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Despite the proved usefulness of drones in biodiversity studies, acquisition costs and difficulties in operating, maintaining and repairing these systems constrain their integration in conservation projects, particularly for low-income countries. Here we present the steps necessary to build a low-cost fixed-wing drone for environmental applications in large areas, along with instructions to increase the reliability of the system and testing its performance. Inspired by DIY (Do It Yourself) and open source models, this work prioritizes simplicity and accounts for cost-benefit for the researcher. The DIY fixed-wing drone developed has electric propulsion, can perform pre-programmed flight, can carry up to 500 g payload capacity with 65 minutes flight duration and flies at a maximum distance of 20 km. It is equipped with a RGB (Red, Green and Blue) sensor capable of obtaining 2.8 cm per pixel Ground Sample Distance (GSD) resolution at a constant altitude of 100 m above ground level (AGL). The total cost was $995 which is substantially less than the average value of similar commercial drones used in biodiversity studies. We performed 12 flight tests in auto mode using the developed model in protected areas in Brazil, obtaining RGB images that allowed us to identify deforestation spots smaller than 5 m2 and medium-sized animals. Building DIY drones requires some technical knowledge and demands more time than buying a commercial ready-to-fly system, but as proved here, it can be less expensive, which is often crucial in conservation projects. [ABSTRACT FROM AUTHOR]

Structural batteries are attractive for weight reduction in vehicles, such as cars and airplanes, which requires batteries to have both excellent mechanical properties and electrochemical performance. This work develops a scalable and feasible tree‐root‐like lamination at the electrode/separator interface, which effectively transfers load between different layers of battery components and thus dramatically enhances the flexural modulus of pouch cells from 0.28 to 3.1 GPa. The underlying mechanism is also analyzed by finite element simulations. Meanwhile, the interfacial lamination has a limited effect on the electrochemical performance of Li‐ion cells. A graphite/LiNi0.5Mn0.3Co0.2O2 full cell with such interfacial lamination delivers a steady discharge capacity of 148.6 mAh g−1 at C/2 and 95.5% retention after 500 cycles. Moreover, the specific energy only decreases by 3%, which is the smallest reduction reported so far in structural batteries. A prototype of "electric wings" is also demonstrated, which allows an aircraft model to fly steadily. This work illustrates that engineering interfacial adhesion is an effective and scalable approach to develop structural batteries with excellent mechanical and electrochemical properties. [ABSTRACT FROM AUTHOR]

This paper explores the potential of active control in end-to-end power trains, with an explicit goal of expanding the operating envelope beyond compressor stall and surge limits to allow a smaller engine to attain the same performance as a larger one. The proposed controllers are derived using novel multi-layered dynamical models of both the compressor and the end-to-end power train. The higher-level models explicitly state the dynamics of stored energy and its derivative, which depend on these aggregate variables and the shared variables at the interfaces of system components. The derivatives of these shared variables are instantaneous power and rate of change of generalized instantaneous reactive power. Thus, the proposed framework for the first time describes the detailed mathematical modeling and control of energy dynamics in end-to-end hybrid power trains. In addition, the proposed multi-layered controller directly supports distributed cooperative exchanges of instantaneous reactive power within and across different parts of the power train, making the effects of active control on energy dynamics almost transparent. Simulations illustrate these new modeling and control concepts on state-of-the-art examples of complex engine stall/surge instabilities exhibiting bifurcations. In particular, there is a non-zero rotor acceleration in the power train for challenging missions, which is not observed by traditional controllers, leading to persistent oscillations. The proposed energy control aligns the rates at which subsystems process energy through reactive power control implemented either through the throttle valve or electric actuation, leading to better transient and steady-state performance. Notably, our proposed controller does not require much energy, thereby opening the door to exploring the potential of small storage (battery) in Turbo-electric Distributed Propulsion (TeDP) systems. Preliminary results show that this cooperative control makes a case for hybrid aircraft relying on fast nonlinear control in the electric part of the power train. [ABSTRACT FROM AUTHOR]

