Modeling Method and Control Strategy for Hose-Drogue Aerial Refueling System

Conventional method for hose-drogue model of aerial refueling system is known to be complex due to the flexible body of hose.And as reported,drogues are unstable in atmospheric turbulence,which greatly decreases docking success rates.This paper proposes a dynamic model for a hose-drogue aerial refueling system based on Kane equation and rigid multi-body dynamics,and analyzes its performance.Furthermore,the nonlinear dynamic model is linearized at the equilibrium point and simplified from full order to 2 nd order.Based on the simplified 2 nd order model,active control strategies,including proportion integral derivative(PID)and liner quadratic regulator(LQR)control laws,are designed to inhibit the pendulum movement of drogue due to,atmospheric turbulences.Numerical simulation results show the significant correctness of the proposed dynamic model by steady-state drag and balance position of drogue when the tanker flights under different conditions.Moreover,the steady state position error varies within 1 cm,thanks to either controller,when the drogue suffers from moderate-level atmospheric turbulences.Further,the PID controller exhibits better control effect and higher control precision than LQR controller.

A Stochastic Flight Problem Simulation to Minimize Cost of Refuelling

Commercial airline companies are continuously seeking to implement strategies for minimizing costs of fuel for their flight routes as acquiring jet fuel represents a significant part of operating and managing expenses for airline activities.A nonlinear mixed binary mathematical programming model for the airline fuel task is presented to minimize the total cost of refueling in an entire flight route problem.The model is enhanced to include possible discounts in fuel prices,which are performed by adding dummy variables and some restrictive constraints,or by fitting a suitable distribution function that relates prices to purchased quantities.The obtained fuel plan explains exactly the amounts of fuel in gallons to be purchased from each airport considering tankering strategy while minimizing the pertinent cost of the whole flight route.The relation between the amount of extra burnt fuel taken through tinkering strategy and the total flight time is also considered.A case study is introduced for a certain flight rotation in domestic US air transport route.The mathematical model including stepped discounted fuel prices is formulated.The problem has a stochastic nature as the total flight time is a random variable,the stochastic nature of the problem is realistic and more appropriate than the deterministic case.The stochastic style of the problem is simulated by introducing a suitable probability distribution for the flight time duration and generating enough number of runs to mimic the probabilistic real situation.Many similar real application problems are modelled as nonlinear mixed binary ones that are difficult to handle by exact methods.Therefore,metaheuristic approaches are widely used in treating such different optimization tasks.In this paper,a gaining sharing knowledge-based procedure is used to handle the mathematical model.The algorithm basically based on the process of gaining and sharing knowledge throughout the human lifetime.The generated simulation runs of the example are solved using the proposed algorithm,and the resulting distribution outputs for the optimum purchased fuel amounts from each airport and for the total cost and are obtained.

Guidance and Control for UAV Aerial Refueling Docking Based on Dynamic Inversion with L_1 Adaptive Augmentation

The guidance and control for UAV aerial refueling docking based on dynamic inversion with L1 adaptive augmentation is studied.In order to improve the tracking performance of UAV aerial refueling docking,aguidance algorithm is developed to satisfy the tracking requirement of position and velocity,and it generates the UAV flight control loop commands.In flight control loop,based on the 6-DOF nonlinear model,the angular rate loop and the attitude loop are separated based on time-scale principle and the control law is designed using dynamic inversion.The throttle control is also derived from dynamic inversion method.Moreover,an L1 adaptive augmentation is developed to compensate for the undesirable effects of modeling uncertainty and disturbance.Nonlinear digital simulations are carried out.The results show that the guidance and control system has good tracking performance and robustness in achieving accurate aerial refueling docking.

Safety Assessment for Autonomous Aerial Refueling Based on Reachability Analysis

Autonomous aerial refueling(AAR)has demonstrated significant benefits to aviation by extending the aircraft range and endurance.It is of significance to assess system safety for autonomous aerial refueling.In this paper,the reachability analysis method is adopted to assess system safety.Due to system uncertainties,the aerial refueling system can be considered as a stochastic system.Thus,probabilistic reachability is considered.Since there is a close relationship between reachability probability and collision probability,the collision probability of the AAR system is analyzed by using reachability analysis techniques.Then,the collision probability is accessed by using the Monte-Carlo experiment method.Finally,simulations demonstrate the effectiveness of the proposed safety assessment method.

