Journal of Aerospace Engineering

This paper is concerned with vibration control of a single-link flexible beam structure. The proposed beam is controlled by a servo motor through a harmonic gear reducer. After obtaining the models by system identification, a time-delayed optimal controller based on model output prediction and optimal control theory was designed to compensate the unknown time delay in the controlled system. Then, experiments on the proposed control scheme were conducted in a set-point vibration control process. The experimental results demonstrate that the performance of vibration suppression can be improved substantially when applying the proposed method in the presence of time delay compensation, as compared to the traditional proportional and derivative (PD) controller. The accuracy of models was validated according to experimental results, and the factors that influence the output prediction accuracy are analyzed in this paper.

The steady two-dimensional boundary layer slip flow of a viscous incompressible Cu-water nanofluid past a moving radiating plate in a quiescent fluid (Sakiadis flow) and the flow induced over a stationary radiating flat plate by a uniform free stream (Blasius flow) are investigated simultaneously numerically. The experimental correlations for the effective density, thermal conductivity, and viscosity of nanofluid are used in the governing equations. Similarity equations of the governing transport equations are derived using similarity variables developed by a scaling group of transformation. The transformed equations are solved numerically using an implicit finite-difference numerical method. The emerging parameters are Prandtl number, radiation conduction, velocity ratio, thermal slip, and hydrodynamic slip. Sample results for the dimensionless axial velocity profiles, temperature profiles, friction factor, and rate of heat transfer have been presented graphically and discussed in detail. The friction factor for the Sakiadis flow is higher than that for the Blasius flow, whereas heat transfer rates for the Sakiadis flow are lower than that for the Blasius flow. The present results of the skin friction factor and the heat transfer rate are also compared with the published results for several special cases and are found to be in good agreement.

The authors have developed an electrostatic force–based sampler to reliably and autonomously sample asteroid regolith. After applying a rectangular high voltage between parallel screen electrodes mounted at the lower end of a tube, the resultant electrostatic force acts on nearby regolith particles. Some agitated particles are captured when passing through the screen electrode openings and transported to a collection capsule through the tube. In a microgravity environment, effective particle sampling was expected because particle motions are not affected by the negligible gravitational force. The authors confirmed the sampler’s performance in a microgravity environment through numerical calculations and a model experiment. The calculation using the distinct element method predicted successful regolith capture, including conductive and insulative particles, under air and microgravity. The sampler shows much better performance in vacuum than in air. Lunar regolith simulant was sampled experimentally in a zero-$g$ environment reproduced by the parabolic flight of an aircraft. A large amount of simulant ($\sim 900\mathrm{mg}$) containing small and large (diameter: $>0.5\mathrm{mm}$) particles was successfully collected.

Fluid actuated cellular structures are morphing structures inspired by the nastic movement of plants. These materials have a wide array of applications from morphing aircraft wings to soft robotics. The nonlinear shape-morphing behaviors of the fluid actuated cellular structures composed of randomly distributed polygonal motor cells are investigated in this work. A new multiscale modeling framework based on multiscale finite-element methods is proposed to simulate the nonlinear behaviors of such adaptive materials with irregular polygonal microstructures. The multiscale displacement and hydraulic pressure base functions are firstly constructed to establish the relationship between the microstructures of the fluidic actuating cells and the macroscopic deformation on the polygonal coarse-scale mesh. Then, the corotational formulation for geometrically nonlinear analysis is integrated to this multiscale method to decompose the nonlinear deformations of the polygonal coarse-grid element into rigid-body motions and pure deformational displacements. In addition, a master–slave displacement relationship is employed to ensure the displacement continuity at the interface between the polygonal multiscale coarse-grid elements and the traditional fine-scale elements in a same computational model. Several representative examples including a smart wing structure are investigated to validate the accuracy and efficiency of the proposed polygonal multiscale corotational method.

The need for accurate material models to simulate the deformation, damage, and failure of polymer matrix composites under impact conditions is becoming critical as these materials are gaining increased usage in the aerospace and automotive industries. There are a variety of material models currently available within commercial transient dynamic finite-element codes to analyze the response of composite materials under impact conditions. However, there are several features that are lacking in the currently available models that could improve the predictive capability of the impact simulations. To address these needs, a combined elasto-plastic model with damage suitable for implementation within transient dynamic finite-element codes has been developed. A key feature of the improved material model is the use of tabulated stress-strain data in a variety of coordinate directions to fully define the stress-strain response of the material. Currently, the model development efforts have focused on creating the plasticity portion of the model. A commonly used composite failure model has been generalized and extended to a strain-hardening-based orthotropic yield function with a non-associative flow rule. The coefficients of the yield function are computed based on the input stress-strain curves using the effective plastic strain as the tracking variable. The coefficients of the flow rule are determined in a systematic manner based on the available stress-strain data for the material. The evolution of the yield surface is examined, in detail, for a sample composite. A numerical algorithm based on the classic radial return method is employed to compute the evolution of the effective plastic strain. A specific laminated composite is examined to demonstrate the process of characterizing and analyzing the response of a composite using the developed model. The developed material model is suitable for use within commercial transient dynamic finite-element codes for use in analyzing the nonlinear response of polymer composites.

