Air-breathing Hypersonic Flight Research Articles

Reliability analysis for air-breathing hypersonic vehicles based on a new dynamic PHI2 method

Purpose This paper aims to present a novel dynamic reliability model that considers the interval mixed uncertainty for the air-breathing hypersonic flight vehicle (AHFV) to guarantee flight safety and structural reliability. Design/methodology/approach Initially, the force condition of the fuselage is analyzed based on the longitudinal elastic model of an AHFV. Subsequently, a new high-efficiency dynamic reliability model is presented to describe the failure probability evolution of the fuselage structure. For the random uncertainty problem with interval distribution parameters, the interval PHI2 method of time-dependent reliability is used to obtain the time-dependent reliability interval of the AHFV. Finally, the key variables that affect the failure probability accumulation are determined, which provide an important reference for ensuring structural reliability and improving the life span of AHFVs. Findings It is demonstrated that the proposed reliability model can obtain more accurate dynamic reliability results for the fuselage, and it is confirmed the key variables that affect the failure probability accumulation. The results also provide an important reference for the reliability analysis of hypersonic vehicles. Originality/value The novelty of this work comes from the first application of the PHI2 method (considering the interval mixed uncertainty) in the AHFV and the development of a new reliability model for the entire body of AHFVs. The proposed analysis scheme is implemented on the dynamic model of the AHFV, which provides a more accurate reference for improving the structural reliability and life span of AHFVs.

Analysis of damage characteristics of an aeroelastic model for air-breathing hypersonic vehicles

PurposeTo suppress fatigue damage and ensure structural safety, this paper aims to analyze the effect of the damage accumulation on the aeroelastic model of an air-breathing hypersonic flight vehicle (AHFV).Design/methodology/approachInitially, by constructing the modified longitudinal elastic model of an AHFV, the stress condition of the fuselage is analyzed, and the model differences with the rigid body are studied. Then, a new damage dynamic model is presented to describe the damage dynamic evolution. Finally, combining the damage model and the longitudinal model of the AHFV, the key variables affecting the damage accumulation are determined.FindingsIt is demonstrated that the elastic deformation must be considered when analyzing the damage characteristics of the fuselage and to determine the key variables that affect the damage accumulation, which provides a more accurate reference for improving the structural reliability and lifespan of AHFVs.Originality/valueThe novelty of this paper comes from the application of the force and stress models for the damage evolution of the AHFV and the development of a new damage model for the entire body with the elastic dynamics of AHFVs.

A brief review on the recent advancement in the field of jet engine - scramjet engine

SCRAMJET engine has become one of the most recent advancement in the field of air breathing hypersonic flight. This paper gives a brief review on recent developments of scramjet combustor and fuels used in scramjet engine. For this purpose, various research works is going on to find new conclusions associated with supersonic engines. The parameters that affect the efficiency of scramjet engine are angle of injection, injector number, and geometry etc. There are various challenges that must be overcome in the combustion process to develop an efficient scramjet engine. By proper air–fuel mixing at the cost of pressure loss, the efficiency of scramjet engine can be improved. Efficiency may also be enhanced by injecting the fuel inside the cavity. Hydrogen fueled scramjet engines have become the most encouraging propulsion systems in this field. Hydrogen has a number of advantages such as high flammability, low density, least pollution and availability makes it suitable for supersonic engines.

Flow and combustion mechanism of oblique detonation engines

<p indent="0mm">Oblique detonation engine is a novel type of ram propulsion system employed in air-breathing hypersonic flight vehicle. It utilizes oblique detonation waves to achieve the high-efficient combustion in supersonic flow. Benefiting from the scientific and technological advantages such as rapid energy release, high specific impulse, short combustor and fewer moving parts, research on the oblique detonation engines becomes the frontier of hypersonic propulsion technologies. To initiate and adjust the wave structures of the oblique detonations, it is critical to conduct systematic investigation on flow and combustion mechanism in the engine combustors. Due to the coupling of shock waves and combustion, the initiation zone of oblique detonations has the feature of complicated multi-wave structures, which are affected by the properties of the mixtures. Furthermore, these structures are constrained to the wedge by the high speed inflow, very sensitive to the change of inflow parameters. Hence, research on the related unsteady processes is also critical. Finally, the oblique detonation waves in confined spaces involve the interaction of the shock waves and the geometry structures, which is an unavoidable problem in the engineering application. In this paper, research progress of the above aspects has been summarized and commented, clarifying the underlying problems in the application and pointing out the future research trends.

