Aerial Mode Research Articles

A sub-μs accuracy GPS alternative using electrical transmission grids as precision timing networks.

It is widely recognised that over-reliance on GNSS (e.g GPS) for time synchronisation represents an acute threat to modern society, and a diversity of alternatives are required to mitigate the threat of an outage. This paper proposes a GNSS alternative using time dissemination over national scale transmission or distribution networks. The method utilises the same frequency bandwidth and coupling technology as established power line carrier technology in conjunction with modern chirp Spread Spectrum modulation. The basis of the method is the transmission of a time synchronised chirp from a central substation, coupled into the aerial modes of the transmission line. During GNSS operation, all substations can estimate the time of flight by correlating the received chirp with a time-synchronised local copy. During GNSS outage, time sychronisation to the central substation is maintained by correcting for the precalculated time of flight. It is shown that recent advances in chirp spread spectrum allow for a computationally efficient algorithm with the capacity to compute hundreds of thousand of chirp correlations every second, facilitating timing accuracy which satisfies the majority of smart grid applications. ATP-EMTP simulations of the method on large transmission networks demonstrate sub-μs timing accuracy even in the presence of low SNR and impulsive noise. An FPGA prototype demonstrates experimentally sub-μs accuracy for time dissemination over a distance of 700 m. Averaging over time is shown to facilitate satisfactory performance down to , which could extend the range of the system to a national scale and a time dissemination network invulnerable to wireless spoofing and jamming attack vectors.

Switched Control of HyTAQs: A Framework of Stochastic Hybrid Fuzzy Systems With Variable Dimensions.

This article is concerned with the switched control of hybrid terrestrial and aerial quadrotors (HyTAQs) via stochastic hybrid fuzzy system methodology, in which the terrestrial and aerial mode switching is subject to a Markov process with lower-bounded sojourn time. For the first time, the bimodal nonlinear attitude dynamics of HyTAQs is analyzed and modeled based on the Takagi-Sugeno (T-S) fuzzy model, and switched fuzzy controllers are developed to stabilize the hybrid fuzzy system. The characteristic of state dimension switching caused by ground contact is modeled via the singular system presentation with mode-dependent singularity matrices, based on which numerically testable criteria of stability and stabilization in the stochastic sense are derived. Compared with the previous control approaches based on Markov jump systems, the proposed one is able to describe the deterministic dwelling duration in practice and integrate multiple subsystems with algebraic equations of different dimensions, while achieving lower conservatism. Illustrative examples are provided to demonstrate the effectiveness and potential of the designed variable-dimension fuzzy controllers.

Fault nature identification and location scheme for distribution network based on active injection from IIDG

In view of the difficulty in passively identifying the nature of faults in distribution networks and the high equipment cost of existing active detection schemes, a permanent fault identification and location scheme using an inverter-interfaced distributed generator (IIDG) connected to feeders for signal injection is proposed. After the faulty feeder is isolated, the power electronics in the IIDG are switched on for a short time and a voltage signal is injected into the feeder through the modified LCL filter and grid-connected transformer. The analysis shows that the aerial mode voltage of the feeder will not remain 0 under permanent faults. A highly sensitive criterion with fixed thresholds is constructed using approximate entropy (ApEn) to identify fault nature. Then the fault distance is further calculated based on the detected mutation point of the aerial mode voltage under permanent faults. The correctness of the theory and the effectiveness of the scheme are verified in PSCAD/EMTDC simulations.© 2017 Elsevier Inc. All rights reserved.

Vertiport Selection in Hybrid Air–Ground Transportation Networks via Mathematical Programs With Equilibrium Constraints

Urban air mobility is a concept that promotes aerial modes of transport in urban areas. In these areas, the location and capacity of the vertiports–where the travelers embark and disembark the aircraft–not only affect flight delays, but can also aggravate the congestion of ground vehicles by creating extra ground travel demands. We introduce a mathematical model for selecting the location and capacity of the vertiports that minimizes traffic congestion in hybrid air-ground transportation networks. Our model is based on a mathematical program with bilinear equilibrium constraints. Furthermore, we show how to compute a global optimal solution to this mathematical program by solving a mixed integer linear program. We demonstrate our results via the Anaheim transportation network model, which contains more than 400 nodes and 900 links.

