Feasibility study of Unmanned Aerial Vehicles (UAV) application for ultrasonic Non-Destructive Testing (NDT) of Wind Turbine Rotor Blades. Preliminary experiments of handheld and UAV utrasonic testing on glass fibre laminate

In this thesis, we have conducted a feasibility study on UAV application for ultrasonic pulsed non-destructive testing of wind turbine rotor blades. Due to the high initial cost of wind turbines, and their decreasing availability due to increasing size and offshore locations, it is imperative to properly maintain these structures over their 10-30-year lifetime. Operation and maintenance costs can account for 25-30% of the overall energy generation costs (MartinezLuengo, et al., 2016), where the wind turbine rotor blade can be considered the most critical component, accounting for 15-20% of the manufacturing costs. Thus, an increase in O&M efficiency of wind turbine rotor blades through condition monitoring can yield substantial financial benefits. Currently, Unmanned Aerial Vehicles (UAV) are in use for visual and thermography inspection of wind turbines. These techniques for structural condition monitoring does have serious limitations, as the condition of internal components in blades, built from glass fibre laminates, cannot be visually inspected. However, pulsed ultrasonic echo technique have proven highly efficient for wind turbine rotor blade inspection. The ultrasonic transducer requires surface contact with the examined material, and we investigated the potential of UAV implementation for fast, safe and reliable measurements of wind turbine rotor blades. This feasibility study investigates the applicability of ultrasonic testing of glass fibre laminates, specifically glass fibre produced by Lyngen Plast A/S. Firstly, we conducted handheld ultrasonic tests on simulated delamination defects, looking for damage indications on a voltage-time graph. Secondly, we induced damage on a 27mm thick sample through a 3-point bending test and measured the echo response from the ultrasonic pulse. The second experiment was repeated using a Storm AntiGravity UAV, producing promising results with preliminary instrumentation. A significant challenge to the feasibility of this study was the operational risks. We carried out a preliminary and qualitative risk assessment of the intended UAV operation by using the SWIFTanalysis and Bow-Tie method. The results were two important risk-mitigating measures. Risk reductive: “Design UAV for impact with wind turbine rotor blades,” and risk preventive: “Develop statistical data on wind conditions at wind turbine site, calculate low-risk dates for flight.” The implementation of the said measures, quality of our results, experiences from the UAV flight and concept considerations are presented throughout this paper. In the end, a conclusion is drawn and topics for future studies is presented

Safety Considerations for Operation of Unmanned Aerial Vehicles in the National Airspace System

There is currently a broad effort underway in the United States and internationally by several organizations to craft regulations enabling the safe operation of UAVs in the NAS. Current federal regulations governing unmanned aircraft are limited in scope, and the lack of regulations is a barrier to achieving the full potential benefit of UAV operations. To inform future FAA regulations, an investigation of the safety considerations for UAV operation in the NAS was performed. Key issues relevant to operations in the NAS, including performance and operating architecture were examined, as well as current rules and regulations governing unmanned aircraft. In integrating UAV operations in the NAS, it will be important to consider the implications of different levels of vehicle control and autonomous capability and the source of traffic surveillance in the system. A system safety analysis was performed according to FAA system safety guidelines for two critical hazards in UAV operation: midair collision and ground impact. Event-based models were developed describing the likelihood of ground fatalities and midair collisions under several assumptions. From the models, a risk analysis was performed calculating the expected level of safety for each hazard without mitigation. The variation of expected level of safety was determined based on vehicle characteristics and population density for the ground impact hazard, and traffic density for midair collisions. The results of the safety analysis indicate that it may be possible to operate small UAVs with few operational and size restrictions over the majority of the United States. As UAV mass increases, mitigation measures must be utilized to further reduce both ground impact and midair collision risks to target levels from FAA guidance. It is in the public interest to achieve the full benefits of UAV operations, while still preserving safety through effective mitigation of risks with the least possible restrictions. Therefore, a framework was presented under which several potential mitigation measures were introduced and could be evaluated. It is likely that UAVs will be significant users of the future NAS, and this report provides an analytical basis for evaluating future regulatory decisions

