Hypersonic Reentry Vehicle Research Articles

A longitudinal trajectory tracking method with L1 adaptive control for hypersonic reentry vehicles

This paper presents a longitudinal trajectory tracking scheme with [Formula: see text] adaptive control for hypersonic reentry vehicles (HRVs). A linear time-varying (LTV) multiple input multiple output (MIMO) model, in which influences of lateral states, earth rotation, and linearization are considered as model uncertainties, is derived based on state and input errors of longitudinal model. The normalization of error model is used to reduce differences of magnitude orders in state and input matrix elements which may affect the stability of [Formula: see text] adaptive controller. In order to achieve an accurate tracking performance, a linear quadratic regulator (LQR) controller is employed as the baseline controller, augmented with an [Formula: see text] adaptive controller to attenuate the matched and unmatched uncertainties. Based on the augmented controller, the optimization process is executed with the estimate of uncertainties at the same time. The simulation results of LQR controller, [Formula: see text] augmentation controller and robust [Formula: see text] controller show that the [Formula: see text] adaptive control method can reduce the terminal and integral of squared state errors validly. Terminal state errors in all simulation scenarios are less than 2.5m/s, 1e-3 and 10m, respectively, which reflects its effectiveness in increasing robustness of baseline controller.

THE INFLUENCE OF PERMEABILITY ON THE ABLATION PROCESS FOR AN ABLATIVE MATERIAL

The heat and mass transfer in the ablation process is of great importance for the ablation protection engineering. Accurate temperature assessment can provide effective support for the design of thermal protection structure and ablative material of reentry hypersonic vehicle. In this work, we studied the effect of permeability on heat and mass transfer and ablation thermal protection of gases produced during ablation. Since the carbide formed by ablation of material is a typical porous medium, its structure has self-similarity and can be described by fractal theory. Taking into account the angle of global coordinates and the local coordinates, this paper derived the permeability in any direction as a function of three different fractal dimensions in [Formula: see text], [Formula: see text] and [Formula: see text] directions. In order to verify the correctness of this method, the new model is introduced into the ablation process. Aiming at the ablation process and the diffusion equation of pyrolysis gas in the carbide layer, the temperature, material density and pyrolysis gas density distribution of three-dimensional spherical head under different permeability were simulated numerically. It is found that the permeability of carbides formed by ablative reaction of ablative materials related to fractal structure has an effect on ablation process. From our preliminary results, the higher the permeability, the faster the ablation speed, and the more obvious the overall temperature rise is.

Robust Tracking for Hypersonic Reentry Vehicles via Disturbance Estimation-Triggered Control

This note presents a novel control framework based on disturbance estimation information to exploit the potential performance improvement. Disturbances in the hypersonic reentry vehicles are revisited, and a disturbance effect indicator (DEI) is defined to demonstrate the pros and cons of disturbances’ influence on the system. Based on the disturbance estimation, a disturbance estimation-triggered control scheme for the attitude tracking is established. Furthermore, the ultimately bounded stability of the closed-loop system is guaranteed. Distinguished from eliminating the disturbance directly in the state-of-the-art disturbance observer-based control, the proposed control switches its structure to counteract or retain the disturbance according to the DEI, and thus is capable of improving the transient performance. Simulation results verify the effectiveness and superiority of the proposed approach.

Nussbaum gain adaptive control scheme for moving mass reentry hypersonic vehicle with actuator saturation

This paper addresses an actuator saturation problem of the moving mass hypersonic vehicles (HSVs) in the reentry phase. The saturation nonlinearity is modeled using a hyperbolic tangent function and the concomitant time-varying coefficients problem is handled via Nussbaum gain technique. Then backstepping technique is applied in control design and the explosion of complexity in traditional backstepping design is avoided by utilizing dynamic surface control. Subsequently, a Nussbaum gain adaptive controller is constructively framed to deal with the actuator saturation. Based on the disturbance observers, the robustness of the proposed controller is enhanced. The semiglobal stability of the closed-loop system is ensured via Lyapunov synthesis. Finally, numerical simulation results are presented to show the effectiveness of the designed control scheme.

Dynamics and Control for Hypersonic Gliding Vehicles Equipped with a Moving Mass and RCS

AbstractTo solve the problems of a hypersonic unpowered gliding reentry vehicle controlled by only one actuator, a combination bank-to-turn control mode with a moving mass and nonredundant reaction...

