Journal of Aerospace Engineering

This work investigates the performance of a cantilevered piezoelectric energy harvester (PEH) for harvesting energy from bridge vibrations induced by moving vehicles. The bridge is simplified as a simply supported beam. Three models have been considered for modeling the vehicle moving on the bridge, namely a moving load, a moving mass, and a moving oscillator. The influence of surface unevenness on the energy harvested by the PEH has been taken into account. A comprehensive parametric study is conducted to show the effect of the PEH installation position, vehicle speed, and configuration of the PEH on the harvested energy. The results indicate that the difference in harvested energy calculated by various vehicle models is less than 10% if surface unevenness of the bridge is ignored. If surface unevenness is considered, more energy can be harvested. However, the maximum accumulated energy calculated using the moving oscillator model is less than 5% of that predicted by the moving mass model. The unevenness effect is not applicable in the moving load model.

A novel strategy combining an extended state observer (ESO) and a backstepping sliding mode (BSM) controller is proposed for station-keeping of unstable collinear libration point orbits (LPOs) in the Sun-Earth/Moon system. The framework of the circular restricted three-body problem is utilized. The control thrusts are assumed to be generated by electric propulsion and, thus, continuous. In the proposed method, the system dynamics and uncertainties are treated as total disturbance and estimated by an ESO using only the input and output information. The BSM controller is designed to compensate for the total disturbance and ensure the actual trajectory converge to the nominal orbit. A rigorous stability analysis of the ESO-BSM controller is presented. A pure BSM controller without an extra observer is employed for comparison. Numerical simulations and a set of Monte Carlo simulations are presented to illustrate the proposed controller’s effectiveness and robustness. The results indicate that the model-free ESO-BSM controller is adequate for station-keeping of unstable LPOs, and performs better than the model-based BSM controller in the presence of orbital insertion errors, external disturbances, and random uncertainties.

This paper presents a novel model for the aeroelastic analysis of composite wings with attached piezoelectric actuators, using the concept of geometric stiffness. The mathematical model is introduced and validated against numerical and experimental results, and good agreement is obtained. It is consequently used to investigate the effect of piezoelectric forces on the aeroelastic behavior of composite wings. In the present analyses, the piezoelectric effect is studied for a voltage range from 0 to 100 V. Two wing configurations are considered: one with the piezoelectric sheets attached at the wing root (root configuration), and the second with the piezoelectric patches distributed along the wing span (staggered configuration). The present numerical examples show that both piezoelectric configurations significantly increase the divergence and flutter speeds, and hence improve the aeroelastic stability of composite wings. In general, the piezoelectric effect is more significant in the staggered configuration. In case of a straight wing, for instance, the divergence speed increases by 26.9%, and the flutter speed increases by 34.3% because of the change of the flutter mode. The staggered configuration is more effective than the root configuration for all other cases. It is concluded that the way piezoelectric patches are distributed on the wing and the magnitude of the applied voltage can considerably improve aeroelastic performance of the wings.

This study proposes a concept of a single-layer deployable truss structure driven by elastic components which is applicable to small satellites. The structure is self-deployable from its stowed state to a planar regular hexagon configuration, and the concept is compared with other three competing concepts in terms of some geometric metrics. The deployability and serviceability of the model are verified through both numerical analyses and experiments. The deployment process of the structure is investigated and demonstrated by a deployment test. Robustness and stability analyses for the deployment are also conducted by considering failure of some elastic components. Flatness of the deployed structure is analyzed and measured. Modal analysis and frequency identification tests reveal that the fundamental frequency of the deployed structure is around 2.3 Hz. It is concluded that the proposed single-layer deployable truss structure is valid and has high potential application to small satellites.

In this paper, a novel consistency monitoring method is proposed for spacecraft attitude estimator. The method allows for consistent evaluation of the estimator as a key index to determine whether the estimators are running normally. Compared with the theoretical consistency monitoring method, the proposed method replaces the true state with the prior state estimates, which can avoid the problem that true states cannot be obtained accurately. Then, the consistency monitoring method can be embedded into the attitude estimator as a block, and work in the state-space domain directly. Moreover, the probability of false alert specified by the required index can be used as a threshold, and the user interaction is avoided. The performance of the proposed method is tested and analyzed by simulations in several cases, and the results indicate that the method can detect the inconsistent estimate accurately.

