Photostrictive actuators can produce photodeformation strains under illumination of ultraviolet lights. They can realize non-contact micro-actuation and vibration control for elastic plate structures. Considering the ...Photostrictive actuators can produce photodeformation strains under illumination of ultraviolet lights. They can realize non-contact micro-actuation and vibration control for elastic plate structures. Considering the switching actuation and nonlinear dynamic characteristics of photostrictive actuators, a variable structure fuzzy active control scheme is presented to control the light intensity applied to the actuators. Firstly, independent modal vibration control equations of photoelectric laminated plates are established based on modal analysis techniques. Then, the optimal light switching function is derived to increase the range of sliding modal area, and the light intensity self-adjusting fuzzy active controller is designed. Meanwhile, a continuous function is applied to replace a sign function to reduce the variable structure control （VSC） chattering. Finally, numerical simulation is carried out, and simulation results indicate that the proposed control strategy provides better performance and control effect to plate actuation and control than velocity feedback control, and suppresses vibration effectively.展开更多
There is a problem of unfairness in allocation of radio resources among heterogeneous mobile terminals in heterogeneous wireless networks. Low-capability mobile terminals (such as single-mode terminals) suffer high ca...There is a problem of unfairness in allocation of radio resources among heterogeneous mobile terminals in heterogeneous wireless networks. Low-capability mobile terminals (such as single-mode terminals) suffer high call blocking probability whereas high-capability mobile terminals (such as quad-mode terminals) experience very low call blocking probability, in the same heterogeneous wireless network. This paper proposes a Terminal-Modality-Based Joint Call Admission Control (TJCAC) algorithm to reduce this problem of unfairness. The proposed TJCAC algorithm makes call admission decisions based on mobile terminal modality (capability), network load, and radio access technology (RAT) terminal support index. The objectives of the proposed TJCAC algorithm are to reduce call blocking/dropping probability, and ensure fairness in allocation of radio resources among heterogeneous mobile terminals in heterogeneous networks. An analytical model is developed to evaluate the performance of the proposed TJCAC scheme in terms of call blocking/dropping probability in a heterogeneous wireless network. The performance of the proposed TJCAC algorithm is compared with that of other JCAC algorithms. Results show that the proposed algorithm reduces call blocking/dropping probability in the networks, and ensure fairness in allocation of radio resources among heterogeneous terminals.展开更多
In this paper,an experimental model of a horizontal cantilever beam with a rotating/oscillating attached to the shaker for harmonic excitation at the one end and a gyrostabilizer at the other end is built to verify th...In this paper,an experimental model of a horizontal cantilever beam with a rotating/oscillating attached to the shaker for harmonic excitation at the one end and a gyrostabilizer at the other end is built to verify the equations of the Lagrangian model.The primary focus of the study was to investigate the parameters of excitation amplitude,natural frequency,rotating mass(disk mass),and disk speed of gyro that would minimize the amplitude of the beam to identify these effects.Numerical and experimental results indicate that the angular momentum of the gyrostabilizer is the most effective parameter in the reduction of beam displacement.展开更多
The magnetorheological （MR） fluid damper-based semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds. In this pap...The magnetorheological （MR） fluid damper-based semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds. In this paper, a novel modal controller using wavelet packet transform （WPT） is proposed for the vibration control of distributed structures. In the proposed control system, the WPT method is utilized to decompose the acceleration measurement and select the modes containing most of the WPT energy component as the dominant modes. Then, a modal controller is designed to control the dominant modes and the optimal active control force is solved. Finally, Clipped-optimal con- trol law is adopted to determine the voltage applied to each MR damper. A Kalman-filter observer, which estimates the full controlled modal states from local accelerometer feedbacks, is designed for rendering the controller to be more applicable to distributed structures with a large number of degrees of freedom. A numerical example of a stadium root structure installed with MRF-04K damper is presented. The effectiveness of the controller is evaluated under both Tianjin and E1 Centro earthquake excitations. The superior performance and adaptability of the controller for versatile loading conditions are demonstrated through the comparison with traditional truncated modal controller.展开更多
