Journal of Aerospace Engineering

Attitude control performance of spacecraft is inevitably affected by internal and external disturbances such as vibrations of flexible appendages, payload motions, actuator faults, and environmental disturbances. To suppress the effects of these disturbances on attitude control performance, this paper proposes a reduced-order sliding mode disturbance observer (SMDO)-based nonsingular terminal sliding mode controller (NTSMC). First, a reduced-order SMDO is designed to estimate the lumped disturbance including all the internal and external disturbances. Compared with conventional SMDOs, the proposed SMDO has enough robustness to the uncertainties of the disturbance model, but with a lower observer order because estimation of the system state is not required. Second, a nonsingular terminal sliding mode controller plus a feedforward compensator are designed to achieve finite-time attitude stabilization of the spacecraft in the presence of internal and external disturbances. Because most of the disturbances are compensated by SMDO-based feedforward, only a small switching gain is needed in the sliding mode controller. As a result, the chattering phenomenon of the controller can be alleviated. Finally, both the theory analysis and simulation results show the effectiveness of the proposed control scheme.

Physical modeling experiments related to lunar in situ resource utilization activities use suitable soil simulants such as GRC-3. Only the index properties (e.g., specific gravity, particle size distribution, and maximum and minimum densities) compression indices, and shear strength parameters (peak angle of internal friction) of GRC-3 are currently available in the literature. In addition to the shear strength parameters, this work determined other important mechanical parameters such as critical state angle of internal friction, dilatancy angle, elastic modulus, and Poisson’s ratio using triaxial compression tests conducted at three different confining stresses of 25, 50, and 100 kPa. An additional set of triaxial specimens incorporated bender elements, which were used to determine small-strain shear wave velocity and shear modulus of GRC-3 at confining stresses ranging between 12.5 and 150 kPa. The confining stresses used in this work were lower than those used in other works on GRC-3 found in the literature. For extrapolating the behavior of terrestrial simulants to in situ surface lunar regolith, results obtained at smaller confining stresses are generally more relevant. The shear strength parameters of GRC-3 determined as part of this investigation compared well with those for GRC-3 and lunar regolith found in the literature, as well as lunar simulants GRC-1 and JSC-1A. Simple empirical correlations relating mechanical properties (angle of internal friction, dilatancy angle, elastic modulus, small-strain shear wave velocity, and maximum shear modulus) of GRC-3 as a function of its relative density or void ratio and confining stress are provided, so these properties can be readily estimated to support further analytical studies involving GRC-3.

The need for accurate material models to simulate the deformation, damage, and failure of polymer matrix composites under impact conditions is becoming more and more critical, because these materials are gaining increased usage in the aerospace and automotive communities. Although there are several composite material models currently available within commercial transient dynamic finite-element codes, several features have been identified as lacking in these models, which could substantially enhance the predictive capability of composite impact simulations. One specific desired feature includes incorporating both plasticity and damage within the material model. Another desired feature relates to using experimentally based tabulated input to define the evolution of yield stresses, plastic strains, and damage parameters as opposed to specifying discrete input properties (such as modulus and strength) and using analytical functions to track the response of the material. To begin to address these needs, an orthotropic, macroscopic constitutive model incorporating both plasticity and damage is being developed for implementation within a commonly used commercial transient dynamic finite-element code. The plasticity model is based on extending the Tsai-Wu composite failure model into a strain hardening-based orthotropic plasticity model with a nonassociative flow rule. The evolution of the yield surface is determined based on tabulated stress-strain curves in the various normal and shear directions, and is tracked by using the effective plastic strain. To compute the evolution of damage, a strain-equivalent semicoupled formulation is used, in which a load in one direction results in a stiffness reduction in multiple material coordinate directions. A detailed analysis is carried out to ensure that the strain-equivalence assumption is appropriate for the derived plasticity and damage formulations that are used in the current model. Procedures to develop the appropriate input curves for the damage model are presented and the process required to develop an appropriate characterization test matrix is discussed.

The nonlinear dynamics of a tethered space solar power station are presented. Dynamic formulations are developed for a solar power station system that consists of two main parts: the bus system and the solar power panel. The orbital motions of the system, the rotation of the solar power panel, the deployment/retrieval of the tethers, and the vibration of the tethers are taken into account. The dynamic behavior of the tethered space solar power station is studied via numerical simulation. Without any initial state errors, the in-orbit movement of the tethered space solar power station is simulated. Then, a stability analysis is conducted for different types of initial state errors. The influences of the initial attitude errors of the solar power panel and the tether’s longitudinal and transverse vibrations on the tethered solar power station are analyzed. The numerical results demonstrate that initial attitude errors in different directions have different influences on the system. Compared with axial vibrations, transverse vibrations in the tethers have more significant impacts on the system.

