and effective manner can have significant impact in reducing inspection time and cost. However, active thermography inspection using drone is challenging because the drone carrying the optical and thermal cameras is subjected to vibration and undesired motion. Since active thermography relies on the pixel temperature evolution over time, an unstable thermal video from a flying drone can cause error in the output results as any movement between the acquired images will affect the pixel position in the successive frames and thus disrupt the monitoring of the temperature evolution. This paper presents the outcome of experimental runs, where a commercially available drone equipped with both thermal and optical cameras was used to inspect a helicopter Main Rotor Blade (MRB) in a laboratory environment.
Diagnosis and prognosis of failures for aircrafts’ integrity are some of the most important regular functionalities in complex and safety-critical aircraft structures. Further, development of failure diagnostic tools such as Non-Destructive Testing (NDT) techniques, in particular, for aircraft composite materials, has been seen as a subject of intensive research over the last decades. The need for diagnostic and prognostic tools for composite materials in aircraft applications rises and draws increasing attention. Yet, there is still an ongoing need for developing new failure diagnostic tools to respond to the rapid industrial development and complex machine design. Such tools will ease the early detection and isolation of developing defects and the prediction of damages propagation; thus allowing for early implementation of preventive maintenance and serve as a countermeasure to the potential of catastrophic failure. This paper provides a brief literature review of recent research on failure diagnosis of composite materials with an emphasis on the use of active thermography techniques in the aerospace industry. Furthermore, as the use of unmanned aerial vehicles (UAVs) for the remote inspection of large and/or difficult access areas has significantly grown in the last few years thanks to their flexibility of flight and to the possibility to carry one or several measuring sensors, the aim to use a UAV active thermography system for the inspection of large composite aeronautical structures in a continuous dynamic mode is proposed.
Unmanned aerial vehicles are a modern day solution for reducing the time of inspections. This work aims to address the difficulties of using a UAV to inspect aircraft structures. Challenges such as non-uniform heating, low spatial resolution, and environmental noise cause some difficulties for defect detection and characterisation. Contrary to this, mounting sensors onto a UAV’s will further increase the noise, due to the motion, vibrations and sequence mismatching. Methods to tackle stabilisation and indoor localisation are used by utilising a Vicon system, this aims to increase the accuracy of the captured data when inspecting without GPS i.e. inspecting indoors. Other than active thermography, various methods were trialled to locate defects, passive thermography, photogrammetry and RGB image processing.
The conventional methods for inspection of industrial sites involve the revision of data by an experienced inspector during the acquisition process to avoid possible data missing and misinterpretation. Despite all the advantages of drone-based inspection, inspectors often do not easily have physical access to the site to check for any data ambiguity. Therefore, it is essential for autonomous or semi-autonomous systems to check for missing data or to highlight possible data ambiguity. Reflection in thermal imagery data is one of the main sources of misinterpretation, and it can be problematic when there is no physical access to the site for a secondary inspection. In this paper, we present a novel algorithm based on the analysis and stitching of consecutive aerial thermal images to detect areas with reflection effect and possibly reduce these effects. The conducted experiments have shown significant results in the detection of reflection in drone-based thermographic inspections.
Transient thermography is a method used successfully in the evaluation of composite materials and aerospace structures. It has the capacity to deliver both qualitative and quantitative results about hidden defects or features in a composite structure. Aircraft must undergo routine maintenance – inspection to check for any critical damage and thus to ensure its safety. This work aims to address the challenge of NDT automated inspection and improve the defects’ detection by suggesting an autonomous thermographic imaging approach using a UAV (Unmanned Aerial Vehicle) active thermographic system. The concept of active thermography is discussed and presented in the inspection of aircraft CFRP panels along with the mission planning for aerial inspection using the UAV for real time inspection. Results indicate that the suggested approach could significantly reduce the inspection time, cost, and workload, whilst potentially increase the probability of detection of defects on aircraft composites.
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