Beyond LOS Detection of Hypersonic Vehicles

This article investigates a novel fuzzy-approximation-based nonaffine control strategy for a flexible air-breathing hypersonic vehicle (FHV). Firstly, the nonaffine models are decomposed into an altitude subsystem and a velocity subsystem, and the nonaffine dynamics of the subsystems are processed by using low-pass filters. For the unknown functions and uncertainties in each subsystem, fuzzy approximators are used to approximate the total uncertainties, and norm estimation approach is introduced to reduce the computational complexity of the algorithm. Aiming at the saturation problem of actuator, a saturation auxiliary system is designed to transform the original control problem with input constraints into a new control problem without input constraints. Finally, the superiority of the proposed method is verified by simulation.

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Fuzzy-approximation-based prescribed performance control of air-breathing hypersonic vehicles with input constraints

Science Progress ◽

10.1177/0036850419877359 ◽

2019 ◽

Vol 103 (1) ◽

pp. 003685041987735

Author(s):

Xingge Li ◽

Gang Li ◽

Yan Zhao ◽

Xuchao Kang

Keyword(s):

Control Method ◽

Hypersonic Vehicle ◽

Hypersonic Vehicles ◽

Input Constraints ◽

Air Breathing ◽

Performance Control ◽

Prescribed Performance ◽

Fuzzy Approximation ◽

Prescribed Performance Control ◽

Control Scheme

In this article, aiming at the longitudinal dynamics model of air-breathing hypersonic vehicles, a fuzzy-approximation-based prescribed performance control scheme with input constraints is proposed. First, this article presents a novel prescribed performance function, which does not depend on the sign of initial tracking error. And combining prescribed performance control method with backstepping control, the control scheme can ensure that system can converge at a prescribed rate of convergence, overshoot, and steady-state error. In order to solve the problem that backstepping control method needs to be differentiated multiple times, fuzzy approximators are used to estimate the unknown functions, and norm estimation approach is used to simplify the computation of fuzzy approximator. Aiming at the problem of input saturation of actuator in subsystem of air-breathing hypersonic vehicle, the new auxiliary system is designed to ensure the stability and robustness of air-breathing hypersonic vehicle system under input constraints. Finally, the effectiveness of the proposed control strategy is verified by simulation analysis.

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Ionospheric Plasma Density Measurements by Swarm Langmuir Probes: Limitations and possible Corrections

10.5194/angeo-2019-136 ◽

2019 ◽

Author(s):

Piero Diego ◽

Igino Coco ◽

Igor Bertello ◽

Maurizio Candidi ◽

Pietro Ubertini

Keyword(s):

Electron Density ◽

Ionospheric Plasma ◽

Operating Mode ◽

Plasma Sheath ◽

Langmuir Probes ◽

Plasma Parameters ◽

Density Measurements ◽

Voltage Ripple ◽

Electron Density And Temperature ◽

Ionospheric Plasma Density

Abstract. The ESA Swarm constellation includes three satellites, which have been observing the Earth's ionosphere since November 2013, following polar orbits. The main ionospheric plasma parameters, such as electron density and temperature, are measured by means of Langmuir probes (Lps); electron density measurements, in particular, are nowadays largely considered as qualitatively reliable, and have been used in several published papers to date. In this work, we aim to discuss how some technical characteristics of Swarm Lps, such as their size and location on board the satellites, as well as the operational setup of the instruments, could lead to limitations in their accuracy if one underestimates the influence of satellite proximity, and the larger extension of the plasma sheath surrounding the probes due to the operational point of the voltage ripple. Two specific corrections are proposed for the assessment and possible mitigation of such effects. Finally, a comparison is made with electron density measurements from CSES-01 mission, which relies on Langmuir probes as well, whose geometry and operating mode are standard.

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Nonlinear Adaptive Equivalent Control Based on Interconnection Subsystems for Air-Breathing Hypersonic Vehicles

Journal of Applied Mathematics ◽

10.1155/2013/560785 ◽

2013 ◽

Vol 2013 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Chaofang Hu ◽

Yanwen Liu

Keyword(s):

Control Method ◽

Hypersonic Vehicle ◽

Flight Path ◽

Attack Angle ◽

Hypersonic Vehicles ◽

Air Breathing ◽

Flight Path Angle ◽

Equivalent Control ◽

Small Gain ◽

Aerodynamic Parameters

For the nonminimum phase behavior of the air-breathing hypersonic vehicle model caused by elevator-to-lift coupling, a nonlinear adaptive equivalent control method based on interconnection subsystems is proposed. In the altitude loop, the backstepping strategy is applied, where the virtual control inputs about flight-path angle and attack angle are designed step by step. In order to avoid the inaccurately direct cancelation of elevator-to-lift coupling when aerodynamic parameters are uncertain, the real control inputs, that is, elevator deflection and canard deflection, are linearly converted into the equivalent control inputs which are designed independently. The reformulation of the altitude-flight-path angle dynamics and the attack angle-pitch rate dynamics is constructed into interconnection subsystems with input-to-state stability via small-gain theorem. For the velocity loop, the dynamic inversion controller is designed. The adaptive approach is used to identify the uncertain aerodynamic parameters. Simulation of the flexible hypersonic vehicle demonstrates effectiveness of the proposed method.