An experimental and numerical investigation was conducted to study the skin–stiffener separation of single T-shape stiffener specimens in postbuckling condition. Three specimens were manufactured with a centrally located Teflon insert, and were loaded in compression until collapse. Deformation patterns and separation evolution were monitored during the tests. To measure the full-field displacements and the strain distributions of the specimens, a digital image correlation (DIC) system was used. Skin–stiffener separation was observed and measured with an ultrasound system. Finite-element (FE) analyses were conducted to capture interlaminar damage mechanism based on the virtual crack closure technique. The numerical analysis accurately predicted the postbuckling deformation and the skin–stiffener separation behavior. The close correlation between the experimental and numerical results allows for further exploitation of the strength reserve in the postbuckling region and wider design options for the next generation of composite aircraft designs.

A new three-dimensional trans-scale crack growth model, developed from the microscale to macroscale, is presented based on the concept of restraining stress zone. It aims to simulate the growth behaviors of fatigue cracks in a welded joint of orthotropic steel decks. In the study, the crack shape was first simplified as a semielliptical surface crack, and analyzed in a finite-element mode considering the trans-scale stress intensity factors (SIFs). Subsequently, the trans-scale SIFs served as controlling parameters for the propagation of fatigue crack from the microscale to macroscale. The proposed model can simulate the overall process of fatigue failure of orthotropic steel deck details. Comparison between numerical simulations and results from the experimental $S\text{-}N$ curves given in the literature provides two conclusions: (1) the three-dimensional trans-scale crack growth model accurately depicts the trans-scale behaviors of fatigue failure of the weld joint between the longitudinal ribs and deck plate of the orthotropic steel deck; and (2) the model well explained the scatter phenomenon of the fatigue test data due to the microscopic effects. In addition, the initial microdefects have a significant influence on the fatigue life, and the microscopic effects in a fatigue process can be considered by the proposed model.

A constrained coning correction form is proposed for designing efficient coning algorithms. This new coning correction form, which includes only one vector cross product, is directly presented first, and then it is constructed by simplifying the traditional uncompressed coning correction form with the given constraint relationship. The constraint relationship is necessary for designing the constrained coning algorithm. On the basis of the traditional uncompressed coning correction form and the given constraint relationship, the constrained coning algorithm can be designed. Two types of algorithm error models and an algorithm throughput model are given for analyzing and evaluating the coning and maneuver performance of coning algorithms. The analytical results and numerical simulation show that the constrained coning algorithm compared with the uncompressed coning algorithm has a coning accuracy equivalent to that of the compressed version, the equivalent maneuver accuracy is higher than that of the compressed version, and the algorithm throughput is lower.

Flow field characteristics of and regression rate distribution for the solid-fuel ramjet (SFRJ) with star solid fuel were investigated by numerical and experimental methods. The experimental data were obtained by burning polyethylene using a connected-pipe facility. The three-dimensional code developed in the present study adopted third-order monotonic upwind scheme for conservation laws (MUSCL) and central difference schemes, advection upstream splitting method by pressure-based weight functions (AUSMPW+), flux vector splitting method, and second-order moment turbulence-chemistry model, together with the $k\text{-}\omega$ shear stress transport (SST) turbulence model. The solid-fuel surface temperature was calculated with the fluid-solid heat coupling method. The numerical results show that obvious circumferential flow exists in the SFRJ with star solid fuel. The regression rates are higher at the star tip and lower at the star bottom. The space-averaged regression rate of star solid fuel is slightly higher than that of the traditional single-port cylindrical solid fuel. Turbulent viscosity is a critical parameter affecting the regression rate distribution, and the circumferential flow in the SFRJ has an important influence on turbulent viscosity. Comparing the numerical and experimental regression rates, it is indicated that the developed code can generally predict the effect of fuel configuration on the regression rate, and further investigation is needed to improve the accuracy and reliability of the developed code. A sudden increase in pressure during the combustion of star solid fuel was observed experimentally, which requires further investigations.

