scholarly journals Evasion guidance for air-breathing hypersonic vehicles against unknown pursuer dynamics

2021 ◽  
Author(s):  
Tian Yan ◽  
Yuanli Cai ◽  
Bin Xu
Keyword(s):  
Parameter Estimation ◽  
Gradient Descent ◽  
Rapid Development ◽  
Energy Optimization ◽  
Hypersonic Vehicles ◽  
Air Breathing ◽  
Related Research ◽  
Practical Guidance ◽  
Simulation Results ◽  
Guidance Algorithm

AbstractThe rapid development of hypersonic vehicles has motivated the related research dramatically while the evasion of the hypersonic vehicles becomes one of the challenging issues. Different from the work based on the premise that the pursuers’ information is fully known, in this paper the evasion guidance for air-breathing hypersonic vehicles (AHVs) against unknown pursuer dynamics is studied. The gradient descent is employed for parameter estimation of the unknown dynamics of the pursuer. The energy-optimized evasion guidance algorithm is further developed by taking the acceleration constraint and energy optimization into consideration. Under the proposed algorithm, the system can deal with the unknown pursuer dynamics effectively and provide more practical guidance for the evasion process. The simulation results show that the proposed method can enable the AHV to achieve successful evasion.

On-line Ascent Phase Trajectory Optimal Guidance Algorithm based on Pseudo-spectral Method and Sensitivity Updates

2015 ◽  
Vol 68 (6) ◽  
pp. 1056-1074 ◽  
Author(s):  
Da Zhang ◽  
Lei Liu ◽  
Yongji Wang
Keyword(s):  
Spectral Method ◽  
Direct Method ◽  
Lipschitz Constant ◽  
Model Parameters ◽  
Hypersonic Vehicles ◽  
Air Breathing ◽  
Optimal Guidance ◽  
Guidance Algorithm ◽  
Pseudo Spectral Method ◽  
Pseudo Spectral

The objective of this paper is to investigate an online method to generate an optimal ascent trajectory for air-breathing hypersonic vehicles. A direct method called the Pseudo-spectral method shows promise for real-time optimal guidance. A significant barrier to this optimisation-based control strategy is computational delay, especially when the solution time of the non-linear programming problem exceeds the sampling time. Therefore, an online guidance algorithm for an air-breathing hypersonic vehicles with process constraints and terminal states constraints is proposed based on the Pseudo-spectral method and sensitivity analysis in this paper, which can reduce online computational costs and improve performance significantly. The proposed ascent optimal guidance method can successively generate online open-loop suboptimal controls without the design procedure of an inner-loop feedback controller. Considering model parameters' uncertainties and external disturbance, a sampling theorem is proposed that indicates the effect of the Lipschitz constant of the dynamics on sampling frequency. The simulation results indicate that the proposed method offers improved performance and has promising ability to generate an optimal ascent trajectory for air-breathing hypersonic vehicles.

The Scoping Review of Smart Healthcare Applications in Medical Health (Preprint)

2020 ◽  
Author(s):  
Cheng Hang Wu ◽  
Ching Ju Chiu ◽  
Yen Ju Liou ◽  
Chun Ying Lee ◽  
Susan C. Hu
Keyword(s):  
Systematic Reviews ◽  
Mobile Health ◽  
Scoping Review ◽  
Search Strategy ◽  
Rapid Development ◽  
Related Research ◽  
Geographic Access ◽  
Smart Healthcare ◽  
Research Findings ◽  
Healthcare Interventions