This paper presents a new robust output feedback guidance scheme for autonomous spacecraft rendezvous during the final phase in elliptical orbit. The proposed approach is essentially a compound control method, which consists of an input-to-state stable (ISS) concept and high-gain observer (HGO) methodology. More specifically, the HGO is used to estimate the relative velocity between two neighboring spacecrafts, while the ISS-based controller is used to regulate the relative position and the relative velocity to a small region around zero asymptotically. Stability analysis of the closed-loop system is also established by using Lyapunov theory. Numerical simulations are performed to demonstrate the robustness and effectiveness of the proposed method.

Interference fit can lead to better fatigue behavior of mechanical fastened joints. To explore the fatigue enhancement mechanism of interference fit, an analytical model of an interference-fit pinned sheet under subsequent tensile loading is presented. This model is employed to correlate the bypass load with the external longitudinal tensile load of the sheet, and the range of the two forces. Three-dimensional (3D) finite element (FE) analysis is performed using ABAQUS and comparison between the results of the two models shows a good agreement. Analytical results reveal that the key to the reduction of the bypass load amplitude lies in the elastic deformation of connected members of interference-fitted joints and the contact between them. This effect is accomplished through the automatic adjustment of the contact at the interfaces of the pin and sheet. For a specific joint, the effective affecting range (EAR) of interference for external loading is dependent on the interference and stiffness of its members. Specifically, the bypass load amplitude can be reduced only when external loads intersect EAR with a nonempty subset. If exerted loads are entirely within EAR, the bypass load amplitude can be minimized and the reduction ratio depends solely upon the stiffness of the connected members. It is also concluded that taking into consideration the external loads, especially its maximum value, is essential in the optimizing of interference. Finally, the optimum interference is deduced via the analytical model.

Nanofluid hydrothermal behavior in a channel is investigated for potential use in the regenerative cooling channel of a semicryogenic engine. The basic partial differential equations are reduced to ordinary differential equations, which are solved analytically using the differential transformation method. The effects of pertinent parameters such as nanofluid volume fraction, suction parameter, viscosity parameter, and Eckert number on the flow and heat transfer characteristics are discussed. Results indicate that skin friction is an increasing function of nanofluid volume fraction, while it is a decreasing function of viscosity parameter and suction parameter. The Nusselt number has a direct relationship with nanofluid volume fraction and suction parameter, but it has a reverse relationship with viscosity parameter and Eckert number.

Three different applications of a commercially available desktop flight simulator were demonstrated in flight test training. The first case examined the visual reproduction of spins executed at National Research Council (NRC) Canada in the CT-133 aircraft. The reproduced in-cockpit views were found in agreement with video footage recorded during the spins, while the characteristics of the reconstructed spin flight path were found to be in qualitative agreement to the values resulting from the flight data analysis. The second case considered the testing of basic attitude hold control systems coupled around the simulator’s Boeing 747 flight model. The resulting time responses of the pitch and bank angles were compared to those of the aircraft’s linear state-space model and were found to predict satisfactory the stable gain cases. Finally a simulated control room environment was setup using the flight simulator and other modeling software through a local network, providing real-time plotting of flight test parameters in a number of displays. Overall, the commercial simulator software was found to be a useful low-cost aid for various parts of flight test training.