Bridge Inspection: Human Performance, Unmanned Aerial Systems and Automation

Unmanned aerial systems (UASs) have become of considerable private and commercial interest for a variety of jobs and entertainment in the past 10 years. This paper is a literature review of the state of practice for the United States bridge inspection programs and outlines how automated and unmanned bridge inspections can be made suitable for present and future needs. At its best, current technology limits UAS use to an assistive tool for the inspector to perform a bridge inspection faster, safer, and without traffic closure. The major challenges for UASs are satisfying restrictive Federal Aviation Administration regulations, control issues in a GPS-denied environment, pilot expenses and availability, time and cost allocated to tuning, maintenance, post-processing time, and acceptance of the collected data by bridge owners. Using UASs with self-navigation abilities and improving image-processing algorithms to provide results near real-time could revolutionize the bridge inspection industry by providing accurate, multi-use, autonomous three-dimensional models and damage identification

Comprehensive review on controller for leader-follower robotic system

985-1007This paper presents a comprehensive review of the leader-follower robotics system. The aim of this paper is to find and elaborate on the current trends in the swarm robotic system, leader-follower, and multi-agent system. Another part of this review will focus on finding the trend of controller utilized by previous researchers in the leader-follower system. The controller that is commonly applied by the researchers is mostly adaptive and non-linear controllers. The paper also explores the subject of study or system used during the research which normally employs multi-robot, multi-agent, space flying, reconfigurable system, multi-legs system or unmanned system. Another aspect of this paper concentrates on the topology employed by the researchers when they conducted simulation or experimental studies

Comprehensive computational investigations on various aerospace materials under complicated loading conditions through conventional and advanced analyses: a verified examination

Most failures develop as a result of a lack of resistivity information at the internal structure level during typical loading situations such as shock load and impact load. Impact loads have a significant impact on a component’s structural performance. A careful, organized examination of impact load settings and their side effects can reveal how well something can withstand peak loads. First, this study investigated the impact analyses on nine varied lightweight composite materials through a conventional experimental setup and computational tools. So, the best three lightweight materials are shortlisted for further investigation under complicated explicit analysis. Second, the study investigated the behavior of composite materials subjected to rapid loading circumstances in several real-time applications. The applications chosen include bullet crash analysis, unmanned aerial vehicle (UAV) propellers, and car bumpers. The three different principal composites, carbon fiber-reinforced polymer (CFRP), glass fiber-reinforced polymer (GFRP), and Kevlar fiber-reinforced polymer (KFRP), are selected and applied in crash analysis using ANSYS Workbench’s explicit technique-based finite element analysis (FEA). The comparison assessments are conducted using stumpy structural characteristics such as impact stress and equivalent strain. Two distinct grid convergence tests were performed to check whether the computational processes and discretization were correct. The standard methodologies were used on all three selected real-time applications, resulting in error percentages that were within acceptable bounds, ensuring the generation of dependable structural outputs. The ideal composite material is a Kevlar fiber-based composite with minimal defect affectability for all types of crash applications. Furthermore, multidisciplinary optimizations are performed, and the KFRP is verified to give good crash load resistance with reduced dense contribution

Applications of Finite Element Modeling for Mechanical and Mechatronic Systems

Modern engineering practice requires advanced numerical modeling because, among other things, it reduces the costs associated with prototyping or predicting the occurrence of potentially dangerous situations during operation in certain defined conditions. Thus far, different methods have been used to implement the real structure into the numerical version. The most popular uses have been variations of the finite element method (FEM). The aim of this Special Issue has been to familiarize the reader with the latest applications of the FEM for the modeling and analysis of diverse mechanical problems. Authors are encouraged to provide a concise description of the specific application or a potential application of the Special Issue