BACKGROUND There is still no consensus on research terms for smart healthcare worldwide. The study conducted by Lewis 10 years ago showed extending geographic access was the major health purpose of health-related information communication technology (ICT), but today's situation may be different because of the rapid development of smart healthcare. Objective: The main aim of this study is to classify recent smart healthcare interventions. Therefore, this scoping review was conducted as a feasible tool for exploring this domain and summarizing related research findings. OBJECTIVE The main aim of this study is to classify recent smart healthcare interventions. Therefore, this scoping review was conducted as a feasible tool for exploring this domain and summarizing related research findings. METHODS The scoping review relies on the analysis of previous reviews of smart healthcare interventions assessed for their effectiveness in the framework of a systematic review and/or meta-analysis. The search strategy was based on the identification of smart healthcare interventions reported as the proposed keywords. In the analysis, the reviews published from January 2015 to December 2019 were included. RESULTS The number of publications for smart healthcare's systematic reviews has continued to grow in the past five years. The search strategy yielded 210 systematic reviews and/or meta-analyses addressed to target groups of interest. 68.5% of these publications used mobile health as a keyword. According to the classification by Lewis, 37.62% of the literature was applied to extend geographic access. According to the classification by the Joint Commission of Taiwan (JCT), 48.84% of smart healthcare was applied in clinical areas, and 60% of it was applied in outpatient medical services. CONCLUSIONS Smart healthcare interventions are being widely used in clinical settings and for disease management. The research of mobile health has received the most attention among smart healthcare interventions. The main purpose of mobile health was used to extend geographic access to increase medical accessibility in clinical areas. CLINICALTRIAL none

scholarly journals Stability and Manoeuvrability Simulation of a Semi-Autonomous Submarine Free-Running Model SUBOFF with an Autopilot System

2021 ◽  
Vol 11 (1) ◽  
pp. 410
Author(s):  
Yu-Hsien Lin ◽  
Yu-Ting Lin ◽  
Yen-Jun Chiu
Keyword(s):  
Optimal Control ◽  
Experimental Tests ◽  
Degree Of Freedom ◽  
Line Of Sight ◽  
Pd Controller ◽  
Free Running ◽  
Simulation Results ◽  
Guidance Algorithm ◽  
Logic Operations ◽  
Six Degree Of Freedom

On the basis of a full-appendage DARPA SUBOFF model (DTRC model 5470), a scale (λ = 0.535) semi-autonomous submarine free-running model (SFRM) was designed for testing its manoeuvrability and stability in the constrained water. Prior to the experimental tests of the SFRM, a six-degree-of-freedom (6-DOF) manoeuvre model with an autopilot system was developed by using logic operations in MATLAB. The SFRM’s attitude and its trim polygon were presented by coping with the changes in mass and trimming moment. By adopting a series of manoeuvring tests in empty tanks, the performances of the SFRM were introduced in cases of three sailing speeds. In addition, the PD controller was established by considering the simulation results of these manoeuvring tests. The optimal control gains with respect to each manoeuvring test can be calculated by using the PID tuner in MATLAB. Two sets of control gains derived from the optimal characteristics parameters were compared in order to decide on the most appropriate PD controller with the line-of-sight (LOS) guidance algorithm for the SFRM in the autopilot simulation. Eventually, the simulated trajectories and course angles of the SFRM would be illustrated in the post-processor based on the Cinema 4D modelling.

scholarly journals Financial inclusion in China: an overview

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Weidong Chen ◽  
Xiaohui Yuan
Keyword(s):  
Sustainable Development ◽  
Development Strategy ◽  
Digital Technology ◽  
Rapid Development ◽  
Financial Inclusion ◽  
Significant Progress ◽  
Research Directions ◽  
Related Research ◽  
Development Path ◽  
Important Development

AbstractFinancial inclusion has become an important development strategy in many countries, and related research is increasing. Financial inclusion in China has had significant progress recently. It has gradually formed a unique and sustainable development path with supporting policies and regulations as well as rapid development and application of digital technology. While challenges remain, the experience of Chinese financial inclusion provides valuable lessons and research directions for policymakers and researchers.