When dealing with adaptive lifting surfaces, the level of complexity of the structural design naturally increases as a consequence of the augmented functionality of the resulting system. Specifically, an adaptive structure ensures a controlled and fully reversible transition from a baseline shape to a set of different configurations, each one characterized by different external loads and transmission paths of the internal stresses. The Consortium de recherche et d’innovation en aérospatiale au Québec (CRIAQ) MD0-505 research project, born from an efficient transatlantic cooperation among Italian and Canadian academic departments, research centers, and leading companies, suggests a possible solution to more stringent government requirements on emissions and safety: an innovative morphing aileron implemented to increase both structural stability and the in-cruise load control, was designed, manufactured, and tested. The aim of this article is to predict the aero-servo-elastic impact of a true-scale prototype on a regional aircraft, following an experimental test campaign and the development of a well-correlated finite-element model of the device. A detailed trade-off flutter analysis was performed by means of SANDY, an in-house code, in compliance with European Aviation Safety Agency (EASA) CS-25 airworthiness requirements and referring—initially—to nominal aileron functioning. Furthermore, a sensitivity investigation was carried out to assess the dynamic stability of the adaptive aileron, verifying the flutter clearance in the presence of critical scenarios related to malfunctions of the actuation system. Safety values for the aileron control harmonic were investigated looking at potential certification and industrialization issues.

The hypothesis of a conventional traveling wave model cannot cover the aerodynamic coupling effect of tandem blade cascades, while the aerodynamic interference between the front and rear blades of the cascade has a remarkable effect not only on the pressurized capacity but also the flutter characteristics. In order to investigate the flutter characteristics of the tandem cascade aeroelastic system, a fluid-structure coupling aeroelastic method and a system identification technique are used to establish a reduced order model (ROM). We analyzed the stability and vibration modes of the system through eigenvalues provided by the ROM. By this method, we can not only get the Inter Blade Phase Angle (IBPA) between blades in the same row, but also, at the same time, the vibration phase relationship between the front and rear tandem blades. Results showed that the stability would be lost when the natural frequencies of front and rear cascades were close to each other. Besides, the fluid-structure coupling effect is more obvious in the case of low mass ratio.

The subject of vibration-based structural health monitoring (SHM) has attracted increasing attention, especially in the field of civil engineering. However, the development of these monitoring processes is not a simple task, with user interaction playing a significant role in the extraction of modal characteristics. In this paper, an automated operational modal analysis methodology based on an eigensystem realization algorithm (ERA) and a two-stage clustering strategy is proposed. Three crucial steps are addressed in this study. In the first phase, ERA is adopted to calculate modes from state-space models of different orders. Subsequently, the dissimilarity of modal parameters is employed as the features of fuzzy C-means (FCM) clustering to separate stable modes from unstable ones. The final step consists of grouping stable modes with similar structural properties to select physical modes. No user-specified parameter is required in the clustering procedure to single out physical modes. A practical bridge example is used to verify that the proposed method can estimate modal parameters effectively in real time.

The high structural deficient rate poses serious risks to the operation of many bridges and buildings. To prevent critical damage and structural collapse, a quick structural health diagnosis tool is needed during normal operation or immediately after extreme events. In structural health monitoring (SHM), many existing methods will have limited usefulness in the quick damage identification process because (1) the damage event needs to be identified quickly, and (2) postdamage information is usually unavailable. To address these drawbacks, we propose a new damage detection and localization approach based on stochastic time series analysis. Specifically, damage sensitive features, which are extracted from vibration signals, follow different distributions before and after a damage event. Hence, we use optimal change-point detection theory to find the time of damage occurrence. Because existing change-point detectors require the postdamage feature distribution, which is unavailable in SHM, we propose a maximum likelihood method for learning the distribution parameters from the time-series data. The proposed damage detection using estimated parameters achieves optimal performance. Also, we utilize the detection results to find damage location without any further computation. Validation results show highly accurate damage identification in American Society of Civil Engineers benchmark structures and two shake table experiments.