An on-line guidance algorithm for high L/D hypersonic reentry vehicles

An on-line guidance algorithm is presented for high L/D hypersonic reentry vehicles using plane-symmetry bank-to-turn control method. The proposed guidance algorithm can generate a feasible trajectory at each guidance cycle during the reentry flight. In the longitudinal profile, height-range (H-R) and height-velocity (H-V) joint design method is proposed to rapidly generate the reference trajectory and the controlled bank angle to satisfy all constraints. Then, the quasi-equilibrium glide phenomenon is employed to extract the other controlled angle of attack corresponding to the reference trajectory. In the lateral profile, the bank angle reversal strategy is designed according to the cross-range angle threshold and the proportional navigation approach to reduce heading error. Simulation results for nominal and dispersed cases show that the proposed guidance algorithm is capable of generating a feasible trajectory rapidly that satisfies both path and terminal constraints.

Fault-tolerant control for over-actuated hypersonic reentry vehicle subject to multiple disturbances and actuator faults

In this paper, a fault-tolerant control scheme is proposed for attitude tracking problem of hypersonic reentry vehicle subjected to multiple disturbances and time-varying actuator faults. For convenience of fault-tolerant controller design, conventional hypersonic reentry vehicle model is transformed into control-oriented model by incorporating actuator faults into lumped disturbance. Based on the lumped disturbance estimate provided by high order sliding mode observer, fault-tolerant controllers are developed within the frame of active disturbance rejection control in attitude loop and angular rate loop according to time-scale separation and singular perturbation principle. Then, the desired control moment is allocated to actuators based on recurrent neural network. With the well-designed fault-tolerant controllers and control allocation, a novel meta-heuristic dynamic adaptation salp swarm algorithm is employed to optimize control parameters to achieve minimum attitude tracking error. Comparative simulations are conducted to verify the effectiveness of the developed dynamic adaptation salp swarm algorithm and the investigated fault-tolerant control scheme.

Compound fault-tolerant attitude control for hypersonic vehicle with reaction control systems in reentry phase

In this paper, a novel compound fault-tolerant attitude control (FTC) scheme is proposed for reentry hypersonic vehicles with aerodynamic surfaces and reaction control systems (RCS) in the presence of parameter uncertainties, external disturbances and aerodynamic surfaces faults. Aerodynamic surfaces work as the primary actuators and RCS serve as auxiliary actuators. When aerodynamic surfaces cannot provide the required attitude control torque due to low dynamic pressure or faults, RCS are activated to assist aerodynamic surfaces to generate the residual torque. A nonlinear disturbance observer-based sliding mode controller is designed to calculate the required attitude control torque which can handle the parametric uncertainties and external disturbances together. The quadratic programming method is applied to obtain the optimal aerodynamic surfaces deflections from the required control torque. An innovative fuzzy rule-based decision-making system is design to solve the RCS control allocation problem, which is conceptually easy to understand and computationally efficiently compared with existing approaches. Based on quantized control theory, the closed-loop control system stability is rigorously analyzed. Simulation results are given to demonstrate the effectiveness and efficiency of developed FTC scheme.

Design exploration of combinational spike and opposing jet concept in hypersonic flows based on CFD calculation and surrogate model

The combined thermal protection system has led the drag and heat reduction of hypersonic reentry vehicles to a new developing direction. In order to obtain better resistance to aerodynamic drag and heat while maintain the work stability of the aircraft at the same time, the optimization design of the combined thermal protection system is indispensable. In this paper, a CFD numerical simulation method is combined with a surrogate model based multi-objective optimization algorithm to optimize the configuration of a combinatorial spike and opposing jet thermal protection system in a hypersonic flow with the freestream Mach number of 5.75. The obtained results show that when the total drag coefficient (Cd) and the heat fluxes on the head of the blunt body (Q) are the objective functions, the diameter ratio of the aerodisk to the blunt body bottom (d/D) has no significant effect on the drag and heat flux reduction, and it can be neglected in the optimization process. While the objective functions Cd and Q are affected by the three variables the length-to-diameter ratio of the aerospike (L/D), the jet pressure ratio (PR), and the nozzle radius (r0) in similar ways. Therefore, in this case, the optimization problem can be transformed into a single-objective optimization problem. The quadratic response surface model established by sample points obtained by the orthogonal experimental design method is of high simulation accuracy, with the determination coefficients of Cd and Q are 0.964 and 0.965 respectively, and there is only a difference of −6.96% in the objective function Cd, −0.93% in Q between the optimization results and the CFD results. The combined thermal protection system has better performance in both drag and heat reduction than the single spike or opposing jet systems. Compared with the pure blunt body, the total drag coefficient and heat flux on the head of the blunt body with the combined thermal protection system have significantly decreased, with the Cd goes down 86.66%, and the wall heat flux Q drops off 96.37%.