Expedition to Mars North Pole and Creation There a Scientific Research Base

A project of the expedition to the north pole of Mars, which is carried out in two stages, has been developed. In the first stage, a space refueller and a mobile solar battery are delivered to the icy surface of the north pole of Mars. The delivery is carried out with the help of electric rocket ER-7, driven by the electric rocket engine “MARS”, and the source of electricity is a solar battery from gallium arsenide. In the second stage, the space train is formed from two interconnected ER-7 rockets and an orbital takeoff-landing capsule TLC-2, in which three astronauts land on the surface and carry out a complex of physical, biological and geological researches on Mars surface. The space refueller has been developed, which melts the water ice on the surface of Mars and with the help of an electrolyser and a liquefier produces fuel and oxidizer for the operation of the chemical rocket engine of the takeoff-landing capsule. To move astronauts from the north pole to the equator, a spacecraft—?marsoplane, which consists of the electric rocket ER-7 and the takeoff-landing capsule TLC-1 is developed. The duration of the expedition is 110 days at a cost of 2 billion dollars.

Interpretation of GB/T 26779-2021,Hydrogen fuel cell electric vehicles refueling receptacle

With the development of fuel cell electric vehicle industry in China,the 70-MPa hydrogen storage cylinders have been widely applied on vehicles in recent years.The revised standard,GB/T 26779-2021,Hydrogen fuel cell electric vehicle refueling receptacle,was released on March 9,2021 with added stipulations for the 70-MPa hydrogen refuelling receptacle.The main technical contents of GB/T 26779-2021 and its similarities and differences with GB/T 26779-2011 are discussed in this paper.

Numerical Analysis of Refueling Drogue Oscillation During Refueling Docking

Refueling docking at different velocities is simulated by using computational fluid dynamics(CFD)method.The Osher scheme and S-A turbulence model are used to solve the compressible Navier-Stokes equations,and the Delaunay mapping dynamic grid method is also employed.All the numerical results show that the velocity of refueling docking is very important for aerial refueling.When the velocity is lower than 3m/s,the refueling drogue will move upward with obvious cycle staggering,while moving upward with slight cycle staggering at the speed of3m/s.The results can be referenced by aerial refueling design.

LQR Integrated with Fuzzy Control for Aerial Refueling Autopilot

Linear Quadratic Regulator （LQR） is modem linear control that is suitable for multivariable state feedback and is known to yield good performance for linear systems or for nonlinear systems where the nonlinear aspects are presented. The fuzzy control is known to have the ability to deal with nonlinearities without having to use advanced mathematics. The LQR integrated fuzzy control （LQRIFC） simultaneously makes use of the good performance of LQR in the region close to switching curve, and the effectiveness of fuzzy control in region away from switching curve. A new analysis of the fuzzy system behavior presented helps to make possible precise integration of LQR features into fuzzy control. The LQRIFC is verified by simulation to suppress the uncertainty instability more effectively than the LQR besides minimizing the time of the mission proposed.

Modeling and Simulation for Refueling Boom and Receiver inCoupled Mode

In coupled mode,the major problem of boom refueling system is undesirable nozzle loads.An automated load alleviation system(ALAS)is needed to alleviate nozzle loads.In order to simulate dynamic of the system and to validate ALAS,dynamic model is developed.Two models are established,which are the static model and the moving model,named after the two relative states between the fixed boom and the extension boom.Kane method is employed as main method considering system′s multi-body characteristics.D′Alembert′s principle is used to calculate nozzle loads.Simulation is conducted to research the effects of position disturbance and velocity disturbance on nozzle loads.Results indicate that position disturbance plays a more significant role in inducing nozzle loads.A fuzzy control law based ALAS is validated using the formulated model.It is concluded that this model can simulate system dynamic and validate ALAS.