The new exploration programs of the Moon set up by various countries require a good understanding of the mechanical behavior of lunar soil, especially for the construction of facilities and the soft-landing process of lunar rovers. Plate load tests (PLTs) of lunar soil simulants are routinely used to gain accurate understanding of engineering properties of real lunar soil and to predict the load-settlement behavior of foundation systems on the Moon. In this paper, a test apparatus and testbed are carefully designed to account for the grain-size effect and boundary effect. A series of plate load tests of Tongji-1 lunar soil simulant (TJ-1 simulant) is conducted with a foot pad and four circular plates at different loading velocities using the strain-loading method (soft-landing process of a lunar rover). For comparison, tests using the stress-loading method are also carried out (traditional shallow foundation system). In addition, the experimental results are compared with those predicted by the Terzaghi and the modified Terzaghi methods. The results show that with the same loading method and loading velocity, the bearing capacity of TJ-1 simulant under a foot pad with top diameter $R_t$ and bottom diameter $R_b$, can be estimated using the data under the plates with diameters $R_t$ and $R_b$, whereas the deformation modulus is close to the data under the plate with diameter $R_b$; the values of ultimate bearing capacity and bearing capacity factor using the stress-loading method lie in the range of those using the strain-loading method at different velocities, whereas the values of the deformation modulus using the stress-loading method are larger than those using the strain-loading method; and the Terzaghi method overpredicts the bearing behavior of TJ-1 simulant, whereas the modified Terzaghi method underpredicts it. Hence, more experimental and engineering tests are required to find a better modified method.

A sonic elliptic jet issuing from a convergent elliptic nozzle with aspect ratio (AR) 2, controlled with flat tabs in their limiting length, with straight edges and corrugated edges is studied in the presence of different levels of pressure gradients. The corrugation geometries studied are triangular and semicircular. Nozzle pressure ratios ($\mathrm{NPR}=P_0/P_a$) studied range from 2 to 5. For all flow conditions, the aerodynamic mixing of the uncontrolled jet and the jet controlled with these tabs placed along the major and minor axes of the nozzle exit is analyzed. The results show that the tab promotes mixing when orientated along major axis and retards mixing when it is oriented along the minor axis. Among the corrugations studied, the mixing promotion caused by semicircular corrugations is better than that caused by triangular corrugations. In addition, the mixing-promoting superiority of semicircular corrugations is found to be independent of nozzle expansion level. The tab with semicircular corrugations fixed along the major axis in the presence of a favorable pressure gradient corresponding to nozzle pressure ratio 5 causes a core length reduction of as much as 72%. The maximum core length reduction associated with the tab with triangular corrugations as well as the uncorrugated tab (plain tab), placed along the major axis, is about 34% at nozzle pressure ratio 3. The waves present in the core of controlled and uncontrolled jets, visualized using the shadowgraph technique, compliment the results inferred from the centerline pressure decay.

This paper develops a comprehensive methodology to address the attitude control problem of hypersonic vehicles in the presence of matched model uncertainties and external disturbances. Initially, a nonlinear dynamic model was established dedicated to attitude control. Afterward, a multivariable disturbance observer was constructed to estimate the lumped disturbance for compensation. Moreover, the dynamic inversion technique was adopted to cancel the nonlinear dynamics for decreasing complexity of controller design. To proceed, a novel fuzzy fast terminal sliding mode control strategy was designed to achieve a significant performance of attitude command tracking with the integrated consideration of robustness, chattering alleviation, and actuator saturation rejection. The finite-time stability of the closed-loop system was proven by means of the finite-time bounded function method and the Lyapunov theory. Simulation results demonstrated that the proposed synthetic scheme showed preferable performance and strong robustness in view of attitude command tracking.

Understanding the mechanical behavior of lunar regolith is of great importance to address the building of structures on the Moon, as well as for predicting the response of some equipment or facilities interacting with the lunar soil (i.e., rovers). Because the number of lunar regolith samples on Earth is quite low due to the difficulties of bringing it back during space missions, in the last decades, researchers started to develop similar materials, usually named lunar regolith simulants. This paper reports the geotechnical characterization of the De NoArtri (DNA) lunar simulant carried out in the laboratory. Compositional analyses and mechanical tests have been carried out to characterize this simulant; particle-size distribution analysis, chemical analysis, and scanning electron microscope (SEM) analysis have been performed to identify the DNA-1A from a compositional point of view, as well as triaxial compression, direct shear, and oedometer tests for depicting its mechanical behavior, with some comparison with original lunar soil and other simulants.

The flexural analysis of functionally graded carbon nanotube (CNT)-reinforced doubly curved singly ruled composite truncated cone is studied. The mathematical model contains the expansion of Taylor’s series up to third degree of thickness coordinate and normal curvatures in in-plane displacement fields. Because the distribution of transverse shear strain across the thickness coordinate is parabolic, the need of shear correction factor is removed. The condition of zero-transverse shear strain at the upper and lower surface of the truncated cone is applied in the present formulation. The advancement in the present mathematical model is the simultaneous inclusion of normal curvatures in deformation field and twist curvature in strain-displacement equations. The proposed new mathematical model is implemented in finite-element code written in FORTRAN. The present results are in good agreement with the experimental results as well as results from other methods. After validation, a large number of flexural problems are presented by varying different boundary conditions, volume fraction, loading pattern, and geometric parameters.