Urban On-Demand Delivery via Autonomous Aerial Mobility: Formulation and Exact Algorithm

The implementation of the autonomous unmanned aerial mobility is a game changer for the on-demand delivery service in the crowded urban setting. In this study, the first of its kind commercial unmanned aerial vehicle (UAV) urban delivery program in China is targeted. Different from the traditional ground pickup and delivery services, the aerial mode considers not only the time window constraints, but also the spatial conflicts incurred during the take-off and landing operations of UAVs. To obtain the optimal flying routes of the focused problem, a mixed integer programming model is formulated. Due to its inherent complexity, the optimal schedule cannot be attained within acceptable time via the off-the-shelf solvers. To help speed up the solving process, a branch-and-cut based exact algorithm is proposed, together with a series of customized valid inequalities. To further accelerate, a greedy insertion heuristic is designed to secure high-quality initial solutions. In the numerical section, it is observed that the algorithm proposed in this paper can help solve the real-life on-demand UAV delivery problem to near optimum (within 5% optimality gap) within reasonable computation time (in 5 minutes). <i>Note to Practitioners</i>&#x2014;With the increase of labor cost, the distribution cost increases very rapidly. In the meantime, the employment of automated vehicles for logistics reshapes the landscape of the urban last-mile delivery. As an efficient courier carrier, the unmanned aerial vehicle (UAV) is trending the autonomous delivery endeavour. When integrating UAVs into the urban delivery program, practitioners need to pay special attention to the scheduling of UAVs at the operational level in addition to the hardware of the UAVs. To help solve the UAV dispatch problem, we propose an online scheduling scheme, considering the spatial conflict constraints in the actual UAV operations. And an exact algorithm is designed to accelerate the solving process. Numerical experiments demonstrate that the proposed algorithm can achieve near optimal dispatch plan with 5% optimality gap in 5 minutes. Furthermore, it is discovered that the demand pooling is an essential decision to make for UAV-based delivery. Longer pooling time can increase the UAV efficiency with more realized demand information, but too much pooling could lead to prolonged customer waiting and a low service level.

Rogowski coil-based autonomous fault management strategy using Karen Bell Transformation for earthed active distribution networks

This paper introduces fault type identification, fault section selection, and fault phase selectivity using a Karen Bell Transformation matrix in earthed distribution grids coupled with Doubly Fed Induction Generator (DFIG). Rogowski Coil’s (RC) model is estimated using a system identification toolbox to obtain the precise terminal voltage. This model is calculated and verified using experimental results for the RC’s primary input current and output voltage. Then, the estimated voltage relies on the current signals in the measuring point. The transient slope of the ground and aerial modes voltages is extracted during the fault to classify the fault type, discriminate the fault section and identify the faulted phase in every cycle. Further, earth faults are detected using ground and phase faults using aerial modes. The relative polarity of the front slopes at the terminals of each section created by the fault voltage is extracted to perform faulty section discrimination. The value of aerial modes is used to identify the defective phase selectivity. The overall protection selectivity function’s integration procedure with modified autonomous control is proposed for earthed distribution systems. The Transient Selectivity Function (TSF) was presented in unearthed and compensated grids in the literature. After estimating the RC voltage output at each agent, the discrete Fourier transform (DFT) phasor extraction is done. Different standard fault cases and system conditions are investigated to evaluate the proposed scheme’s behavior. Simulation results are designed using the ATP-EMTP program. The simulation results obtained validate the effectiveness of the scheme proposed in this work.