The paper deals with a command tracking–control system (CTCS) design problem for plants involving both continuous and discrete effecters, namely hybrid effecters. Firstly, a reaction control system (RCS) model of a hypersonic re-entry vehicle (HRV) is established, and then linearization around the trim points is carried out for both longitudinal-direction and lateral-directional nonlinear models of HRV, respectively. Second, a general command-tracking problem is converted to a regulation problem by constructing a deviation system, and an optimal state feedback controller is designed to generate a continuous torque command. Then, a daisy-chained control-allocation method is applied to assign the torque command between the aerosurfaces and RCS, and an innovative control-allocation strategy of integrating model predictive control with mixed-integer linear programming (MPC/MILP) is proposed to distribute the torque to RCS among thrusters, where the switching-time constraints of the thrusters can be taken into account explicitly. Finally, the proposed control-allocation strategy is demonstrated to the longitudinal angle-of-attack (AOA) CTCS and the lateral-directional bank angle CTCS design for HRV. Compared with MILP, the MPC/MILP control-allocation strategy is more reasonable in on/off switching of the RCS thrusters and effective in reducing the wastage of the RCS fuel. Simulation results using a six-degree-of-freedom (6-DOF) nonlinear dynamics model of HRV show that the proposed strategy is suitable for the CTCS design of HRV driven by both the aerosurfaces and the RCS.

Buildings may suffer serious damage when subjected to extreme loadings such as strong winds and earthquakes. In seismic events, the error time histories between measured and estimated responses should contain the information of the structural deterioration, i.e., the locations, levels, and time of occurrences. Therefore, this study presents a new damage detection method based on prediction errors using a bank of Kalman estimators. A representative model of a building was derived from a frequency-domain multiinput, multioutput system identification method under ambient vibration prior to earthquakes. This model was then converted into a bank of estimators that calculate estimation errors. Damage was interpreted by statistical indices from these errors and allowed determining the occurrence, levels, and locations of damage. A numerical example is presented to demonstrate the proposed damage detection method as well as to exhibit the damage detection performance. A series of experimental tests were carried out with this damage detection method implemented in various scenarios. The experimental verification shows that this proposed method is quite effective for seismic damage detection.

Strings or cables can be used to mitigate unfavorable vibrations. This paper proposes a novel isolator that comprises a cable network and a fluid damper. Equations of the coupled transverse and longitudinal vibrations of a prestressed cable are established to analyze vibration characteristics, which reveal that the transverse vibration is dominant, whereas the longitudinal vibration can be neglected. The structural synthesis method is utilized to obtain the dynamic model of a network with eight cables. The frequency response function (FRF) of the cable network coupled with a vibration source is calculated. Results show that the equivalent stiffness of the cable network changes with the tension linearly. The damper is constructed with fluid filled bellows, and its equivalent damping is analyzed. Tests and experiments are carried out to validate the performance of the isolator. Acceleration transmissibility of the cable network, the fluid damper, and their combination are compared.

In this paper, the problem of precise autonomous orbit maintenance of a satellite using output feedback and quadratic optimal regulators in a low Earth orbit is investigated. Autonomous on-board orbit maintenance refers to automatic control of different operational parameters within their control windows. In this paper, the problem of autonomous absolute orbit control is converted to a relative orbit control problem in which reference orbit includes the orbital elements of a virtual satellite, which is influenced only by the Earth’s gravity field. The paper focuses on increasing the accuracy of orbit control during the satellite mission lifetime. This is accomplished by considering satellite mass reduction due to fuel consumption in the dynamic model. Also, a precise passive control of the eccentricity vector is presented by choosing an appropriate in-orbit location of the along-track maneuvers. Analysis of both the in-plane and out-of-plane relative motion of satellite with respect to reference orbit is presented. Numerical simulations are performed to show validation of the proposed control methods and techniques.

This paper presents a scheduled composite off-line output feedback model predictive control strategy for a constrained hypersonic vehicle (HV) in the presence of external persistent disturbances. First, multiple linear time invariant (LTI) models are constructed to represent the nominal longitudinal dynamics of HV without external persistent disturbances. Then, by combining the construction of asymptotically stable polyhedral invariant sets for explicitly handling asymmetric constraints of control inputs and angle of attack and the state estimator for estimating partial unmeasured states, a set of local off-line output feedback model predictive control schemes are first developed for multiple LTI models. Additionally, based on the strong nonlinear approximation ability of a recurrent cerebellar model articulation controller (RCMAC), a RCMAC disturbance observer (RCMACDO) is presented to estimate the actual disturbances, and then an auxiliary compensation controller is appended to attenuate the influences of external persistent disturbances. Furthermore, by designing a proper scheduling strategy, the proposed control strategy with the overlapped stable regions is proposed for the wide tracking task. Finally, the comparative simulation results for tracking reference commands of velocity and altitude verify the effectiveness of the proposed control strategy.

