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The complex nonlinear and strongly coupled dynamics of small unmanned helicopters make mathematical modeling challenging. Traditional approaches often rely on least squares support vector machine (LSSVM) algorithms using standard kernel functions, which are limited in their learning and generalization capabilities, resulting in insufficient accuracy for flight control systems. This paper proposes an adaptive particle swarm optimization-based LSSVM (APSO-LSSVM) method, incorporating a self-constructed kernel function. Using Mercer’s theorem, the custom kernel addresses the limitations of conventional kernels and is integrated into the LSSVM framework. An adaptive particle swarm optimization algorithm, capable of dynamically adjusting inertia weights and learning factors, optimizes the model parameters, overcoming the standard particle swarm optimization’s tendency to get trapped in local optima. The model is trained using flight test data from a self-developed small unmanned helicopter, and its identification performance is cross-validated in the time domain against traditional models. Experimental results show that the proposed method significantly improves the modeling accuracy of small unmanned helicopters. [ABSTRACT FROM AUTHOR]

This paper introduces an adaptive neural network compensatory control approach designed for a 2-degree-of-freedom (2-DOF) helicopter system facing challenges such as input backlash and state constraints. The proposed methodology leverages a radial basis function (RBF) neural network to effectively approximate system uncertainties, mitigating the impact of nonlinear dynamics on control performance. To address the presence of nonlinear input backlash, a compensation technique is introduced to enhance the smoothness of input signals. In addition, for enhanced system safety, a barrier Lyapunov function is integrated to impose restrictions on position and velocity states, resulting in constrained control. Through a rigorous analysis using the Lyapunov direct method, this paper demonstrates the effectiveness of the proposed approach in achieving bounded stability of the system. The validation of the approach is further established through the presentation of simulation and experimental results, showcasing its effectiveness and feasibility in real-world applications. [ABSTRACT FROM AUTHOR]

Helicopter imaging classification and detection are crucial for autonomous navigation, military operations, search and rescue, and civil aviation management. This study utilized two helicopter image datasets, applying data augmentation techniques such as random resizing, cutting, horizontal rotation, rotation, and color adjustments, along with histogram equalization for contrast enhancement. Twentyfour helicopter classes were trained using GoogleNet and AlexNet architectures, while the YOLOv9c model was employed for object detection. The results revealed that the GoogleNet classification model achieved an 81% F1 score, and AlexNet reached 73%. In contrast, the YOLOv9c model demonstrated an average mean Average Precision (mAP) of 87%. These findings indicate that CNN architectures and YOLO are effective for helicopter image classification and detection, highlighting their potential applications in military, search and rescue, and civil aviation contexts. [ABSTRACT FROM AUTHOR]

A comprehensive flight control law design method based on adaptive control is presented in this paper. The proposed method consists of three basic modules—model decoupling, online system identification and adaptive pole placement. The model decoupling module decouples the helicopter flight dynamics model based on dynamic inversion technique. This procedure helps to reduce the difficulties in online system identification and adaptive controller design. In online system identification module, a recursive extended least squares algorithm is established to identify the augmented linear flight dynamics model which is composed of helicopter model and unideal noise model. The helicopter model parameters and the noise parameters are identified simultaneously which improves the identification accuracy as well as robustness. Pole placement is implemented in the last module, and an optimization method is developed to help selecting ideal poles. The adaptive rule in this step is designed based on eigenvalue analysis of the model to remove all unnecessary oscillations of the control parameters. An adaptive controller is designed according to the developed method for the UH-60A helicopter based on a nonlinear simulation program. Typical response types are also implemented. The simulation results show that the designed adaptive controller has high performance as well as robustness in both hover and forward flight. [ABSTRACT FROM AUTHOR]

Turbulent ship airwakes can present a major challenge for a pilot landing a helicopter to the ship. A recent study has proposed modifications to the hangar of a simple ship, the SFS2, to improve the air flow over the deck. To assess the effect of the proposed hangar modification on the helicopter and pilot, the unsteady air flow over the modified ship has been computed using time-accurate CFD, and then integrated with a full-motion flight simulator for a pilot to conduct deck landings to the original and modified ship geometries in wind speeds from 30 kt to 50 kt. The effectiveness of the proposed modification was assessed through pilot workload ratings for the landing task, and by recording pilot control inputs and helicopter states. The study has shown that there are some benefits from the hangar modifications. In the headwind the helicopter was deemed to be at the safe limit at 50 kt when operating to the original SFS2, while the limit was not reached in the 50 kt wind for the modified ship. In an oblique wind, the safe wind speed limit was found to be 40 kt for the original ship and 50 kt for the modified version. Although the improvements are not substantial, they do represent a positive outcome. [ABSTRACT FROM AUTHOR]