This paper concerns modeling, simulations and control design of turbo-electric distributed propulsion (TeDP) systems needed to power future hybrid aircraft systems. The approach taken is the one of control co-design by which the sizing and hardware selection of components and the TeDP architecture design are pursued so that potential effects of control and automation are accounted for from the very beginning. Unique to this approach is a multi-layered modular modeling and control approach in which technology-specific modules comprising the complex dynamical system are characterized using unified interaction variables at their interfaces with the rest of the system. The dynamical performance of the interconnected system is assessed using these technology-agnostic interface variable specifications and, as such, can be applied to any candidate architecture of interest. Importantly, even the inputs to the TeDP system coming from pilot commands are modeled using such interface variables. This new multi-layered modeling captures the dynamics of energy and power as interactions. It also has a rather straightforward physical interpretation. The paper builds on our earlier results introduced for terrestrial power systems, including small micro-grids. We show how system feasibility and stability can be checked in real-time operations by modules exchanging the information about their interaction variables and adjusting in a near-autonomous manner so that, as system conditions vary, the interconnected system still functions. No such systematic control co-design exists to the best of our knowledge, but it is needed as both new technologies and more complex, often conflicting performance objectives emerge. We illustrate the approach on a representative TeDP architecture and compare it to today's state-of-the-art. We close with a discussion on the generalization of the method for any given candidate architecture. Having such an approach dramatically reduces the R&D&D of novel candidate architectures. [ABSTRACT FROM AUTHOR]

The more-electric aircraft concept has made the extraction of electrical power from both high-pressure shaft and low-pressure shaft of the aircraft engine essential for future aircraft. With each shaft driving one electrical generation channel, an advanced dual-channel enhanced power generation system can be formed. This article aims to address the power quality issues of this dual-channel power generation system, specifically focusing on the reduction of harmonics on a common dc bus. A simplified model to estimate second carrier harmonic of dc current in two-level converters is developed and reveals the fact that while this second carrier harmonic component magnitude can be determined by modulation index and dc-link current, its phase angle is solely dependent on the angle of carrier signals. Based on the developed model and these key findings, a new harmonic cancellation method is proposed through active power sharing and phase angle shifting of the carrier signals within different power sources. The method has demonstrated high robustness and is effective under different fundamental frequencies and power sharing ratio. Both simulation and experimental results are presented in this article to validate the proposed harmonic model and the enhanced cancellation method. [ABSTRACT FROM AUTHOR]

Numerical analysis of the scattering of a plane monochromatic electromagnetic wave from a discrete parabolic reflector made of parallel cylinders (wires) with perfect electric conductivity is carried out in the exact and approximate formulations, the latter neglecting all interactions between the wires. Both the TE and the TM polarizations of the incident field are considered. It is shown that the difference between the exact and approximate solutions strongly depends on the frequency of the incident wave and that the TM-polarized plane wave is focused better by the discrete reflector than the TE-polarized wave. The field in the vicinity of the geometrical focus is investigated. It is found that the focusing ability, oscillating, gradually decreases with frequency. This behavior is in stark contrast to a solid perfectly electrically conducting parabolic reflector. [ABSTRACT FROM AUTHOR]

This paper improves the fuel efficiency of a student-made parallel hybrid electric racing car whose internal combustion engine (ICE) either operates with peak efficiency or is turned off. The control to the ICE thus becomes a binary problem. Owing to the very limited computation resource onboard, the energy management strategy (EMS) for this car must have small time and space complexities. A computationally efficient controller that combines the advantages of dynamic programming (DP) and Pontryagin's minimum principle (PMP) is developed to run on a low-cost microprocessor. DP is employed offline to calculate the optimal speed trajectory, which is used as the reference for the online PMP to determine the real-time ICE on/off status and the electric motor (EM) torques. The normal PMP derives the optimal costate trajectory through solving partial differential equations. The proposed quasi-PMP (Q-PMP) method finds the costate from the value function obtained by DP. The fuel efficiency and computational complexity of the proposed controller are compared against several state of the art methods through both model-in-the-loop (MIL) and processor-in-the-loop (PIL) simulations. The new method reaches similar fuel efficiency as the explicit DP, but requires less than 1% onboard flash memory. The performance of the Q-PMP controller is compared between binary-controlled and continuously controlled ICEs. It achieves roughly 12% higher fuel efficiency for the binary ICE with only approximately 1/3 CPU utilization. [ABSTRACT FROM AUTHOR]

A new device, referred to as Superconducting Power Filter (ScPF), is introduced to improve the stability of aircraft electric DC grids. This device is made of a non-inductive superconducting coil connected in series with a conventional RLC filter. The superconducting coil behaves as a nonlinear current-dependent resistance. By design, the superconductor does not undergo a full transition to the normal-resistive state and remains in the current-sharing regime. Thus, a quick response and recovery of the superconductor to transients can be achieved. In the present work, the thermo-electric model of the device incorporates a refined description of the transition from the superconducting state to the normal-resistive state of the superconductor. To check the feasibility of passive stabilization of embedded DC grids using ScPF, different widths and lengths of commercially available 2nd generation High Temperature Superconducting (2G HTS) tapes were considered. We chose a case study simulating an equivalent circuit of a More Electric Aircraft (MEA) with an EPS-A3 architecture. For this particular case study, it is shown that the stability limit of the DC grid can be significantly increased, while preserving the reliability (no quench) and low cost (only a few meters of superconducting tape) of the ScPF. [ABSTRACT FROM AUTHOR]