In the third phase of the Chang’E project, a drilling and coring device mounted on a lunar probe will be sent to the moon to acquire samples of lunar soil within a certain depth (subsurface lunar soil). Interaction between the sampling drill and lunar soil simulant must be investigated to evaluate the drilling load and coring rate on the Earth in advance. It is necessary to measure the mechanical properties that are distributed in a vertical direction in the preparation of the lunar soil simulant. Until now, only a few preliminary attempts based on a simple penetrometer for measurement estimation are reported in the literature. The flat dilatometer test (DMT) is an in situ civil empirical method for soil type identification and settlement prediction that analyzes the test results by depth. Because the empirical formulas used in the standard DMT method aimed to cover various soil types, the accuracy of mechanical properties estimation for a specific soil type was limited, especially for well-distributed artificial soil, such as lunar soil simulant. This paper proposes a modified DMT method considering relations of compressibility, shear strength, and bulk density as additional information for the DMT results analysis. Based on the relationship between the DMT constrained modulus ($M_{\text{DMT}}$) and depth, the distributions of bulk density and shear strength could be derived accurately for the subsurface lunar soil simulant. The test results were consistent with both theoretical analysis and Apollo estimation in bulk density. The contribution of this paper is to provide a feasible approach to obtain the vertical distribution of the mechanical properties for the subsurface lunar soil simulant.

Switching control theory is introduced to solve regulation and protection control problems in multiobjective control systems. Switching performance objectives and a switching strategy are given, and a family of proportion-integration-differentiation (PID) controllers and compensators is designed. The simulation shows that using the switching control design method in aircraft engine multiloop control systems can not only improve the dynamic performance of the engine control system and reduce the switching times but also guarantee stability in certain situations.

A one-dimensional (1D) finite-volume implementation, based on the second-order Godunov method for predicting dynamic response of foams that exhibit irreversible compaction, is presented. Cellular foams, with an upward concave stress-strain relationship associated with densification of the material resulting from collapse of the cell structure, have the possibility of a strong discontinuity with shock-type characteristics. An approximate solution to the local Riemann problem is developed considering all possible wave structure(s) in the material based on the quasi-static response of the material. The prediction of dynamic compaction response of the foam subjected to solid impact is shown to compare favorably with experimental results. For an applied blast pressure loading, attenuation of transmitted stress wave in the foam is shown to be a result of the energy dissipation provided by compaction of the foam.

Wing stiffness is very crucial in augmenting aerodynamic forces in flapping wing flyers. In this work, the effect of wing deformation was studied using three-dimensional numerical analysis (two-way fluid structure interaction), coupling the flow solver (FLUENT) and the structural (ABAQUS) solver via the MpCCI platform. Three different degrees of bending stiffness corresponding to rigid, flexible, and highly flexible case wings were investigated. Moreover, the wings were tested for both low Reynolds number ($\mathsf{R}=\mathrm{9,000}$) and high Reynolds number ($\mathsf{R}=\mathrm{40,000}$), at a flapping frequency of 9 Hz corresponding to an angle of attack (AoA) ranging from $\alpha =0$ to 50°. The results of mean aerodynamic lift and drag coefficients showed good agreement between numerical and experimental findings. Also, the time-averaged lift-to-drag ratio reveals that the highly flexible wing exhibited the best overall aerodynamic performance when compared to the rigid and flexible wing.

This paper deals with two-dimensional peristaltic flow of a viscous fluid in a symmetric channel for variable temperature-dependent viscosity. The effects of Hall current, ion slip, viscous dissipation, and Ohmic heating are also taken into consideration. The problem is formulated in terms of governing equations using conservation laws of mass, momentum, and energy. Using a series solution an approximate asymptotic solution is obtained by the method of perturbation expansion in terms of a small viscosity parameter under standard assumptions of long wavelength and low Reynolds number for the peristaltic transport of fluid. The results are presented graphically to demonstrate the behavior of field quantities under the influence of different physical parameters. However, special attention is given to the effects of variable viscosity and dissipation on the peristaltic flow (the new features added in the present study). It is observed that the maximum pressure rise against which peristalsis works as a pump decreases as a result of increasing viscosity parameter and Brinkman number. The heat transfer in variable-viscosity fluid is found to be smaller in comparison with constant-viscosity fluid.

In this paper, a nonlinear guidance law is developed for the approach and landing (A&L) phase of a reusable launch vehicle (RLV). First, a novel time-varying sliding mode control (TVSMC) technique is introduced. The main feature of this technique is that it enables the system states to converge to zero at the desired finite time. Then, the developed technique is applied to the A&L guidance law design. The guidance law possesses the capability of generating trajectories online according to the current system states and the terminal constraints. Therefore, there is no need to design any reference trajectories in advance. In addition, the analytic solutions of the altitude and flight path angle can be obtained in advance by solving a first-order linear differential equation. These analytic solutions can also be used to estimate the boundary of the normal load factor of the RLV. The effectiveness of the proposed guidance strategy and the accuracy of the analytic solutions are demonstrated through numerical simulations.

