Journal of Aerospace Engineering

In this research, a novel algorithm for real-time orbit determination (RTOD) is presented using the robust unscented Kalman filter (RUKF) with global positioning system (GPS) group and phase ionospheric correction (GRAPHIC) observables. To increase the reliability of the solution, a robust approach is included in the UKF to cope with the bad, invalid, or degraded measurements leading to the divergence or inaccurate output of the filter. Robustness is provided by making the filter less sensitive to faulty measurements using a scale matrix that is multiplied with the covariance matrix of the observation noises. Real data collected during a massive solar storm are used in the algorithm. For external validation, the outputs of RUKF and classical UKF are compared with the precision orbit ephemerides of the Challenging Minisatellite Payload (CHAMP). The results show that RUKF slightly outperforms classical UKF and possesses the capability to be used as an efficient and reliable algorithm in case of bad observations or malfunctioning of the system.

This study proposes a surrogate model that yields significant reduction in aerodynamic calculation for the initial sizing of the high-altitude long-endurance solar unmanned aerial vehicle (UAV) that uses solar and regenerative fuel cells. In contrast to the traditional aerodynamic surrogate model that correlates the wing drag with wing area, aspect ratio, and flight speed, the proposed surrogate model simplifies the correlation using the Reynolds number. As a result, the significant numerical error that the previous model suffers is removed, and considerable reduction in calculation time is achieved. Furthermore, the proposed model eliminates the cumbersome invocation of the aerodynamic analysis tool for altitude changes. In addition, this study conducts case studies of initial sizing using the proposed surrogate model and investigates the effects of flight date, wing area, and solar cell efficiency on the optimal configuration, which yields minimum weight under the constraints that consider the daily energy required for cruising and energy available in the daytime, i.e., power balance, nighttime energy balance, and $C_L$ limit.

In this paper, a second-order sliding mode control (SMC) is proposed to improve the performance of quadrotor. The sliding surface of the proposed controller is based on the proportional integral derivative (PID) dynamics. The control law is derived on the basis of the Lyapunov stability theory, which guarantees that all the system state trajectories reach and stay on the sliding surfaces. The proposed control method is compared with conventional sliding mode control, backstepping-based sliding mode control, and existing second-order sliding mode control from the literature. It is demonstrated that the proposed PID-based second-order sliding mode control improves the performance of quadrotor with better altitude tracking specification and faster convergence while maintaining stability even after the occurrence of external disturbances and parameter uncertainties.

In general, staged combustion-cycle engines have higher propulsion efficiency than that of open-cycle engines, prompting further research to develop the next generation of the former type of engines. Especially when it is on the development stage, a liquid rocket engine system may show unpredictable behavior affected by pressure and/or temperature variation. In addition, it is more dangerous when the engine is on the starting process. Therefore, prediction of the engine start up is very important both for the development of liquid rocket engines, and for preventing unfortunate accidents. In this study, a startup analysis simulator was developed for staged combustion-cycle engine powerpacks. This simulator can predict such various engine parameters as propellant flow rates, pressures temperature, and rotational speed of the turbopumps as functions of time. It is validated by comparison to real combustion test results. The tests were performed for an 8-tonf class engine. As a result, this simulator showed good agreement with the test results, not only qualitatively, but also quantitatively. This study confirms that the proposed simulator is suitable for starup analysis; furthermore, it can indicate appropriate startup operation.

Carrier-phase-based global navigation satellite system (GNSS) dynamic relative navigation is essential for fields that require high integrity and accuracy. Code-based receiver autonomous integrity monitoring (RAIM) has been studied extensively; however, carrier-phase-based integrity monitoring requires further study to meet the requirements of high-performance navigation. This paper proposes a quality-control method for carrier-phase-based GNSS relative navigation. It proposes the double difference (DD) model of carrier-phase-based relative navigation, which includes high-integrity difference navigation architecture and a novel closed-loop extended Kalman filter (EKF) using partial ambiguity resolution. Quality-control procedures based on least-squares principle are extended to EKF, in which fault detection using carrier-phase-based RAIM (CRAIM) and fault identification using a double $w$-test are carried out, and the integrity performance of reliability and separability are studied. The field trial data are tested and analyzed, and it is shown that the proposed method is able to detect and identify both step and ramp failures. The proposed method can be used not only for code measurements but also for carrier-phase measurements, thus improving the performance of GNSS relative navigation significantly.

