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SARISTU was a big cooperation project granted by the European Commission, 7th Framework Programme, carried out between 2011 and 2015. It dealt with smart aeronautic structures, both morphing and sensored; its main target was to demonstrate the feasibility of designing, manufacturing and operating in representative environment, instrumented structures. Till now, it represents the major effort carried out within the European Union on the development of adaptive architectures for air systems. Inside that big activity, the realization of an Adaptive Trailing Edge Device (ATED) for wing camber adaptations aimed at compensating the weight reduction following the fuel consumption during cruise was addressed. It made the core of investigations target variable geometry aircraft components together with two other analyses concerning the development of shape-changing winglet and droop nose. ATED activities were conducted by the Italian Aerospace Research Centre (CIRA) in tight cooperation with the University of Napoli, “Federico II”, who coordinated a group of 12 different partners from 8 different nations (France, Germany, Greece, the Netherlands, Israel, Spain, Turkey, and Italy). In this paper, an integral synthesis of that work is reported, with a focus on the definition and realization of the components of the presented device. The publication is in fact meant as the first part of a series that is aimed at overviewing the whole adaptive trailing edge development, till wind tunnel tests execution. Such a concise report is a critical and harmonized review of what have been performed by many colleagues spread all over Europe, all of which are duly recalled in the reported bibliography where the reader may access more detailed information and descriptions. In detail, the paper starts with a general introduction of the concept and its aims, to move to the specs definition immediately after. Then, it deals with a short but comprehensive description of the main ATED components: structural skeleton, skin, actuation and sensing systems. It is worth remarking that the paragraph dedicated to the body frame includes some discussion about aeroelastic assessment and manufacture, seen as complementation for a complete assessment of the design constraints.

Unmanned Aerial Vehicles (UAVs) and Unmanned Ground Vehicles (UGVs) have been used in research and development community due to their strong potential in high-risk missions. One of the most important civilian implementations of UAV/UGV cooperative path planning is delivering medical or emergency supplies during disasters such as wildfires, the focus of this paper. However, wildfires themselves pose risk to the UAVs/UGVs and their paths should be planned to avert the risk as well as complete the mission. In this paper, wildfire growth is simulated using a coupled Partial Differential Equation (PDE) model, widely used in literature for modeling wildfires, in a grid environment with added process and measurement noise. Using principles of Proper Orthogonal Decomposition (POD), and with an appropriate choice of decomposition modes, a low-dimensional equivalent fire growth model is obtained for the deployment of the space–time Kalman Filtering (KF) paradigm for estimation of wildfires using simulated data. The KF paradigm is then used to estimate and predict the propagation of wildfire based on local data obtained from a camera mounted on the UAV. This information is then used to obtain a safe path for the UGV that needs to travel from an initial location to the final position while the UAV’s path is planned to gather information on wildfire. Path planning of both UAV and UGV is carried out using a PDE based method that allows incorporation of threats due to wildfire and other obstacles in the form of risk function. The results from numerical simulation are presented to validate the proposed estimation and path planning methods.

An accurate estimation of tool wear morphology can provide the opportunity to investigate the influence of tool wear on cutting performance as well as reduce the overall production cost. However, tool wear prediction is still a very challenging research issue. In this paper, a novel method for simulating the actual chip formation and wear evolution thorough the 3D finite element model has been carried out. In order to improve the accuracy of simulation results, the influence of worn tool, stress and temperature distribution on wear rate are considered. Then cutting experiment has been conducted by turning AISI1045 with uncoated carbide tools to validate the accuracy of the proposed model. The comparison between experimental and simulation results show good agreement which proves the ability of the proposed model in forecasting the tool wear. The validated finite element model has been further utilized studying how the worn tool affects the cutting performance including actual cutting rake, stress distribution, cutting force and temperature. The results of this paper not only provide a clear understanding of wear evolution between tool rake face and chip, but also are meaningful to optimize tool design and cutting parameters.

Unmanned Aircraft Systems (UASs) have advanced technologically and surged exponentially over recent years. Currently, due to safety concerns, most civil operations of UAS are conducted in low-level uncontrolled area or in segregated controlled airspace. As the industry progresses, both operational and technological capabilities have matured to the point where UASs are expected to gain greater freedom of access to both controlled and uncontrolled airspace. Extensive technical and regulatory surveys have been conducted to enable the expanded operations. However, most surveys are derived from the perspective of UAS own operating mechanism and barely consider interactions of their non-segregated activities with the Air Traffic Management (ATM) system. Hence, to fill the gap, this paper presents a survey conducted from the perspective of Air Navigation Service Provider (ANSP), which serves to accommodate these new entrants to the overall national airspace while continuing flight safety and efficiency. The primary objectives of this paper are to: (A) describe what typical ANSP-supplied UAS Traffic Management (UTM) architecture is required to facilitate all types of civil UAS operations; (B) identify three major ANSP considerations on how UAS can be accommodated safely in civil airspace; (C) outline future directions and challenges related with UAS operations for the ANSP.

Topology optimization is an effective method to obtain a lightweight structure that meets the requirements of structural strength. Whether the optimization results meet the actual needs mainly depends on the accuracy of the material properties and the boundary conditions, especially for a tiny Flapping-wing Micro Aerial Vehicle (FMAV) transmission system manufactured by 3D printing. In this paper, experimental and numerical computation efforts were undertaken to gain a reliable topology optimization method for the bottom of the transmission system. First, the constitutive behavior of the ultraviolet (UV) curable resin used in fabrication was evaluated. Second, a numerical computation model describing further verified via experiments. Topology optimization modeling considering nonlinear factors, e.g. contact, friction and collision, was presented, and the optimization results were verified by both dynamic simulation and experiments. Finally, detailed discussions on different load cases and constraints were presented to clarify their effect on the optimization. Our methods and results presented in this paper may shed light on the lightweight design of a FMAV.

