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The two main purposes of this paper are looking for a navigation plan for formations with total autonomy, good accuracy and least requirements; and examining the aspects of a formation configuration that affect the performance of ...
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The two main purposes of this paper are looking for a navigation plan for formations with total autonomy, good accuracy and least requirements; and examining the aspects of a formation configuration that affect the performance of absolute and relative navigation methods. The newly developed X-ray pulsar navigation (XNAV) is employed, and two XNAV modes are introduced: standard XNAV is used for its good autonomy and observability, and relative XNAV is used to examine the effectiveness of relative navigation methods in the navigation of formations. Also crosslink measurement is employed for its great accuracy and low requirement. Two analysis tools are developed to examine the effect of formation configuration on navigation methods. Error amplification factor (EAF) is a useful tool describing the observability levels of navigation plans, and observation variance factor (OVF) is used to evaluate the effectiveness of a navigation method when the formation configuration changes. With the tools and simulations, the effects of the height, tightness and shape of formations on navigation methods are revealed. The performances of relative navigation methods deteriorate as the formation becomes tighter, higher or have a new shape with less relative movements. Under common formation settings, relative navigation methods cannot provide sufficient observability. But the absolute navigation method - standard XNAV is hardly affected by any changes of the formation configuration, with only two pulsars standard XNAV can achieve total observability. The only exception is when the orbit is low enough that the orbit plain rotates fast enough for only one pulsar to achieve total observability. The integrated navigation plan with two pulsars in standard XNAV and crosslink measurement is chosen for its total autonomy, low requirements and good performance. Under various formation settings the positioning accuracy of this plan is within 20m, and the relative accuracy is within 8m. A hardware reduction method by using only one X-ray detector observing multiple pulsars at different periods is proposed and examined with simulations. Comparing to the multiple detectors method, the positioning accuracy is only 10m larger, and the relative accuracy is 6m larger at most. The analysis and simulation results prove that the proposed autonomous integrated navigation plan is suitable for all formation configurations, and it has good accuracy and low requirement, especially after implementing the hardware reduction method.
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Autonomous navigation of Global Navigation Satellite Systems (GNSS) can be realized with the newly developed X-ray pulsar navigation (XNAV). XNAV is an autonomous navigation method using the periodic signals of X-ray pulsars. Base...
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Autonomous navigation of Global Navigation Satellite Systems (GNSS) can be realized with the newly developed X-ray pulsar navigation (XNAV). XNAV is an autonomous navigation method using the periodic signals of X-ray pulsars. Based on the reference point of phase comparison, the concepts of three XNAV modes are defined: standard mode, incremental mode, and relative mode. Their performances and requirements in the navigation of GNSS are examined, and the last two modes are recommended for their immunity to clock error and low requirement on pulsar timing model. Integrated navigation consists of XNAV and crosslink measurement is proposed to improve the navigation accuracy. Simulations are conducted to examine the effects of XNAV modes, pulsar number, estimation methods and clock error on navigation accuracy. The results show that when using XNAV alone in GNSS, only 2 pulsars are sufficient for total observability, and a positioning accuracy within 80m can be achieved; when using integrated navigation, only 1 pulsar is needed to achieve a positioning accuracy within 4m. The limitations and benefits of XNAV in GNSS are analyzed, based on the analysis and simulation results, XNAV is considered as a very promising autonomous navigation method for GNSS.
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For the purpose of solving the multi-objective reentry trajectory optimization problem with multiple path and terminal constraints for a hypersonic reentry-gliding vehicle, the energy-like dynamic equations are introduced by origi...
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For the purpose of solving the multi-objective reentry trajectory optimization problem with multiple path and terminal constraints for a hypersonic reentry-gliding vehicle, the energy-like dynamic equations are introduced by original time-varying equations so that the problem can be finally transformed to a non-linear program NLP problem with fixed terminal values. After that, a numerical optimization method based on PSO algorithm is considered, where the adaptive penalty technique and Normalized Non-dominated Sorting technique are used to handling the multi-constraints and multi-objectives, respectively. The simulation shows that the complete longitudinal multi-objective trajectories can be generated by the proposed algorithm and the optimized angles of attack can provide multiple references for practical engineering.
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摘要 :
For the purpose of solving the multi-objective reentry trajectory optimization problem with multiple path and terminal constraints for a hypersonic reentry-gliding vehicle, the energy-like dynamic equations are introduced by origi...
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For the purpose of solving the multi-objective reentry trajectory optimization problem with multiple path and terminal constraints for a hypersonic reentry-gliding vehicle, the energy-like dynamic equations are introduced by original time-varying equations so that the problem can be finally transformed to a non-linear program NLP problem with fixed terminal values. After that, a numerical optimization method based on PSO algorithm is considered, where the adaptive penalty technique and Normalized Non-dominated Sorting technique are used to handling the multi-constraints and multi-objectives, respectively. The simulation shows that the complete longitudinal multi-objective trajectories can be generated by the proposed algorithm and the optimized angles of attack can provide multiple references for practical engineering.
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摘要 :
For the purpose of solving the multi-objective reentry trajectory optimization problem with multiple path and terminal constraints for a hypersonic reentry-gliding vehicle, the energy-like dynamic equations are introduced by origi...