Research on control-oriented coupling modeling for air-breathing hypersonic propulsion systems

A control-oriented coupling hypersonic propulsion system model is proposed to enable the rapid development of a propulsion model for air-breathing hypersonic flight vehicles (ABHV) in early stages of the design process and facilitate design control and analysis. An airframe/propulsion coupling hypersonic inlet model was established based on oblique shock wave theory. An isolator model in which the effects of the back pressure of the combustion chamber were adjusted by the static pressure ratio of the isolator was established. A hypersonic combustion model was also established, taking into account the fuel flow, cross-sectional area, wall friction, combustion efficiency, and exothermic reactions based on quasi-1D flow theories. Nozzle/afterbody modeling was established based on identification of the free boundary (i.e., the location of the shear layer) by Newton collision theory, and flow parameters were determined according to the influence coefficient method. The mass flow rates of air in the design state and two typical non-design states were determined geometrically based on the application of oblique shock wave theory. A propulsion coupling model that reflects the coupling of propulsion system and aerodynamics, as well as the physical mechanisms of the propulsion mechanism, was then established based on air flow rates obtained and the momentum theorem. Simulation results of airframe/propulsion integrated module air-breathing hypersonic flight vehicles (ABHVs) by the proposed model were compared to results achieved by numerical 3D Computational Fluid Dynamics (CFD) models. Results indicated that the efficacy and accuracy of the proposed models met the established requirements of control-oriented modeling, thus facilitating dynamic modeling and control in the early stage of the design process.

Preliminary Analysis of the Hexafly-International Vehicle

Airbreathing hypersonic flight is an ongoing challenge with the potential to cut air travel time and provide cheaper access to space. Waveriders are potential candidates for achieving hypersonic cruise speed or proper acceleration within the atmosphere. Current research tends to focus on key issues like flight mechanics, thermal loading, aero-elasticity, aerodynamic and aerothermodynamics at hypersonic speeds. Design problems in each of these areas must be solved if the design of a hypersonic waverider-like vehicle is to be viable. In this framework, the HEXAFLY-INT project aims at testing in free-flight conditions an innovative gliding vehicle with several breakthrough on-board technologies to be launched along a suborbital trajectory. Its preliminary conceptual design has been carried out by means of tools suitable to design vehicles to fly in hypersonic conditions. Aerodynamic and trajectory analyses have been carried out to assess mission capability as well. Once the aeroshape and the reference mission have been identified, system and sub-system analysis have been performed to close the system loop. The main results of the design analysis carried out during the preliminary phase of the study (such as vehicle aerodynamics and aerothermodynamics, re-entry trajectories, structures and mechanisms, and on the overall system, as well), are presented in this work.

Neuro-adaptive tracking control of a hypersonic flight vehicle with uncertainties using reinforcement synthesis

Abstract In this paper, the neuro-adaptive optimal nonlinear control approach and algorithm are proposed for the tracking control of an air-breathing hypersonic aircraft considering uncertainties. Based on the reinforcement learning mechanism, the neuro-adaptive control agent is constructed using actor-critic architecture, which consists of two interacting neural networks, one for optimal control protocol, known as the actor NN, and the other for policy evaluation, known as critic NN. The optimality conditions for this adaptive controller are derived by using the discrete minimum principle. In the meanwhile, the parametric and mismatched uncertainty and unmodeled nonlinearity are handled by using another neural network named as UNN with aid of the concept of a virtual plant. The output of the network in the virtual plant helps to estimate the optimal control with varying dynamics of air-breathing hypersonic flight aircraft. Simulation results are presented to verify the effectiveness of this design method for the tracking control of the air-breathing hypersonic aircraft in the presence of uncertainties.