Modal analysis is a fundamental and important task for modeling and control of the flexible manipulator. However, almost all of the traditional modal analysis methods view the flexible manipulator as a pure mechanical...Modal analysis is a fundamental and important task for modeling and control of the flexible manipulator. However, almost all of the traditional modal analysis methods view the flexible manipulator as a pure mechanical structure and neglect feedback action of joint controller. In order to study the effects of joint controller on the modal analysis of rotational flexible manipulator, a closed-loop analytical modal analysis method is proposed. Firstly, two exact boundary constraints, namely servo feedback constraint and bending moment constraint, are derived to solve the vibration partial differential equation. It is found that the stiffness and damping gains of joint controller are both included in the boundary conditions, which lead to an unconventional secular term. Secondly, analytical algorithm based on Ritz approach is developed by using Laplace transform and complex modal approach to obtain the natural frequencies and mode shapes. And then, the numerical simulations are performed and the computational results show that joint controller has pronounced influence on the modal parameters： joint controller stiffness reduces the natural frequency, while joint controller damping makes the shape phase non-zero. Furthermore, the validity of the presented conclusion is confirmed through experimental studies. These findings are expected to improve the performance of dynamics simulation systems and model-based controllers.展开更多
When using H_∞ techniques to design decentralized controllers for large systems, the whole system is divided into subsystems, which are analysed using H_∞ control theory before being recombined. An analogy was estab...When using H_∞ techniques to design decentralized controllers for large systems, the whole system is divided into subsystems, which are analysed using H_∞ control theory before being recombined. An analogy was established with substructural analysis in structural mechanics, in which H_∞ decentralized control theory corresponds to substructural modal synthesis theory so that the optimal H_∞ norm of the whole system corresponds to the fundamental vibration frequency of the whole structure. Hence, modal synthesis methodology and the extended Wittrick_Williams algorithm were transplanted from structural mechanics to compute the optimal H_∞ norm of the control system. The orthogonality and the expansion theorem of eigenfunctions of the subsystems H_∞ control are presented in part (Ⅰ) of the paper. The modal synthesis method for computation of the optimal H_∞ norm of decentralized control systems and numerical examples are presented in part (Ⅱ).展开更多
Imagine how many times your attention is distracted by the surrounding sounds or sights irrelevant to your work or study.To maintain concentrated,you have to control yourself intentionally,which is called"attenti...Imagine how many times your attention is distracted by the surrounding sounds or sights irrelevant to your work or study.To maintain concentrated,you have to control yourself intentionally,which is called"attentional control"or"cognitive control"in psychology.An interesting question arises:when we successfully direct our attention away from one visual distractor,can we be immune to another展开更多
This paper is concerned with the attitude control of a three-axis-stabilized spacecraft which consists of a central rigid body and a flexible sun-tracking solar array driven by a solar array drive assembly. Based on t...This paper is concerned with the attitude control of a three-axis-stabilized spacecraft which consists of a central rigid body and a flexible sun-tracking solar array driven by a solar array drive assembly. Based on the linearization of the dynamics of the spacecraft and the modal identi- ties about the flexible and rigid coupling matrices, the spacecraft attitude dynamics is reduced to a formally singular system with periodically varying parameters, which is quite different from a space- craft with fixed appendages. In the framework of the singular control theory, the regularity and impulse-freeness of the singular system is analyzed and then admissible attitude controllers are designed by Lyapunov＇s method. To improve the robustness against system uncertainties, an H∞ optimal control is designed by optimizing the H∞ norm of the system transfer function matrix. Comparative numerical experiments are performed to verify the theoretical results.展开更多
Our previous study shows that the lateral disturbance motion of a model drone fly does not have inherent stability （passive stability）,because of the existence of an unstable divergence mode.But drone flies are obse...Our previous study shows that the lateral disturbance motion of a model drone fly does not have inherent stability （passive stability）,because of the existence of an unstable divergence mode.But drone flies are observed to fly stably.Constantly active control must be applied to stabilize the flight.In this study,we investigate the lateral stabilization control of the model drone fly.The method of computational fluid dynamics is used to compute the lateral control derivatives and the techniques of eigenvalue and eigenvector analysis and modal decomposition are used for solving the equations of motion.Controllability analysis shows that although inherently unstable,the lateral disturbance motion is controllable.By feeding back the state variables （i.e.lateral translation velocity,yaw rate,roll rate and roll angle,which can be measured by the sensory system of the insect） to produce anti-symmetrical changes in stroke amplitude and/or in angle of attack between the left and right wings,the motion can be stabilized,explaining why the drone flies can fly stably even if the flight is passively unstable.展开更多
In this paper, by using quaternion models, the problem of attitude control is investigated for a class of flexible satellites. Two control laws are presented for the considered flexible satellite models to guarantee c...In this paper, by using quaternion models, the problem of attitude control is investigated for a class of flexible satellites. Two control laws are presented for the considered flexible satellite models to guarantee convergence of the closed-loop systems without using angular velocity measurement. One is in the form of a partial state feedback for the case where the modal variable is available, and the other is in the form of an observer-based partial state feedback for the case where the modal variable cannot be measured. Finally, an example is employed to illustrate the effectiveness of the proposed control laws.展开更多