Empirical Evaluation of Ground, Ceiling, and Wall Effect for Small-Scale Rotorcraft

Ground effect refers to the apparent increase in lift that an aircraft experiences when it flies close to the ground. For helicopters, this effect has been modeled since the 1950\u27s based on the work of Cheeseman and Bennett, perhaps the most common method for predicting hover performance due to ground effect. This model, however, is based on assumptions that are often not realistic for small-scale rotorcraft because it was developed specifically for conventional helicopters. It is clear that the Cheeseman-Bennett model cannot be applied to today\u27s multirotor UAVs. Experimental findings suggest that some of the conventional thinking surrounding helicopters cannot be applied directly to rotorcraft using fixed propellers at variable speeds (e.g. multirotors). A parametric multirotor-specific ground effect model is developed and presented to overcome some of the limitations in classical helicopter theory. Likewise, ceiling effect refers to the apparent increase in lift that a rotorcraft experiences when flying close to a ceiling or any similar surface that is present above the rotor(s). Ceiling effect is similar in principle to ground effect, and can be explained using a similar equation. Ceiling effect, however, was never explored in detail for conventional helicopters because large manned aircraft do not operate in enclosed spaces. For multirotors, the work presented in this dissertation suggests that the classical helicopter theory adequately describes ceiling effect performance. Wall effect is the phenomena that occurs when a rotorcraft flies near a vertical wall, and has the tendency to pitch towards the wall and be drawn into it. Wall effect is the least-understood of these three areas of interest. Wall effect has not been explored in great detail for any aircraft, and is addressed in detail in this dissertation. The recent widespread use of small-scale UAVs and the demand for increased autonomy when flying in enclosed environments has created a need for detailed studies of ground effect, ceiling effect and wall effect. Ultimately, this work provides foundations for the development of an improved UAV flight controller that can accurately account for various aerodynamic disturbances that occur near surfaces and structures to improve flight stability

Empirical Evaluation of Ground, Ceiling, and Wall Effect for Small-Scale Rotorcraft

Ground effect refers to the apparent increase in lift that an aircraft experiences when it flies close to the ground. For helicopters, this effect has been modeled since the 1950\u27s based on the work of Cheeseman and Bennett, perhaps the most common method for predicting hover performance due to ground effect. This model, however, is based on assumptions that are often not realistic for small-scale rotorcraft because it was developed specifically for conventional helicopters. It is clear that the Cheeseman-Bennett model cannot be applied to today\u27s multirotor UAVs. Experimental findings suggest that some of the conventional thinking surrounding helicopters cannot be applied directly to rotorcraft using fixed propellers at variable speeds (e.g. multirotors). A parametric multirotor-specific ground effect model is developed and presented to overcome some of the limitations in classical helicopter theory. Likewise, ceiling effect refers to the apparent increase in lift that a rotorcraft experiences when flying close to a ceiling or any similar surface that is present above the rotor(s). Ceiling effect is similar in principle to ground effect, and can be explained using a similar equation. Ceiling effect, however, was never explored in detail for conventional helicopters because large manned aircraft do not operate in enclosed spaces. For multirotors, the work presented in this dissertation suggests that the classical helicopter theory adequately describes ceiling effect performance. Wall effect is the phenomena that occurs when a rotorcraft flies near a vertical wall, and has the tendency to pitch towards the wall and be drawn into it. Wall effect is the least-understood of these three areas of interest. Wall effect has not been explored in great detail for any aircraft, and is addressed in detail in this dissertation. The recent widespread use of small-scale UAVs and the demand for increased autonomy when flying in enclosed environments has created a need for detailed studies of ground effect, ceiling effect and wall effect. Ultimately, this work provides foundations for the development of an improved UAV flight controller that can accurately account for various aerodynamic disturbances that occur near surfaces and structures to improve flight stability