Air-breathing Hypersonic Vehicle Research Articles

Flight and Vibration Control of Flexible Air-Breathing Hypersonic Vehicles Under Actuator Faults.

The issue of modeling and fault-tolerant control (FTC) design for a class of flexible air-breathing hypersonic vehicles (FAHVs) with actuator faults is investigated in this article. Different from previous research, the shear deformation of the fuselage is considered, and an ordinary differential equations-partial differential equations (ODEs-PDEs) coupled model is established for the FAHVs. A feedback control is proposed to ensure flight stable and an adaptive FTC method is designed to deal with actuator faults while suppressing the system's vibrations. Besides, the stability analysis of the closed-loop system is given via the Lyapunov direct method and an algorithm that transfers the bilinear matrix inequalities (BMIs) feasibility problem to the linear matrix inequalities (LMIs) feasibility problem is provided for determining the control gains. Finally, the numerical simulation results show that the proposed controller can stabilize the flight states and suppresses the vibration of the fuselage efficiently.

Variable-horizon predictive tracking control for air-breathing hypersonic vehicle based on composite disturbance observer

In this paper, a variable-horizon predictive tracking control (VHPTC) scheme based on composite disturbance observer (CDO) is proposed to investigate the attitude tracking problem for an air-breathing hypersonic vehicle (AHV) subject to external matched and mismatched disturbances. An explicit predictive tracking control term with the variable horizon is employed to reduce the online computation and improve the control performance of the AHV system. To comprehensively suppress the negative influences caused by the matched and mismatched disturbances, a CDO is constructed to estimate the unknown disturbances. Moreover, to further guarantee the stability of the closed-loop system affected by the resulting disturbance estimation error, the auxiliary control term is presented. Combining the predictive tracking control term with the variable horizon, the auxiliary control term, and the disturbance compensation control term obtained by CDO, the entire VHPTC law for the AHV system is obtained. Through the Lyapunov analysis, the rigorously exponential stability of the closed-loop system is ensured by the proposed CDO-based VHPTC scheme. The simulation results demonstrate the effectiveness of the presented strategy for the AHV attitude system.

Study on Dynamic Pressure Control of Air-Breathing Hypersonic Vehicle

To satisfy the strict requirements of dynamic pressure for air-breathing hypersonic vehicle during the initiation, a dynamic pressure control method based on the model reference sliding mode theory is designed. Firstly, the motion equation of the air-breathing hypersonic vehicle is built, and the dynamic pressure linearization model is established by the small perturbation method. Secondly, the control system, designed by the model reference sliding mode control theory, can quickly track the reference model. Finally, the six degrees of freedom simulation model is built and used for digital simulation. The simulation results show that the designed control system can accurately track the dynamic pressure command with great robustness.

Disturbance observer–based neural adaptive fault-tolerant control for flexible air-breathing hypersonic vehicles with multiple model uncertainties

One of the critical problems for flexible vehicles is how to simultaneously address the multiple uncertainty compensation and flexible vibration suppression. This paper focuses on the smooth adaptive fault-tolerant control design problem of a two-layer framework for flexible air-breathing hypersonic vehicles subject to contingent actuator failures and multiple model uncertainties. The first layer provides a disturbance observer–based neural adaptive fault-tolerant controller overcoming actuator failures and multiple model uncertainties. The second layer relies on the tracking differentiator and filter combined with the controller seamlessly, generating smooth reference information, which is highly desirable for flexible vibration suppression. Then, the analysis by the Lyapunov theory strictly proves the uniform ultimately boundedness of all the control and filter state variables. Finally, the simulation results demonstrate the dominant tracking control performance of the proposed control method.