Sliding mode disturbance observer-enhanced adaptive control for the air-breathing hypersonic flight vehicle

This paper presents a backstepping procedure to design an adaptive controller for the air-breathing hypersonic flight vehicle (AHFV) subject to external disturbances and actuator saturations. In each step, a sliding mode exact disturbance observer (SMEDO) is exploited to exactly estimate the lumped disturbance in finite time. Specific dynamics are introduced to handle the possible actuator saturations. Based on SMEDO and introduced dynamics, an adaptive control law is designed, along with the consideration on “explosion of complexity” in backstepping design. The developed controller is equipped with fast disturbance rejection and great capability to accommodate the saturated actuators, which also lead to a wider application scope. A simulation study is provided to show the effectiveness and superiority of the proposed controller.

A novel adaptive dynamic surface control scheme of hypersonic flight vehicles with thrust and actuator constraints

In this paper, the nonlinear adaptive velocity and altitude tracking controller is developed for the longitudinal dynamics of generic air-breathing hypersonic flight vehicles. The proposed control scheme is designed using dynamic surface control method. The velocity and altitude subsystems are transformed into the linearly parameterized form for the convenience of adaptive law design. Both of the thrust and actuator constraints are explicitly considered. For thrust constraint, two cases are analyzed when the fuel-to-air ratio reaches its max and min values. A novel adaptive law is proposed to avoid over or less estimation in thrust saturation occasion. For actuator constraint, a magnitude and rate limiting filter is incorporated. The filter guarantees that the control signal is applicable for the actuator. It is shown that with the application of the proposed control scheme, all signals of the closed-loop system are uniformly ultimately bounded and the velocity and altitude tracking errors converge to a residual set which is arbitrarily small. Simulation results are demonstrated to show the effectiveness and superiority of the proposed control scheme.

Improved State Feedback H∞Control for Flexible Air-Breathing Hypersonic Vehicles on LMI Approach

Focusing on a nonlinear longitudinal dynamical model for Air-breathing Hypersonic Flight Vehicles (AHFV), a linearized model on a nominal trim condition is proposed. To stabilize the flight of an AHFV in the presence of external disturbances and actuator uncertainties, a state feedback H ∞ control is designed. With bounds on the uncertainties, a feedback stabilization problem is converted to an optimal control problem and the cost function is minimized by solving a set of linear matrix inequalities. Since uncertainties in the design of AHFV are inevitable, to make a comparison, a general H ∞ robust controller is constructed by only considering the disturbances firstly. Then the results are extended by incorporating the actual existing uncertainties as well as the external disturbances in the AHFV system. Numerical simulation shows that the controller, which takes both disturbances and uncertainties into account, can effectively stabilize the AHFV system.

Modified shuffled frog leaping algorithm optimized control for air-breathing hypersonic flight vehicle

This article addresses the flight control problem of air-breathing hypersonic vehicles and proposes a novel intelligent algorithm optimized control method. To achieve the climbing, cruising and descending flight control of the air-breathing hypersonic vehicle, an engineering-oriented flight control system based on a Proportional Integral Derivative (PID) method is designed for the hypersonic vehicle, which including the height loop, the pitch angle loop and the velocity loop. Moreover, as a variant of nature-inspired algorithm, modified shuffled frog leaping algorithm is presented to optimize the flight control parameters and is characterized by better exploration and exploitation than the standard shuffled frog leaping algorithm. A nonlinear model of air-breathing hypersonic vehicle is used to verify the dynamic characteristics achieved by the intelligent flight control system. Simulation results demonstrate that the proposed swarm intelligence optimized PID controllers are effective in achieving better flight trajectory and velocity control performance than the traditional controllers.