In this article, a fuzzy controller mathematical model synthesising method that uses cognitive computing and a genetic algorithm for automated tuning and adaptation to changing environmental conditions has been developed. The technique consists of 12 stages, including creating the control objects' mathematical model and tuning the controller coefficients using classical methods. The research pays special attention to the error parameters and their derivative fuzzification, which simplifies the development of logical rules and helps increase the stability of the systems. The fuzzy controller parameters were tuned using a genetic algorithm in a computational experiment based on helicopter flight data. The results show an increase in the integral quality criterion from 85.36 to 98.19%, which confirms an increase in control efficiency by 12.83%. The fuzzy controller use made it possible to significantly improve the helicopter turboshaft engines' gas-generator rotor speed control performance, reducing the first and second types of errors by 2.06...12.58 times compared to traditional methods. [ABSTRACT FROM AUTHOR]

This research introduces an input-shaping strategy for a firefighter helicopter evacuating water from a bucket suspended by a cable. A three-degree-of-freedom model analyzes the dynamics to minimise the bucket’s sway. The study explores various scenarios, including those involving variable mass, to assess the bucket’s swing and the helicopter’s kinematic stability during water evacuation. The input shaping technique is employed to enhance the speed of evacuation manoeuvres and achieve desired end conditions. The study also takes into account the system’s constraints and limitations during these manoeuvres. System parameters such as water mass, cable length, and input functions were analysed. Numerical simulations were performed, demonstrating the technique’s ability to reduce the system’s swinging. These results were benchmarked against an unoptimised reference case, confirming the method’s efficacy. [ABSTRACT FROM AUTHOR]

The tail drive shaft is easily hit by the ground antiaircraft machine gun in low-altitude helicopter combat, resulting in projectile penetration damage and directly jeopardizing the helicopter’s safety during flight. The projectile penetration damage will cause elastic–plastic deformation and failure damage to the tail drive shaft, and excite high-frequency stress waves suitable for projectile impact monitoring. To examine the effects of different impact parameters on the stress wave characteristics and damage from the tail drive shaft during projectile impact, the LS-DYNA is used to establish a dynamic model of projectile impact on the tail drive shaft. The passive monitoring experiment of projectile impact on the tail drive shaft is carried out based on the PZT piezoelectric sensor. It is concluded that both methods can obtain reliable stress wave signals and damage conditions through the comparison of experimental and simulation results. Then, the wavelet transform and short-time Fourier transform three-dimensional time–frequency are used to select the best frequency band for extracting the stress wave eigenvalues, along with the statistics and analysis of the stress wave characteristic values and damage degree under different impact parameters. The results show that the impact stress waveforms and high-frequency components are significantly different with the change in projectile impact parameters. There are significant differences among different impact parameters on the first trough amplitude, the two peak time intervals, the kurtosis factor, and the bullet hole damage generation laws. The functional relationship between the projectile impact parameters and the characteristic parameters of the stress wave, as well as the damage degree, are established. The research conclusion can provide theoretical reference and data support for projectile impact monitoring and damage assessment of the helicopter tail drive shaft. [ABSTRACT FROM AUTHOR]

Many police agencies – especially large police agencies – employ helicopter units as part of their operations. Helicopter units exhibit the potential to impact an array of policing outcomes, including efficiency and effectiveness. Helicopter units, however, have received only scant attention among scholarly literature. Drawing upon data from two different police agencies in the U.S.A., I provide an empirical snapshot of helicopter units as they operate in frontline policing. My analyses reveal that helicopter units engage in a variety of different activities, most of which are related to crime control, and contribute to a variety of different policing outputs, such as arrests and recoveries of stolen vehicles. My analyses also reveal that approximately half of calls for service handled by helicopter units are classified as crime-specific call-types and that helicopter units are generally quick to arrive at calls once dispatched. I discuss my findings with respect to both policing research and policing practice. I also use my findings to call for future research regarding the use of helicopter units in contemporary policing. [ABSTRACT FROM AUTHOR]

Differing from the traditional helicopter landing on land, due to ship motions induced by actual waves, the landing safety of shipboard helicopter on vessels in waves deserves to be studied. To provide a judgment basis for the timing of shipboard helicopter landing, a hydrodynamic analysis method based on the Long-Short-Term Memory (LSTM) neural network is proposed to achieve the real-time prediction of ship motions in this study. Firstly, the hydrodynamic formulations based on potential flow theory for nonlinear ship motions in waves are presented. The implementation details of the LSTM neural networks are described. Secondly, the numerical verification study is carried out in regular and irregular waves, respectively. Furthermore, a destroyer model is employed to illustrate the proposed framework, and the results corresponding to the different time scales in waves are presented. Finally, the work of this paper is summarized and the certain conclusions are drawn. [ABSTRACT FROM AUTHOR]