Heat alleviation studies on hypersonic re-entry vehicles

ABSTRACTA numerical simulation has been carried out to investigate the effects of leading edge blowing upon heat alleviation on the surface of hypersonic vehicles. The initial phase of this work deals with the ability of the present CFD-based techniques to solve hypersonic flow field past blunt-nosed vehicles at hypersonic speeds. Towards this end, the authors selected three re-entry vehicles with published flow field data against which the present computed results could be measured. With increasing confidence on the numerical simulation techniques to accurately resolve the hypersonic flow, the boundary condition at the solid blunt surface was then equipped with the ability to blow the flow out of the solid boundary at a rate of at least 0.01–0.1 times the free stream (ρ∞u∞) mass flow rate. The numerical iterative procedure was then progressed until the flow at the surface matched this new ‘inviscid like’ boundary condition. The actual matching of the flow field at the ejection control surface was achieved by iterating the flow on the adjacent cells until the flow conformed to the conditions prescribed at the control surface. The conditions at the surface could be submitted as a ρ∞u∞at the surface or could be equipped as a simple static pressure condition providing the desired flow rate. The comparison between the present engineering approach and the experimental data presented in this study demonstrate its ability to solve complex problems in hypersonic.

Reentry attitude tracking via coupling effect-triggered control subjected to bounded uncertainties

ABSTRACTThe attitude tracking control issue for hypersonic reentry vehicle subjected to bounded uncertainties is investigated in this paper. The uncertainties are estimated by a disturbance observer with a simple structure whose parameter tuning methodology is provided to guarantee the system robustness. The coupling effect of the hypersonic reentry vehicle is analysed with a binary form based on a coupling effect indicator. The positive or negative value of indicator represents the harmful or beneficial coupling effect on the system. Then, a coupling effect-triggered control is developed to cancel the harmful couplings while utilising the beneficial couplings. The trigger point in the controller occurs when the property of the coupling effect happens to change. The specific criterion is introduced to quantify the performance improvement via the proposed scheme. Application to the hypersonic reentry tracking is presented to demonstrate the validity of the proposed method.

Composite Learning Control of MIMO Systems With Applications

Considering the unknown dynamics of the multiple-input-multiple-output strict-feedback nonlinear systems, this paper proposed the neural composite learning control using the online recorded data. The control structure follows the back-stepping scheme, while neural networks (NNs) are employed for uncertainty approximation. Through the error dynamics analysis, the critical prediction error is constructed to indicate the performance of intelligent learning over the interval. Furthermore, the novel composite learning law is proposed for NN weights update. The stability of the closed-loop system is analyzed via the Lyapunov approach and the signals are guaranteed to be bounded. Through simulation test of two-input and two-output systems, the proposed controller can achieve better tracking performance, while with the composite learning algorithm, the NNs can efficiently approximate nonlinear functions. Similar conclusions are obtained on the control of the hypersonic reentry vehicle.

Polymer-Derived Nano-Sized SiC-Containing ZrB<sub>2</sub> Composites: Densification, Microstructure and Flexural Strength

Silicon carbide (SiC)-containing zirconium diboride (ZrB2) composites have become an important class of ultra-high temperature ceramic materials for the thermal protection systems of re-entry hypersonic vehicles with sharp leading edge profiles. Previous studies in ZrB2-SiC composites showed that nano-sized SiC particles-containing ZrB2 composites had a greater strength and a better oxidation resistance compared to ZrB2-beased composites with micron-sized SiC particles. However, it is difficult for obtaining a homogenous microstructural ZrB2-based composite with nano-sized SiC particles because of agglomerates of the SiC particles. In this study, homogenously dispersed nano-sized SiC particles-containing ZrB2 composites were prepared using polymer-derived SiC-dispersed ZrB2 composite powders followed by hot pressing at different temperatures between 1750°C and 1900°C. The microstructure of the resulting composites was characterized by field emission scanning electron microscopy. Four-point flexural strength of the obtained composites was measured at room temperature. The effects of the sintering temperatures and SiC content on the microstructure and the flexural strength of the composites were discussed.

A novel adaptive Gauss pseudospectral method for nonlinear optimal control of constrained hypersonic re‐entry vehicle problem

SummaryOptimal control of constrained hypersonic re‐entry vehicle is difficult due to the complex nonlinear dynamics and nonlinear constraints. A novel adaptive Gauss pseudospectral method with some new strategies is therefore proposed to deal with the optimal control problem of hypersonic re‐entry vehicle to ensure that the complex constraints are satisfied all the way. First, state transformation is applied to make the variables more uniform in quantities. Second, some extreme points are applied in designing appropriate subintervals to track the control profiles effectively and the collocation points are adaptively redistributed based on the evaluated approximation errors. Third, a detection procedure is proposed to ensure that the constraints are satisfied all the way during the whole re‐entry process. The proposed method is illustrated by testing a hypersonic re‐entry vehicle problem. The results reveal that path constraints and terminal conditions are well satisfied. The research results, including the comparison with other methods, such as the classical Gauss pseudospectral method and the control vector parameterization method, show the effectiveness of the proposed adaptive approach.