The sensor-based backstepping control law, which is not sensitive to model uncertainty, uses less model knowledge and the measurements of state derivatives. A flight control law based on a sensor-based backstepping method for unmanned aerial vehicles (UAVs) is proposed in this paper. The nonlinear model uncertainties of a UAV and sensor noise are concerning. Moreover, command filters are used to handle dynamics and saturation effects of the actuators for carrying out the flight control law. The simulation results show the proposed flight control law can guarantee the closed-loop system stability and has better tracking control performance than the block backstepping control law with model uncertainty.

It is a challenging task to simulate the situation involving nonstationary motions, one crucial requirement of which is an efficient algorithm to realize the high-quality computational mesh deformation. The inverse distance weighting (IDW) method is a very simple mesh deformation method and the moving submesh approach (MSA) can improve the efficiency significantly. In this paper, by combining IDW with MSA, a new hybrid mesh deformation method (IDW-MSA) is proposed, which only depends on the point information of mesh and does not need to build large tables of mesh connectivity data. For the translation and rotation movements, the index parameter has different value ranges that affect mesh quality differently. The default settings of index parameter are 2.2 for translation and 6.0 for rotation, which have been shown to handle large deformations without difficulty. The results demonstrate the efficiency and robustness of this algorithm via four test cases. From the point of deformed mesh quality, it is comparable to the disk relaxation algorithm and radial basis functions (RBFs). The computational cost can be reduced by more than an order of magnitude compared with the RBFs-MSA and spring analogy approach. For these benefits, the new algorithm has the capacity for unsteady flow simulations involving boundary movements.

In this article, an analysis of a manufacturing process for small aerodynamic elements is presented. Two manufacturing methods—selective laser sintering (SLS) and fused deposition modeling (FDM)—were investigated. For both, the same additional surface-processing method was applied to obtain the desired surface properties. The geometry of the manufactured elements at different stages of surface processing was observed and tested with a profilometer and a scanner to quantify deviations. Process deviations were classified and quantified. The aerodynamic performance and practical application of the models and methods are discussed in this article.

A multidisciplinary design methodology for a launch vehicle (LV) with a hybrid rocket was proposed in order to obtain qualitative design knowledge. In this study, a propulsion system performance and aerodynamic performance were empirically evaluated using a theoretical approach, and flight evaluation was performed by solving equations of motion to evaluate the motion along the horizontal/vertical directions and rotation around the body axis. To demonstrate the applicability of the proposed method, two types of multiobjective design problems were solved using multiobjective evolutionary algorithms, and the results were visualized using the parallel coordinate plot, which is a data mining technique. The first design problem has two objective functions: the maximization of the highest altitude and the minimization of the total mass. In this case, the effect of the constraint related to the body length and diameter ratio was evaluated. The second design problem also had two objective functions and two constraints for a realistic LV design: the maximization of the downrange and the minimization of the total mass. The target altitude was different for these problems although the objective functions were identical. As a result, the trade-off information was successfully acquired for each design problem. It was also found that the body length and diameter ratio were key factors in deciding the maximum altitude. Furthermore, during the downrange maximization, the characteristic geometries observed in the obtained nondominated solutions revealed the design required to fulfill the constraint related to the target altitude.

A cokriging model incorporating gradient information and the function value of sample points can reduce the computational cost with a given level of accuracy. In this paper, the hierarchical kriging, a recently proposed cokriging method is employed, and a new method called gradient-enhanced hierarchical kriging (GEHK) is developed. First of all, a low-fidelity kriging model is built using derived samples, which are obtained by Taylor approximation using gradients and selected step sizes. Then a high-fidelity model is built by adjusting the low-fidelity kriging model with initial sample points. The GEHK model is more efficient than the traditional gradient-based cokriging model in the aerodynamic optimization, and could get a better optimum value. Taking the advantage of the modeling strategy, the global accuracy of the GEHK is not sensitive to step sizes, and the accuracy of prediction is enhanced evidently. The GEHK method is able to overcome limitations of traditional gradient-based cokriging models, and the prediction accuracy of the model is improved globally.