As an important part in sortie/recovery process, the dispatch of carrier aircraft not only affects the sortie/recovery efficiency and safety, but also has severe influence on the carrier’s combat efficiency and the comprehensive support capability. Path planning is the key to improve the efficiency and safety during the dispatch process. The main purpose of this paper is to propose a comprehensive investigation of techniques and research progress for the carrier aircraft’s dispatch path planning on the deck. Three different dispatch modes of carrier aircraft and the corresponding modeling technologies are investigated, and the aircraft’s dispatch path planning techniques and algorithms have been classified into different classes. Moreover, their assumptions and drawbacks have been discussed for single aircraft and multiple aircraft. To make the research work more comprehensive, the corresponding tracking control methodologies are also discussed. Finally, due to the similarity of path planning problem between the carrier aircraft’s dispatch and those in other fields, this paper provides an exploratory prospect of the knowledge or method learned from other fields.

Recent years have witnessed a booming of the industry of civil Unmanned Aircraft System (UAS). As an emerging industry, the UAS industry has been attracting great attention from governments of all countries and the aviation industry. UAS are highly digitalized, informationized, and intelligent; therefore, their integration into the national airspace system has become an important trend in the development of civil aviation. However, the complexity of UAS operation poses great challenges to the traditional aviation regulatory system and technical means. How to prevent collisions between UASs and between UAS and manned aircraft to achieve safe and efficient operation in the integrated operating airspace has become a common challenge for industry and academia around the world. In recent years, the international community has carried out a great amount of work and experiments in the air traffic management of UAS and some of the key technologies. This paper attempts to make a review of the UAS separation management and key technologies in collision avoidance in the integrated airspace, mainly focusing on the current situation of UAS Traffic Management (UTM), safety separation standards, detection system, collision risk prediction, collision avoidance, safety risk assessment, etc., as well as an analysis of the bottlenecks that the current researches encountered and their development trends, so as to provide some insights and references for further research in this regard. Finally, this paper makes a further summary of some of the research highlights and challenges.

This paper investigates the consensus disturbance rejection problem among multiple high-order agents with directed graphs. Based on disturbance observers, distributed consensus disturbance rejection protocols are constructed in leaderless and leader-follower consensus setups. Different from the previous related papers, the consensus protocols in this paper are developed in a fully distributed fashion, relying on only the state information of each agent and its neighbors. Sufficient conditions are provided to guarantee that the asymptotic stability of high-order multi-agent systems can be reached with matched disturbances.

The rotational motion of a tumbling target brings great challenges to space robot on successfully capturing the tumbling target. Therefore, it is necessary to reduce the target’s rotation to a rate at which capture can be accomplished by the space robot. In this paper, a detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target is proposed. This strategy can reduce the target’s rotational velocity while maintaining base attitude stability through the establishment of the rotation attenuation controller and base attitude adjustment controller. The rotation attenuation controller adopts the multi-space hybrid impedance control method to control the friction precisely. The base attitude adjustment controller applies the dual-arm extended Jacobian matrix to stabilize the base attitude. The main contributions of this paper are as follows: (1) The compliant control method is adopted to achieve a precise friction control, which can reduce the target angular velocity steadily; (2) The dual-arm extended Jacobian matrix is applied to stabilize the base attitude without affecting the target capture task; (3) The detumbling strategy of dual-arm space robot is designed considering base attitude stabilization, realizing coordinated planning of the base attitude and the arms. The strategy is verified by a dual-arm space robot with two 7-DOF (degrees of freedom) arms. Simulation results show that, target with a rotation velocity of 20 (°)/s can be effectively controlled to stop within 30 s, and the final deflection of the base attitude is less than 0.15° without affecting the target capture task, verifying the correctness and effectiveness of the strategy. Except to the tumbling target capture task, the control strategy can also be applied to other typical on-orbit operation tasks such as space debris removal and spacecraft maintenance. Keywords: Detumbling strategy, Dual-arm space robot, Free-floating base, Friction control, Tumbling target capturing

Angle of Attack (AOA) is a crucial parameter which directly affects the aerodynamic forces of an aircraft. The measurement of AOA is required to ensure a safe flight within its designed flight envelop. This paper intends to summarise a comprehensive survey on the measurement techniques and estimation methods for AOA, specifically in Unmanned Aerial Vehicle (UAV) applications. In the case of UAVs, weight constraint plays a major role as far as sensor suites are concerned. This results in selecting a suitable estimation method to extract AOA using the available data from the autopilot. The most feasible and widely employed AOA measurement technique is by using the Multi-Hole Probes (MHPs). The MHP measures the AOA regarding the pressure variations between the ports. Due to the importance of MHP in AOA measurement, the calibration methods for the MHP are also included in this paper. This paper discusses the AOA measurement using virtual AOA sensors, their importance and the operation. Keywords: Angle of attack estimation, Angle of attack measurement, Angle of attack vane, Five-hole probe, Multi-hole probe, Multi-hole probe calibration, Nine-hole probe, Seven-hole probe, Virtual angle of attack sensor

In this paper, a framework is established for nonlinear flutter and gust response analyses based on an efficient Reduced Order Model (ROM). The proposed method can be used to solve the aeroelastic response problems of wings containing geometric nonlinearities. A structural modeling approach presented herein describes the stiffness nonlinearities with a modal formulation. Two orthogonal spanwise modes describe the foreshortening effects of the wing. Dynamic linearization of the ROM under nonlinear equilibrium states is applied to a nonlinear flutter analysis, and the fully nonlinear ROM coupled with the non-planar Unsteady Vortex Lattice Method (UVLM) is applied to gust response analysis. Furthermore, extended Precise Integration Method (PIM) ensures accuracy of the dynamic equation solutions. To demonstrate applicability and accuracy of the method presented, a wind tunnel test is conducted and good agreements between theoretical and test results of nonlinear flutter speed and gust response deflection are reached. The method described in this paper is suitable for predicting the nonlinear flutter speed and calculating the gust responses of a large-aspect-ratio wing in time domain. Meanwhile, the results derived highlight the effects of geometric nonlinearities obviously. Keywords: Aeroelasticity, Flutter, Geometric nonlinearity, Reduced order models, Response analysis, Structural model