Fault location of flexible grounding distribution system based on multivariate modes and kurtosis calibration

Aiming at the problems of large fault location errors when the traditional traveling wave fault location is applied to flexible ground distribution systems. This paper proposed the fault location of flexible grounding distribution system based on multivariate modes and kurtosis calibration. Firstly, a disturbance signal is generated by putting a small resistor in parallel. This signal reaches the fault point and undergoes a sudden change, generating an aerial mode traveling wave signal. Secondly, it used the multivariate variational mode decomposition algorithm to decompose the aerial mode current and extracts the fault features. Then, the discrete kurtosis value is calculated for the highest frequency intrinsic mode function component. The moment of maximum kurtosis is the arrival time of the aerial mode current. Finally, it adopted the head-end detection device to calculate the fault distance. For the complex topology of the flexible ground distribution systems, the localization equation of the overhead line, cable line, and hybrid lines are studied, and the pseudo-fault points are excluded by adding auxiliary devices at the branch end. The simulation results demonstrate that the proposed method can accurately locate faults and is not affected by the fault's initial phase angle, transition resistance, and location.

Teager energy assisted variational mode decomposition‐based fault location technique for STATCOM compensated system

AbstractModern power systems are structurally complex and thus experience transient events. For secure and reliable operation, quick system restoration is required whenever transient phenomenon like line faults occurs. Fault location techniques (FLTs) aid in faster restoration process. However, the accuracy of FLTs gets affected in presence of static synchronous compensator (STATCOM) since STATCOM compensates the dip in measured voltage during fault thereby affecting the fault current signals. Therefore, in this paper, a Teager energy assisted variational mode decomposition (VMD) based traveling wave FLT is developed for transmission lines with STATCOM. The proposed FLT considers two‐terminal instantaneous voltage signals for locating faults. In this FLT, the signals are first decoupled into modal signals and then aerial mode of the signals is chosen for decomposition using VMD. The signals are decomposed via VMD to level three producing mode three signals. Teager energy of the resultant signals is obtained and from the first peak of the energy signals, arrival time of waves (ATWs) is estimated. These estimated ATWs are used to calculate fault location and percentage error. To validate the performance of proposed FLT, several test cases with different fault scenarios are considered and the results are compared with existing techniques. The results prove efficacy of proposed FLT for studied system.

Two-terminal traveling wave fault location based on successive variational mode decomposition and frequency-dependent propagation velocity

This paper proposes a two-terminal traveling wave fault location method based on Successive Variational Mode Decomposition (SVMD) and frequency-dependent propagation velocity. Firstly, SVMD is used to extract all Intrinsic Mode Functions (IMFs) and their center frequencies of the aerial mode voltages in a successive manner. The maximum IMF with the highest center frequency is used for further processing. Secondly, The propagation velocity is obtained by frequency–velocity characteristic curve and the arrival time of traveling wavefront is determined by the normalized Teager Energy Operator (TEO). Finally, considering the time-domain and frequency-dependent characteristics of traveling wave, the fault distance is estimated by combining the arrival time, frequency and propagation velocity. PSCAD/EMTDC simulation results show that the proposed method achieves reliable and robust performance under different fault scenarios and outperforms compared existing methods. • SVMD is introduced to adaptively decompose the fault traveling wave signal. • The propagation velocity is treated as a variable and estimated for fault location. • The proposed method is reliable and robust under different fault scenarios.

Fault Location Based on Comprehensive Grey Correlation Degree Analysis for Flexible DC Distribution Network

Flexible DC distribution networks have a strong capacity for new energy consumption and have received extensive attention from scholars in recent years, but fault location for DC distribution lines is a difficult task. To solve this problem, we propose using a comprehensive grey correlation degree analysis to analyze the similarity of aerial mode traveling differential current waveforms at the first and last ends of a DC line, thus achieving fault location by obtaining the optimal time shift. Additionally, we built a six-terminal flexible DC distribution network model in Matlab/Simulink for simulation and validation, showing that the method can complete the rapid and accurate location of all types of faults on a DC line, and that it possesses an anti-transition resistance capability, making it suitable and highly reliable for cases of low sampling frequency.