A practical parameter determination strategy based on improved hybrid PSO algorithm for higher-order sliding mode control of air-breathing hypersonic vehicles

A hybrid particle swarm optimization (PSO) algorithm for longitudinal dynamic models of air-breathing hypersonic flight vehicles (HFV) is proposed and applied to determine design parameters for a higher-order sliding model controller (HOSMC) while considering the effects of parameter uncertainty on trajectory tracking control. The input and output linearization of air-breathing HFV longitudinal dynamic models were achieved using the feedback linearization approach. Also, an HOSMC was designed for air-breathing HFV trajectory tracking control, and the design parameters were determined based on stochastic robustness analysis and hybrid PSO algorithm. Simulations revealed that the HOSMC design parameters can be optimized effectively and easily using the parameter determination strategy based on an improved hybrid PSO algorithm. The proposed HOSMC was used to stabilized the trajectory tracking of air-breathing HFV and the controller proposed exhibited great robustness.

Three Dimensional Trajectory Linearization Control for Flight of Air-breathing Hypersonic Vehicle

An integrated guidance and control design approach for air-breathing hypersonic flight vehicle (ABHV) with strong aero-propulsion couplings and aerodynamic constraints is proposed in this paper. By exploiting the inherent nature of multi-time scale of hypersonic flight vehicle dynamics, the guidance and control system is designed based on time scales of subsystem dynamics, with the fast dynamics serving as the pseudo-control for the slow dynamics. Feedback gains are computed online as symbolic functions of the state variable along the reference trajectory, and no explicit gain scheduling or mode-switching is needed. Comparison with linear quadratic regulator control is conducted and performance of the proposed approach is demonstrated via high fidelity simulations with considerable aerodynamic uncertainty and environmental perturbation.

Three Dimensional Trajectory Linearization Control for Flight of Air-breathing Hypersonic Vehicle

An integrated guidance and control design approach for air-breathing hypersonic flight vehicle (ABHV) with strong aero-propulsion couplings and aerodynamic constraints is proposed in this paper. By exploiting the inherent nature of multi-time scale of hypersonic flight vehicle dynamics, the guidance and control system is designed based on time scales of subsystem dynamics, with the fast dynamics serving as the pseudo-control for the slow dynamics. Feedback gains are computed online as symbolic functions of the state variable along the reference trajectory, and no explicit gain scheduling or mode-switching is needed. Comparison with linear quadratic regulator control is conducted and performance of the proposed approach is demonstrated via high fidelity simulations with considerable aerodynamic uncertainty and environmental perturbation.

Robust Gain-Scheduling Controller for Airbreathing Hypersonic Flight Vehicle

This paper addresses issues related to robust control for an airbreathing hypersonic flight vehicle. Owing to aero-propulsion couplings caused by the unique structure shape, the model of the vehicle is greatly nonlinear and complex, which presents an enormous technical challenge for control. The nonlinear model is transformed into a linear fractional transformation (LFT) model, and a robust gain-scheduling controller based on linear parameter-varying control (LPV) with full block multipliers is obtained. Simulations illustrate great improvements of the dynamic performance in closed-loop system.

&lt;i&gt;H∞&lt;/i&gt;-Based LQR Control for Flexible Air-Breathing Hypersonic Vehicles with Pole Placement

Focusing on a nonlinear longitudinal dynamical model for air-breathing hypersonic flight vehicles (AHFV), we propose a state feedback linearized model on a nominal trim condition. To stabilize the flight of an AHFV in the presence of external disturbances, a newHbased Linear Quadratic Regulator (LQR) control law with pole placement is designed. Indexes forHperformance, quadratic performance and pole placement are considered together. As a result, the robustness of system is improved and the AHFV system is effectively stabilized. Numerical simulation shows that the controller can effectively stabilize the AHFV system with some disturbances and assign the poles into a desired region.

Command filtered back-stepping control of a flexible air-breathing hypersonic flight vehicle

&lt;AQ*/&gt;Abstract A theoretical framework of nonlinear flight control is exploited and applied to nonlinear longitudinal dynamics of a generic air-breathing hypersonic flight vehicle. A combination of novelty command filtered back-stepping technology and dynamic inversion methodology is adopted for designing a dynamic state-feedback controller that provides stable tracking of the altitude and velocity reference commands. The novel command filtered back-stepping altitude control obviates the need to compute analytic derivatives in the traditional back-stepping design, providing a simple and effective way for controlling non-linear hypersonic flight vehicle. An input-to-state stability-modular approach is presented by combining command filtered back-stepping method with sliding-mode-based integral filters, input-to-state stability analysis, and small-gain theorem. The stability analysis of the closed-loop system including the flexible dynamic, and the convergence of the system outputs are derived. The proposed control scheme is verified in simulations in a climbing maneuver case of separate velocity and altitude reference commands.

