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.

GYRO BIAS ON-ORBIT CALIBRATION FOR MICRO SATELLITES

According to gyro application in micro-satellites, a new gyro bias real-time on-orbit calibration technology is presented and it is independent of any other sensors. The approach relies on gyro on-orbit measurements restricted by satellite attitude dynamics and estimates the gyro bias generated when the gyro is electrified. Observability of the calibration model is analyzed and applicable conditions of the technology are derived. Simulation results indicate that the calibration algorithm is accurate and robust at gyro sampling rate, and its convergence speed is fast. Within the given attitude dynamics model error, the convergence time is less than 100 s and the convergence accuracy is about 1.0 （°）/h. Calibration performance can meet requirements of spacecraft operations.

On-orbit sleep problems of astronauts and countermeasures

Sufficient sleep duration and good sleep quality are crucial to ensure normal physical and mental health, cognition and work performance for the common people, as well as astronauts. On-orbit sleep problem is very common among astronauts and has potential detrimental influences on the health of crewmembers and the safety of flight missions. Sleep in space is becoming a new medical research frontier. In this review we summarized on-orbit sleep problems of astronauts and six kinds of causes, and we presented the effects of lack of sleep on performance as well as mental and physical health, then we proposed seven kinds of countermeasures for sleep disturbance in spaceflight, including pharmacologic interventions, light treatment, crew selection and training, Traditional Chinese Medicine and so on. Furthermore, we discussed and oriented the prospect of researches on sleep in space.

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.

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.

On-orbit target tracking and inspection by satellite formation

A new type of estimator is developed for the satellite formation to track and inspect on-orbit targets. The follower satellite in the formation works without relative sensors, and its target pointing commands are derived based on relative orbital dynamics. The centralized estimator based on truth measurement is designed, however, this estimator is proved unstable because of the lack of necessary measurement information. After that, an alternative estimator based on pseudo measurement is designed, and its observability and controllability are analyzed to qualitatively evaluate the convergence performance. Finally, an on-orbit target inspection scenario is numerically simulated to verify the performance of the estimator based on pseudo measurement.

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.

On-orbit Geometric Calibration of Linear Push-broom Optical Satellite Based on Sparse GCPs

The paper presents a geometric calibration method based on the sparse ground control points (GCPs), aiming to the linear push-broom optical satellite. This method can achieve the optimal estimate of internal and external parameters with two overlapped image pair along the charge-coupled device (CCD), and sparse GCPs in the image region, further get rid of the dependence on the expensive calibration site data. With the calibrated parameters, the line of sight (LOS) of all CCD detectors can be recovered. This paper firstly establishes the rigorous imaging model of linear push-broom optical satellite based on its imaging mechanism. And then the calibration model is constructed by improving the internal sensor model with a viewing-angle model after an analysis on systematic errors existing in the imaging model is performed. A step-wise solution is applied aiming to the optimal estimate of external and internal parameters. At last, we conduct a set of experiments on the ZY-3 NAD camera and verify the accuracy and effectiveness of the presented method by comparison.

GF-5 VIMI On-Orbit Calibration Instrument and Performance

The Visible and Infrared Multispectral Imager (VIMI) is one of the main payloads of the GF-5 satellite. It has 12 spectral bands covering the wavelength from visible light to thermal infrared. The imager designed life is 8 years. In order to monitor and correct the radiometric performance of the imager for a long time and meet the user’s demand for the quantitative remote sensing application, the expandable diffuser used for calibration in full FOV and full optical path method is designed. The solar diffuser is installed on the front side of the optical system and does not affect the normal imaging of VIMI. When VIMI need calibration, the diffuser is expand to the front of optical system via the driving mechanism. According to the characteristics of the GF-5 satellite orbit, the requirement of the calibration energy and the installation matrix of the imager relative to the satellite, the expansion angle of the diffuser is 39 degrees. The 430 mm × 430 mm large-size PTEE diffuser is manufactured to ensure full FOV and full optical path calibration. The diffuser’s directional hemispherical reflectance is higher than 95% from 420 nm to 2400 nm and variation of BRDF in the direction of imager observation is better than 2.5%. The diffuser stability monitoring radiometer is designed to monitor the on-orbit attenuation performance of the diffuser. Results of ground simulation experiments and preliminary on-board calibration experiments were introduced.