Monopolar Grounding Fault Location Method of DC Distribution Network Based on Improved ReliefF and Weighted Random Forest

Compared with the pole-to-pole short circuit, the fault characteristics are not obvious when a monopolar grounding fault occurs in a DC distribution network, and it is difficult to locate the fault accurately. To solve this problem, this paper proposes a fault location method based on improved ReliefF and Weighted random forest (WRF). The 24 time and frequency-domain fault features of the postfault aerial mode current are calculated, and the most useful features are selected to form the optimal feature subset for input to the fault location estimator. In this paper, the ReliefF algorithm is utilized for automatic feature selection and obtaining the weights of features. In addition, the WRF algorithm is used to build the fault location estimator. Considering the fault location, fault resistance, noise and time window length, the Matlab/Simulink simulation platform is used to simulate the fault situation and compare it with other algorithms. The simulation results show that the average positioning error of the fault location method is less than 0.1%, which is not affected by the fault resistance and has strong robustness.

SytaB: A Class of Smooth-Transition Hybrid Terrestrial/Aerial Bicopters

This work details the design, modeling and control of SytaB, a vehicle capable of hybrid terrestrial/aerial mobility with smooth transition, where the structure embedding a bicopter is adopted for the first time. In contrast to previous hybrid terrestrial/aerial vehicles with a quadrotor embedded, SytaB not only requires less energy for the same takeoff weight, but also regulates its attitude less frequently to restrain the vibration of sensors. Three modes, the terrestrial/aerial/transitional modes, are considered <styled-content style="color:black" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">for the vehicle</styled-content> , and the dynamics modeling and controller design of each mode are <styled-content style="color:black" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">carried out</styled-content> . The transition between terrestrial and aerial locomotions is smooth compared with the case of non-inclusion <styled-content style="color:black" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">of</styled-content> transitional mode such that the bounce and shake of the vehicle are alleviated. The energy efficiency is compared between the terrestrial and aerial modes, and between the energy-saving and high-maneuverability paradigms (a choice enabled in the terrestrial mode of SytaB). Experimental results are presented to demonstrate the potential of SytaB, the effectiveness of the designed controllers, and the necessity of considering the transition process.

Air Medical Casualty Evacuation in High Altitude: An Experience of 100 Cases in High Altitude and Hilly Terrain of Northern India

Objectives: This article describes the on ground challenges faced by the medical care team deployed for transferring critically ill patients by air from remote locations of the high altitude and hilly terrain to definitive health care facility. Methods: All intubated critical patients requiring definitive and super specialty medical care, transferred by air from high altitude hilly terrain to tertiary care hospital during Jan 2016 to Dec year 2020, analyzed in this retrospective study. Results: The total duration of flight was between 40 – 150 min and average being 83 min. Twenty four patients were transferred by fixed wing aircraft and rest 76 by helicopters. All patient were given sedation in form of injection fentanyl 1mcg/kg in dividing doses and boluses of propofol 10 mg intravenously during transfer. The most common change noticed was fall in oxygen saturation with incidence almost 100% of the patients. The mean fall in saturation was 17.29%. Four patients required injection atropine for bradycardia which resulted with decrease of Saturation of peripheral oxygen (SpO2). Conclusion: Transferring a critically ill patient by road to distant medical centers is often not an option because of losing the golden hour of the medical care. Here comes the importance of aeromedical evacuation for a timely transfer for early medical attention. But shifting the critical patients through aerial mode requires planning and poses a variety of challenges. Keywords: Air­evacuation, High altitude, Air ambulance

A new traveling‐wave detection method for fault location based on two sequential sliding windows and curve fitting

The basis of traveling wave-based fault location methods is to extract the arrival times of transient signals in the power network. In this paper, a new method for extracting the traveling wave arrival times is presented. For this purpose, the aerial modes of three-phase voltage signals are extracted and two sequential sliding windows of unequal length move along with this signal. By fitting a line to the samples inside each of the two windows and calculating the angle between them, the traveling wave arrival times can be determined with high accuracy. Because this takes place in the time domain, there is no need to switch between time and frequency domains similar to those in Fourier transforms. On the other hand, fitting curves reduce the negative effects of noise and sampling frequency changes. EMTP-ATP is applied to perform the transient simulations and the results are then analysed in MATLAB to conduct the sensitivity analysis against the measurement noises, the sampling frequency, and the fault parameters. The proposed technique is compared to the common techniques such as discrete wavelet transforms and Hilbert Huang transforms. The results demonstrate that the proposed technique has acceptable performance and covers the drawbacks of common methods.