The idea of electric propulsion for transportation is not new; indeed, the first cars, nearly 200 years ago, were electric. However, our dependence on fossil fuels over the last 100 years is now being questioned, and as a global society, we are moving toward more-electric transportation solutions. Electric propulsion of aircraft is part of this trend, either all-electric or through a large variety of the proposed hybrid propulsion systems. This article considers some of these systems, their technological requirements, and the ongoing research and development in motors and drives necessary to make this technological change a feasible option for the future of passenger flight. [ABSTRACT FROM AUTHOR]

In this article, an improved pulsewidth modulation (PWM) strategy is introduced for three-level active neutral point clamped converters based on a hybrid configuration of silicon carbide (SiC) mosfets and silicon (Si) insulated gate bipolar transistor (IGBTs). Compared with the conventional PWM strategies in the literature, this proposed PWM strategy enables the SiC switches only to interface with small commutation loops, thus the turn-off voltage overshoots caused by the parasitic loop inductance and high di/dt are much lower. Soft switching is achieved across all the IGBTs, and the switching losses of the converter only dissipate from the SiC mosfets, leading to high efficiency of the converter. Also, with this improved PWM strategy, the conduction loss at zero voltage output of this converter is reduced due to the turn-on of two parallel conduction paths. Furthermore, this proposed PWM strategy can protect the body diodes of the SiC mosfets from conducting large load current. All these advantages with the proposed PWM strategy are experimentally verified in a megawatt-scale three-phase three-level “SiC+Si” hybrid active neutral point clamped inverter developed for electric aircraft propulsion applications. [ABSTRACT FROM AUTHOR]

This study developed a framework of the self-identity-based electric product adoption model to comprehend air travelers' intentions to adopt eco-friendly electric airplanes. Through a quantitative process and survey method, our analysis revealed that the model satisfactorily accounted for the travelers' eco-friendly airplane adoption intentions. The model comprised the concepts of green self-identity, care for environmental consequences, green moral obligation, attitude, and anticipated feelings. Moreover, we extended the model by considering the moderating impact of perceived risks. Overall, this study successfully provided a sufficient understanding of travelers' eco-friendly technology product adoption behaviors in the airline context. [ABSTRACT FROM AUTHOR]

In this paper, we considered the Length-biased weighted Lomax distribution and constructed new acceptance sampling plans (ASPs) where the life test is assumed to be truncated at a pre-assigned time. For the new suggested ASPs, the tables of the minimum samples sizes needed to assert a specific mean life of the test units are obtained. In addition, the values of the corresponding operating characteristic function and the associated producer’s risks are calculated. Analyses of two real data sets are presented to investigate the applicability of the proposed acceptance sampling plans; one data set contains the first failure of 20 small electric carts, and the other data set contains the failure times of the air conditioning system of an airplane. Comparisons are made between the proposed acceptance sampling plans and some existing acceptance sampling plans considered in this study based on the minimum sample sizes. It is observed that the samples sizes based on the proposed acceptance sampling plans are less than their competitors considered in this study. The suggested acceptance sampling plans are recommended for practitioners in the field. [ABSTRACT FROM AUTHOR]

For the direct-current (dc) electrical power distribution system onboard more electric aircraft, the voltage quality of dc bus is of a great concern since there could be significant harmonics distortions when feeding different power electronics loads. This problem can be potentially addressed by introducing a dc filter to the point-of-load converters regulated by the finite control set model predictive control (FCS-MPC). To optimize this filter, genetic algorithm (GA) is utilized for searching the optimal design, which guarantees a low mass and low power losses. Different from the conventional filter design methods, the proposed method treats $LC$ as design variables, which need to be optimized while ensuring the output power quality. First, relations among variables, operation conditions, and constraints are built based on commercial data and circuit simulations. Then, the design and optimization are developed with these relations and a Pareto front is finally given by GA. After that, the best design is obtained by an index integrating two objectives. Lastly, the design approach is verified by an experiment where an FCS-MPC regulated converter was used as a particular example fed by three different LC filters. [ABSTRACT FROM AUTHOR]