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.

Calibration chain design based on integrating sphere transfer radiometer for SI-traceable on-orbit spectral radiometric calibration and its uncertainty analysis

In order to satisfy the requirement of SI-traceable on-orbit absolute radiation calibration transfer with high accuracy for satellite remote sensors,a transfer chain consisting of a fiber coupling monochromator（FBM） and an integrating sphere transfer radiometer（ISTR） was designed in this paper.Depending on the Sun,this chain based on detectors provides precise spectral radiometric calibration and measurement to spectrometers in the reflective solar band（RSB） covering 300–2500 nm with a spectral bandwidth of 0.5–6 nm.It shortens the traditional chain based on lamp source and reduces the calibration uncertainty from 5% to 0.5% by using the cryogenic radiometer in space as a radiometric benchmark and trap detectors as secondary standard.This paper also gives a detailed uncertainty budget with reasonable distribution of each impact factor,including the weak spectral signal measurement with uncertainty of 0.28%.According to the peculiar design and comprehensive uncertainty analysis,it illustrates that the spectral radiance measurement uncertainty of the ISTR system can reach to 0.48%.The result satisfies the requirements of SI-traceable on-orbit calibration and has wider significance for expanding the application of the remote sensing data with high-quality.

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.

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.

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.

Multi-Feature Fusion Based Relative Pose Adaptive Estimation for On-Orbit Servicing of Non-Cooperative Spacecraft

On-orbit servicing, such as spacecraft maintenance, on-orbit assembly, refueling, and de-orbiting, can reduce the cost of space missions, improve the performance of spacecraft, and extend its life span. The relative state between the servicing and target spacecraft is vital for on-orbit servicing missions, especially the final approaching stage. The major challenge of this stage is that the observed features of the target are incomplete or are constantly changing due to the short distance and limited Field of View (FOV) of camera. Different from cooperative spacecraft, non-cooperative target does not have artificial feature markers. Therefore, contour features, including triangle supports of solar array, docking ring, and corner points of the spacecraft body, are used as the measuring features. To overcome the drawback of FOV limitation and imaging ambiguity of the camera, a "selfie stick" structure and a self-calibration strategy were implemented, ensuring that part of the contour features could be observed precisely when the two spacecraft approached each other. The observed features were constantly changing as the relative distance shortened. It was difficult to build a unified measurement model for different types of features, including points, line segments, and circle. Therefore, dual quaternion was implemented to model the relative dynamics and measuring features. With the consideration of state uncertainty of the target, a fuzzy adaptive strong tracking filter( FASTF) combining fuzzy logic adaptive controller (FLAC) with strong tracking filter(STF) was designed to robustly estimate the relative states between the servicing spacecraft and the target. Finally, the effectiveness of the strategy was verified by mathematical simulation. The achievement of this research provides a theoretical and technical foundation for future on-orbit servicing missions.

On-orbit Geometric Calibration and Preliminary Accuracy Evaluation of GF-14 Satellite

GF-14 satellite is a new generation of sub-meter stereo surveying and mapping satellite in China,carrying dual-line array stereo mapping cameras to achieve 1∶10000 scale topographic mapping without Ground Control Points(GCPs).In fact,space-based high-precision mapping without GCPs is a challenging task that depends on the close cooperation of several payloads and links,of which on-orbit geometric calibration is one of the most critical links.In this paper,the on-orbit geometric calibration of the dual-line array cameras of GF-14 satellite was performed using the control points collected in the high-precision digital calibration field,and the calibration parameters of the dual-line array cameras were solved as a whole by alternate iterations of forward and backward intersection.On this basis,the location accuracy of the stereo images using the calibration parameters was preliminarily evaluated by using several test fields around the world.The evaluation result shows that the direct forward intersection accuracy of GF-14 satellite images without GCPs after on-orbit geometric calibration reaches 2.34 meters(RMS)in plane and 1.97 meters(RMS)in elevation.