A new analytic formulation to express the time derivatives of the instantaneous impact point (IIP) of a rocket is proposed. The geometric relationship on a plane tangential to the IIP is used to decompose the inertial IIP rate vector into the downrange and crossrange components, and a systematic procedure to determine the component values is presented. The new formulation shows significant advantages over the existing formulation such that the procedure and final expressions for the IIP derivatives are easy to understand and more compact. The validity of the proposed formulation was demonstrated through numerical simulation.

For the last few decades, an extensive research has been focused on flapping-wing aerodynamics to understand the generation of thrust due to pitching and plunging motions of an airfoil. However, most of the research emphasized an airfoil undergoing simple harmonic motion in either pitching or plunging motion. In this paper, a numerical study has been performed to estimate the thrust generated from a NACA0012 airfoil undergoing a periodic motion. The prescribed motion is created by an expression for harmonic and nonharmonic but periodic motions. The effects of these prescribed motions on thrust generation have been studied numerically for a Reynolds number of 20,000. It is observed that the thrust generated by the square and trapezoidal (periodic) plunging motions is much higher than the sinusoidal (harmonic) plunging motion. The effects of reduced frequency and amplitude of oscillations on the generation of thrust have also been studied. At higher reduced frequency and amplitudes, trapezoidal plunging motion generates higher thrust.

Active shape adjustment of a cable-mesh reflector is a significant procedure to compensate the effects of a complicated space environment in orbit. In this paper, the active shape adjustment of a large cable-mesh reflector with actuators is addressed, and the dynamic input voltage profiles of actuators are estimated using a novel fast model predictive control method. The electromechanical coupling dynamic model of the cable-mesh reflector with piezoceramic (PZT) actuators is first established by using piezoelectric constitutive equations and Hamilton’s principle. For a certain shape distortion, the dynamic control voltage profiles are then obtained via the novel fast model predictive control method in which the structural dynamics model is reformulated as a novel explicit repression form to avoid the computations of matrix exponential. Additionally, some fast computation strategies based on the Newmark-$\beta$ method are used to increase computational efficiency. Finally, a 30-meter diameter cable-mesh reflector is chosen as a numerical example, and the simulation results demonstrate that the proposed control algorithm provides a valid and efficient solution for the shape control of large cable-mesh reflectors.

Stellar refraction navigation is an effective method for autonomous celestial navigation of satellites. Compared with the refraction apparent height, a better navigation performance can be achieved via the stellar refraction angle. Nevertheless, this causes the measurement model to become an implicit function, in which the measurements and states are restricted to implicit equations. The available filters, applied to a system with an implicit measurement model, are based on linearization, which needs to compute the Jacobian matrices and introduces linearization errors. In this paper, a type of unscented Kalman filter (UKF), referred to as an implicit augmented unscented Kalman filter (IAUKF), is proposed, in which the state is augmented via the measurement. The zero is regarded as the equivalent measurement vector for updating the estimation of the augmented state as well as its covariance matrix. The performance of the IAUKF is tested and demonstrated via simulation. Simulations reveal that the navigation performance of the IAUKF is better than that of the implicit extended Kalman filter (IEKF), the implicit augmented extended Kalman filter (IAEKF), the iterative IEKF, and the implicit UKF.

A numerical simulation is carried out in this study to assess the performance of a shape memory microgripper operating under the nonconventional zero-load two-way shape memory effect (TWSME). To this end, a recently developed multimechanism material model is parameterized to reproduce the TWSME of shape memory alloys (SMAs). The gripper is designed to open and close (as it grasps and releases an object) a number of times. The results obtained are compared to that of an experiment in which the actuation device worked under the traditional method of antagonistic or selective heating and cooling of the gripper components. The contact force generated under the TWSME was found to be of the same order as that obtained in the experimental test. Moreover, when the device is needed to operate under extended cycles, the TWSM microgripper actuator appears suitable, considering the simplicity of operational steps and long-term stable behavior of the device under cycles.