Emerging robust and data‐driven control methods for uncertain learning systems

Emerging robust and data‐driven control methods for uncertain learning systems

Adaptive control of hypersonic vehicles using intelligent allocation

This paper proposes an intelligent allocation-based adaptive controller for the longitudinal motion of air-breathing hypersonic vehicles (AHVs). A control-allocation (CA) module is developed to deal with composite actuator servo constraints that have usually been neglected in existing AHV control works. This CA process is realized with the help of the recent deep deterministic policy gradient algorithm without involving any online optimization. In the followed adaptive controller design, several auxiliary signals are constructed to compensate for the possible CA error, while adaptive super-twist differentiators are employed to fast estimate the lumped effect of uncertain aerodynamic coefficients and unknown external disturbances. As a result, the adaptive control algorithm only needs three parameter updating laws, whose dimension is much lower than traditional adaptive control strategies for AHVs. Simulations are provided to verify the proposed intelligent allocation-based adaptive controller.

An experimental study on the stability of hypersonic plate boundary layer regulated by a plasma actuation array

Laminar–turbulent transition control is one of the key problems in the design of hypersonic vehicles. In particular, for air-breathing hypersonic vehicles, early onset turbulence in the boundary layer of a scramjet inlet precursor is desirable. Plasma actuation has become a popular flow control method in recent years and has made progress in regulating the stability of supersonic boundary layers. However, there have been few studies on the regulation of the stability of hypersonic boundary layers. In this paper, an experimental study on the stability of the hypersonic plate boundary layer is carried out using a spanwise plasma actuation array. The characteristics and evolution of different kinds of unstable waves in the hypersonic plate boundary layer (especially the dominant first mode wave) are analyzed based on the results of linear stability theory and high-frequency pulsation sensors. The typical morphological characteristics of the boundary layer and the macro-control effect of the plasma actuation array are explored through a high-speed schlieren method. Finally, based on grayscale mode extraction and proper orthogonal decomposition, the influences of three different actuation frequencies on the instability waves and characteristic structure of the boundary layer are studied, including the dominant frequency of the first mode wave, the half-frequency of the dominant frequency of the first mode wave, and the dominant frequency of the second mode wave, the change of characteristic structures under the regulation of plasma actuation is further discussed. The corresponding regulation rules and mechanisms are summarized. The results show that the plasma actuation array can advance the starting position of laminar discontinuities and that the induced coherent structure can excite instabilities at an earlier flow-direction position. The actuation can be used to control the stability of the boundary layer by acting on the first mode wave to break the original unstable wave spectrum characteristics. This verifies the ability of extensional array plasma actuation to regulate the stability of the hypersonic plate boundary layer and suggests it has great potential in the promotion of hypersonic boundary layer transition.

Adaptive Multiple-Model-Based Fault-Tolerant Control for Non-minimum Phase Hypersonic Vehicles With Input Saturations and Error Constraints

In this article, an adaptive multiple-model-based fault-tolerant controller is developed for nonminimum phase air-breathing hypersonic vehicles (HSVs) in the presence of parametric uncertainties, elevator faults, input saturations, and time-varying error constraints. Compared with the existing works, the elevator-to-lift couplings are taken into account, which makes the HSV longitudinal models exhibit unstable internal-dynamics that impedes the applicability of common nonlinear control methods for control design. In order to solve this problem, a two-layer cascade control strategy is proposed in which the external inputs control the external states and the external state deviations control the internal states: 1) A multiple-model linear quadratic control strategy, based on gap metric, is proposed to guarantee the stability of the internal dynamics; 2) a fault-tolerant control scheme, based on tan-barrier Lyapunov functions, is developed by using a low-pass filter and an auxiliary system in conjunction with adaptive backstepping design. In the control law, the uncertain parameters are replaced by their estimates updated by adaptive laws. Additionally, the stability of the whole system is rigidly proved through standard Lyapunov approach, while the other states and signals in the closed-loop system are guaranteed to be bounded. Simulation results are provided to illustrate the effectiveness of the proposed adaptive multiple-model-based fault-tolerant controller.