Unmanned Aerial Vehicle (UAV) swarms have been foreseen to play an important role in military applications in the future, wherein they will be frequently subjected to different disturbances and destructions such as attacks and equipment faults. Therefore, a sophisticated robustness evaluation mechanism is of considerable importance for the reliable functioning of the UAV swarms. However, their complex characteristics and irregular dynamic evolution make them extremely challenging and uncertain to evaluate the robustness of such a system. In this paper, a complex network theory-based robustness evaluation method for a UAV swarming system is proposed. This method takes into account the dynamic evolution of UAV swarms, including dynamic reconfiguration and information correlation. The paper analyzes and models the aforementioned dynamic evolution and establishes a comprehensive robustness metric and two evaluation strategies. The robustness evaluation method and algorithms considering dynamic reconfiguration and information correlation are developed. Finally, the validity of the proposed method is verified by conducting a case study analysis. The results can further provide some guidance and reference for the robust design, mission planning and decision-making of UAV swarms. Keywords: Complex networks, Dynamic reconfiguration, Information correlation, Robustness evaluation, Unmanned Aerial Vehicles (UAV)

This paper addresses a target-enclosing problem for multiple spacecraft systems by proposing a two-layer affine formation control strategy. Compared with the existing methods, the adopted two-layer network structure in this paper is generally directed, which is suitable for practical space missions. Firstly, distributed finite-time sliding-mode estimators and formation controllers in both layers are designed separately to improve the flexibility of the formation control system. By introducing the properties of affine transformation into formation control protocol design, the controllers can be used to track different time-varying target formation patterns. Besides, multi-layer time-varying encirclements can be achieved with particular shapes to surround the moving target. In the sequel, by integrating adaptive neural networks and specialized artificial potential functions into backstepping controllers, the problems of uncertain Euler-Lagrange models, collision avoidance as well as formation reconfiguration are solved simultaneously. The stability of the proposed controllers is verified by the Lyapunov direct method. Finally, two simulation examples of triangle formation and more complex hexagon formation are presented to illustrate the feasibility of the theoretical results. Keywords: Affine formation control, Collision avoidance, Lyapunov stability, Target enclosing, Two-layer strategy

This paper addresses the problem of real-time object tracking for unmanned aerial vehicles. We consider the task of object tracking as a classification problem. Training a good classifier always needs a huge number of samples, which is always time-consuming and not suitable for real-time applications. In this paper, we transform the large-scale least-squares problem in the spatial domain to a series of small-scale least-squares problems with constraints in the Fourier domain using the correlation filter technique. Then, this problem is efficiently solved by two stages. In the first stage, a fast method based on recursive least squares is used to solve the correlation filter problem without constraints in the Fourier domain. In the second stage, a weight matrix is constructed to prune the solution attained in the first stage to approach the constraints in the spatial domain. Then, the pruned classifier is used for tracking. To evaluate proposed tracker’s performance, comprehensive experiments are conducted on challenging aerial sequences in the UAV123 dataset. Experimental results demonstrate that proposed approach achieves a state-of-the-art tracking performance in aerial sequences and operates at a mean speed of beyond 40 frames/s. For further analysis of proposed tracker’s robustness, extensive experiments are also performed on recent benchmarks OTB50, OTB100, and VOT2016. Keywords: Correlation filter, Discrete Fourier transform, Least squares, Object tracking, Unmanned aerial vehicle

The conception of aircraft morphing wings thrives in aeronautics since the appearance of shape memory alloys (SMAs). An aircraft morphing wing device, manipulated by an SMA actuator, inherits the intrinsic nonlinear hysteresis from the SMA actuator, ending up with control disadvantages. Conventionally, systems with SMA actuators are constrained to bi-stable states to bypass the hysteresis region. Rather than retreating a morphing wing device to bi-stable states, this paper is dedicated to transcend the morphing wing device beyond the customary limit. A methodology of discrete Preisach modeling, which identifies the hysteresis of the morphing wing device, is proposed herein. An array of discrete equal-distance points is applied to the Preisach plane in order to derive the Preisach density over the partitioned unit of the Preisach plane. Discrete Preisach modeling is fulfilled by the discrete first-order reversible curve (DFORC). By utilizing the discrete Preisach model, the aircraft morphing wing device is simulated; the validity and accuracy of discrete Preisach modeling are demonstrated by contrasting the simulated outcome with experimental data of the major hysteretic loop and the wingspan-wise displacement over time; a comparison between simulation and experimental results exhibits consistency. Afterwards, a hysteresis compensation strategy put forward in this paper is implemented for quasi-linear control of the aircraft morphing wing device, which manifests a compensated shrinking hysteresis loop and attains the initiative of extending the morphing range to the intrinsic hysteretic region. Keywords: Actuator, Compensation, Hysteresis, Morphing wing, Preisach model, Shape memory effect

Use of composite structures is exponentially growing in different fields due to their higher strength-to-weight ratio. This application trend requires that accurate theoretical explanations and their finite element models be developed for analyzing sandwich plates before finalizing the designs. This paper reviews the recent research trends of finite element formulations developed for analyzing sandwich plates. This paper reviews the finite element models developed after the year 2000. Initially, the finite element formulations based on first order shear deformation theory, higher order shear deformation theories, mixed solid-shell elements, zig-zag theories and global–local theories are presented. Then, some finite element formulations developed to analyze a very new class of structures called piezoelectric structures are presented. At the end, some formulations to analyze a very critical phenomenon called buckling are presented. Keywords: Buckling, Finite element, FSDT, HSDT, Laminated composites, Piezoelectric, Sandwich plates, Zig-zag theory

Chatter is a self-excited vibration of parts in machining systems. It is widely present across a range of cutting processes, and has an impact upon both efficiency and quality in production processing. A great deal of research has been dedicated to the development of technologies that are able to predict and detect chatter. The purpose of these technologies is to facilitate the avoidance of chatter during cutting processes, which leads to better surface precision, higher productivity, and longer tool life. This paper summarizes the current state of the art in research regarding the problems of how to arrive at stable chatter prediction, chatter identification, and chatter control/suppression, with a focus on milling processes. Particular focus is placed on the theoretical relationship between cutting chatter and process damping, tool runout, and gyroscopic effect, as well as the importance of this for chatter prediction. The paper concludes with some reflections regarding possible directions for future research in this field. Keywords: Chatter, Gyroscopic effects, Milling, Process damping, Tool runout