Based on the actual process of dipping sonar in on-call submarine searching, combined with the classic extended spiral search method, a multi machine dipping sonar on-call submarine searching model was established. A submarine motion model was built based on the possible avoidance measures that submarines may take during the on-call submarine searching. We calculate the variation of detection probability of suspended sonar with response time and response distance of dipping sonar. Moreover, we also analyze the military force requirements of dipping sonar for submarine search under different response time and response distance of dipping sonar. So the obtained relevant conclusions can provide theoretical basis for tactical decision-making of anti-submarine helicopter response submarine search. [ABSTRACT FROM AUTHOR]

For the unmanned helicopter system, the full-degree-of-freedom control problem is studied, while ensuring that the attitude constraints are within the specified range. Considering that the characteristics of the system such as strong nonlinearity, strong coupling, under driving, and intermediate control variables need to be guaranteed to be bounded, this paper reduces the strength of the nonlinearity and coupling through the feedback linearization method, and designs the controller to directly control the three positional degrees of freedom and the yaw angle. At the same time, this paper utilizes the obstacle Lyapunov function method to locally constrain the intermediate variables to indirectly control the roll angle and the pitch angle, thus ensuring that the helicopter's attitude is bounded. Combined with the nonlinear system control theory, the tracking error system is guaranteed to be bounded, while the system is analyzed for stability. Finally, the method effectiveness is validated through simulation examples. [ABSTRACT FROM AUTHOR]

In order to guarantee the model switching stability of uncertain tilt-rotor aircraft from the helicopter mode to the fixed-wing mode, a fuzzy adaptive switching control strategy is proposed based on the model-dependent average residence dwell time method. Firstly, the longitudinal motion system model of tilt-rotor aircraft is established. Secondly, the fuzzy logic system is constructed to approximate and handle the unknown uncertainty in the mode transition process of tilt-rotor aircraft. The fuzzy adaptive robust flight control strategy is presented to ensure the smooth switching of tilt-rotor aircraft, and the effectiveness of the proposed controller is strictly proved via the theoretical analysis. Finally, the simulation results show that the proposed control method can effectively realize the trajectory tracking in the mode transition process of tilt-rotor aircraft, and improve the maneuverability and stability of the aircraft. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Transporting passengers to maritime units is one of the most critical factors in the oil industry. Optimizing costs and reducing workforce exposure to flight hours is paramount. The target scenario for this study is Petrobras' operations in the Campos Basin, where more than 500 thousand passengers are transported annually. A model inspired by Murthy (Operations research (linear programming). bohem press, 2005) transportation problems is proposed, which aims to answer which helicopters from each base will have to fly how many flights per week to meet the demand of each of the maritime units. Current scenarios are analyzed with changes in the configuration of marine units, helicopter fleets, and airport bases. The results showed that the model represents very well the characteristics taken into account by the company, which presented financial gains with the optimization of the scenario today. Also, the scenarios with changes showed even more significant financial gains than the scenario currently adopted, indicating that the model helps support decisions to improve helicopter transport operations. [ABSTRACT FROM AUTHOR]

In this study, we present an improved linear quadratic closed-loop rotor vibration controller that uses a steady-state Kalman filter and an augmented integral controller to improve the traditional T-matrix-based rotor vibration controller. The proposed linearized vibration controller features closed-loop stability more rigorously than the conventional algebraic T-matrix-based controller. A relative multi-loop stability margin analysis was performed and examined using a nonlinear aeroservoelastic rotor software-in-the-loop simulation. The rotor aeroservoelastic simulation was performed using the multi-body dynamic analysis software DYMORE, equipped with a new improved inflow model employing multiple trailer time-marching free-vortex wakes. A linear time periodic representation of the rotor was identified from the exponentially modulated periodic response obtained using a recursive Fourier series filter. We found that the proposed linear controller showed improved numerical phase-margin prediction accuracy compared with the T-matrix-based method. Finally, the trade-off between the rotor vibratory load reduction performance and closed-loop stability was evaluated and discussed. We found that the proposed controller asymptotically reduced the N/rev vibratory loads that were included in the Kalman filter, and the amount of load reduction was similar to that predicted from the LTP rotor harmonic system.