Event-triggered adaptive control of hypersonic vehicles subject to actuator nonlinearities

This paper investigates the event-triggered adaptive control problem for air-breathing hypersonic vehicles (AHVs) subject to physical actuator nonlinearities. In contrast with abundant AHV control strategies belonging to the traditional sample-data framework, the presented adaptive control works with an event-triggered mechanism, which naturally reduces the executing frequency of scramjet fuel-to-air equivalency ratio (FER) and aerodynamic control surface (ACS). During the event-triggered controller design, practical actuator characteristics including magnitude-rate composite constraints and servo transient dynamics are synthetically considered. In the velocity loop, the built-in FER saturation, which is a fusion of physical FER magnitude and rate constraints, is handled by reshaping the velocity reference with the help of an adaptive reference governor. Meanwhile in the altitude loop, a neural control allocator directly generates feasible ACS commands via a neural network that is well trained by means of the optimal control allocation. As the result, ACS magnitude-rate composite constraints and servo transient dynamics can be accommodated without implementing any time-consuming optimization searching process. Theoretical analysis indicates the guaranteed closed-loop stability and tracking performance while excluding the undesired Zeno behavior. Simulations validate the effectiveness of the proposed event-triggered adaptive control.

Robust approximate optimal control for air‐breathing hypersonic vehicle

AbstractThis paper investigates the robust approximate optimal control problem for air‐breathing hypersonic vehicle (AHV). By input‐output linearzation and introducing auxiliary variables, the high‐order nonlinear AHV dynamics are transformed to a second‐order feedback decoupling model. Then a virtual command is designed by back‐stepping strategy to guarantee the practical finite‐time convergence of tracking error. In order to drive the AHV with uncertainties to follow the virtual command, a robust approximate optimal controller based on adaptive dynamic programming (ADP) is proposed. Different from the conventional robust method, both the robustness and the input cost are taken into consideration in the proposed controller, which can optimize the control actions and hence avoid the chattering. Besides, the proposed controller adopts a single critic network design instead of actor‐critic structure, which ensures the stability of the system autonomously and simplifies the implementation procedure. The simulation results show the effectiveness of the proposed scheme.

Hipersoničnu letelicu sa Airbreathing pogonom

The paper uses the state feedback technique to provide a control design method for a dynamic linear 6-degree-of-freedom (DOF) model of an Airbreathing Hypersonic Vehicle (AHV). A linear model of AHV with a state space model is developed for the open loop simulation for the level flight with Mach number 5 and a height of 65000 ft (19812 m). The dynamic stability of AHV is analyzed, and state feedback with the pole placement method is implemented for the controller design. The dynamic stability, response, and comparison for the PI and PID controller are presented for the aileron deflection da and rudder deflection dr for the AHV linear model.

Appointed-Time Control for Flexible Hypersonic Vehicles with Conditional Disturbance Negation

This paper investigates the anti-disturbance control design for flexible air-breathing hypersonic vehicles (FAHVs) with appointed-time prescribed tracking performances. The challenging issues include multisource disturbances, cross-coupling effects of the vehicle dynamics, and asymmetric amplitude and rate saturations. To address these issues, we propose an appointed-time prescribed performance control scheme for FAHVs via conditional disturbance negation technique. In contrast to existing disturbance rejection approaches, the proposed control scheme not only estimates the disturbances first in a fixed time, but also evaluates the estimated disturbances and selectively conducts compensation actions according to the insight of the FAHV dynamic characteristics. To further enhance convergence rate, the composite appointed-time prescribed performance controllers are designed for FAHVs via time-varying barrier Lyapunov function and nonsmooth backstepping technique, which ensure satisfactory transient response and steady-state performances. In addition, the asymmetric amplitude and rate saturation problem of actuators are dealt with by introducing unified approximation dynamics. It is rigorously proved that the practical appointed-time convergence of the tracking errors and the fixed-time convergence of all signals in the resultant FAHV closed-loop system can be achieved under the proposed control scheme. Finally, extensive comparative simulations are provided to demonstrate the feasibility and superiority of the proposed approach.