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For the purpose of solving the multi-objective reentry trajectory optimization problem with multiple path and terminal constraints for a hypersonic reentry-gliding vehicle, the energy-like dynamic equations are introduced by original time-varying equations so that the problem can be finally transformed to a non-linear program NLP problem with fixed terminal values. After that, a numerical optimization method based on PSO algorithm is considered, where the adaptive penalty technique and Normalized Non-dominated Sorting technique are used to handling the multi-constraints and multi-objectives, respectively. The simulation shows that the complete longitudinal multi-objective trajectories can be generated by the proposed algorithm and the optimized angles of attack can provide multiple references for practical engineering.
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In this paper, we analyze the stability of distributed Hopfield neural networks. Distributed parameter Hopfield neural networks model is established by PDEs so state space of the controlled system belongs infinity dimensions, whic...
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In this paper, we analyze the stability of distributed Hopfield neural networks. Distributed parameter Hopfield neural networks model is established by PDEs so state space of the controlled system belongs infinity dimensions, which is different from ODEs and DAEs models. Reaction-Diffusion Hopfield neural networks model is a new class of net systems which exist widely in control science, intelligent computation, cells of neurology and biology mathematica. Most of papers about Hopfield neural networks apply average Lyapunov function and M-matrix theory to study stability. Now, we use operator spectral theory to obtain stability of the system, which does not need complex calculation. At last, we make some simulations verify our criterions.
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Underactuated mechanical systems have their own difficulties within the control criterion. As a particular and complex underactuated mechanical system, underactuated truss-like robotic finger (UTRF) is studied by establishing its ...
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Underactuated mechanical systems have their own difficulties within the control criterion. As a particular and complex underactuated mechanical system, underactuated truss-like robotic finger (UTRF) is studied by establishing its dynamic model. The control problems include high nonlinearity, model inaccuracy and uncertainties. Type-2 fuzzy logic control method is supposed to be a proper way to solve these problems, because fuzzy logic control itself does not depend on an accurate model of the controlled object, and type-2 fuzzy logic control is able to handle uncertainties. The basic principle of type-2 fuzzy logic control is then analyzed. Moreover, an interval type-2 fuzzy logic controller is designed for UTRF to accomplish the goal of stabilization in its equilibrium point. Simulation result shows that the designed interval type-2 fuzzy logic controller is correct and effective.
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We consider a nonlinear reaction-diffusion competition model with Neumann boundary condition. The main goal of this article is to research the existence and uniqueness of positive periodic solution when most of parameters are func...
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We consider a nonlinear reaction-diffusion competition model with Neumann boundary condition. The main goal of this article is to research the existence and uniqueness of positive periodic solution when most of parameters are functions of time t and space x. We apply the lower and upper solutions method to present existence conditions of positive periodic solution. We obtain uniqueness conditions of positive periodic solution from priori estimates of the system. Moreover, Numerical simulation is carried out to illustrate feasibility of our main results.
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A constructive approach to design asymptotically stabilizing control laws for an inertia-wheel pendulum system is presented in this paper. The control scheme is based on immersion and invariance(I&I) which is derived starting from the selection of a target dynamical system. The process that the off-the-manifold variable converges to the origin in finite time has been strictly ensured by the proposed stabilizing control laws. A detailed stability proof and analysis is provided for the resulting closed-loop system, and the computation for the finite time is also shown as an important contribution of this work. Moreover, a saturation function is employed to update the control laws, which is effective for reducing the manifold chattering. The validity of the obtained control method is illustrated via various simulations....
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A constructive approach to design asymptotically stabilizing control laws for an inertia-wheel pendulum system is presented in this paper. The control scheme is based on immersion and invariance(I&I) which is derived starting from the selection of a target dynamical system. The process that the off-the-manifold variable converges to the origin in finite time has been strictly ensured by the proposed stabilizing control laws. A detailed stability proof and analysis is provided for the resulting closed-loop system, and the computation for the finite time is also shown as an important contribution of this work. Moreover, a saturation function is employed to update the control laws, which is effective for reducing the manifold chattering. The validity of the obtained control method is illustrated via various simulations.
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摘要 :
A constructive approach to design asymptotically stabilizing control laws for an inertia-wheel pendulum system is presented in this paper. The control scheme is based on immersion and invariance(I&I) which is derived starting from the selection of a target dynamical system. The process that the off-the-manifold variable converges to the origin in finite time has been strictly ensured by the proposed stabilizing control laws. A detailed stability proof and analysis is provided for the resulting closed-loop system, and the computation for the finite time is also shown as an important contribution of this work. Moreover, a saturation function is employed to update the control laws, which is effective for reducing the manifold chattering. The validity of the obtained control method is illustrated via various simulations....
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A constructive approach to design asymptotically stabilizing control laws for an inertia-wheel pendulum system is presented in this paper. The control scheme is based on immersion and invariance(I&I) which is derived starting from the selection of a target dynamical system. The process that the off-the-manifold variable converges to the origin in finite time has been strictly ensured by the proposed stabilizing control laws. A detailed stability proof and analysis is provided for the resulting closed-loop system, and the computation for the finite time is also shown as an important contribution of this work. Moreover, a saturation function is employed to update the control laws, which is effective for reducing the manifold chattering. The validity of the obtained control method is illustrated via various simulations.
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