A RELAX Based Method for Spotlight SAR Imaging

2012 ◽  
Vol 500 ◽  
pp. 362-367
Author(s):  
Xiao Zhen Ren ◽  
Yao Qin ◽  
Hong Liang Fu
Keyword(s):  
Parameter Estimation ◽  
Estimation Problem ◽  
Noisy Environment ◽  
Parameter Estimation Problem ◽  
Imaging Algorithm ◽  
Imaging Results ◽  
Sar Imaging ◽  
Simulation Results ◽  
Noisy Condition

The imaging problem of spotlight SAR is converted to a parameter estimation problem of several monochromatic signals in additive white Gaussian noisy condition in this paper. Moreover, a spotlight SAR imaging algorithm based on RELAX is presented in detail. Traditional polar format algorithm and the presented method are applied to spotlight SAR imaging respectively, and the imaging results are compared. Simulation results show that the polar format algorithm doesn’t give satisfactory imaging results, while the proposed method adapts the noisy environment better and obtains better results.

scholarly journals Research on an Improved Method for Foot-Mounted Inertial/Magnetometer Pedestrian-Positioning Based on the Adaptive Gradient Descent Algorithm

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4105 ◽  
Author(s):  
Qiuying Wang ◽  
Juan Yin ◽  
Aboelmagd Noureldin ◽  
Umar Iqbal
Keyword(s):  
Kalman Filter ◽  
Gradient Descent ◽  
Rapid Development ◽  
Alignment Algorithm ◽  
Magnetic Disturbance ◽  
Misalignment Angle ◽  
Initial Alignment ◽  
Positioning Systems ◽  
Descent Algorithm ◽  
Gradient Descent Algorithm

Foot-mounted Inertial Pedestrian-Positioning Systems (FIPPSs) based on Micro Inertial Measurement Units (MIMUs), have recently attracted widespread attention with the rapid development of MIMUs. The can be used in challenging environments such as firefighting and the military, even without augmenting with Global Navigation Satellite System (GNSS). Zero Velocity Update (ZUPT) provides a solution for the accumulated positioning errors produced by the low precision and high noise of the MIMU, however, there are some problems using ZUPT for FIPPS, include fast-initial alignment and unobserved heading misalignment angle, which are addressed in this paper. Our first contribution is proposing a fast-initial alignment algorithm for foot-mounted inertial/magnetometer pedestrian positioning based on the Adaptive Gradient Descent Algorithm (AGDA). Considering the characteristics of gravity and Earth’s magnetic field, measured by accelerometers and magnetometers, respectively, when the pedestrian is standing at one place, the AGDA is introduced as the fast-initial alignment. The AGDA is able to estimate the initial attitude and enhance the ability of magnetic disturbance suppression. Our second contribution in this paper is proposing an inertial/magnetometer positioning algorithm based on an adaptive Kalman filter to solve the problem of the unobserved heading misalignment angle. The algorithm utilizes heading misalignment angle as an observation for the Kalman filter and can improve the accuracy of pedestrian position by compensating for magnetic disturbances. In addition, introducing an adaptive parameter in the Kalman filter is able to compensate the varying magnetic disturbance for each ZUPT instant during the walking phase of the pedestrian. The performance of the proposed method is examined by conducting pedestrian test trajectory using MTi-G710 manufacture by XSENS. The experimental results verify the effectiveness and applicability of the proposed method.

Immersion and invariance adaptive finite-time control of air-breathing hypersonic vehicles

2018 ◽  
Vol 233 (7) ◽  
pp. 2626-2641 ◽  
Author(s):  
Chao Han ◽  
Zhen Liu ◽  
Jianqiang Yi
Keyword(s):  
Control System ◽  
Finite Time ◽  
Control Method ◽  
Sliding Mode ◽  
Second Order ◽  
Hypersonic Vehicles ◽  
Terminal Sliding Mode ◽  
Air Breathing ◽  
Immersion And Invariance ◽  
Time Control

In this paper, a novel adaptive finite-time control of air-breathing hypersonic vehicles is proposed. Based on the immersion and invariance theory, an adaptive finite-time control method for general second-order systems is first derived, using nonsingular terminal sliding mode scheme. Then the method is applied to the control system design of a flexible air-breathing vehicle model, whose dynamics can be decoupled into first-order and second-order subsystems by time-scale separation principle. The main features of this hypersonic vehicle control system lie in the design flexibility of the parameter adaptive laws and the rapid convergence to the equilibrium point. Finally, simulations are conducted, which demonstrate that the control system has the features of fast and accurate tracking to command trajectories and strong robustness to parametric and non-parametric uncertainties.

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