Air sac and gill vasotocin receptor gene expression in the air-breathing catfish Heteropneustes fossilis exposed to water and air deprivation conditions.

Heteropneustes fossilis is a facultative air-breathing freshwater catfish and inhabits ponds, ditches, swamps, marshes and rivers that dry up in summers. It possesses a pair of unique tubular accessory respiratory organ (air sac), which is a modification of the gill chamber and enables it to live in water-air transition zones. In the catfish, three vasotocin (Vt) receptor gene paralogs viz., v1a1, v1a2 and v2a were identified for Vt actions. In the present study, the receptor gene transcripts were localized in the gill and air sac by in situ hybridization, and their expression levels in relation to water and air deprivation conditions were investigated by quantitative RT-PCR. The catfish were exposed to 1h and 2h in gonad inactive (resting) and gonad active (prespawning) phases. The gene paralogs showed overlapping distribution in the respiratory epithelium of primary and secondary lamellae of gills and reduced lamellae of the air sacs. In water deprivation (forced aerial mode of respiration) experiment, v2a expression showed a high fold increase in the air sac, which was unchanged or inhibited in the gill. Both v1a1 and v1a2 expression was significantly upregulated in the air sac but showed varied responses in the gill. The gill v1a1 expression was unchanged in the resting phase and modestly upregulated in the prespawning phase. The gill v1a2 expression was modestly upregulated at 1h in both phases but unchanged at 2h. In the air deprivation experiment (forced aquatic respiration), the v2a expression in the air sac was inhibited except for a mild stimulation at 1h in the prespawning phase. In the gill, the v2a expression was stimulated with a steep upregulation at 2h in the prespawning phase. Both v1a1 and v1a2 expression was significantly high in the gill but only modestly increased or unchanged in the air sac. The expression patterns point to a functional distinction; the V2 type receptor expression was higher in the air sac during forced aerial respiration, and the V1 type receptor expression was highly prominent in the gill during forced aquatic respiration. Water and air deprivation treatments caused a significant increase in plasma cortisol level, and the stimulation was higher in the water deprivation fish in the resting phase but equally prominent in the water and air deprivation groups in the prespawning phase. The results indicate that the changes in the expression patterns of Vt receptor genes may be a sequel to stress (hypoxic, metabolic and osmotic), and both Vt and cortisol may interact to counter the stress responses. This study shows that Vt has a new role in the control of air sac functions.

A hybrid artificial neural network and wavelet packet transform approach for fault location in hybrid transmission lines

This paper presents a single-ended traveling-wave-based fault location (F.L.) method in a hybrid transmission line (HTL) with an overhead section combined with a cable section. For this, the software has been developed in a MATLAB programming environment. Wavelet packet transform is used to extract transient information of the aerial mode current and voltage signals. The normalized current and voltage wavelet entropy (features) are fed to the feature selection part of the software. Regarding the HTL construction, the optimal features are obtained using the support vector machine and particle swarm optimization. A three-layer artificial neural network is trained to identify the faulty section and half using the optimal features of post fault signals. The square of the aerial mode voltage wavelet coefficients is applied to locate the fault using Bewley's diagram. The proposed approach is applied for F.L. in HTL. Transient simulations are obtained through EMTP-RV software for various fault scenarios, including fault types, resistances, inception angles, and locations. The post fault signals are fed to the developed software. The results illustrate the high accuracy of the proposed method in comparison to previous works.

Traveling-Wave-Based Fault Location Method for Hybrid Distribution Network Mixed with Three-Phase and Phase to Phase Supply Lines

In China, a hybrid distribution network mixed with three-phase main lines and phase to phase supply lines can be found in many MV distribution networks due to lower cost of using two lines from three-phase main lines as well as lower cost of phase to phase transformer. For such a hybrid distribution network it is a challenge for traditional fault location techniques. This paper presents a traveling wave fault location method based on double-terminal measurement techniques. The proposed method analyses the traveling wave propagation mechanism of both aerial mode and zero mode components for a fault. The method then determines which mode component is used for the fault location according to fault types. The method has been developed and assessed on a typical distribution network using ATP power network simulation tool. The tests were conducted under various fault scenarios. The results show that zero mode component is more effective for a fault on the phase of three-phase main lines which is not linked to the phase to phase supply lines. However for a phase-to-phase fault, aerial mode component is more effective. For the remaining fault types, either aerial or zero mode component can be used.