The principles and methods of active vibration control on a flexible cantilever beam using piezoelectric patches as actuators is studied. Active control of the first two modes of the flexible can- tilever beam is impl...The principles and methods of active vibration control on a flexible cantilever beam using piezoelectric patches as actuators is studied. Active control of the first two modes of the flexible can- tilever beam is implemented based on the independent modal control law. Experimental results show that the structural damping of the flexible cantilever beam is effectively improved and an excellent degree of vibration suppression is achieved with the active vibration control strategy.展开更多
Applying Lagrange-Germain＇s theory of elas- tic thin plates and Hamiltonian formulation, the dynamics of cantilever plates and the problem of its vibration control are studied, and a general solution is finally given...Applying Lagrange-Germain＇s theory of elas- tic thin plates and Hamiltonian formulation, the dynamics of cantilever plates and the problem of its vibration control are studied, and a general solution is finally given. Based on Hamiltonian and Lagrangian density function, we can obtain the flexural wave equation of the plate and the relationship between the transverse and the longitudinal eigenvalues. Based on eigenfunction expansion, dispersion equations of propagation mode of cantilever plates are deduced. By satisfying the boundary conditions of cantilever plates, the natural frequencies of the cantilever plate structure can be given. Then, analytic solution of the problem in plate structure is obtained. An hybrid wave/mode control approach, which is based on both independent modal space control and wave control methods, is described and adopted to analyze the active vibration control of cantilever plates. The low-order （controlled by modal control） and the high-order （controlled by wave control） frequency response of plates are both improved. The control spillover is avoided and the robustness of the system is also improved. Finally, simulation results are analyzed and discussed.展开更多
In telerobotic system for remote welding, human-machine interface is one of the most important factor for enhancing capability and efficiency. This paper presents an architecture design of human-machine interface for ...In telerobotic system for remote welding, human-machine interface is one of the most important factor for enhancing capability and efficiency. This paper presents an architecture design of human-machine interface for welding telerobotic system： welding multi-modal human-machine interface. The human-machine interface integrated several control modes, which are namely shared control, teleteaching, supervisory control and local autonomous control. Space mouse, panoramic vision camera and graphics simulation system are also integrated into the human-machine interface for welding teleoperation. Finally, weld seam tracing and welding experiments of U-shape seam are performed by these control modes respectively. The results show that the system has better performance of human-machine interaction and complexity environment welding.展开更多
基金supported by National Natural Science Foundation of China (Nos. 10872090 and 50830201)Qing Lan Project
文摘Photostrictive actuators can produce photodeformation strains under illumination of ultraviolet lights. They can realize non-contact micro-actuation and vibration control for elastic plate structures. Considering the switching actuation and nonlinear dynamic characteristics of photostrictive actuators, a variable structure fuzzy active control scheme is presented to control the light intensity applied to the actuators. Firstly, independent modal vibration control equations of photoelectric laminated plates are established based on modal analysis techniques. Then, the optimal light switching function is derived to increase the range of sliding modal area, and the light intensity self-adjusting fuzzy active controller is designed. Meanwhile, a continuous function is applied to replace a sign function to reduce the variable structure control （VSC） chattering. Finally, numerical simulation is carried out, and simulation results indicate that the proposed control strategy provides better performance and control effect to plate actuation and control than velocity feedback control, and suppresses vibration effectively.
文摘There is a problem of unfairness in allocation of radio resources among heterogeneous mobile terminals in heterogeneous wireless networks. Low-capability mobile terminals (such as single-mode terminals) suffer high call blocking probability whereas high-capability mobile terminals (such as quad-mode terminals) experience very low call blocking probability, in the same heterogeneous wireless network. This paper proposes a Terminal-Modality-Based Joint Call Admission Control (TJCAC) algorithm to reduce this problem of unfairness. The proposed TJCAC algorithm makes call admission decisions based on mobile terminal modality (capability), network load, and radio access technology (RAT) terminal support index. The objectives of the proposed TJCAC algorithm are to reduce call blocking/dropping probability, and ensure fairness in allocation of radio resources among heterogeneous mobile terminals in heterogeneous networks. An analytical model is developed to evaluate the performance of the proposed TJCAC scheme in terms of call blocking/dropping probability in a heterogeneous wireless network. The performance of the proposed TJCAC algorithm is compared with that of other JCAC algorithms. Results show that the proposed algorithm reduces call blocking/dropping probability in the networks, and ensure fairness in allocation of radio resources among heterogeneous terminals.