Abstract This study investigates a novel tracking control with prescribed performance for an uncertain nonlinear 2‐DOF helicopter subject to actuator failure. The control design aims to address partial actuator faults, and to mitigate their effects, an adaptive auxiliary variable is introduced. Additionally, a neural network is employed to accurately approximate the system uncertainties. The prescribed performance is formulated as time‐varying constraints, and the barrier Lyapunov function (BLF) technique is applied to achieve the constrained control. Finally, the stability analysis of the closed‐loop system is provided, and the validity of the proposed control scheme is illustrated through a simulation study on the 2‐DOF helicopter system.

Abstract The critical role of specifying micro‐Doppler mode performance in the modelling and development of modern radar systems is investigated. The authors focus on the detection of micro‐Doppler modulation from light aircraft, analysing data from eight helicopters and nine propeller aircraft. With the growing need for accurate target classification in radar technology, incorporating micro‐Doppler detection metrics into radar performance specifications has become increasingly important. This research offers a novel approach to measuring the detectability of micro‐Doppler modulation relative to returns from the main fuselage. The investigation covers the impacts of various preprocessing techniques, polarisation, and aspect angle on detection capabilities. Findings reveal that, on average, micro‐Doppler modulation from propellers is detectable at distances between 50% and 100% of the range at which the fuselage is detected. For helicopters, this range decreases to between 30% and 80%. Additionally, the study introduces empirically derived statistical models designed to predict micro‐Doppler detection ranges in relation to fuselage returns, enhancing the predictability and specificity of radar system performance. This novel contribution presents a basis for improving radar system specifications, leading ultimately to more predictable and reliable light aircraft classification.

The research explores transition strategies of a coaxial compound helicopter transitioning to pure coaxial-rotor mode following a complete aft propeller failure. For that, a flight dynamics model is developed to predict the transition path, which is formulated as a multiphase trajectory optimization problem. Additionally, a revised aggressiveness indicator is proposed to quantify the transition difficulty. Next, the flight dynamics with and without the propeller and the accelerations at the propeller loss instant are discussed from a trim perspective. Finally, dynamic transitions are meticulously analyzed and compared using a multidimensional radar map to identify an effective strategy. Contrary to the static trim analysis, dynamic simulation results highlight the critical importance of pitch attitude control, longitudinal speed stability, and incidence instability. The potential threats include blade tip collision, significant height increase up to 300 m, and reverse longitudinal stick control regarding pitch attitude. To mitigate these risks and reduce pilot workload, we recommend gradually pitching up to enter the quasi-autorotation state. Additionally, slightly lowering the position of the propeller and maintaining a positive pitch attitude during normal flight can help improve aircraft transition stability. [ABSTRACT FROM AUTHOR]

This article introduces an enhanced non-approximated control technique for the pitch and altitude control systems of unmanned helicopters. It takes into account unpredictable external disturbances and system dynamics. The integration of prescribed performance control into unmanned helicopter systems significantly improves the transient and steady-state response capabilities. This approach avoids the computational complexities often associated with neural networks and fuzzy control methods. By avoiding the need for function approximation, which can introduce inaccuracies and computational overhead, the controller design process is streamlined. This method's simplicity and ability to handle unknown disturbances make it highly suitable for real-world implementation, where robustness and efficiency are paramount. Finally, simulations are conducted to showcase the improved transient and steady-state response capabilities achieved by the proposed approach. [ABSTRACT FROM AUTHOR]

This work presents a construction of a novel system for autonomous inspection of power transmission lines using a quadrotor helicopter. The aircraft follows the power lines at a constant distance and acquires high‐resolution images of the conductors, dampers, and towers. Monitoring of the vegetation under the power lines is also performed. The traditional inspection is carried out by helicopters equipped with high‐resolution cameras or by direct visual examination by personnel climbing over de‐energized power lines. However, visual inspection is time‐consuming, labor‐intensive, and dangerous, and often, helicopter cameras cannot capture the acute details needed for accurate and comprehensive examinations. This work successfully evaluates a mathematical model for the quadrotor helicopter used in autonomous inspection through simulations and flight experiments. Two control strategies for power line tracking are compared: a classical PID and a fuzzy PD control. Several simulations and experimental results confirm the efficiency of both control laws, but the fuzzy controller performs better under strong wind disturbances. The results of this work will be implemented by an electric power company to inspect electrical transmission facilities regularly. © 2024 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Aim: This initial Norwegian study aimed to quantify the vibrations and sounds experienced by neonates when they were transported by helicopter in an incubator. Methods: Two neonatal manikins weighing 500 and 2000 g were placed in a transport incubator and transported in an Airbus H145 D3 helicopter during standard flight profiles. The vibrations were measured on the mattress inside the incubator and the sound levels were measured inside and outside the incubator. Results: The highest vibration levels were recorded during standard flight profiles when the lighter manikin was used. These ranged 0.27–0.94 m/s2, compared to 0.27–0.76 m/s2 for the heavier manikin. The measurements exceeded the action levels set by the European Union Vibration Directive for adult work environments. The sound levels inside the incubator ranged 84.6–86.3 A‐weighted decibels, with a C‐weighted peak level of 122 decibels. The sound levels inside the incubator were approximately 10 decibels lower than outside, but amplification was observed in the incubator at frequencies below 160 Hz. Conclusion: Vibrations were highest for the lighter manikin. The sound levels during helicopter transport were higher than recommended for neonatal environments and sounds were amplified within the incubator at lower frequencies. [ABSTRACT FROM AUTHOR]