A rational simulation of the interactions between random traffic and bridges is significant for evaluating existing bridges’ performance. In this paper, an innovative time-variant dimension updating method (TVDUM) for random traffic and bridges is proposed for coupled vehicle and bridge dynamic interactions. A detailed procedure for the TVDUM is provided based on the traditional fully coupled vehicle–bridge dynamic system. Starting from introducing the random traffic flow simulation and establishing a typical vehicle dynamic model database, the implementation process of the TVDUM and important treatment strategies of the integrated coupled dynamic system are described in detail. The numerical case study on an existing bridge indicates that the new method has better calculation efficiency and can avoid the iterative calculation in a time step and uncertainty of computing time compared with the classic iterative method, especially for short-span and medium-span bridges.

Under thermomechanical fatigue (TMF) loading, the thermal cyclic temperature may change with decreasing or increasing applied stress upon unloading or reloading. The damage inside of fiber-reinforced ceramic-matrix composites (CMCs) is affected by the phase angle. In this paper, the thermomechanical fatigue behavior of fiber-reinforced CMCs corresponding to different phase angles of $\theta =0$, $\pi /3$, $\pi /2$, and $\pi$ has been investigated. The damage accumulation processes considered the coupling effects of the temperature changing with applied stress in each applied cycle and the degradation of fiber/matrix interface shear stress with increasing applied cycles. The relationships between the thermomechanical fatigue damage mechanisms, hysteresis parameters (i.e., hysteresis energy and peak strain), phase angle, and interface damage condition have been established. The thermomechanical fatigue behavior for different fiber volume content, peak stress, and matrix crack spacing have been analyzed for different phase angles. The damage accumulation of cross-ply SiC/magnesium aluminosilicate (MAS) composite under thermomechanical fatigue loading have been predicted for different phase angles of $\theta =0$ and $\pi$.

This study proposes a variable shock angle osculating flowfield waverider design method. The flow field structure and aerodynamic characteristics of osculating flowfield waveriders are also analyzed. In this method, the constraint of imposing the same conical flowfield on each osculating plane is removed because the shock angle of each osculating plane is different, which can be chosen according to the specific needs of waveriders. The obtained results show that the shock angle distribution is an important factor in the design of osculating flowfield waveriders. A waverider whose shock angle increases as a parabolic curve along the spanwise direction has a larger volume and lower lift-to-drag ratio. In contrast, a waverider whose shock angle decreases as a parabolic curve along the spanwise direction has a smaller volume and higher lift-to-drag ratio. Providing different shock angle distributions can lead to greater flexibility in the design and optimization of hypersonic waverider vehicles.

It has been discovered that water (ice) exists at the polar regions of the Moon and Mars, and it is expected that water would be used to maintain life support for astronauts and to provide a raw material of hydrogen and oxygen. Because it is necessary to mine, sample, and transport water ice for in-situ water utilization, electrostatic sampling and transport systems for crushed water ice have been developed. A high voltage is applied between parallel screen electrodes of the sampling device. It was demonstrated that crushed ice particles, as well as regolith particles, can be captured successfully by the screen electrodes as a result of the electrostatic force if the lower screen electrode is placed in contact with the surface of the ice bulk. Ion-exchanged water ice, tap-water ice, ${\mathrm{CuSO}}_4$-doped water ice, and ice mixed with lunar regolith simulant were captured. Captured ice particles are transported by the electrostatic transport system that uses electrostatic traveling waves. The conveyer consists of parallel electrodes printed on a plastic substrate. A four-phase rectangular voltage is applied to the electrodes to transport particles on the conveyer. It was demonstrated that crushed ice particles mixed with lunar regolith simulant, as well as regolith particles and liquid water droplets, are transported successfully by this system.

In April 2014 an aircraft accident occurred at Jämijärvi aerodrome when a Comp Air 8 aircraft crashed into the woods. According to the scenario of the investigation report, the pilot reduced the engine power in such a way that the thrust became negative. Simultaneously the prop-washed kinetic pressure of the tail was reduced, which rapidly evoked a nose-down moment and a corresponding angular velocity. This led to a negative angle of attack and a large negative wing load and finally resulted in a wing strut buckling and the wing folding toward the aircraft’s body. In this study, six degree-of-freedom (6-dof) simulations are carried out for the aircraft to assess the supposed accident scenario. The simulations show that the proposed mechanism is possible, but there existed other potential courses of events after the thrust adjustment.