Small-scale rotorcraft unmanned robotic systems (SRURSs) are a kind of unmanned rotorcraft with manipulating devices. This review aims to provide an overview on aerial manipulation of SRURSs nowadays and promote relative research in the future. In the past decade, aerial manipulation of SRURSs has attracted the interest of researchers globally. This paper provides a literature review of the last 10 years (2008–2017) on SRURSs, and details achievements and challenges. Firstly, the definition, current state, development, classification, and challenges of SRURSs are introduced. Then, related papers are organized into two topical categories: mechanical structure design, and modeling and control. Following this, research groups involved in SRURS research and their major achievements are summarized and classified in the form of tables. The research groups are introduced in detail from seven parts. Finally, trends and challenges are compiled and presented to serve as a resource for researchers interested in aerial manipulation of SRURSs. The problem, trends, and challenges are described from three aspects. Conclusions of the paper are presented, and the future of SRURSs is discussed to enable further research interests. Keywords: Aerial manipulation, Mechanical structure design, Modeling and control, Research groups, Small-scale rotorcraft unmanned aerial systems, Trends and challenges

As a kind of actuation mechanism for power-by-wire (PBW) actuation systems of more/all electrical aircraft, an electro-hydrostatic actuator (EHA) is a highly integrated local hydraulic actuation system. It is a volume control system consisting of a motor, a pump, an actuator, etc., which has features of high efficiency and reliability. However, the poor dynamic characteristic is one of the main factors restricting its wide application in aircraft. In this paper, the reason for the poor dynamic characteristic of an EHA is revealed from the perspectives of the natural frequency characteristic and the power requirement, respectively. In other words, the insufficiency of the motor output power at a high frequency is the main factor causing the poor dynamic characteristic of the system, and methods which include increasing the maximum output torque of the motor, reducing the rotational inertia of the motor-pump group, and adopting a double-motor-pump group configuration are proposed in this paper, by which the dynamic characteristic of the system can be improved. The feasibility of those methods are verified by simulations. Finally, the dynamic characteristic is tested on an EHA prototype, and results show that saturation of the output torque of the motor is the main factor restricting the dynamic characteristic of the EHA system. Keywords: Dynamic characteristic, Motor-pump group, Power requirement, Rotational inertia

A unified theoretical aeroservoelastic stability analysis framework for flexible aircraft is established in this paper. This linearized state space model for stability analysis is based on nonlinear coupled dynamic equations, in which rigid and elastic motions of aircraft are both considered. The common body coordinate system is utilized as the reference frame in the deduction of dynamic equations, and significant deformations of flexible aircraft are also fully concerned without any excessive assumptions. Therefore, the obtained nonlinear coupled dynamic models can well reflect the special dynamic coupling mechanics of flexible aircraft. For aeroservoelastic stability analysis, the coupled dynamic equations are linearized around the nonlinear equilibrium state and together with a control system model to establish a state space model in the time domain. The methodology in this paper can be easily integrated into the industrial design process and complex structures. Numerical results for a complex flexible aircraft indicate the necessity to consider the nonlinear coupled dynamics and large deformation when dealing with aeroservoelastic stability for flexible aircraft. Keywords: Aeroservoelasticity, Flexible aircraft, Geometric nonlinearity, Nonlinear coupled dynamics, Stability control

This paper deals with the multi-index assessment method for evaluating coverage effectiveness of remote sensing satellite. Because a series of satellite activities such as imaging, moving target observation, and environment investigation need to know the coverage characteristics, the coverage capability of the remote sensing satellite is the most important index. Thus, it is very important to establish the method of effectiveness evaluation of coverage characteristics. This paper focuses on the assessment of coverage effectiveness of remote sensing satellite, and proposes and designs a multi-index evaluation method based on index weight using entropy weight method and analytic hierarchy process. With a simulation case, the effectiveness evaluation results of single satellite coverage and multi-satellite coverage performance are given for the proposed assessment. The experimental results show that the established coverage characteristic model and the proposed assessment method are effective and right. Keywords: Analytic hierarchy process, Coverage ability, Effectiveness evaluation, Entropy weight method, Remote sensing satellite

In the present paper, high-order finite volume schemes on unstructured grids developed in our previous papers are extended to solve three-dimensional inviscid and viscous flows. The high-order variational reconstruction technique in terms of compact stencil is improved to reduce local condition numbers. To further improve the efficiency of computation, the adaptive mesh refinement technique is implemented in the framework of high-order finite volume methods. Mesh refinement and coarsening criteria are chosen to be the indicators for certain flow structures. One important challenge of the adaptive mesh refinement technique on unstructured grids is the dynamic load balancing in parallel computation. To solve this problem, the open-source library p4est based on the forest of octrees is adopted. Several two- and three-dimensional test cases are computed to verify the accuracy and robustness of the proposed numerical schemes. Keywords: Adaptive mesh refinement, Compact stencil, High-order finite volume scheme, Unstructured grids, Variational reconstruction

A synchronous control of relative attitude and position is required in separated ultra-quiet spacecraft, such as drag-free, disturbance-free, and distributed spacecraft. Thus, a twistor-based synchronous sliding mode control is investigated in this paper to solve the control problem of relative attitude and position among separated spacecraft modules. The twistor-based control design and the stability proof are implemented using the Modified Rodrigues Parameter (MRP). To evaluate the effectiveness of the proposed control method, this paper presents a case study of separated spacecraft flying control considering the mass uncertainty and external disturbances. In addition, a simulation study of the Proportional-Derivative (PD) control is also presented for comparison. The results indicate that the twistor-based sliding mode controller can ensure global asymptotic stability. The states converge fast with ultra-precision and ultra-stability in both the attitude and position. Moreover, the proposed twistor-based sliding mode control system is robust to the mass uncertainty and external disturbances. Keywords: Distributed spacecraft, Gravitational wave detection, Synchronous control, Ultra-precision, Ultra-stability

Sensor-fusion based navigation attracts significant attentions for its robustness and accuracy in various applications. To achieve a versatile and efficient state estimation both indoor and outdoor, this paper presents an improved monocular visual inertial navigation architecture within the Multi-State Constraint Kalman Filter (MSCKF). In addition, to alleviate the initialization demands by appending enough stable poses in MSCKF, a rapid and robust Initialization MSCKF (I-MSCKF) navigation method is proposed in the paper. Based on the trifocal tensor and sigma-point filter, the initialization of the integrated navigation can be accomplished within three consecutive visual frames. Thus, the proposed I-MSCKF method can improve the navigation performance when suffered from shocks at the initial stage. Moreover, the sigma-point filter is applied at initial stage to improve the accuracy for state estimation. The state vector generated at initial stage from the proposed method is consistent with MSCKF, and thus a seamless transition can be achieved between the initialization and the subsequent navigation in I-MSCKF. Finally, the experimental results show that the proposed I-MSCKF method can improve the robustness and accuracy for monocular visual inertial navigations.