The usage areas of rotary or fixed wing unmanned aerial vehicles (UAV) have become very widespread with technological developments. For this reason, UAV designs differ in terms of aerodynamic design, flight performance and endurance depending on the intended use. In this study, maximising of the autonomous flight performance of the unmanned helicopter produced at Erciyes University using an optimisation algorithm is discussed. For this purpose, the input parameters of the dynamic model are chosen as blade length, blade mass density, blade chord width and blade twist angle of the unmanned helicopter and the proportional, integral, derivative gain coefficients of the lateral axis of the autopilot. The output parameters of the dynamic model are selected as settling time, rise time and maximum overshoot, which are autonomous performance parameters. The dynamic model consisting of helicopter and autopilot parameters is integrated into the back-tracking search optimisation (BSO) algorithm as an objective function. In the optimization process, where mean squared error (MSE) is used as the performance criterion, optimum input and output values were determined. Thus, helicopter and autopilot parameters, which are among the factors affecting autonomous performance, are taken into account with equal importance and simultaneously. Simulations show that the obtained values are satisfactory. With this approach based on the optimisation method, complex and time-consuming dynamic model calculations are reduced, time and cost are saved, and practicality is achieved in applications. Therefore, this approach can be an innovative and alternative method to improve UAV designs and increase flight performance compared to classical methods. [ABSTRACT FROM AUTHOR]

In the present paper, a flight dynamics model is adopted to represent the trim and stability characteristics of a side-by-side helicopter in hovering conditions. This paper develops a numerical representation of the rotorcraft behavior and proposes a set of guidelines for trimming and linearizing the highly coupled rotor dynamics derived by the modeling approach. The trim algorithm presents two nested loops to compute a solution of the steady-state conditions averaged around one blade's revolution. On the other hand, a 38-state-space linear representation of the helicopter and rotor dynamics is obtained to study the effects of flap, lead–lag, and inflow on the overall stability. The results are compared with an analytical framework developed to validate the rotorcraft stability and compare different modeling approaches. The analysis showed that non-uniform inflow modeling led to a coupled longitudinal inflow–phugoid mode which made the vehicle prone to dangerous instabilities. The flap and lead–lag dynamics introduced damping in the system and can be considered beneficial for rotor dynamics. [ABSTRACT FROM AUTHOR]

This research work emphasizes on the development aspects of a cartridge cable cutter for helicopter application. This cartridge is used to rescue hoist system during emergency for helicopter application under adverse conditions. It is an electrically initiated cartridge in which two electrical squibs are used with specified current and voltage. As the cartridge is initiated, the squib gets incandescent and initiates an explosive train. A cartridge cable cutter is a propellant actuated device (PAD) that generates hot combustion gases having high temperature and pressure on burning of gun powder and propellant inside the cartridge case. The cable cutter cartridge under study is filled with energetic materials (EM) such as propellants and gun powder. It releases the energy very quickly which acts on the projectile i.e. the cutter in actual system. A projectile velocity measurement was carried out using Doppler RADAR (radio detection and ranging). To assess the projectile velocity is the unique design feature in armament field. It is responsible for the measurement of the projectile velocity at the muzzle end of velocity test rig (VTR). The minimum and maximum projectile velocities were experimentally measured in between 70 ms−1 and 150 ms−1. The projectile velocity measurement is an evaluation methodology as performance parameter of this cartridge. The cartridge under study has been developed meeting structural, functional and mechanical requirements. The cartridge has undergone various exhaustive qualification tests during development phase. The cartridge was thus designed, qualified and validated through rigorous development trials. The main objective of this article is to address development aspects of the cartridge cable cutter for helicopter application. In conclusion, after successful design, development and qualification trials, the cartridge was found to meet all the functional and operational requirements considering the end use. [ABSTRACT FROM AUTHOR]