Feedback linearization-based robust nonlinear control design for hypersonic flight vehicles

A new approach to designing a robust nonlinear controller for longitudinal flexible body models of canard configured air-breathing hypersonic flight vehicles with significant couplings and interactions is presented. The methodology uses a robust feedback linearization method to feedback linearize the nonlinear air-breathing hypersonic flight vehicle model with 24 uncertainty parameters. Using this approach, a linearized uncertainty model of the air-breathing hypersonic flight vehicle is obtained in the first step by considering an upper bound on each uncertain parameter. In the second step, a minimax linear quadratic regulator-based velocity and altitude robust tracking controller is synthesized for the linearized model. Simulation studies are conducted using the original nonlinear model of the air-breathing hypersonic flight vehicle with a large flight envelope and time-varying uncertainties. Simulation results show that the feedback linearization-based minimax linear quadratic regulator controller effectively achieves the tracking requirement and robustly stabilizes the air-breathing hypersonic flight vehicle.

Uncertainty modeling and robust minimax LQR control of multivariable nonlinear systems with application to hypersonic flight

AbstractFor a class of multi‐input and multi‐output nonlinear uncertainty systems, a novel approach to design a nonlinear controller using minimax linear quadratic regulator (LQR) control is proposed. The proposed method combines a feedback linearization method with the robust minimax LQR approach in the presence of time‐varying uncertain parameters. The uncertainties, which are assumed to satisfy a certain integral quadratic constraint condition, do not necessarily satisfy a generalized matching condition. The procedure consists of feedback linearization of the nominal model and linearization of the remaining nonlinear uncertain terms with respect to each individual uncertainty at a local operating point. This two‐stage linearization process, followed by a robust minimax LQR control design, provides a robustly stable closed loop system. To demonstrate the effectiveness of the proposed approach, an application study is provided for a flight control problem of an air‐breathing hypersonic flight vehicle (AHFV), where the outputs to be controlled are the longitudinal velocity and altitude, and the control variables are the throttle setting and elevator deflection. The proposed method is used to derive a linearized uncertainty model for the longitudinal motion dynamics of the AHFV first, and then a robust minimax LQR controller is designed, which is based on this uncertainty model. The controller is synthesized considering seven uncertain aerodynamic and inertial parameters. The stability and performance of the synthesized controller is evaluated numerically via single scenario simulations for particular cruise conditions as well as a Monte‐Carlo type simulation based on numerous cases. It is observed that the control scheme proposed in this paper performs better, especially from the aspect of robustness to large ranges of uncertainties, than some controller design schemes previously published in the literature.Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

Model reference adaptive switching control of a linearized hypersonic flight vehicle model with actuator saturation

In order to address the control of an air-breathing hypersonic flight vehicle (AHFV) with actuator saturation, a model reference adaptive switching control (MRASC) approach is proposed. The design of the MRASC system is centred around a linearized longitudinal-motion flexible model at a Mach 8, altitude of 10 000 ft, and dynamic pressure of 1017 lb/ft2 flight condition. A switched reference system (SRS) is established to describe the desired dynamics of the AHFV with/without actuator saturation, and correspondingly, a switched adaptive controller (SAC) is constructed utilizing the hyperstability method. By switching between the subsystems of the SRS and the corresponding subcontrollers of the SAC, the MRASC system achieves the desired performance and is globally asymptotically stable under limited disturbances, provided that a simple linear-matrix-inequality-based sufficient condition holds. Although it is too early to say that the proposed scheme gives desired anti-saturation performance with respect to large disturbances, within a large flight envelope, there are still some advantages that will improve performance.