MARSZUG—A Space Train for Regular Delivery of Astronauts onto Mars

A project of the space train MARSZUG intended for regular delivery of astronauts to Mars is considered. In the first stage of the flight, the astronauts with the help of the carrier rocket equipped with a chemical rocket engine are delivered to the international space station (ISS). To deliver astronauts from Earth’s orbit to Mars orbit, a space train design consisting of two rockets, which have superconductive magnetoplasma electric engine MARS, has been developed. For the first time, a combined propulsion system MARS-M has been developed for the train movement, allowing carrying out the pitching, yaw and rotation of the rocket. This greatly simplifies the rocket control system and increases its reliability. The energy source of the electric engines is a sliding solar panel made of gallium arsenide. Working substance to create reactive thrust of electrorocket engines—hydrogen is stored in a liquid state in the cryogenic tank located along the longitudinal axis of the rocket. In the nasal part of the front electric rocket, a shaft rotating in a superconductive bearing is located. The shaft has a cylindrical nozzle, on which with the help of docking units two takeoff-landing capsules TLC-1 and TLC-2 are installed with which help landing and takeoff from the surface of Mars is carried out. This allows astronauts to constantly stay during the flight under the influence of gravity. To refuel the space train with liquid hydrogen in the orbit of Mars, the design of a space refueler with a chemical rocket engine is developed. The developed space train is able to regularly deliver astronauts to the surface near the northern pole of Mars.

Assessing the Effects of Atmospheric Properties on Energy Commodity Storage and Distribution:Focus on Correlation with Temperature and Wind Variations

Gasoline vapour emission is an insidious topical air pollution and hazardous health issue underestimated at both storage and utilization levels.Since gasoline station is one public built environment found in every locality,the problem of unguarded vapour emission through this facility needs serious attention.This study measures the close relationship between the emission rate and the ambient properties with specific objectives including evaluating operational emission level and determining the correlation coefficient.Field measurements of evaporated quantities were conducted at selected station in Enugu State.For the random variation in emission quantity,the wheel spun approach was used to obtain all round mean value per month.Also,meteorological records of Nsukka municipal city for the period under consideration were obtained and analyzed for possible relationship by calculation of coefficient of correlation.The findings from this study suggest that gasoline evaporation is strongly correlated with ambient temperature and wind speed variations,respectively.Thus,high concentration of emitted gasoline on a hot day constitutes a potential thermal mass,high in embodied energy and if excited by light wind speed,can flow many distances away from the station.This insightful information on the emission will be useful to environmentalist and decision makers and has potential to bring about policy changes within the industry.

Airlines Cost Control in China:An Overlooked Perspective

With the deepening of economic globalization,the business environment has seen profound changes.The cost of aviation fuel has grown to represent a significant portion of air transportation costs for“energy-dependent”airlines.The cost of aviation fuel makes up a sizeable amount of Chinese airlines’cost structure and is increasingly limiting their profitability.The question of how to control the cost of aviation fuel from various perspectives has garnered widespread attention.This paper puts forward an overlooked perspective-the procurement strategy.Firstly,it describes the necessity of aviation fuel cost control,and then analyzes specific cases of aviation fuel procurement cost control.Finally,it proposes several effective suggestions from the perspective of aviation fuel procurement,aiming to improve the refined management of Chinese airlines’aviation fuel procurement.

Dynamic modeling of a hose-drogue aerial refueling system and integral sliding mode backstepping control for the hose whipping phenomenon

Dynamic modeling of a hose-drogue aerial refueling system（HDARS） and an integral sliding mode backstepping controller design for the hose whipping phenomenon（HWP） during probe-drogue coupling are studied. Firstly, a dynamic model of the variable-length hose-drogue assembly is built for the sake of exploiting suppression methods for the whipping phenomenon.Based on the lumped parameter method, the hose is modeled by a series of variable-length links connected with frictionless joints. A set of iterative equations of the hose＇s three-dimensional motion is derived subject to hose reeling in/out, tanker motion, gravity, and aerodynamic loads accounting for the effects of steady wind, atmospheric turbulence, and tanker wake. Secondly,relying on a permanent magnet synchronous motor and high-precision position sensors, a new active control strategy for the HWP on the basis of the relative position between the tanker and the receiver is proposed. Considering the strict-feedback configuration of the permanent magnet synchronous motor, a rotor position control law based on the backstepping method is designed to insure global stability. An integral of the rotor position error and an exponential sliding mode reaching law of the current errors are applied to enhance control accuracy and robustness. Finally,the simulation results show the effectiveness of the proposed model and control laws.