In previouswork, a motion sickness prediction model aimed at vertical lift applications was developed. To validate this model, flight tests with an MBB Bo-105 Helicopter owned and operated by the DLR were conducted. In total, 32 test subjects were flown in 16 sorties on 30 min sinusoidal flight paths of various frequencies. The test design and implementation included the development of a suitable measurement flight instrumentation, auditive cueing systems for accurate following of the test trajectory, and questionnaires for recording motion sickness during flight. The results are analyzed, and it is shown that the previously developed motion sickness prediction model agrees well with the motion sickness observed during flight in the case of medium motion sickness. [ABSTRACT FROM AUTHOR]

Research on helicopter dispatching has received considerable attention, particularly in relation to post-disaster rescue operations. The survival chances of individuals trapped in emergency situations decrease as time passes, making timely helicopter dispatch crucial for successful rescue missions. Therefore, this study investigates a collaborative helicopter rescue routing problem with time window and limited survival time constraints, solving it using an improved iterative greedy (IIG) algorithm. In the proposed algorithm, a heuristic initialization strategy is designed to generate an efficient and feasible initial solution. Then, a feasible-first destruction-construction strategy is applied to enhance the algorithm's exploration ability. Next, a problem-specific local search strategy is developed to improve the algorithm's local search effectiveness. In addition, the simulated annealing (SA) method is integrated as an acceptance criterion to avoid the algorithm from getting trapped in local optima. Finally, to evaluate the efficacy of the proposed IIG, 56 instances were generated based on Solomon instances and used for simulation tests. A comparative analysis was conducted against six efficient algorithms from the existing studies. The experimental results demonstrate that the proposed algorithm performs well in solving the post-disaster rescue helicopter routing problem. [ABSTRACT FROM AUTHOR]

Nighttime affects pilot visual scan patterns and increase the risks of helicopter operations, contributing to many helicopter accidents and incidents. Several past studies have attempted to examine the effect of nighttime on helicopter pilot gaze behavior, but researchers had limited success due to the difficulty of collecting representative data under real flight conditions. The present study attempted to address this challenge by conducting a real flight study involving daytime and nighttime traffic pattern tasks and using a Tobii Glasses 3 eye-tracking device to collect helicopter pilot eye-tracking data. This study preliminarily explored the feasibility of data collection in real flight conditions in the context of eye-tracking research on civil helicopter pilots in China. Due to safety considerations, only one pilot was recruited to collect data in multiple tasks. Differences and correlations were examined for all gaze behavior metrics. The results suggested that pilot gaze behavior metrics and their correlations differed between daytime and nighttime flights in aspects critical to aviation safety. Pilot gaze behavior also varied with the flight phase. The findings from this study serve as a reference for optimizing helicopter pilot training systems, improving pilot performance during nighttime flights, and ensuring flight safety on helicopters. [ABSTRACT FROM AUTHOR]

This study investigates a novel tracking control with prescribed performance for an uncertain nonlinear 2‐DOF helicopter subject to actuator failure. The control design aims to address partial actuator faults, and to mitigate their effects, an adaptive auxiliary variable is introduced. Additionally, a neural network is employed to accurately approximate the system uncertainties. The prescribed performance is formulated as time‐varying constraints, and the barrier Lyapunov function (BLF) technique is applied to achieve the constrained control. Finally, the stability analysis of the closed‐loop system is provided, and the validity of the proposed control scheme is illustrated through a simulation study on the 2‐DOF helicopter system. [ABSTRACT FROM AUTHOR]

The critical role of specifying micro‐Doppler mode performance in the modelling and development of modern radar systems is investigated. The authors focus on the detection of micro‐Doppler modulation from light aircraft, analysing data from eight helicopters and nine propeller aircraft. With the growing need for accurate target classification in radar technology, incorporating micro‐Doppler detection metrics into radar performance specifications has become increasingly important. This research offers a novel approach to measuring the detectability of micro‐Doppler modulation relative to returns from the main fuselage. The investigation covers the impacts of various preprocessing techniques, polarisation, and aspect angle on detection capabilities. Findings reveal that, on average, micro‐Doppler modulation from propellers is detectable at distances between 50% and 100% of the range at which the fuselage is detected. For helicopters, this range decreases to between 30% and 80%. Additionally, the study introduces empirically derived statistical models designed to predict micro‐Doppler detection ranges in relation to fuselage returns, enhancing the predictability and specificity of radar system performance. This novel contribution presents a basis for improving radar system specifications, leading ultimately to more predictable and reliable light aircraft classification. [ABSTRACT FROM AUTHOR]