The state of the art avionics system adopts switched networks for airborne communications. A major concern in the design of the networks is the end-to-end guarantee ability. Analytic methods have been developed to compute the worst-case delays according to the detailed configurations of flows and networks within avionics context, such as network calculus and trajectory approach. It still lacks a relevant method to make a rapid performance estimation according to some typically switched networking features, such as networking scale, bandwidth utilization and average flow rate. The goal of this paper is to establish a deterministic upper bound analysis method by using these networking features instead of the complete network configurations. Two deterministic upper bounds are proposed from network calculus perspective: one is for a basic estimation, and another just shows the benefits from grouping strategy. Besides, a mathematic expression for grouping ability is established based on the concept of network connecting degree, which illustrates the possibly minimal grouping benefit. For a fully connected network with 4 switches and 12 end systems, the grouping ability coming from grouping strategy is 15â20%, which just coincides with the statistical data (18â22%) from the actual grouping advantage. Compared with the complete network calculus analysis method for individual flows, the effectiveness of the two deterministic upper bounds is no less than 38% even with remarkably varied packet lengths. Finally, the paper illustrates the design process for an industrial Avionics Full DupleX switched Ethernet (AFDX) networking case according to the two deterministic upper bounds and shows that a better control for network connecting, when designing a switched network, can improve the worst-case delays dramatically. Keywords: Deterministic bound, Grouping ability, Network calculus, Networking features, Switched networks

Software defect prevention is an important way to reduce the defect introduction rate. As the primary cause of software defects, human error can be the key to understanding and preventing software defects. This paper proposes a defect prevention approach based on human error mechanisms: DPeHE. The approach includes both knowledge and regulation training in human error prevention. Knowledge training provides programmers with explicit knowledge on why programmers commit errors, what kinds of errors tend to be committed under different circumstances, and how these errors can be prevented. Regulation training further helps programmers to promote the awareness and ability to prevent human errors through practice. The practice is facilitated by a problem solving checklist and a root cause identification checklist. This paper provides a systematic framework that integrates knowledge across disciplines, e.g., cognitive science, software psychology and software engineering to defend against human errors in software development. Furthermore, we applied this approach in an international company at CMM Level 5 and a software development institution at CMM Level 1 in the Chinese Aviation Industry. The application cases show that the approach is feasible and effective in promoting developers’ ability to prevent software defects, independent of process maturity levels.

Sparse signal is a kind of sparse matrices which can carry fault information and simplify the signal at the same time. This can effectively reduce the cost of signal storage, improve the efficiency of data transmission, and ultimately save the cost of equipment fault diagnosis in the aviation field. At present, the existing sparse decomposition methods generally extract sparse fault characteristics signals based on orthogonal basis atoms, which limits the adaptability of sparse decomposition. In this paper, a self-adaptive atom is extracted by the improved dual-channel tunable Q-factor wavelet transform (TQWT) method to construct a self-adaptive complete dictionary. Finally, the sparse signal is obtained by the orthogonal matching pursuit (OMP) algorithm. The atoms obtained by this method are more flexible, and are no longer constrained to an orthogonal basis to reflect the oscillation characteristics of signals. Therefore, the sparse signal can better extract the fault characteristics. The simulation and experimental results show that the self-adaptive dictionary with the atom extracted from the dual-channel TQWT has a stronger decomposition freedom and signal matching ability than orthogonal basis dictionaries, such as discrete cosine transform (DCT), discrete Hartley transform (DHT) and discrete wavelet transform (DWT). In addition, the sparse signal extracted by the self-adaptive complete dictionary can reflect the time-domain characteristics of the vibration signals, and can more accurately extract the bearing fault feature frequency.

This paper focuses on aeroelastic prediction and analysis for a transonic fan rotor with only its “hot” (running) blade shape available, which is often the case in practical engineering such as in the design stage. Based on an in-house and well-validated CFD solver and a hybrid structural finite element modeling/modal approach, three main aspects are considered with special emphasis on dealing with the “hot” blade shape. First, static aeroelastic analysis is presented for shape transformation between “cold” (manufacturing) and “hot” blades, and influence of the dynamic variation of “hot” shape on evaluated aerodynamic performance is investigated. Second, implementation of the energy method for flutter prediction is given and both a regularly used fixed “hot” shape and a variable “hot” shape are considered. Through comparison, influence of the dynamic variation of “hot” shape on evaluated aeroelastic stability is also investigated. Third, another common way to predict flutter, time-domain method, is used for the same concerned case, from which the predicted flutter characteristics are compared with those from the energy method. A well-publicized axial-flow transonic fan rotor, Rotor 67, is selected as a typical example, and the corresponding numerical results and discussions are presented in detail.

The purpose of this paper is to demonstrate an integrated optimization scheme for a solar-powered drone structure. Consider a primary beam in the wing of large aspect ratio, where 100 lithium batteries are assembled. In the proposed integrated optimization, the batteries are considered here as parts of the load-carrying structure. The corresponding mechanical behaviors are simulated in the structural design and described with super-elements. The batteries layout and the structural topology are then introduced as mixed design variables and optimized simultaneously to achieve an accordant load-carrying path. Geometrical nonlinearity is considered due to the large deformation. Different periodic structural configurations are tested in the optimization in order to meet the structural manufacturing and assembly convenience. The optimized designs are rebuilt and tested in different load cases. Maintaining the same structural weight, the global mechanical performances are improved greatly compared with the initial design.

This paper proposes a backstepping technique and Multi-dimensional Taylor Polynomial Networks (MTPN) based adaptive attitude tracking control strategy for Near Space Vehicles (NSVs) subjected to input constraints and stochastic input noises. Firstly, considering the control input has stochastic noises, and the attitude motion dynamical model of the NSVs is actually modeled as the Multi-Input Multi-Output (MIMO) stochastic nonlinear system form. Furthermore, the MTPN is used to estimate the unknown system uncertainties, and an auxiliary system is designed to compensate the influence of the saturation control input. Then, by using backstepping method and the output of the auxiliary system, a MTPN-based robust adaptive attitude control approach is proposed for the NSVs with saturation input nonlinearity, stochastic input noises, and system uncertainties. Stochastic Lyapunov stability theory is utilized to analysis the stability in the sense of probability of the entire closed-loop system. Additionally, by selecting appropriate parameters, the tracking errors will converge to a small neighborhood with a tunable radius. Finally, the numerical simulation results of the NSVs attitude motion show the satisfactory flight control performance under the proposed tracking control strategy.

