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Fully Adaptive Feedforward Feedback Synchronized Tracking Control for Stewart Platform Systems
Dongya Zhao,Shaoyuan Li,Feng Gao 대한전기학회 2008 International Journal of Control, Automation, and Vol.6 No.5
In this paper, a fully adaptive feedforward feedback synchronized tracking control approach is developed for precision tracking control of 6 degree of freedom (6DOF) Stewart Platform. The proposed controller is designed in decentralized form for implementation simplicity. Interconnections among different subsystems and gravity effect are eliminated by the feedforward control action. Feedback control action guarantees the stability of the system. The gains of the proposed controller can be updated on line without requiring any prior knowledge of Stewart Platform manipulator. Thus the control approach is claimed to be fully adaptive. By employing cross-coupling error technology, the proposed approach can guarantee both of position error and synchronization error converge to zero asymptotically. Because the actuators work in synchronous manner, the tracking performances are improved. The corresponding stability analysis is also presented in this paper. Finally, simulation is demonstrated to verify the effectiveness of the proposed approach.
A New TSMC Prototype Robust Nonlinear Task Space Control of a 6 DOF Parallel Robotic Manipulator
Dongya Zhao,Shaoyuan Li,Quanmin Zhu 제어·로봇·시스템학회 2010 International Journal of Control, Automation, and Vol.8 No.6
In this study, a new terminal sliding mode control (TSMC) prototype robust nonlinear task space control approach is developed for 6 degree of freedom (DOF) parallel robotic manipulators in light of TSMC principle integrated with Lyapunov redesign method. Corresponding stability analysis is presented to lay a foundation for analytical understanding in generic theoretical aspects and safe op-eration for real systems. An illustrative example of a 6 DOF parallel robot is bench tested to validate the effectiveness of the proposed approach.
Nonlinear sloshing in rectangular tanks under forced excitation
Dongya Zhao,Zhiqiang Hu,Gang Chen,Serena Lim,Shuqi Wang 대한조선학회 2018 International Journal of Naval Architecture and Oc Vol.10 No.5
A numerical code is developed based on potential flow theory to investigate nonlinear sloshing in rectangular Liquefied Natural Gas (LNG) tanks under forced excitation. Using this code, internal freesurface elevation and sloshing loads on liquid tanks can be obtained both in time domain and frequency domain. In the mathematical model, acceleration potential is solved in the calculation of pressure on tanks and the artificial damping model is adopted to account for energy dissipation during sloshing. The Boundary Element Method (BEM) is used to solve boundary value problems of both velocity potential and acceleration potential. Numerical calculation results are compared with published results to determine the efficiency and accuracy of the numerical code. Sloshing properties in partially filled rectangular and membrane tank under translational and rotational excitations are investigated. It is found that sloshing under horizontal and rotational excitations share similar properties. The first resonant mode and excitation frequency are the dominant response frequencies. Resonant sloshing will be excited when vertical excitation lies in the instability region. For liquid tank under rotational excitation, sloshing responses including amplitude and phase are sensitive to the location of the center of rotation. Moreover, experimental tests were conducted to analyze viscous effects on sloshing and to validate the feasibility of artificial damping models. The results show that the artificial damping model with modifying wall boundary conditions has better applicability in simulating sloshing under different fill levels and excitations.
Dongya Huang,Li Zhang 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.11
In the field of scene segmentation, the precise segmentation of object boundaries in sports movement scene images is a great challenge. The geometric information and spatial information of the image are very important, but in many models, they are usually easy to be lost, which has a big influence on the performance of the model. To alleviate this problem, a parallel dense dilated convolution merging Network (termed PDDCM-Net) was proposed. The proposed PDDCMNet consists of a feature extractor, parallel dilated convolutions, and dense dilated convolutions merged with different dilation rates. We utilize different combinations of dilated convolutions that expand the receptive field of the model with fewer parameters than other advanced methods. Importantly, PDDCM-Net fuses both low-level and high-level information, in effect alleviating the problem of accurately segmenting the edge of the object and positioning the object position accurately. Experimental results validate that the proposed PDDCM-Net achieves a great improvement compared to several representative models on the COCO-Stuff data set.