This study investigates the potential of an optimized combination of active nose droop and active Gurney flap (CADAG) in a new flow control strategy to manage dynamic stall over a pitching blade section under variable Mach number flow. The optimization method employs the genetic algorithm coupled with a computational fluid dynamic (CFD) solver and artificial neural network. The base blade section belongs to a section positioned at r/R=0.865 of the rotor blade of the UH-60A helicopter in forward flight condition. A high relative angle of attack on the retreating side makes the flow susceptible to dynamic stall. A nose droop is employed to control the dynamic stall of the blade section, and a Gurney flap is used to maintain the balance of the generated lift of the blade during 360° of rotation. A comprehensive investigation is performed to determine the most significant parameters affecting the performance of the present combined active flow control. The ratio of the total generated lift to the drag is chosen as the objective function of the optimization. Results show that this ratio and the total generated lift in one rotation cycle increase by 193% and 13%, respectively, at the optimum condition of the present combined active flow control, while the ratio of the generated lift over the advancing side to the retreating side is equal to that of the base blade section. In addition, the dynamic stall hysteresis loop reduces significantly, and the maximum value of the drag coefficient and the negative aerodynamic damping decrease up to 87% and 83% compared to the base blade section, respectively. In general, the proposed innovative combined active flow control is an adjustable method to alleviate dynamic stall and improve the aerodynamic performance of rotary wings in different operation conditions. Practical Applications: The rotary blades are extensively used in rotorcraft, turbo engines, and wind turbines. Despite their massive use, they suffer from some essential issues, of which the most important one is the so-called dynamic stall. Dynamic stall is a complex phenomenon that limits the performance of the rotary blades. Due to the physics governing a rotary wing, such as a helicopter rotor blade, dynamic stall and flow separation are very common. Understanding dynamic stall physics and providing solutions to prevent it is still one of the main challenges of aerodynamic scientists. The present study introduces a novel adjustable method for practically alleviating the dynamic stall on helicopter blade section in forward flight conditions to improve its aerodynamic performance in different operational conditions. A comprehensive investigation is carried out to determine the key parameters affecting the proposed method. These findings can serve as a valuable tool for other researchers to develop various active flow control strategies. This article applies an optimization process using artificial neural networks, genetic algorithms, and CFD tools, which forms a comprehensive framework that can be easily extended to other applications. [ABSTRACT FROM AUTHOR]

The coaxial compound helicopter has been offered as an idea for a high-performance rotorcraft that possesses high-speed qualities that conventional helicopters do not. This work seeks to create a flight dynamics model of a coaxial compound helicopter and investigate its trim, stability, and controllability. Regarding this, this study builds aerodynamic models for each component of a coaxial compound helicopter (coaxial rotor, fuselage, horizontal stabilizer, vertical stabilizer, and propeller). For coaxial rotor configuration, an equivalent flapping model, a reflected model, an inflow model taking the upper and lower rotor's impact into account, and a phased cyclic pitch model are done. A nonlinear coaxial compound helicopter mathematical model is constructed, and the trim across the entire flight envelope is carried out. The nonlinear model is linearized in order to evaluate stability and control derivatives. The trim results exhibit a high degree of concordance with the reference, thereby validating the flight dynamics model. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to describe a numerical simulation method of ice accretion on BO105 helicopter blades for predicting the effects of trailing edge flap deflection on ice accretion. Design/methodology/approach: A numerical simulation method of ice accretion is established based on Myers model. Next, the shape and location of ice accretion of NACA0012 airfoil are calculated, and a comparison between calculated results and experimental data is made to validate the method. This method is used to investigate the effect of trailing edge flap deflection on ice accretion of a rotor blade. Findings: The numerical method is feasible and effective to study the ice accretion on helicopter rotor blades. The downward deflection of the trailing edge flap affects the shape of the ice. Practical implications: This method can be further used to predict the ice accretion in actual flights of the helicopters with multielement airfoils. Originality/value: The numerical simulation method here can lay a foundation of the research about helicopter flight performance in icing condition through predicting the shape and location of ice accretion on rotor blades. [ABSTRACT FROM AUTHOR]