In the manufacturing of thin wall components for aerospace industry, apart from the side wall contour error, the Remaining Bottom Thickness Error (RBTE) for the thin-wall pocket component (e.g. rocket shell) is of the same importance but overlooked in current research. If the RBTE reduces by 30%, the weight reduction of the entire component will reach up to tens of kilograms while improving the dynamic balance performance of the large component. Current RBTE control requires the off-process measurement of limited discrete points on the component bottom to provide the reference value for compensation. This leads to incompleteness in the remaining bottom thickness control and redundant measurement in manufacturing. In this paper, the framework of data-driven physics based model is proposed and developed for the real-time prediction of critical quality for large components, which enables accurate prediction and compensation of RBTE value for the thin wall components. The physics based model considers the primary root cause, in terms of tool deflection and clamping stiffness induced Axial Material Removal Thickness (AMRT) variation, for the RBTE formation. And to incorporate the dynamic and inherent coupling of the complicated manufacturing system, the multi-feature fusion and machine learning algorithm, i.e. kernel Principal Component Analysis (kPCA) and kernel Support Vector Regression (kSVR), are incorporated with the physics based model. Therefore, the proposed data-driven physics based model combines both process mechanism and the system disturbance to achieve better prediction accuracy. The final verification experiment is implemented to validate the effectiveness of the proposed method for dimensional accuracy prediction in pocket milling, and the prediction accuracy of AMRT achieves 0.014 mm and 0.019 mm for straight and corner milling, respectively.

The morphing trailing edge based compliant mechanism is a developing technology which can increase lift-drag ratio for variable flight modes by bending down the trailing edge. Composite material design is integrated into topology optimization for the morphing trailing edge based compliant mechanism in the paper. A two-step optimization strategy is established to solve the integrated design problem. Initially, lamination parameters are introduced and viewed as a bridge between structure stiffness and fiber angles for composite material. Design variables include the lamination parameters and element density. The least-squares between actual and desired displacements at output points along trailing edge is adopted to evaluate the deformed capability of the trailing edge. An integrated optimization model for the composite morphing trailing edge is established with the volume constraints. The optimal topologic shape and lamination parameters are initially obtained. Subsequently, a least-squares optimization between fiber angles and the optimal lamination parameters is implemented to obtain optimal fiber angles. Finally, morphing capability of composites trailing edge based compliant mechanism is investigated by simulation and experiments. The results indicate the composites trailing edge based compliant mechanism can approximately bend down 8 degrees and satisfies the design requirement.

In an effort to maintain safety while satisfying growing air traffic demand, air navigation service providers are considering the inclusion of advisory systems to identify potential conflicts and propose resolution commands for the air traffic controller to verify and issue to aircraft. To understand the potential workload implications of introducing advisory conflict-detection and resolution tools, this paper examines a metric of controller taskload: how many resolution commands an air traffic controller issues under the guidance of an advisory system. Through a simulation study, the research presented here evaluates how the underlying protocol of a conflict-resolution tool affects the controller taskload (system demands) associated with the conflict-resolution process, and implicitly the controller workload (physical and psychological demands). Ultimately, evidence indicates that there is significant flexibility in the design of conflict-resolution algorithms supporting an advisory system.

There is a strong demand for Planetary Exploration Mobile robots (PEMRs) that have the capability of the traversability, stability, efficiency and high load while tackling the specialized tasks on planet surface. In this paper, an electric parallel wheel-legged hexapod robot which has high-adaption locomotion on the unstructured terrain is presented. Also, the hybrid control framework, which enables robot to stably carry the heavy loads as well as to traverse the uneven terrain by utilizing both legged and wheeled locomotion, is also proposed. Based on this framework, robot controls the multiple DOF leg for performing high-adaption locomotion to negotiate obstacles via Gait Generator (GG). Additionally, by using Whole-Body Control (WBC) of framework, robot has the capability of flexibly accommodating the uneven terrain by Attitude Control (AC) kinematically adjusting the length of legs like an active suspension system, and by Force/torque Balance Control (FBC) equally distributing the Ground Reaction Force (GRF) to maintain a stable body. The simulation and experiment are employed to validate the proposed framework with the physical system in the planetary analog environments. Particularly, to smoothly demonstrate the performance of robot transporting heavy loads, the experiment of carrying 3-person load of about 240 kg is deployed.

Vibrations in aircraft hydraulic pipeline system, due to multi-source excitation of high fluid pressure fluctuation and serious vibration environment of airframe, can cause the pipeline system vibration failures through overload in engineering field. Controlling the vibrations in hydraulic pipeline is a challenging work to ensure the flight safety of aircraft. The common vibration control technologies have been demonstrated to be effective in typical structures such as aerospace structures, shipbuilding structures, marine offshore structures, motor structures, etc. However, there are few research literatures on vibration control strategies of aircraft hydraulic pipeline. Combining with the development trend of aircraft hydraulic pipeline system and the requirement of vibration control technologies, this paper provides a detailed review on the current vibration control technologies in hydraulic pipeline system. A review of the general approaches following the passive and active control technologies are presented, which are including optimal layout technique of pipeline and clamps, constrained layer damping technique, vibration absorber technique, hydraulic hose technique, optimal pump structure technique, and active vibration control technique of pipeline system. Finally, some suggestions for the application of vibration control technologies in engineering field are given.

A nonlinear dynamic modeling method for primary mirror of Flower-like Deployable Space Telescope (F-DST) undergoing large deployment motion is proposed in this paper. To ensure pointing accuracy and attitude stability of the paraboloidal primary mirror, the mirror is discretized into equal thickness shell elements by considering shell curvature. And the material nonlinear constitutive relation of flexible mirror is acquired using Absolute Nodal Coordinate Formulation (ANCF). Furthermore, the primary mirror of F-DST can be regarded as a clustered multi-body system, and its dynamic equations of elastic deformation and deployment motion are established by virtual work principle. Finally, the deployment motion of primary mirror by different driving conditions are simulated, the results show that the vibrations of mirrors that driven by elastic hinge device are more than that driven by servo motor. In addition, single sub-mirror deployment process will perturb the pointing accuracy of primary mirror, and the multiple sub-mirrors simultaneously deploying will seriously affect all the sub-mirrors surface accuracy because of the coupling effect. Thus, there are theoretical value and practical significance for the controlling surface accuracy and attitude accuracy of space telescope.