The present analysis deals with the study of time-dependent flow of a second-order fluid on a rotating cone in the presence of chemical reaction and heat generation or absorption effects under prescribed heat flux conditions. The boundary-layer nonlinear partial differential equations of second grade fluid are first reduced into a system of ordinary differential equations with the help of transformations and nondimensional similar and nonsimilar quantities, and then solved analytically by optimal homotopy analysis method (OHAM). The effects of relevant parameters such as chemical reaction, heat generation, or absorption on local skin friction coefficients, local Nusselt number, and local Sherwood number are discussed. These effects are illustrated graphically as well as in tabular form to describe special features of the solutions.

The vibration isolation and mitigation of a platform, such as aerospace or precision instrument platforms, is an important research topic. However, previous studies only address high-frequency excitations; they disregard the control effect of low-frequency excitations. Thus, a new vibration control scheme for a platform is proposed to reduce the dynamic responses of a platform that is subjected to wide-frequency excitations, which range from 0 to 500 Hz, using vibration isolation and mitigation devices, magnetorheological (MR) dampers, and viscoelastic (VE) dampers. The motion equations of a complex dynamic system with these three different types of dampers are deduced considering seven degree-of-freedom coupling vibration. The idea of multistate control is adopted to control the inputting currents of the MR damper, and the dynamic responses of the platform to sinusoidal excitation, white noise excitation, and load spectrum excitation are calculated, respectively. The analysis results indicate that the proposed vibration control scheme is effective and suitable for vibration control of the platform.

The $J_2$ effect is the dominating perturbation for satellite formation flying missions. In this paper, a linearized satellite relative motion model considering $J_2$ perturbation and eccentricity was derived first. Then, a real-time fuel-optimal continuous low-thrust control approach was proposed for satellite formation control in eccentric orbits on the basis of the developed linear $J_2$ dynamic model. This optimal control problem was converted into a mathematical programming problem by the application of the Legendre pseudospectral method, which makes real-time optimal control feasible. Finally, comprehensive simulation results validated the proposed linearized $J_2$ model and formation control approach.

In this paper, an active fault-tolerant flight control system against sensor/actuator failures for unmanned aerial vehicles (UAVs) is proposed. First, an approach to detecting and isolating UAV sensor failures affecting the mean of the Kalman filter (KF) innovation sequence is proposed. Second, an adaptive two-stage linear Kalman filtering algorithm is used to isolate the sensor and actuator faults and to estimate the loss of control effectiveness and the magnitude of degree of stuck faults in a UAV model. Control effectiveness factors and stuck magnitudes are used to quantify the faults entering the UAV flight control system through actuators. In the case of a sensor fault, the faulty sensor is isolated, and the KF that ignores the feedback from the faulty sensor is built. If the fault is an actuator fault, then the actuator fault isolation and identification are performed using the adaptive two-stage KF. The parameters of the feedback controller are tuned by the control reconfiguration procedure. In the simulations, the longitudinal and lateral dynamics of the UAV model is considered, and the detection and isolation of sensor failures are examined. Some simulation results for the actuator fault isolation and identification are given. Partial loss and stuck faults in actuators are considered. A design of reconfigurable flight control against sensor/actuator failures is implemented.

Magnetohydrodynamic (MHD) mixed convection flow of an incompressible Jeffrey fluid induced by a bidirectional stretching surface was investigated. Heat and mass transfer analysis was carried out in the presence of thermophoresis particle deposition and thermal radiation. Convective heat and mass conditions at the boundaries were taken. Mathematical analysis is presented subject to boundary layer assumptions. Homotopic procedure was implemented for the computations of solutions. Impacts of various physical parameters on the dimensionless temperature and concentration fields are plotted and discussed. Physical quantities of interest, namely, the local Nusselt and Sherwood numbers are analyzed through numerical values.

The blade element method is an indispensible engineering design tool. It executes rapidly on a personal computer and is capable of accurate propeller performance predictions. An extensive literature survey reveals that for conventional high-aspect ratio propeller blades lifting surface and computational fluid dynamics approaches add a large degree of complexity without providing significantly improved performance prediction capabilities as compared to the blade element/vortex theory. The accuracy of the blade element method is, however, highly dependent on the fidelity of the airfoil aerodynamic model. The primary focus of this paper is on presenting a nonlinear aerodynamic model of airfoils that can be used in combination with the blade element method for enhanced propeller performance prediction over a wide range of advance ratios. The proposed nonlinear airfoil model includes effects of angles of attack up to 90 degrees and compressibility corrections. Results of this method are validated against experimental measurements. Excellent agreement between experiment and prediction is shown for subsonic helical tip Mach numbers.