A parallel pipeline connected-component labeling method for on-orbit space target monitoring

The paper designs a peripheral maximum gray differ-ence(PMGD)image segmentation method,a connected-compo-nent labeling(CCL)algorithm based on dynamic run length(DRL),and a real-time implementation streaming processor for DRL-CCL.And it verifies the function and performance in space target monitoring scene by the carrying experiment of Tianzhou-3 cargo spacecraft(TZ-3).The PMGD image segmentation method can segment the image into highly discrete and simple point tar-gets quickly,which reduces the generation of equivalences greatly and improves the real-time performance for DRL-CCL.Through parallel pipeline design,the storage of the streaming processor is optimized by 55%with no need for external me-mory,the logic is optimized by 60%,and the energy efficiency ratio is 12 times than that of the graphics processing unit,62 times than that of the digital signal proccessing,and 147 times than that of personal computers.Analyzing the results of 8756 images completed on-orbit,the speed is up to 5.88 FPS and the target detection rate is 100%.Our algorithm and implementation method meet the requirements of lightweight,high real-time,strong robustness,full-time,and stable operation in space irradia-tion environment.

基于低损耗热压缩的新型液氢加氢站工艺系统构建

为解决国内现有液氢加氢站中核心设备短期内无法实现国产化以及液氢站加注过程中氢浪费量过大等问题,基于机械压缩增压和热压缩增压机理,构建了基于低损耗热压缩的新型液氢加氢站工艺系统,并利用Aspen HYSYS软件对该新型液氢加氢站工艺系统进行了稳态模拟,得出了系统运行工况参数,确定了优化工艺方案。在此基础上对现有液氢加氢站和新型液氢加氢站系统及其热压缩模块分别进行了能耗分析,结果表明,现有的“增压与汽化并行”式液氢加氢站系统比能耗为0.912 kWh/kg,而低损耗热压缩的新型液氢加氢站系统比能耗为0.322 kWh/kg,其比能耗比现有液氢加氢站降低了64.8%。这表明基于低损耗热压缩的新型液氢加氢站系统更节能,系统中关键部件的[火用]效率也更高。

Overview of Key Technologies and On-orbit Verification of China Space Station

Tiangong space station is a space station independently designed and developed by China.In order to build and operate the space station,it was necessary to make breakthroughs in many fields and master several key technologies,which were characterized over a long technological span and underwent difficult verifications.Therefore,in addition to ground verification,on-orbit flight tests of key technologies for the assembly,construction and operation of the space station were planned to be conducted used by the core module,taking into account the differences in the gravity environment between space and the Earth,in order to lay a foundation for the subsequent comprehensive assembly,construction and long-term on-orbit operation of the space station.In this paper,the mission characteristics of the space station are briefly introduced,along with the key technologies for the assembly and construction of the space station,and then the on-orbit verification tests are comprehensively introduced.

考虑不同制氢方法的高速公路加氢站布局规划

针对高速公路加氢设施不完善的问题,提出一种基于改进自适应遗传算法的高速公路加氢站布局方法。根据高速公路特性及电子收费记录,建立高速公路网络和加氢判断模型。基于多层次-模糊综合评价方法,从经济性、环保性以及安全性角度,提供适合高速公路加氢站的制氢方法和制氢地点的组合。再结合分布式光伏的投入,以经济效益最优为目标,构建高速公路站外和站内制氢2组目标函数,利用改进自适应遗传算法分别进行优化布局和容量配置。以沈海高速(浙江段)作为研究对象进行分析,提供了不同制氢方法下加氢站布局方案及相关设施的容量配置,算例结果与模糊综合评价结果相互验证了模型的有效性。