Finite-time model-assisted active disturbance rejection control with a novel parameters optimizer for hypersonic reentry vehicle subject to multiple disturbances

In this paper, a scheme which combines finite-time model-assisted active disturbance rejection control and novel greedy criterion-based salp swarm algorithm is developed for attitude tracking problem of hypersonic reentry vehicle with multiple disturbances. To simplify control structure, the control scheme is designed within the framework of active disturbance rejection control completely. To lessen tuning parameters, a sigmoid function-based tracking differentiator is employed to generate a more realizable attitude transient profile instead of utilizing conventional nonlinear tracking differentiator. Taking known model information as model-assisted term, finite-time model-assisted extended state observers are constructed to estimate the lumped disturbance in attitude and angular rate loop with employment of function fal. To achieve rapid response and strong robustness, finite-time model-assisted control laws are derived by utilizing function fhan. Finally, a novel greedy criterion-based salp swarm algorithm is used to optimize control parameters in finite-time model-assisted control laws to achieve optimal solution that minimizes the tracking error and energy consumption. Comparative simulations are conducted to illustrate the effectiveness of the proposed scheme.

English

English

Effect of Counter Flowing Jet on Heat Transfer and Drag in Hypersonic Re-entry Vehicle

All the re-entry vehicles usually travel at hypersonic velocities, there are some design constraints pertaining to them such as aerodynamic drag and heat, which are mutually conflicting. A sharp edged slender body offers longer range and lesser drag but it causes higher aerodynamic heat. Generally, blunt shaped nose is used for the re-entry vehicles as it can disperse the accumulated heat to the surroundings better than sharp edged bodies. The current work focuses on reduction of aerodynamic heating by the introduction of a single jet injection on the stagnation point. Different jet angle configurations are used for the analysis by maintaining the angle of attack of the body constant. It is found that for body at 6-degree angle of attack the optimum jet angle is 9 degrees and the corresponding reduction in peak heat flux is 22.7% compared to the heat flux when the jet is at zero degrees and 33% compared to the case without jet.

An effective flux scheme for hypersonic heating prediction of re-entry vehicles

In this article, an effective computational method called TVM is proposed for the hypersonic heating prediction of the re-entry vehicles. Aimming at resolving the boundary layer accurately, the method adopted the splitting manner of the Toro and Vzquez’s splitting procedure with an improved low-dissipation modification. Also, the method is robust against the shock anomaly in hypersonic flows. The detailed construction of the scheme is presented and a series of testcases are conducted to validate the performance of the newly developed scheme. Finally, the scheme is applied to the simulation of the hypersonic re-entry vehicles. Numerical results show its high performance in the prediction of the re-entry vehicles hypersonic heating load compared to the traditional methods.

A thermoset hybrid sol for the syntheses of zirconium carbide–silicon carbide foam via replica method

Zirconium carbide–silicon carbide (ZrC–SiC) ceramics are amongst the promising candidate materials for thermal protection structures in hypersonic re-entry space vehicles. A thermoset hybrid sol for the syntheses of monolithic ZrC–SiC composites was prepared by a simple sol–gel method. Furfuryl alcohol, polyzirconoxane and tetraethyl orthosilicate were used as raw materials. The as-synthesized sol can be cured at 85 °C for 24 h to obtain a bulk gel. The cured gel is converted into porous ZrC–SiC monolith with porosity of 44.1% after pyrolysis at 1500 °C for 1 h in vacuum. The ZrC–SiC monolith is composed of well distributed nano-sized ZrC and SiC particles. Highly porous ZrC–SiC ceramic foam with density of 0.34 g/cm3 and porosity of 78.1% is prepared by replica method using the hybrid sol as precursor and melamine foam as templates. The hybrid sol and ZrC–SiC composites are characterized by FT-IR, TG–DTA, XRD, SEM, EDS and TEM.

Adaptive twisting sliding mode algorithm for hypersonic reentry vehicle attitude control based on finite-time observer

This paper focuses on the adaptive twisting sliding mode control for the Hypersonic Reentry Vehicles (HRVs) attitude tracking issue. The HRV attitude tracking model is transformed into the error dynamics in matched structure, whereas an unmeasurable state is redefined by lumping the existing unmatched disturbance with the angular rate. Hence, an adaptive finite-time observer is used to estimate the unknown state. Then, an adaptive twisting algorithm is proposed for systems subject to disturbances with unknown bounds. The stability of the proposed observer-based adaptive twisting approach is guaranteed, and the case of noisy measurement is analyzed. Also, the developed control law avoids the aggressive chattering phenomenon of the existing adaptive twisting approaches because the adaptive gains decrease close to the disturbance once the trajectories reach the sliding surface. Finally, numerical simulations on the attitude control of the HRV are conducted to verify the effectiveness and benefit of the proposed approach.