Verification of monocular and binocular pose estimation algorithms in vision-based UAVs autonomous aerial refueling system

With the high focus on autonomous aerial refueling(AAR), it becomes increasingly urgent to design efficient methods or algorithms for solving the AAR problems in complicated aerial environments. A vision-based technology for AAR is developed in this paper, and five monocular and binocular visual algorithms for pose estimation of the unmanned aerial vehicles(UAVs) are adopted and verified in this AAR system. The real-time on-board vision system is also designed for precise navigation in the UAVs docking phase. A series of out-door comparative experiments for different pose estimation algorithms are conducted to verify the feasibility and accuracy of the vision algorithms in AAR.

N-fold Bernoulli probability based adaptive fast-tracking algorithm and its application to autonomous aerial refuelling

Recently,deep learning has been widely utilized for object tracking tasks.However,deep learning encounters limits in tasks such as Autonomous Aerial Refueling(AAR),where the target object can vary substantially in size,requiring high-precision real-time performance in embedded systems.This paper presents a novel embedded adaptiveness single-object tracking framework based on an improved YOLOv4 detection approach and an n-fold Bernoulli probability theorem.First,an Asymmetric Convolutional Network(ACNet)and dense blocks are combined with the YOLOv4 architecture to detect small objects with high precision when similar objects are in the background.The prior object information,such as its location in the previous frame and its speed,is utilized to adaptively track objects of various sizes.Moreover,based on the n-fold Bernoulli probability theorem,we develop a filter that uses statistical laws to reduce the false positive rate of object tracking.To evaluate the efficiency of our algorithm,a new AAR dataset is collected,and extensive AAR detection and tracking experiments are performed.The results demonstrate that our improved detection algorithm is better than the original YOLOv4 algorithm on small and similar object detection tasks;the object tracking algorithm is better than state-of-the-art object tracking algorithms on refueling drogue tracking tasks.

Development of a system configuration for a solar powered hydrogen facility using fuzzy logic control

Solar energy is a natural resource which can be harnessed to provide clean electricity for hydrogen production systems.However, this technology is not widely used because of control issues, particularly for hydrogen refuelling stations. At present,direct or DC-DC converter couplings are the most common system configurations for hydrogen refuelling stations. However, these system configurations are costly and suffer from gas shortage at hydrogen refuelling stations. Furthermore, the hydrogen produced by such system configurations varies considerably depending on the levels of solar radiation. In order to address these issues, a new system configuration is proposed, incorporating the feedback signal of the storage level in the control system. The photovoltaic(PV) system, electrolyzer, and storage tank are integrated with a fuzzy logic controller(FLC) to determine the backup current compensation for electrolyzer operation in order to obtain the minimum power required for hydrogen production. The proposed FLC is constructed with three input variables which are the PV current, hydrogen storage level, and the battery state of charge. The rules-based fuzzy inference process is based on the proposed configuration which combines the advantages of direct and DC-DC converter coupling configurations. The simulation results show that the proposed configuration offers better adaptability to variable radiation conditions compared to other methods. This gives a more promising option for ensuring the adequacy of hydrogen supply at hydrogen refuelling stations.