A stratospheric airship (SSA) is a cost-effective platform for telecommunications and science missions in near space 20 km above the Earth’s surface. However, an accurate model of the structural behavior of the large envelope of a SSA composed of a series of identical gores welded together has not been developed to date owing to the complex mechanical properties of the multilayer laminated envelope materials, complicated manufacturing procedures, stringent operational conditions, and variation of the loading. In this work, biaxial tensile experiments on a typical SSA envelope fabric are first performed to describe the nonlinear mechanical properties based on the response surface method, and a nonlinear material model for numerical analysis is developed. Next, patterning effects and creep influences of a reduced-scale model of the SSA envelope are thoroughly analyzed and discussed. The initial configuration of the scale model is presented and compared to the ideal model generated by the revolution of the design shape profile. Finally, experiments and numerical analyses on the scale model under the inflation process are performed and discussed in detail. Compared to the ideal model, the numerical results of the model considering the initial configuration are in better agreement with the experimental results. This finding demonstrates that patterning effects and creep influences must be considered in the numerical analysis of a SSA envelope.

Identification of an aircraft critical loads envelope requires a lengthy and rigorous analysis procedure that includes simulating the aircraft in thousands of load cases identified in certification requirements. Imposing a global finite-element model (GFEM) in this process is computationally very expensive, so reduced order models (ROMs) of airframes are commonly used, particularly in iterative static and dynamic aeroelasticity analyses. ROMs must be simple enough to be analyzed thousands of times during a iterative aeroelastic simulation but accurate enough to have dynamic characteristics closely matching those of the GFEM within a frequency range of interest. This paper reviews various techniques of model order reduction (MOR) available in the literature including stiffness extraction by unitary loadings, which is commonly used in the aerospace industry, and linear algebraic matrix-based reduction methodologies. This article presents a case study where the discussed MOR methodologies are used in normal-mode analysis, static, and dynamic aeroelasticity loads analyses of a Bombardier aircraft platform to demonstrate the efficiency of each ROM reviewed. Results obtained show that a ROM generated using component mode synthesis (CMS) has superior dynamic characteristics compared to all other reduction methods reviewed. Compared to the GFEM, it is found that errors in RMS values of loads recovered using the fixed and free interface CMS ROM subject to tuned discrete gust are 1.17% and 1.14%, respectively. Similarly, errors found in the RMS values of the magnitude of loads recovered due to von Karman power spectral density gust are 0.56% and 0.75% for the fixed and free interface CMS ROM, respectively.

The estimation of terrain mechanical properties is an important mission of planetary exploration rovers. Since only limited resources and human supervision are available, efficient and accurate methods for terrain estimation are required. In this paper, a nonparametric estimation method for the prediction of the terrain parameters is presented. Four characteristic parameters based on telemetry information of planetary rovers were adopted in the method, including wheel load $W$, torque $T$, rut depth (hereinafter referred to as apparent sinkage $z_a$), and slip ratio $s$, and 72 identification parameters composed by the characteristic parameters were put forward for terrain estimation. The terrain consisted of simulant regolith classified nonparametrically and artificially defined as three states (loose, natural, and compact states) based on different hardnesses, and four terrain estimation criteria (slack, ideal, partially strict, and strict) were established. Wheel–soil interaction tests were conducted for the terrain estimation, and apparent sinkage based on rut noncontact measurement was analyzed. The optimal identification parameters and estimation criteria were derived through the analysis of evaluation indexes (correct rate, accurate rate, and conservation rate). Experimental validation results indicated that the proposed method could accurately and efficiently estimate the mechanical state of deformable terrain for planetary rovers.