Dual-mode control of hypersonic vehicles

This paper presents a dual-mode attitude controller for air-breathing hypersonic vehicles, which strategically switches between cruising and maneuvering modes. Each mode designs a neural inversion to partly decouple attitude dynamics having actuator transient behaviors and magnitude-rate constraints. As a direct benefit, the inverse algorithm for the most-frequently-used cruising mode becomes low-complexity. Aiming at decoupled attitude channels, an enhanced inner-loop controller is proposed to accommodate uncertain modeling, imprecise decoupling and nonzero allocating. In especial, its self-initializing mechanism eliminates fluctuations aroused by mode changes. The dual-mode attitude controller is further integrated with guidance and scramjet control modules to form a general six-degrees-of-freedom control system.

Fast inner-loop control of air-breathing hypersonic vehicles

This paper investigates the inner-loop attitude and velocity control problem for air-breathing hypersonic vehicles subject to practically constrained actuators. Traditional nonlinear dynamic inverse (NDI) is enhanced by an intelligent control allocation (ICA) to realise the low-complexity attitude decoupling. The ICA addresses various characteristics of aerodynamic control surfaces while providing an efficient detecting mechanism for allocation errors. Within the ICA-NDI frame, a finite-time disturbance observer-based terminal sliding mode (FTDO-based TSM) attitude controller regulates Euler angles in the fast manner. This attitude controller employs an improved integral sliding surface containing necessary information from both ICA detection and FTDO estimation, which, therefore, is capable of accommodating constrained control surfaces and rejecting mismatched disturbances. Meanwhile, an adaptive governor adjusts the velocity reference according to the current saturation level of the scramjet fuel-to-air equivalency ratio. The governor is further integrated to a baseline adaptive velocity controller to synthetically handle scramjet input saturations and uncertain factors.

Performance analysis of the hypersonic vehicle with dorsal and ventral intake

The integrated design of the airframe and inlet is the favorite choice for the aerodynamic configuration design of the air-breathing hypersonic vehicle. To better understand the integrated configurations with a dorsal intake, this paper utilizes the computational fluid dynamics (CFD) method to comprehensively compare the performance of integrated configurations with the dorsal and traditionally used ventral intake. The performance indexes include aerodynamic performance, such as lift-to-drag ratio, the inlet performance, and thrust-to-drag balance performance. First, under the same geometric constraints, two integrated aerodynamic configurations with dorsal and ventral intake are designed based on a truncated Busemann inlet. Second, the CFD numerical simulation method based on multi-GPU parallel computing is developed and verified. Then, the flow-field characteristics, the aerodynamic, inlet, and thrust-to-drag balance performance of the two types of configurations in a wide range of Mach numbers are comprehensively compared using the GPU-based efficient numerical simulation method. The advantages and disadvantages of the two types of configurations are then analyzed to provide a meaningful reference for the aerodynamic configuration design of air-breathing hypersonic vehicles.

Fault-Tolerant Control of Hypersonic Vehicle Using Neural Network and Sliding Mode

In this paper, the tracking control of the air-breathing hypersonic vehicle with model parameter uncertainties and actuator faults is studied. Firstly, a high-order linearization model is used to build an adaptive terminal sliding mode that eliminates chattering and provides increased robustness for unknown disturbances in the system. Second, a fault-tolerant control method mixing the radial basis function neural network with adaptive sliding mode control is suggested, with the addition of a hyperbolic tangent function to avoid controller input saturation. Finally, the stability of the controller is proved strictly by the Lyapunov theory, and the robustness and effectiveness of the controller are further verified by numerical simulations of the longitudinal model of the hypersonic vehicle.