文摘In this paper,an experimental model of a horizontal cantilever beam with a rotating/oscillating attached to the shaker for harmonic excitation at the one end and a gyrostabilizer at the other end is built to verify the equations of the Lagrangian model.The primary focus of the study was to investigate the parameters of excitation amplitude,natural frequency,rotating mass(disk mass),and disk speed of gyro that would minimize the amplitude of the beam to identify these effects.Numerical and experimental results indicate that the angular momentum of the gyrostabilizer is the most effective parameter in the reduction of beam displacement.
基金Supported by National Natural Science Foundation of China (No.51108089,No.90715034 and No.90715032)National Natural Science Foundation of Fujian Province (No.2011J05128)
文摘The magnetorheological （MR） fluid damper-based semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds. In this paper, a novel modal controller using wavelet packet transform （WPT） is proposed for the vibration control of distributed structures. In the proposed control system, the WPT method is utilized to decompose the acceleration measurement and select the modes containing most of the WPT energy component as the dominant modes. Then, a modal controller is designed to control the dominant modes and the optimal active control force is solved. Finally, Clipped-optimal con- trol law is adopted to determine the voltage applied to each MR damper. A Kalman-filter observer, which estimates the full controlled modal states from local accelerometer feedbacks, is designed for rendering the controller to be more applicable to distributed structures with a large number of degrees of freedom. A numerical example of a stadium root structure installed with MRF-04K damper is presented. The effectiveness of the controller is evaluated under both Tianjin and E1 Centro earthquake excitations. The superior performance and adaptability of the controller for versatile loading conditions are demonstrated through the comparison with traditional truncated modal controller.
基金Supported by National Natural Science Foundation of China(Grant No.51305039)Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20110005120004)+1 种基金Fundamental Research Funds for the Central Universities,China(Grant No.2014PTB-00-01)National Basic Research Program of China(973 Program,Grant No.2013CB733000)
文摘Modal analysis is a fundamental and important task for modeling and control of the flexible manipulator. However, almost all of the traditional modal analysis methods view the flexible manipulator as a pure mechanical structure and neglect feedback action of joint controller. In order to study the effects of joint controller on the modal analysis of rotational flexible manipulator, a closed-loop analytical modal analysis method is proposed. Firstly, two exact boundary constraints, namely servo feedback constraint and bending moment constraint, are derived to solve the vibration partial differential equation. It is found that the stiffness and damping gains of joint controller are both included in the boundary conditions, which lead to an unconventional secular term. Secondly, analytical algorithm based on Ritz approach is developed by using Laplace transform and complex modal approach to obtain the natural frequencies and mode shapes. And then, the numerical simulations are performed and the computational results show that joint controller has pronounced influence on the modal parameters： joint controller stiffness reduces the natural frequency, while joint controller damping makes the shape phase non-zero. Furthermore, the validity of the presented conclusion is confirmed through experimental studies. These findings are expected to improve the performance of dynamics simulation systems and model-based controllers.
文摘When using H_∞ techniques to design decentralized controllers for large systems, the whole system is divided into subsystems, which are analysed using H_∞ control theory before being recombined. An analogy was established with substructural analysis in structural mechanics, in which H_∞ decentralized control theory corresponds to substructural modal synthesis theory so that the optimal H_∞ norm of the whole system corresponds to the fundamental vibration frequency of the whole structure. Hence, modal synthesis methodology and the extended Wittrick_Williams algorithm were transplanted from structural mechanics to compute the optimal H_∞ norm of the control system. The orthogonality and the expansion theorem of eigenfunctions of the subsystems H_∞ control are presented in part (Ⅰ) of the paper. The modal synthesis method for computation of the optimal H_∞ norm of decentralized control systems and numerical examples are presented in part (Ⅱ).