All-Terrain Cyclocopter Capable of Aerial, Terrestrial, and Aquatic Modes

This paper describes the design and experimental validation of an all-terrain cyclocopter micro air vehicle capable of power-efficient aerial, terrestrial, and aquatic locomotion with seamless transition between the modes. The vehicle has a mass of 1010 g and solely relies on its four cycloidal rotors (cyclorotors) to achieve all modes of locomotion. The cyclorotor rotational speeds and thrust vectors are individually modulated to sustain stable hover in aerial mode. A similar control strategy using aerodynamic forces generated by cyclorotors is also implemented for aquatic locomotion. The wheels are efficiently integrated into the carbon fiber rotor endplates since cyclorotors rotate about the horizontal axis. As a result, the cyclocopter maneuvers in terrestrial mode by directly relying on motor torque. Seamless transition is accomplished using a retractable landing gear system equipped with polystyrene foam pontoons. In aerial mode, the cyclorotors operate at 1550 rpm and consume 232 W to sustain hover. Forward translation at 2 m/s in terrestrial mode requires 28 W, which is a 88% reduction from hover. In aquatic mode, the cyclorotors operate at 348 rpm and consume 19 W, which is a 92% reduction from hover. Overall, a versatile platform capable of multimodal operation is successfully demonstrated with only a modest addition in total mass.

Feeding Ecology, Behaviour and Habitat Utilization of Black Drongo (Dicrurus Macrocercus) in Pothwar Plateau, Pakistan

Black Drongo is an insectivorous bird native to Pakistan. The present study focused on its feeding preferences, behaviour, ecology and habitat relationships. The study was carried out from first week of December, 2019 to the second week of April, 2020 in the two villages of Rawalpindi named as Daultala (Location-I) and Nata Gujarmall (Location-II). Observations were made by point count method on foot using line transect method. Air (52.27%) was the most commonly used feeding substrate. Aerial feeding mode (52.27%) is preferred over plant or tree gleaning (n=58) and ground feeding (n=47). Most common perching site was man made obstacle, wire (37.72%). Thirteen indigenous tree species and two exotic trees including Eucalyptus (Eucalyptus camaldulensis) and Bottle brush (Callistemon citrinus) were used as perching site by Black Drongo throughout the study. Black Drongo remained solitary (36.36%) during feeding rituals and shared (63.63%) its intimate habitat with other birds. At Location-I and Location-II, habitat was shared with 12 and 16 bird species, respectively. The mean time of prey capturing attempt was lower at Location-I (1.93±0.17 min) than Location-II (2.16±0.16 min). The time range of prey capturing attempt was (0.1±0.16 min) to (11.5±0.17 min). Black Drongo captured prey successfully by first attempt (59.54%), maximum attempts noted were 6. After preying attempts Black Drongo came back to same perch site (67.27%); which is a representative of resource abundance.

Fault location in multilateral distribution network with electric vehicle charging load

AbstractIn a multilateral distribution network, faults at different locations can generate the same voltage and current at the substation; hence, the calculated fault location can correspond to several places in the network. To avoid this major problem, a two‐terminal travelling wave‐based fault location method is presented in this article, which at first identifies the faulted lateral in the distribution network and then estimates the exact fault location. The proposed fault location scheme uses wavelet energy entropy of the recorded three‐phase current signals and the magnitude of ground mode component wavelet modulus maxima (WMM) for fault detection and fault type identification in the network. After that, the faulted lateral identification followed by the exact fault location is performed using the aerial mode component WMM of the fault‐generated current transients. Since the integration of electric vehicle (EV) charging load is increasing day by day to the distribution network, the performance of the proposed algorithm is tested with EV charging load along with distributed generation integrated into the distribution network. Modeling and simulation of the distribution network and EV load are performed in MATLAB/SIMULINK. The simulation results show that the proposed method can accurately locate fault under different operating conditions.