Longitudinal Trim and Stability Analysis of Generic Air-Breathing Hypersonic Vehicle using Bifurcation Method

The Air-breathing Hypersonic Vehicle (AHV) can meet the futuristic goals of rapid global travel, to Low-Earth Orbit and into space in near-term decades. This paper presents the study of the trim and stability characteristics of the 3DOF longitudinal model of the generic AHV. Longitudinal 3DOF AHV simulation is developed with the aerodynamic model for trim analysis considering the complete flight envelope for Mach number from M=0 to 24. Dynamic model simulation of the 3DOF AHV is performed for the trim conditions and stability of the AHV flight for the complete envelope. Bifurcation Analysis is implemented with the longitudinal 3DOF AHV model for trim analysis and stability for the complete AHV flight envelope.

Tube-MPC Control via Notch Filter for Flexible Air-Breathing Hypersonic Vehicle with Actuator Fault

In this paper, the tube model predictive control (Tube-MPC) via notch filter is proposed for flexible air-breathing hypersonic vehicle with actuator fault. Firstly, considering the low-order flexible modes, the polytopic linear parameter varying (LPV) model of flexible air-breathing hypersonic vehicle is established using Jacobian linearization and tensor product. Actuator fault and parameter uncertainty are transformed into a lumped disturbance term. The baseline Tube-MPC trajectory tracking controller is developed by designing robust auxiliary feedback control law and nominal control law. In order to weaken the effect of flexibility, a notch filter is introduced to eliminate the frequency response peak of flexible modes. And the effect of notch filter on control performance and stability is analysed. Secondly, an alternative controller design strategy is proposed to ensure stability of the closed-loop system. The filter and the original nonlinear model are combined together such that the new polytopic LPV model is codesigned. On the basis, the adjustable Tube-MPC controller is developed to improve the control performance and ensure the stability of the system. Finally, the effectiveness of the two controllers is verified by simulations.

Measurement technology in hypersonic wind tunnel

Integrated airframe/propulsion aerodynamic tests in a hypersonic wind tunnel are critical for developing an air-breathing hypersonic vehicle. Spurred by the shortcomings of traditional wind tunnel testing technology, this paper proposes a new aerodynamic testing technology called the balance-support integrated device (BSD). Additionally, we suggest a BSD optimization design method to improve BSD’s test performance. To reduce the impact of various interference signals on BSD‘s test accuracy, this study proposes an aerodynamic identification technology that effectively eliminates the influence of the model’s inertia force and the impact force generated by the joint BSD. We evaluate BSD’s performance by conducting several calibration tests, which reveal that the sensitivity of each BSD’s test channel is 2.3525 N/μV (drag test channel), 1.2691 N/μV (lift test channel), 9.7386 N.m/μV (pitching moment test channel). The test channel interference of lift to drag is less than 6.3 %, and drag to lift is less than 2.5 %, demonstrating that the wind tunnel force measurement system has an appealing sensitivity and less interference between the channels. Finally, we further challenge BSD’s test accuracy against the mature box balance technology on aerodynamic tests under Ma5.5, Ma6.0, and Ma6.5 conditions considering a 2-meter vehicle model in the Φ600mm pulse combustion wind tunnel. The test results highlight that the maximum test error of the lift test channel, drag test channel, and pitching moment Mz is 1.60 %, 6.45 %, and 4.99 %, respectively, proving that BSD can accurately measure the aerodynamic force during the test.

Intelligent control of air-breathing hypersonic vehicles subject to path and angle-of-attack constraints

This paper investigates the path and angle-of-attack constrained longitudinal control problem for air-breathing hypersonic vehicles with the help of a two-step intelligent design. The first step generates the path constrained optimal trajectory via a deep neural network, while the second step develops a reinforcement learning-based controller. In the velocity loop, an adaptive tracking controller is designed with specific consideration on the constrained fuel-to-air equivalency ratio of the scramjet. Meanwhile, in the altitude loop, the baseline backstepping design is enhanced by an intelligent parameter adjustment to improve tracking performances as well as to constrain the angle-of-attack, without involving any complex mechanisms like the widely-used prescribed performance functions and barrier Lyapunov functions. Numerical simulations show both effectiveness and superiority of the proposed intelligent control.