文摘Imagine how many times your attention is distracted by the surrounding sounds or sights irrelevant to your work or study.To maintain concentrated,you have to control yourself intentionally,which is called"attentional control"or"cognitive control"in psychology.An interesting question arises:when we successfully direct our attention away from one visual distractor,can we be immune to another
文摘This paper is concerned with the attitude control of a three-axis-stabilized spacecraft which consists of a central rigid body and a flexible sun-tracking solar array driven by a solar array drive assembly. Based on the linearization of the dynamics of the spacecraft and the modal identi- ties about the flexible and rigid coupling matrices, the spacecraft attitude dynamics is reduced to a formally singular system with periodically varying parameters, which is quite different from a space- craft with fixed appendages. In the framework of the singular control theory, the regularity and impulse-freeness of the singular system is analyzed and then admissible attitude controllers are designed by Lyapunov＇s method. To improve the robustness against system uncertainties, an H∞ optimal control is designed by optimizing the H∞ norm of the system transfer function matrix. Comparative numerical experiments are performed to verify the theoretical results.
基金supported by the National Natural Science Foundation of China (10732030)the 111 Project (B07009)
文摘Our previous study shows that the lateral disturbance motion of a model drone fly does not have inherent stability （passive stability）,because of the existence of an unstable divergence mode.But drone flies are observed to fly stably.Constantly active control must be applied to stabilize the flight.In this study,we investigate the lateral stabilization control of the model drone fly.The method of computational fluid dynamics is used to compute the lateral control derivatives and the techniques of eigenvalue and eigenvector analysis and modal decomposition are used for solving the equations of motion.Controllability analysis shows that although inherently unstable,the lateral disturbance motion is controllable.By feeding back the state variables （i.e.lateral translation velocity,yaw rate,roll rate and roll angle,which can be measured by the sensory system of the insect） to produce anti-symmetrical changes in stroke amplitude and/or in angle of attack between the left and right wings,the motion can be stabilized,explaining why the drone flies can fly stably even if the flight is passively unstable.
基金co-supported by the Major Program of National Natural Science Foundation of China (Nos.61690210,61690212)Shenzhen Municipal Basic Research Project for Discipline Layout (No.JCYJ20170413112722597)Shenzhen Municipal Project for Basic Research (Nos.JCYJ20170307150952660,JCYJ20170307150227897)
文摘In this paper, by using quaternion models, the problem of attitude control is investigated for a class of flexible satellites. Two control laws are presented for the considered flexible satellite models to guarantee convergence of the closed-loop systems without using angular velocity measurement. One is in the form of a partial state feedback for the case where the modal variable is available, and the other is in the form of an observer-based partial state feedback for the case where the modal variable cannot be measured. Finally, an example is employed to illustrate the effectiveness of the proposed control laws.
基金Supported by the National Natural Science Foundation of China (11172026)
文摘The principles and methods of active vibration control on a flexible cantilever beam using piezoelectric patches as actuators is studied. Active control of the first two modes of the flexible can- tilever beam is implemented based on the independent modal control law. Experimental results show that the structural damping of the flexible cantilever beam is effectively improved and an excellent degree of vibration suppression is achieved with the active vibration control strategy.
基金supported by the National Natural Science Foundation of China(10572045)
文摘Applying Lagrange-Germain＇s theory of elas- tic thin plates and Hamiltonian formulation, the dynamics of cantilever plates and the problem of its vibration control are studied, and a general solution is finally given. Based on Hamiltonian and Lagrangian density function, we can obtain the flexural wave equation of the plate and the relationship between the transverse and the longitudinal eigenvalues. Based on eigenfunction expansion, dispersion equations of propagation mode of cantilever plates are deduced. By satisfying the boundary conditions of cantilever plates, the natural frequencies of the cantilever plate structure can be given. Then, analytic solution of the problem in plate structure is obtained. An hybrid wave/mode control approach, which is based on both independent modal space control and wave control methods, is described and adopted to analyze the active vibration control of cantilever plates. The low-order （controlled by modal control） and the high-order （controlled by wave control） frequency response of plates are both improved. The control spillover is avoided and the robustness of the system is also improved. Finally, simulation results are analyzed and discussed.
文摘In telerobotic system for remote welding, human-machine interface is one of the most important factor for enhancing capability and efficiency. This paper presents an architecture design of human-machine interface for welding telerobotic system： welding multi-modal human-machine interface. The human-machine interface integrated several control modes, which are namely shared control, teleteaching, supervisory control and local autonomous control. Space mouse, panoramic vision camera and graphics simulation system are also integrated into the human-machine interface for welding teleoperation. Finally, weld seam tracing and welding experiments of U-shape seam are performed by these control modes respectively. The results show that the system has better performance of human-machine interaction and complexity environment welding.