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Analysis of Hypersonic Platform-Borne SAR Imaging: A Physical Perspective

Remote Sensing ◽

10.3390/rs13234943 ◽

2021 ◽

Vol 13 (23) ◽

pp. 4943

Author(s):

Lihao Song ◽

Bowen Bai ◽

Xiaoping Li ◽

Gezhao Niu ◽

Yanming Liu ◽

...

Keyword(s):

High Speed ◽

Signal Propagation ◽

High Plasma ◽

Plasma Sheath ◽

Plasma Parameters ◽

Sar Images ◽

Scatter Matrix ◽

Imaging Quality ◽

Imaging Results ◽

Sar Imaging

The usage of a hypersonic platform for remote sensing application has promising prospects, especially for hypersonic platform-borne synthetic aperture radar (SAR) imaging. However, the high-speed of hypersonic platform will lead to extreme friction between the platform and air, which will cause the ionization of air. The ionized gas forms the plasma sheath wrapped around the hypersonic platform. The plasma sheath will severely affect the propagation of SAR signal and further affect the SAR imaging. Therefore, hypersonic platform-borne SAR imaging should be studied from a physical perspective. In this paper, hypersonic platform-borne SAR imaging under plasma sheath is analyzed. The SAR signal propagation in plasma sheath is computed using scatter matrix method. The proposed SAR signal model is verified by using a ground experiment system. Moreover, the effect of attenuation caused by plasma sheath on SAR imaging is studied under different SAR parameters and plasma sheath. The result shows that attenuation caused by plasma sheath will degrade the SAR imaging quality and even cause the point and area targets to be submerged into the noise. The real SAR images under plasma sheath also illustrate this phenomenon. Furthermore, by studying imaging results under different SAR and plasma parameters, it can be concluded that the severe degradation of SAR imaging quality appears at condition of high plasma sheath electron density and low SAR carrier frequency. The work in this paper will be beneficial for the study of hypersonic platform-borne SAR imaging and design of hypersonic SAR imaging systems in the future.

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A Low-Order Partial Integrated Guidance and Control Scheme for Diving Hypersonic Vehicles to Impact Ground Maneuver Target

Mathematical Problems in Engineering ◽

10.1155/2021/7407739 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Tong An ◽

JianHua Wang ◽

YuLong Pan ◽

HaiShan Chen

Keyword(s):

Analytical Model ◽

Sliding Mode ◽

Design Method ◽

Hypersonic Vehicle ◽

Hypersonic Vehicles ◽

Dynamic Surface ◽

Guidance And Control ◽

Integrated Guidance And Control ◽

And Control ◽

Low Order

In this article, a low-order partial integrated guidance and control (PIGC) design method is proposed for diving hypersonic vehicles to impact ground maneuver target. A three-channel analytical model of body rates is deduced based on acceleration components of the hypersonic vehicle. By combining the analytical model of body rates and relative dynamic model between the hypersonic vehicle and target, three-channel commands of body rates are directly generated based on the extended state observer (ESO) technique, sliding mode control approach, and dynamic surface control theory in the guidance subsystem. In the attitude control subsystem, a sliding mode controller is designed to track the commands of body rates and generate commands of control surface fin deflections. By making full use of acceleration information of the hypersonic vehicle measured by the mounted accelerometer, the proposed PIGC design method provides a novel solution to compensate the unknown acceleration of the ground maneuver target. Besides, the order of design model is also reduced, and the design process is simplified. The effectiveness and robustness of the PIGC design method are verified and discussed by 6DOF simulation studies.

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Modeling the Lunar Wake Response to a CME Using a Hybrid PIC Model

The Planetary Science Journal ◽

10.3847/psj/ac3fba ◽

2022 ◽

Vol 3 (1) ◽

pp. 4

Author(s):

Anthony P. Rasca ◽

Shahab Fatemi ◽

William M. Farrell

Keyword(s):

Solar Wind ◽

Magnetic Cloud ◽

Plasma Sheath ◽

Wake Region ◽

Plasma Parameters ◽

Particle In Cell ◽

Lunar Wake ◽

Wind Spacecraft ◽

Upstream Solar Wind ◽

Mass Ejection

Abstract In the solar wind, a low-density wake region forms downstream of the nightside lunar surface. In this study, we use a series of 3D hybrid particle-in-cell simulations to model the response of the lunar wake to a passing coronal mass ejection (CME). Average plasma parameters are derived from the Wind spacecraft located at 1 au during three distinct phases of a passing halo (Earth-directed) CME on 2015 June 22. Each set of plasma parameters, representing the shock/plasma sheath, a magnetic cloud, and plasma conditions we call the mid-CME phase, are used as the time-static upstream boundary conditions for three separate simulations. These simulation results are then compared with results that use nominal solar wind conditions. Results show a shortened plasma void compared to nominal conditions and a distinctive rarefaction cone originating from the terminator during the CME’s plasma sheath phase, while a highly elongated plasma void reforms during the magnetic cloud and mid-CME phases. Developments of electric and magnetic field intensification are also observed during the plasma sheath phase along the central wake, while electrostatic turbulence dominates along the plasma void boundaries and 2–3 lunar radii R M downstream in the central wake during the magnetic cloud and mid-CME phases. The simulations demonstrate that the lunar wake responds in a dynamic way with the changes in the upstream solar wind during a CME.

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