This paper studies the tracking control problem of hypersonic vehicles under the circumstances of external disturbance, coupling response, and input constraint. First, on the basis of the input-output linearization model of the hypersonic vehicle, an auxiliary error variable is introduced to convert the original model into a second-order system model. Then a back-stepping controller is designed for the situation of external disturbance with a known upper bound. Because a consecutive nonlinear function is introduced in the virtual controller, the closed-loop system has a rapid convergence rate. In order to further solve the external disturbance with an unknown upper bound and input constraint, a robust adaptive back-stepping controller that meets the input constraint is proposed based on the command filter and adaptive theory. Finally, the Lyapunov theory is applied to give strict proofs of the designed controllers. A numerical simulation of the longitudinal dynamics model of the hypersonic vehicle is conducted to further confirm the validity and robustness of the controllers.

Trailing-edge mixing flows associated with coolant injection are complex and result in significant aerodynamics losses. A series of tests on a high-pressure turbine vane cascade with trailing-edge injection were conducted to study the effects of trailing-edge injection on the loss characteristics of the turbine profile. Wake traverses with a five-hole probe and tests of the static pressure distributions on the turbine profile were carried out for test Mach numbers of 0.7, 0.78, and 0.84 and injection mass-flow ratios of 0, 2, 3.6, and 5.5%. Wake total pressure losses and flow angles as well as pressure distributions on the turbine profile were compared with tests without trailing-edge injection, indicating a significant influence of trailing-edge injection on the profile wake development and its blockage effect on the vane passage flow. As the test Mach number increases, there are few variations in the flow angle downstream of the cascade without trailing-edge injection, but its circumferential unevenness is enhanced. Trailing-edge injection of 2% increases the static pressure value in the rear part of the vane suction side, and then reduces the vane loading, but causes increased wake losses at different test Mach numbers. However, the aerodynamic losses start to be reduced as the injection mass-flow ratio increases to 3.6%.

This paper is focused on the position and attitude control of spacecraft with multiple liquid propellant tanks, while considering large amplitude propellant slosh and depletion. The large amplitude liquid slosh is included by using a moving pulsating ball model that is further improved by taking mass varying liquid propellant into account. A hybrid controller that combines sliding mode control with an adaptive algorithm is designed for spacecraft to perform position and large angle maneuvers, and the proposed controller is proved to be asymptotically stable. Numerical simulation results are presented to verify the effectiveness of the control approach when the spacecraft undergoes the disturbance of large amplitude slosh and liquid propellant depleting. Moreover, the influence of propellant depletion on maneuver completion time is also investigated. Finally, the designed adaptive algorithm is validated to be effective to reduce the maneuver completion time and the sensitivity of the controller on the mass varying propellant.

The thrust synergetic maneuver, i.e., during the atmospheric flight, the flight trajectory of the vehicle is modulated by both the aerodynamic force and thrust, can potentially lower fuel consumption in comparison with the all-propulsive maneuver to implement orbital plane changes. This paper fully studies the optimal synergetic maneuver for the orbital plane change problem with heating-rate constraints. By using the $hp$-adaptive pseudospectral method, the global solution of a synergetic maneuver has been found, and the corresponding optimal trajectories have been shown. The trend of the control variables indicates that the global optimal solution is more like a combination of aerocruise and aerobang. In consideration of different maximum allowable heating rates and orbital altitudes, the maximum abilities of orbital plane change and significant features of the trajectories during atmospheric flight are demonstrated. The comparisons between the global solution and aerobang about maximum orbital inclination changes under different constraints have been made to confirm the optimality of the results in this paper and show the gap of the aerobang. The optimal results of this work exactly give the ultimate ability of orbital plane change, and demonstrate that the synergetic maneuver is obviously efficient for orbital plane changes, especially for low orbit and relaxed heating rate constraint.