Zhou, Dongya,Kim, Cheol,Yun, Seongmin Elsevier 2018 Materials letters Vol.224 No.-
<P><B>Abstract</B></P> <P>A new mathematical method that considers the influences of Li-ion concentration, LiC binding energy, and porosity simultaneously in an electrode is suggested for predicting the effective elastic modulus (EEM) of an electrode. EEMs of electrodes are significantly influenced by the porosity and ion concentration. Graphite electrodes are fabricated and tensile tests are conducted at various states of charge by constructing some pouch cells with LiMn<SUB>2</SUB>O<SUB>4</SUB> cathode and graphite anode. EEM of graphite increases dramatically during Li-ions’ intercalation into the electrode, and reaches a value up to 3 times that of the uncharged electrode. The experimental results are compared with analytical predictions to validate, and the two results show good agreement with a maximum error of 8.6%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new method for predicting the effective elastic modulus of graphite electrode. </LI> <LI> Considered the influences of Li-ion concentration, LiC binding energy and porosity. </LI> <LI> Graphite electrodes, with and without Li-ion charges, were manufactured and tested. </LI> <LI> The test results were compared to validate our method and showed good agreement. </LI> </UL> </P>
Nonlinear sloshing in rectangular tanks under forced excitation
Zhao, Dongya,Hu, Zhiqiang,Chen, Gang,Lim, Serena,Wang, Shuqi The Society of Naval Architects of Korea 2018 International Journal of Naval Architecture and Oc Vol.10 No.5
A numerical code is developed based on potential flow theory to investigate nonlinear sloshing in rectangular Liquefied Natural Gas (LNG) tanks under forced excitation. Using this code, internal free-surface elevation and sloshing loads on liquid tanks can be obtained both in time domain and frequency domain. In the mathematical model, acceleration potential is solved in the calculation of pressure on tanks and the artificial damping model is adopted to account for energy dissipation during sloshing. The Boundary Element Method (BEM) is used to solve boundary value problems of both velocity potential and acceleration potential. Numerical calculation results are compared with published results to determine the efficiency and accuracy of the numerical code. Sloshing properties in partially filled rectangular and membrane tank under translational and rotational excitations are investigated. It is found that sloshing under horizontal and rotational excitations share similar properties. The first resonant mode and excitation frequency are the dominant response frequencies. Resonant sloshing will be excited when vertical excitation lies in the instability region. For liquid tank under rotational excitation, sloshing responses including amplitude and phase are sensitive to the location of the center of rotation. Moreover, experimental tests were conducted to analyze viscous effects on sloshing and to validate the feasibility of artificial damping models. The results show that the artificial damping model with modifying wall boundary conditions has better applicability in simulating sloshing under different fill levels and excitations.
Some properties of the exponential distribution class with applications to risk theory
Cheng, Dongya,Ni, Fenglian,Pakes, Anthony G.,Wang, Yuebao 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.4
This paper derives some equivalent conditions for tail equivalence of a distribution G and the convolution G*H, where G belongs to the exponential distribution class and H is another distribution. This generalizes some existing sufficient conditions and gives further insight into closure properties of the exponential distribution class. If G also is O-subexponential, then the new conditions are satisfied. The obtained results are applied to investigating asymptotic behavior for the finite-time ruin probability in a discrete-time risk model with both insurance and financial risks, where the distributions of the insurance risk or the product of the two risks may not belong to the convolution equivalence distribution class.
Some properties of the exponential distribution class with applications to risk theory
Yuebao Wang,Dongya Cheng,Fenglian Ni,Anthony G. Pakes 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.4
This paper derives some equivalent conditions for tail equivalence of a distribution G and the convolution G∗H, where G belongs to the exponential distribution class andH is another distribution. This generalizes some existing sufficient conditions and gives further insight into closure properties of the exponential distribution class. If G also is O-subexponential,then the new conditions are satisfied. The obtained results are applied to investigating asymptotic behavior for the finite-time ruin probability in a discrete-time risk model with both insurance and financial risks, where the distributions of the insurance risk or the product of the two risks may not belong to the convolution equivalence distribution class.