Obtaining accurate development cost estimation results of general aviation aircraft is crucial for companies to adopt the best strategy in the development process. To address this problem, this paper proposes a combination of three commonly used single prediction methods. The optimal weight values of the three single prediction methods are determined by utilizing the shortest ideal point method. Ten cost datasets collected from literature are utilized for fitting and testing the combined prediction method, and the weight coefficients of the three individual prediction methods are calculated as 0.6859, 0.0035 and 0.3106, respectively. The results of this study indicate that the developed method has better fitting and estimation accuracy than that of the three individual methods, with average fitting and predicting error values of 2.60% and 6.43%, respectively. Additionally, the cost data of military and civil aircraft development from literature are collected for verification. The results further confirm that the proposed method is not only superior to the single prediction methods in terms of high precision but has wider applications. More importantly, this research can provide important reference for general aviation aircraft companies in term of product cost planning and corporate sales strategies.

Considering the important applications in the military and the civilian domain, ship detection and classification based on optical remote sensing images raise considerable attention in the sea surface remote sensing filed. This article collects the methods of ship detection and classification for practically testing in optical remote sensing images, and provides their corresponding feature extraction strategies and statistical data. Basic feature extraction strategies and algorithms are analyzed associated with their performance and application in ship detection and classification. Furthermore, publicly available datasets that can be applied as the benchmarks to verify the effectiveness and the objectiveness of ship detection and classification methods are summarized in this paper. Based on the analysis, the remaining problems and future development trends are provided for ship detection and classification methods based on optical remote sensing images.

In this paper, the relative sliding motion between the target and the manipulator’s end-effector is considered and characterized as a unilateral contact constraint. A new possible solution is presented to estimate the inertial parameters of a non-cooperative target while the relative sliding motion exists. First, the detailed analysis of the dynamical model is presented, and a parameter-explicit linear time-varying model is obtained. Then, an extended state observer is constructed based on the new model, which can effectively estimate the unknown inertial parameters of the target when relative sliding motion exists. As the modified reactionless controller requires the knowledge of inertial parameters, a hybrid post-capture control scheme is also established based on the switch law between different controllers. The correctness and efficiency of the proposed algorithm are validated by numerical simulation, which proves a potential framework for the non-cooperative target post-capture operation.

In this paper, a robust adaptive controller is designed for a guided spinning rocket, whose dynamics presents the characteristics of pitch-yaw cross coupling, fast time-varying aerodynamics parameters and wide flight envelop. First, a coupled nonlinear six-degree-of-freedom equation of motion for a guided spinning rocket is developed, and the lateral acceleration motion is modeled as a control plant with time-varying matched uncertainties and unmodeled dynamics. Then, a robust adaptive control method is proposed by combining Bregman divergence and variational method to achieve fast adaption and maintain bounded tracking. The stability of the resulting closed-loop system is proved, and the ultimate bound and convergence rate are also analyzed. Finally, numerical simulations are performed for a single operating point and the whole flight trajectory to show the robustness and adaptability of the proposed method with respect to time-varying uncertainties and unmodeled dynamics.

In view of the separation form of the separator from the back of the carrier upward and from the side of the carrier outward, separation-safety research is carried out by taking the separation of a cluster munition as an example. In previous wind tunnel free-flight tests, the similarity law of vertical, downward, moving submunition was used to design submunitions at different positions in different initial-velocity directions, which resulted in large discrepancies between wind tunnel test results and real flight. In a wind tunnel test, each submunition has an independent time-reduction ratio with respect to the dispenser. Even if the separation trajectory of a single submunition is accurate, there will be errors in the position of each submunition at a given time. Therefore, it is necessary to determine the time-reduction ratio between submunitions, and to modify the test results later. In order to ensure the accuracy of wind tunnel test results, the similarity law of a free-flight test in a wind tunnel is derived in this paper. The time-correction scheme to ensure motion similarity between submunitions is solved. Numerical simulation is used to simulate the separation of a wind tunnel test and real aircraft, and the motion parameters of different submunitions are solved. The results show that the new similarity laws derived for different types of submunitions can greatly reduce the errors caused by previous similarity laws. In addition to the case for the separation of a cluster munition, the similarity law can also be applied to the free-flight test design of wind tunnels for vertical separation and horizontal separation of other kinds of aircraft.

Probabilistic Fault Recoverability (FR) property reveals the capability of a system to accommodate faults under admissible input energy constraints in the sense of satisfactory probability. Motivated by the idea of probabilistic control methods, a class of admissible probability density functions is designed for detailed description of fault parameters, under which several probabilistic FR conditions are established. This significantly enlarges the range of recoverable faults obtained from the deterministic FR analysis. The tradeoffs between the risk of performance degradation and this increased recoverability margin are exactly achieved by allowing a small risk of FR violation. This paper analyzes the probability FR of dynamic systems with switching and interconnection characteristics, and applies the new results to several aircraft models including single longitudinal aircraft dynamic, Highly Maneuverable Technology (HiMAT) vehicle and meta aircraft. Simulation results show the efficiency of the proposed methods based on the comparison between deterministic and probabilistic cases.

Helicopters are widely used in maritime Search and Rescue (SAR) missions. To ensure the success of SAR missions, search areas need to be carefully planned. With the development of computer technology and weather forecast technology, the survivors’ drift trajectories can be predicted more precisely, which strongly supports the planning of search areas for the rescue helicopter. However, the methods used to determine the search area based on the predicted drift trajectories are mainly derived from the continuous expansion of the area with the highest Probability of Containment (POC), which may lead to local optimal solutions and a decrease in the Probability of Success (POS), especially when there are several subareas with a high POC. To address this problem, this paper proposes a method based on a Minimum Bounding Rectangle and K-means clustering (MBRK). A silhouette coefficient is adopted to analyze the distribution of the survivors’ probable locations, which are divided into multiple clusters with K-means clustering. Then, probability maps are generated based on the minimum bounding rectangle of each cluster. By adding or subtracting one row or column of cells or shifting the planned search area, 12 search methods are used to generate the optimal search area starting from the cell with the highest POC in each probability map. Taking a real case as an example, the simulation experiment results show that the POS values obtained by the MBRK method are higher than those obtained by other methods, which proves that the MBRK method can effectively support the planning of search areas and that K-means clustering improves the POS of search plans.

