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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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Time-interval method for structure reliability' is adopted to study wind load of reinforced concrete hyperbolic cooling tower shell during construction, based on 'the reliability of structures during construction equals to that du...
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Time-interval method for structure reliability' is adopted to study wind load of reinforced concrete hyperbolic cooling tower shell during construction, based on 'the reliability of structures during construction equals to that during design reference period'. Both 'tower shell resistance perfect correlation assumption' and 'wind action object conversion assumption' are introduced, under which the standard value of wind load can be calculated. Obtained results can be applied to check the strength and stability of tower shell during construction, and will perfect the Chinese Code for design of cooling for industrial recirculation water.
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Time-interval method for structure reliability' is adopted to study wind load of reinforced concrete hyperbolic cooling tower shell during construction, based on 'the reliability of structures during construction equals to that du...
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Time-interval method for structure reliability' is adopted to study wind load of reinforced concrete hyperbolic cooling tower shell during construction, based on 'the reliability of structures during construction equals to that during design reference period'. Both 'tower shell resistance perfect correlation assumption' and 'wind action object conversion assumption' are introduced, under which the standard value of wind load can be calculated. Obtained results can be applied to check the strength and stability of tower shell during construction, and will perfect the Chinese Code for design of cooling for industrial recirculation water.
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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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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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Underactuated Trussed Robot Finger is a newly proposed underactuated robot. Based on its physical structure, dynamic model is established by using the Lagrange mechanics method. Moreover, the nonlinear system's properties are anal...
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Underactuated Trussed Robot Finger is a newly proposed underactuated robot. Based on its physical structure, dynamic model is established by using the Lagrange mechanics method. Moreover, the nonlinear system's properties are analyzed, including non-integrity and stablizability. Besides, the control goal is considered as being stabilized in the vertical equilibrium point. To achieve this goal, feedback control law is proposed by using pole placement method. Then simulation is conducted in MATLAB/Simulink environment. Simulation results indicate that the feedback control rule can effectively realize the goal of stabilizing the robot finger in the vertical equilibrium point. It can satisfy that the designed control rules are correct and effective, and the system has anti-interference ability.
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In this paper, we consider the problem of delay-dependent robust stabilization for singular nonlinear system with Markovian jumping parameters. The considered systems are not necessarily assumed to be regular and impulse free. A s...
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In this paper, we consider the problem of delay-dependent robust stabilization for singular nonlinear system with Markovian jumping parameters. The considered systems are not necessarily assumed to be regular and impulse free. A state feedback controller is designed in terms of a set of linear coupled matrix inequalities. A numerical example is provided to demonstrate the efficiency of the proposed methods in this paper.
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The problem of robust H∞ stability analysis for a class of uncertain singular time-delay systems with Markovian jumping parameters is addressed in this paper. The considered Markovian jump singular systems involve constant time d...
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The problem of robust H∞ stability analysis for a class of uncertain singular time-delay systems with Markovian jumping parameters is addressed in this paper. The considered Markovian jump singular systems involve constant time delay and norm-bounded uncertainties. Based on linear matrix inequality (LMI) approach, a delay dependent condition is proposed, which ensures the Markovian jump singular system to be regular, impulse-free, and stochastically stable. One numerical example is given to demonstrate the applicability of the proposed method.
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