Tethered-satellite systems have great potential in completing various space missions. However, existing researches mainly focus on the deployment of satellites in a circular orbit, whereas deployment in an elliptical orbit, especially with disturbances, is rarely studied. This study develops a new control strategy to deploy tethered satellites in a low-eccentricity elliptical orbit that also considers system uncertainties and external disturbances. First, the periodical solution of the librational motion of a tethered-satellite system in an elliptic orbit is calculated. Because there is no fixed equilibrium point for deployment in elliptical orbits, the periodical solution is set as the end condition for deployment. After that, the controllability of the system is verified and an open-loop tension-control law is optimized by particle swarm optimization (PSO) and the Nelder-Mead method. To eliminate effects from uncertainties in initial states and errors from the deployment mechanism, an adaptive sliding mode controller is designed to achieve high-precision trajectory tracking. The performance of the proposed controller is compared quantitatively with a proportion-derivative (PD) controller and normal sliding mode controller. Furthermore, Monte Carlo simulations are conducted to demonstrate the effectiveness and robustness of the proposed controller when subjected to uncertain initial states. The simulation results indicate that the proposed control strategy enables the stable deployment of tethered-satellite systems despite the uncertainties and perturbations.

For the design of the grain-processing stations of spacecrafts, such as EXOMARS 2020, reliable estimates are required on the internal and bulk flow characteristics of granular media under low-gravity environments. Using theoretical and computational modeling, the authors present the results on the generic flow behavior of granular materials through flow channels under different gravity levels. For this, the authors use three approaches: (1) a simple one-dimensional discrete-layer approach (DLA) based on hybrid-Lagrange continuum analysis; (2) Kirya’s three-dimensional structural continuum model; and (3) three-dimensional discrete-element modeling (DEM). Each model has its merits and limitations. For the granular simulant considered in this paper, a good level of agreement is obtained between the results of Kirya’s model and the DEM simulations on the flow properties of the grains. Some qualitative comparisons are also reported favorably on the flow characteristics of grains between the results of the experimental parabolic flight campaign and the DEM simulations. The theoretical and DEM simulations presented in this paper could help to minimize relying on the complex experimental programs, such as the parabolic flight campaign, for evaluating the processing behavior of grains under low-gravity environments in the future.

This paper proposes an accurate system model independent resilient control approach with heuristic parameter optimization algorithm for air-breathing hypersonic vehicle tracking control. The control action is generated by the combination of nonlinear fractional-order proportional-integral-derivative (FOPID) and the active disturbance rejection control (ADRC). In particular, the FOPID controller increases two-degree-of-freedom variables, which improves the precision and stability of the control effect. The ADRC controller possesses aspects of the assimilation characteristics of the modern control theory and does not rely on the accurate mathematical model function, which is very suitable for a hypersonic vehicle system with parameter uncertainties and disturbances. Meanwhile, a new differential evolution exponential–cosine mixed migration (DEM) strategy for determining the biogeography-based optimization (BBO) migration rate to improve the optimization algorithm is proposed, which is mainly used for calculating tuning parameters of the FOPID ADRC. The improved hybrid algorithm is verified versus 14 benchmark functions and the practical optimization problems of the hypersonic vehicle vertical FOPID ADRC system are verified to illustrate the improved performance with the proposed approach. The effectiveness and robustness of the proposed method was verified by the simulation results.

This paper introduces a testbed developed from a perspective of soil mechanics that not only focused on wheel design and optimization but also considered the elimination of the boundary effect caused by a soil bin. Using this testbed, a series of experimental investigations were performed by changing the wheel rotational velocity, vertical load, and towed load. Tracks were generated at a regular spacing as the wheel lugs enter and exit the soil periodically. It has been found that there is a relationship between the track length and wheel slip ratio regardless of different mechanical properties of soil. The wheel rotational velocity has little effect on the driving torque and sinkage. The towed load affects the driving torque more than the sinkage. However, the vertical load effects on the driving torque and sinkage are similar. The current models used for parameter estimations may not be appropriate for Tongji-1 lunar soil simulant, which has a relatively high internal friction angle according to the experimental results. But the internal friction angle and cohesion can still be estimated with proper selection of shear deformation modulus.