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Lightweight Topology Optimization with Buckling and Frequency constraints Using the Independent Continuous Mapping Method

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Acta Mechanica Solida Sinica 2019年第3期32卷 310-325页

作者： Hongling Ye Yunkang Sui Weiwei Wang College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology Beijing 100124 China

This research focuses on the lightweight topology optimization method for structures under the premise of meeting the requirements of stability and vibration characteristics. A new topology optimization model with the constraints of natural frequencies and critical buckling loads and the objective of minimizing the structural volume is established and solved based on the independent continuous mapping method. The eigenvalue equations and composite exponential filter functions are applied to convert the optimization formulation into a continuous, solvable mathematical programming model. In the process of topology optimization, suitable initial values of the filter functions are chosen to avoid local modes, and the dynamic frequency gap constraints are added in the optimal model to prevent mode switches. Furthermore, for the optimal structures with grey elements obtained by the continuous optimization model, the bisection-inverse iteration is applied to search the optimal discrete structures. Finally, a detailed scheme is given for the buckling and frequency topology optimization problem. Numerical examples illustrate that the modelling method of minimizing the economic index with given performance requirements is practical and feasible for multi-performance topology optimization problems.

关键词： Topology optimization Lightweight Buckling constraints Frequency constraints ICM method

Models of vacuum energy interacting with cold dark matter:constraints and comparison

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Science China(Physics,Mechanics & Astronomy) 2019年第12期62卷 19-27页

作者： Hai-Li Li Lu Feng Jing-Fei Zhang Xin Zhang Department of Physics College of SciencesNortheastern UniversityShenyang 110819China College of Physical Science and Technology Shenyang Normal UniversityShenyang 110034China Ministry of Education Key Laboratory of Data Analytics and Optimization for Smart Industry Northeastern UniversityShenyang 110819China Center for High Energy Physics Peking UniversityBeijing 100080China

In this paper, we investigate the observational constraints on the scenario of vacuum energy interacting with cold dark *** consider eight typical interaction forms in such an interacting vacuum energy scenario. The observational data used in this work to constrain these models include the JLA sample of type Ia supernovae observation, the Planck 2015 distance priors data of cosmic microwave background anisotropies observation, the baryon acoustic oscillations data, and the Hubble constant direct measurement. We find that the current observational data almost equally favor these interacting vacuum energy models. We also find that for all these models of vacuum energy interacting with cold dark matter the case of no interaction is actually well consistent with the current observational data within 1σ range.

关键词： interacting dark energy interacting vacuum energy models cosmological observations cosmological constraints modelcomparison

Adaptive Control Based on Neural Networks for an Uncertain 2-DOF Helicopter System With Input Deadzone and Output constraints

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IEEE/CAA Journal of Automatica Sinica 2019年第3期6卷 807-815页

作者： Yuncheng Ouyang Lu Dong Lei Xue Changyin Sun IEEE the School of Automation and the Key Laboratory of Measurement and Control of Complex Systems of Engineering Ministry of Education Southeast University

In this paper, a study of control for an uncertain2-degree of freedom(DOF) helicopter system is given. The2-DOF helicopter is subject to input deadzone and output constraints. In order to cope with system uncertainties and input deadzone, the neural network technique is introduced because of its capability in approximation. In order to update the weights of the neural network, an adaptive control method is utilized to improve the system adaptability. Furthermore, the integral barrier Lyapunov function(IBLF) is adopt in control design to guarantee the condition of output constraints and boundedness of the corresponding tracking errors. The Lyapunov direct method is applied in the control design to analyze system stability and convergence. Finally, numerical simulations are conducted to prove the feasibility and effectiveness of the proposed control based on the model of Quanser's 2-DOF helicopter.

关键词： 2-degree of freedom (DOF) helicopter adaptive control input deadzone integral barrier Lyapunov function neural networks output constraints

Adaptive tracking control for air-breathing hypersonic vehicles with state constraints

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Frontiers of Information Technology & Electronic Engineering 2017年第5期18卷 599-614页

作者： Gong-jun LI Science and Technology on Space Intelligent Control Laboratory Beijing Institute of Control EngineeringBeijing 100190China

We investigate the adaptive tracking problem for the longitudinal dynamics of state-constrained airbreathing hypersonic vehicles, where not only the velocity and the altitude, but also the angle of attack(AOA) is required to be tracked. A novel indirect AOA tracking strategy is proposed by viewing the pitch angle as a new output and devising an appropriate pitch angle reference trajectory. Then based on the redefined outputs(i.e., the velocity,the altitude, and the pitch angle), a modified backstepping design is proposed where the barrier Lyapunov function is used to solve the state-constrained control problem and the control gain of this class of systems is *** analysis is given to show that the tracking ob jective is achieved, all the closed-loop signals are bounded,and all the states always satisfy the given constraints. Finally, numerical simulations verify the effectiveness of the proposed approach.