This paper presents a numerical study to show the effects of laminate thickness and tapering on the performance of composite bolted joints made of carbon fiber–reinforced polymer (CFRP) materials. Major weight savings can be achieved by using tapered joints while compromising little in joint stiffness and strength compared to joints having uniform thickness. A numerical investigation is carried out to minimize the weight of a double-lap CFRP composite multibolt joint considering different tapering configurations. The proposed tapering configurations can be useful for designing efficient lightweight aerospace structures, in which weight savings are a great concern. The present analysis is carried out using a novel three-dimensional (3D) finite-element-based progressive damage model developed using the FE software ABAQUS. The material constitutive relations and the progressive damage algorithms are integrated with ABAQUS using the user subroutine UMAT. In addition to the stiffness and strength of the joints, out-of-plane displacements are also calculated for each case in order to determine the effect on secondary bending.

Temperature effects may mask the variation in structural properties or responses due to damage by causing equally or even larger changes in structures, resulting in false positive or false negative detections. These temperature effects should be eliminated during the process of damage detection; however, the complexity of operating civil structures makes it difficult to separate those influences from structural damage using closed form solutions or parametric approaches. In this study, a new damage detection approach based on autoassociative neural networks (AANNs) is proposed to detect the structural damage in bridges by eliminating the temperature effects. First, time series analysis–based damage features extracted from undamaged structure under varying temperature effects only are used to train the AANN. The trained neural networks were then fed by damage features with both damage and temperature effects. The results show that the proposed method can detect and locate the damage by tracking the prediction errors of the AANN under varying temperature effects.

The problem of spacecraft final approach subject to input saturation and a safe constraint is studied in this paper. First, an attitude and orbit-coupling model with input saturation was established for spacecraft final approach. Second, in order to restrict the safe range of motion, a new continuously differentiable collision avoidance safe constraint function was constructed. Combined with the constraint function, an improved fast nonsingular terminal sliding mode manifold was presented. Further, two antisaturation sliding mode control schemes that adopt auxiliary systems to settle the problem of input saturation were proposed. Finally, Lyapunov stability theory was employed to prove that the error states of the closed-loop system under the presented control schemes are finite-time convergent and there are no collisions during the motion process. Meanwhile, simulations were conducted to verify that the chaser can realize the final safe approach with input saturation, which further indicates the effectiveness of the designed control schemes.

A passive radio frequency identification (RFID)-based crack sensor was developed and its sensitivity to crack propagation on metallic plates has been experimentally validated. A crack propagation test method was designed to evaluate any backscatter power-based crack sensor to monitor propagating cracks on a metallic surface. This new method uses plate specimens designed for standard fracture toughness testing. Systematic increases in displacement with a hydraulic universal test machine to propagate the crack were performed. Using digital imagery, the physical characteristics of the crack and fracture mode were determined with high precision. Linear elastic fracture was induced so as to more closely resemble the fracture mode that is to be expected in high strength steel bridge girders. The sensor was tested as a single unit and in various arrays of multiple units for increased pervasiveness in monitoring. A piecewise relationship between the damage index and crack opening was found. This relationship is a significant finding that demonstrates that RFID-based crack sensing is a feasible tool for bridge inspection.

A novel hypersonic aerodynamic configuration of the high-pressure–capturing wing (HCW) based on the lifting body is proposed, and computational fluid dynamics (CFD) is employed to carefully analyze longitudinal and lateral aerodynamic force and flight stability. The major analysis results are as follows. In the longitudinal condition, compared with the lifting body, the HCW configuration shows a 16%–18% rise in lift coefficients while the drag coefficients increase only slightly, so the lift-to-drag ratios are obviously improved, especially when the angle of attack (AOA) is less than 10°, with the lift-to-drag ratios increasing more than 35%. In the lateral condition, lift coefficient, drag coefficient, and lift-to-drag ratio increase by different degrees, and the lateral force and yawing moment presents relatively good linear growth with the angle of side slip. The pressure center coefficient at the theoretical fixed-point of the aircraft is adopted to measure flight stability. Compared with the lifting body, the HCW layout has worse longitudinal stability at a negative AOA and better stability at a positive AOA. The lateral pressure center coefficient grows by about 8% and 5%, respectively, when the AOAs are 0° and 12°. In addition, the leading-edge profile and total length of the capturing wing (CW) are improved according to the characteristics of the flow around the aircraft and the pressure distribution on the lower surface of the CW. Compared with the basic outline, the lift coefficient, drag coefficient, and lift-to-drag ratio of the improved configurations are increased by 7%–27%, 1%–6%, and 6%–25%, respectively. The CW presents more even distribution pressure on the lower surface and a better high-pressure–capturing effect. This study not only further verifies the outstanding lift compensation effect of the HCW but also lays a foundation for the practical design and optimization of this novel aerodynamic configuration.