In this paper, fast setpoint altitude tracking control for Hypersonic Flight Vehicle (HFV) satisfying Angle of Attack (AOA) constraint is studied with a two-loop structure controller, in the presence of parameter uncertainties and disturbances. For the outer loop, phase plane design is adopted for the simplified model under Bang-Bang controller to generate AOA command guaranteeing fast tracking performance. Modifications based on Feedback-Linearization (FL) technique are adopted to transform the phase trajectory into a sliding curve. Moreover, to resist mismatch between design model and actual model, Fast Exponential Reaching Law (FERL) is augmented with the baseline controller to maintain state on the sliding curve. The inner-loop controller is based on backstepping technique to track the AOA command generated by outer-loop controller. Barrier Lyapunov Function (BLF) design is employed to satisfy AOA requirement. Moreover, a novel auxiliary state is introduced to remove the restriction of BLF design on initial tracking errors. Dynamic Surface Control (DSC) is utilized to ease the computation burden. Rigorous stability proof is then given, and AOA is guaranteed to stay in predefined region theoretically. Simulations are conducted to verify the efficiency and superior performance of the proposed method.

Operational Modal Analysis (OMA) refers to the modal analysis of a structure in its operating state. The advantage of OMA is that only the output vibration signal of a system is used in the analysis process. Classic OMA is based on the white noise excitation assumption and many identification methods have been developed in both time domain and frequency domain. But in reality, many environmental excitations are not compliance with the white noise assumption. In this paper, a method of half power bandwidth analysis is applied to power spectrum analysis to deal with the colored noise and trapezoidal spectral excitation. The modal frequencies and modal damping ratios are derived and the error caused by trapezoidal spectral and colored noise excitation are analyzed. It is proved that the OMA algorithm based on the white noise assumption can be extended to the colored noise environments under certain conditions. Finally, a simulation example with a cantilever beam and a vibration test with four kinds of colored noise and trapezoidal spectrum base excitation are carried out and the results support the proposed method.

Tip clearances of multistage rotors and stators greatly affect aero-engines’ aerodynamic efficiency, stability and safety. The inevitable machining and assembly errors, as well as the complicated error propagation mechanism, cause overproof or non-uniform tip clearances. However, it is generally accepted that tip clearances are difficult to predict, even under assembly state. In this paper, a tip clearance prediction model is proposed based on measured error data. Some 3D error propagation sub-models, regarding rotors, supports and casings, are built and combined. The complex error coupling relationship is uncovered using mathematical methods. Rotor and stator tip clearances are predicted and analyzed in different phase angles. The maximum, minimum and average tip clearances can be calculated. The proposed model is implemented by a computer program, and a case study illustrates its performance and verifies its feasibility. The results can be referred by engineers in assembly quality judgement and decision-making.

The composition of the modern aerospace system becomes more and more complex. The performance degradation of any device in the system may cause it difficult for the whole system to keep normal working states. Therefore, it is essential to evaluate the performance of complex aerospace systems. In this paper, the performance evaluation of complex aerospace systems is regarded as a Multi-Attribute Decision Analysis (MADA) problem. Based on the structure and working principle of the system, a new Evidential Reasoning (ER) based approach with uncertain parameters is proposed to construct a nonlinear optimization model to evaluate the system performance. In the model, the interval form is used to express the uncertainty, such as error in testing data and inaccuracy in expert knowledge. In order to analyze the subsystems that have a great impact on the performance of the system, the sensitivity analysis of the evaluation result is carried out, and the corresponding maintenance strategy is proposed. For a type of Inertial Measurement Unit (IMU) used in a rocket, the proposed method is employed to evaluate its performance. Then, the parameter sensitivity of the evaluation result is analyzed, and the main factors affecting the performance of IMU are obtained. Finally, the comparative study shows the effectiveness of the proposed method.

This paper focuses on the issue of reliability and global sensitivity analysis for an airplane slat mechanism considering the uncertainties in the wear process of mechanical components. First, the multi-body kinematic model of the slat mechanism is built in the ADAMS software. The geometrical sizes of the roller wheels after wear degradation are considered as input variables and the angle the slat should turn is considered as the output response. To accurately identify the influential roller wheels to the reliability and robustness of the slat mechanism, the failure probability based sensitivity and variance-based sensitivity indices are introduced. Comprehensive analysis of the results have shown that the reliability analysis and global sensitivity theory can help engineers find significant parts by their contributions, thus provide guidance for mechanical design and maintenance.

Smart morphing wing, which is equipped with smart materials and able to change structural geometry adaptively, can further improve aerodynamic efficiency of aircraft. This paper presents a new integrated layout and topology optimization design for morphing wing driven by shape memory alloys (SMAs). By simultaneously optimizing the layout of smart actuators and topology of wing substrate, the ultimately determined configuration can achieve smooth, continuous and accurate geometric shape changes. In addition, aerodynamic analysis is carried out to compare smart morphing wing with traditional hinged airfoil. Finally, the optimized smart wing structure is constructed and tested to demonstrate and verify the morphing functionality. Application setbacks are also pointed out for further investigation.

This paper proposed a new method for quantitative assessment of visual detectability of damage based on logistic regression, using the Probability of Detection (POD) as a criterion. Experiments were performed to establish the massive hit/miss data of visual inspection. Authoritative investigations verified the reliability of the data. The prediction function concluded comprises more than one flaw size parameters, including the depth and diameter of the dents. The results show that the depth and diameter of the dents are pivotal for the evaluation of detectability; the type of detection, the detection distance, and the qualifications of personnel are critical external factors to be considered. This function, with an accuracy rate of nearly 85%, is capable of predicting the visual detection probability of impact damage under various detection environments, which will provide a reference for the damage tolerance design of composite materials and field maintenance in the Non-Destructive Testing (NDT) field.