A monocular visual measurement system for UAV probe-and-drogue autonomous aerial refueling

Purpose–The purpose of this paper is to develop a monocular visual measurement system for autonomous aerial refueling(AAR)for unmanned aerial vehicle,which can process images from an infrared camera to estimate the pose of the drogue in the tanker with high accuracy and real-time performance.Design/methodology/approach–Methods and techniques for marker detection,feature matching and pose estimation have been designed and implemented in the visual measurement system.Findings–The simple blob detection(SBD)method is adopted,which outperforms the Laplacian of Gaussian method.And a novel noise-elimination algorithm is proposed for excluding the noise points.Besides,a novel feature matching algorithm based on perspective transformation is proposed.Comparative experimental results indicated the rapidity and effectiveness of the proposed methods.Practical implications–The visual measurement system developed in this paper can be applied to estimate the pose of the drogue with a fast speed and high accuracy and it is a feasible measurement strategy which will considerably increase the autonomy and reliability for AAR.Originality/value–The SBD method is used to detect the features and a novel noise-elimination algorithm is proposed.Besides,a novel feature matching algorithm based on perspective transformation is proposed which is robust and accurate.

Hybrid Robotic Arm for Autonomous Aerial Refueling

Autonomous aerial refueling technology is gaining increasing attention to enhance aircraft combat capabilities.Current research on autonomous refueling focuses mainly on flight control laws,with little attention to the automation of refueling pipes.This leads to high demands on control law performance and navigation accuracy,making it difficult to ensure reliability.To address this,we propose a robotic arm system capable of automatic docking during the flexible aerial refueling process.The system uses a conical kinematic space configuration,offering enhanced stability and impact resistance.The frame-type structure achieves a lightweight design.Additionally,we establish a single-objective optimization model for the connecting rod dimensions and apply a genetic algorithm(GA)for their optimization.We also propose a trajectory-fitting calibration theory based on the robotic arm's special configuration and complete its movement accuracy calibration using a laser tracker.This calibration method reduces the robotic arm's motion error by 71%,achieving an absolute positioning accuracy better than 3.5 mm,which meets the requirements for autonomous aerial refueling.In summary,this research presents a hybrid robotic arm that meets automatic docking requirements,offering a new approach to autonomous aerial refueling.

Unmanned autonomous air-to-air refueling intelligent docking technology

Unmanned autonomous Air-to-Air Refueling(AAR)capability is the key guarantee to support the distant-field,high-intensity and durable operations of the penetration counterair combat system.In the future,the long-range unmanned reconnaissance and attack platform can reach the maximum flight range requirement through AAR.At present,large transport aircraft platforms in China are still equipped with probe-and-drogue systems,and the refueling mode is gradually changing from manned to unmanned autonomous operation.The docking process is the riskiest and most important part,and there are strict safety,precision,and efficiency requirements for refueling operation,especially during close-distance docking and formation maintenance phases.In this paper,five issues that need to be solved to achieve autonomous AAR docking are summarized.On this basis,five key technology development needs are proposed to solve these engineering issues.Finally,some prospects are given.

Aerial refueling scheduling of multi-receiver and multi-tanker under spatial-temporal constraints for forest firefighting

Forest fires pose a significant threat to human life and property,so the utilization of unmanned aircraft systems provides new ways for forest firefighting.Given the constrained load capacities of these aircraft,aerial refueling becomes crucial to extend their operational time and range.In order to address the complexities of firefighting missions involving multi-receiver and multi-tanker deployed from various airports,first,a fuel consumption calculation model for aerial refueling scheduling is established based on the receiver path.Then,two distinct methods,including an integrated one and a decomposed one,are designed to address the challenges of establishing refueling airspace and allocating tasks for tankers.Both methods aim to optimize total fuel consumption of the receivers and tankers within the aerial refueling scheduling framework.The optimization problem is established as nonlinear optimization models along with restrictions.The integrated method seamlessly combines refueling rendezvous point scheduling and tanker task allocation into unified process.It has a complete solution space and excels in optimizing total fuel consumption.The decomposed method,through the separation of rendezvous point scheduling and task allocation,achieves a reduced computational complexity.However,this comes at the cost of sacrificing optimality by excluding specific feasible solutions.Finally,numerical simulations are carried out to verify the feasibility and effectiveness of the proposed methods.These simulations yield insights crucial for the practical engineering application of both the integrated and decomposed methods in real-world scenarios.This comprehensive approach aims to enhance the efficiency of forest firefighting operations,mitigating the risks posed by forest fires to human life and property.