A new coring bit with a barrier ring was developed to address the disturbance problem associated with the common method of lunar soil sampling. This new coring bit is presented in this paper along with an analysis of the physical characteristics of regolith and coring bits. The structural parameters of the barrier ring, which disturbs the original state of the soil, are also analyzed. A user-defined material, based on the user-defined material mechanical behavior (UMAT) subroutine in the ABAQUS finite-element software, was used to simulate the contact area between the lunar soil and the barrier. The simulation results showed that the structure of the barrier ring has a significant effect on the stress and displacement produced in the lunar soil below the coring bit, but has little effect on the soil inside the ring. The test results showed that the coring bit with the barrier ring achieves a higher coring rate and causes less disturbance than a common bit.

This paper investigates the attitude tracking control problem for rigid spacecraft with inertia uncertainties and external perturbations. Spacecraft attitude dynamics and kinematics are initially converted into Lagrange-like model and formulated as a state-space form described by the modified Rodrigues parameters (MRPs). Robust controllers contain two parts and use geometric homogeneity, integral sliding mode (ISM) technique, and adaptive laws. One part proposes a class of feedback controllers to accomplish finite-time stabilization of the second order dynamics without the lumped uncertainties. The other part rejects bounded uncertainties based on ISM associated with adaptive laws. Moreover, a rigorous proof of finite-time convergence is developed. The proposed control laws provide finite-time convergence, robustness, and faster and higher control precision, and these algorithms require no information about inertia uncertainties and external disturbances, which cannot be obtained in practical systems. Finally, numerical simulations are also carried out to illustrate the effectiveness of these methodologies.

Special percussive mechanisms have been used to explore the lunar, Martian, and other planetary subsurface and extract soil (regolith)/rock samples for further study. The special type of percussive mechanisms investigated in this study, Auto-Gopher and Ultrasonic/Sonic Driller/Corer (USDC) developed by National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory and Honeybee Robotics Spacecraft Mechanisms Corporation, consists of an ultrasonic horn, a free mass (hammer), and the drill rod. This paper presents a general methodology to perform the dynamic contact analysis of the longitudinal impact of the free mass on the drill rod including the effects of structural vibration and damping of the rod. The contact force caused by impact is obtained by using Hertz force-indentation relation coupled with the structural vibration of the rod obtained by using mode superposition method and finite-element technique. Numerical solution, with equilibrium iterations, of the equations of motion is implemented. The contact force was observed to be consistent with experimental results available in the literature for similar problems. The results obtained with the model developed in this study are also verified by using a commercially available finite-element code. The magnitude of the contact force was observed to increase with increasing damping ratio, whereas the duration of the contact force slightly decreased.

In this paper, the effects of the capsule half-cone angle on the dynamics of supersonic parachute systems are investigated. The supersonic flow over three-dimensional rigid parachute models are studied by numerically solving compressible Navier-Stokes equations. In this study, the parachute system has a capsule and a canopy. The cases with different capsule half-cone angle are carried out. The computational results show that unsteady pulsating flow fields exit in all the cases and are in reasonable agreement with the experimental data. The results also show that the capsule wake–canopy shock interaction causes a significantly higher pressure around the parachute system in comparison to the capsule shock–canopy shock interaction, thus providing the primary source of the unsteadiness in the flow field. As the capsule half-cone angle ($\theta$) is increased, the difference in the pressure distribution inside the canopy also increases, and the wake-shock interaction plays a more significant role in the unsteady flow mode. Moreover, when $\theta$ is increased, this results in weaker aerodynamic interactions, including the wake-shock and shock-shock interactions, which is favorable for a supersonic parachute system.

This paper reports on an experimental study motivated by the issue of vortex formation in fuel tanks of liquid propulsion rockets. In this study, vortex funnel (vortex-air core) formation during draining of liquids from cylindrical tanks is suppressed by means of a simple, yet effective method of controlling or adjusting the size of the base drain port. This is particularly relevant in spacecraft and rocket applications where suppression of such vortex-air core is very much warranted because of the possible drain port blockage they cause and the consequent adverse impact (of vortices) on the generation of propulsive thrust. It is found that in the range of rotational speeds provided to the liquid column (between 120 and 200 rpm) in a cylindrical tank, for $d/D\sim 0.03$ (where $D$ is the tank diameter held constant in the study, and $d$ is the port diameter that is varied in the experiments), vortex funnel formation is completely eliminated for concentric drain ports. For eccentric ports, this occurs at a slightly higher value of port size, viz., $d/D\sim 0.04$. The liquid used is water at room temperature with its free surface open to the atmosphere.