This paper investigates the operational patterns and techniques of aerial fire fighting. It is demonstrated that manoeuvrability and endurance are the main characteristics when choosing air tactical aircraft; focus is on load capability for helicopters and air tankers. Water tank filling and deployment techniques are evaluated. Aircraft using pressure deployment systems are found to produce more uniform and heavy coverage in comparison with gravity systems. ADS-B open source data of flight operations and performance was collected. Operational patterns are found to be independent on the size of particular aircraft category (non-amphibious and amphibious air tanker, helicopter, air-tactical aircraft). Effectiveness and cost are modelled using the retardant dropped per operation and the average number of daily missions. The largest aircraft, Type-I helicopters and very large air tankers (VLAT) are found to be the most effective water- and retardant-dropping aircraft. The best cost-to-litre-dropped ratio for water-dropping aircraft is attributed to Type-III helicopters and amphibious Type-III aircraft; for retardant-dropping aircraft, VLAT are most effective. To maximise fire fighting effectiveness, Type-I helicopters and VLAT should be used as far as possible, with pressure deployment systems. [ABSTRACT FROM AUTHOR]

HeliCAT-DARTS is a high-fidelity rotorcraft dynamics simulator developed for the design and development of rotorcraft for planetary exploration. While initially developed for the life cycle use of the Ingenuity Mars Helicopter mission, the simulator now supports a broad range of rotorcraft configurations and applications. HeliCAT provides a GNC testbed and aerial mobility analysis platform for rotorcraft design, closed-loop flight software development, verification and validation (V&V), and mission operations. This article discusses the design and use of the HeliCAT simulator and results from technology demonstrations and missions. [ABSTRACT FROM AUTHOR]

Sling configurations significantly influence the coupled dynamics of the helicopter with slung load system (HSLS), resulting in alterations to handling qualities (HQs) that remain inadequately understood. This study introduces a computer-oriented, generalized method for constructing the HSLS model with various sling configurations. To evaluate the HQs of 1-point, 2-point, and 4-point sling configurations, both the stability and response criteria outlined in ADS-33E and a newly proposed criterion for slung loads towards the updated ADS-33F were employed. Modal analysis was conducted to elucidate the coupled mechanisms of the HSLS under different sling configurations. The findings reveal that the dynamics of the main rotor can attenuate the lateral swing motions of the load in the 4-point sling configuration. While multiple-point sling configurations can enhance the helicopter's bandwidth, they also amplify the magnitude notch in the helicopter's response. Nevertheless, when a larger hook distance is employed, the notch frequency is sufficiently distant from the load swing bandwidth, leading to a reduced degradation in HQs. A 4-point configuration with lateral and longitudinal hook distances equal to twice the width and length of the slung load is recommended in practice to achieve sufficient swing stability and mitigate HQ degradation. [ABSTRACT FROM AUTHOR]

This paper presents a novel incremental sliding mode control scheme to address the attitude-tracking issue in both the helicopter and airplane modes of an electric vertical takeoff and landing vehicle, guaranteeing the stabilization of the attitude-tracking error within a predefined time. Firstly, an incremental model of the vehicle's attitude control system with external disturbances is established. The high-order terms of the incremental model and instantaneous perturbations are retained as lumped terms rather than directly discarding them to ensure the accuracy of the incremental model. Then, a novel nonsingular sliding surface is developed. Once the ideal sliding motion is established, the states on the sliding surface will converge to the equilibrium point within a predefined time. Furthermore, a predefined-time incremental sliding mode controller is developed by using sliding mode control and incremental control techniques. It effectively reduces the reliance on the model information and attenuates the effects of external disturbances. The predefined-time stability of the entire controlled system is rigorously proven using Lyapunov theory. Finally, numerical simulation examples verify the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Abstract A signal time‐frequency results inversion method is proposed for extracting micro‐motion features of rotor targets under low signal‐to‐noise ratios (SNRs). In the case of low SNRs, the echo's energy of rotor targets is mainly concentrated in the flash's echo component. Conventional micro‐motion feature extraction of rotor targets primarily utilises the sinusoidal modulation feature in time‐frequency results, whose energy is much lower than the flash. Under low SNRs, the sinusoidal modulation in the echo's time‐frequency results will be submerged in the noise, making feature extraction challenging. A deep learning network is used to inverse the time‐frequency results containing sinusoidal modulation based on the flash's features in the time‐frequency results. Based on the inversion time‐frequency results, the GS‐IRadon algorithm is used to extract micro‐motion features, which can significantly reduce the times of IRadon transformations and improve feature extraction speed and accuracy. Through simulation and analysis, a novel method using a deep learning network like UNet can effectively inverse time‐frequency results under low SNRs, providing a new technical approach for micro‐motion feature extraction. Time‐frequency results inversion is a novelty method used to achieve micro‐motion feature extraction of rotor targets.