关键词： Hypersonic vehicle constraints Output redefinition Barrier Lyapunov function

Hydrodynamic constraints on the energy efficiency of droplet electricity generators

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Microsystems & Nanoengineering 2021年第3期7卷 209-218页

作者： Antoine Riaud Cui Wang Jia Zhou Wanghuai Xu Zuankai Wang State Key Laboratory of ASIC and System School of MicroelectronicsFudan UniversityShanghai200433China Department of Mechanical Engineering City University of Hong KongHong Kong999077China

Electric energy generation from falling droplets has seen a hundred-fold rise in efficiency over the past few ***,even these newest devices can only extract a small portion of the droplet *** this paper,we theoretically investigate the contributions of hydrodynamic and electric losses in limiting the efficiency of droplet electricity generators(DEG).We restrict our analysis to cases where the droplet contacts the electrode at maximum spread,which was observed to maximize the DEG ***,the electro-mechanical energy conversion occurs during the recoil that immediately follows droplet *** then identify three limits on existing droplet electric generators:(i)the impingement velocity is limited in order to maintain the droplet integrity;(ii)much of droplet mechanical energy is squandered in overcoming viscous shear force with the substrate;(iii)insufficient electrical charge of the *** all these effects,we found that up to 83%of the total energy available was lost by viscous dissipation during *** this loss by using cascaded DEG devices to reduce the droplet kinetic energy may increase future devices efficiency beyond 10%.

关键词： viscous constraints limiting

Automatic Generation Control of Multi-area Power System with Network constraints and Communication Delays

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Journal of Modern Power Systems and Clean Energy 2020年第3期8卷 454-463页

作者： Ragini Patel Lasantha Meegahapola Liuping Wang Xinghuo Yu Brendan McGrath Royal Melbourne Institute of Technology University MelbourneVic 3000Australia

Newly proposed power system control methodologies combine economic dispatch(ED) and automatic generation control(AGC) to achieve the steady-state cost-optimal solution under stochastic operation conditions. However, a real power system is subjected to continuous demand disturbance and system constraints due to the input saturation, communication delays and unmeasurable feed-forward load disturbances. Therefore, optimizing the dynamic response under practical conditions is equally important. This paper proposes a state constrained distributed model predictive control(SCDMPC)scheme for the optimal frequency regulation of an interconnected power system under actual operation conditions, which exist due to the governor saturation, generation rate constraints(GRCs), communication delays, and unmeasured feed-forward load disturbances. In addition, it proposes an algorithm to handle the solution infeasibility within the SCDMPC scheme, when the input and state constraints are conflicting. The proposed SCDMPC scheme is then tested with numerical studies on a three-area interconnected network. The results show that the proposed scheme gives better control and cost performance for both steady state and dynamic state in comparison to the traditional distributed model predictive control(MPC) schemes.

关键词： Automatic generation control constraints distributed control frequency regulation model predictive control(MPC) tie-lines

Using machine learning models to explore the solution space of large nonlinear systems underlying flowsheet simulations with constraints

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Frontiers of Chemical Science and Engineering 2022年第2期16卷 183-197页

作者： Patrick Otto Ludl Raoul Heese Johannes Höller Norbert Asprion Michael Bortz Fraunhofer ITWM Optimization Department Kaiserslautern 67663Germany Chemical and Process Engineering BASF SE Ludwigshafen 67056Germany

Flowsheet simulations of chemical processes on an industrial scale require the solution of large systems of nonlinear equations,so that solvability becomes a practical *** constraints from technical,economic,environmental,and safety considerations may further limit the feasible solution space beyond the convergence requirement.A priori,the design variable domains for which a simulation converges and fulfills the imposed constraints are usually unknown and it can become very time-consuming to distinguish feasible from infeasible design variable choices by simply running the simulation for each *** support the exploration of the design variable space for such scenarios,an adaptive sampling technique based on machine learning models has recently been ***,that approach only considers the exploration of the convergent domain and ignores additional *** this paper,we present an improvement which particularly takes the fulfillment of constraints into *** successfully apply the proposed algorithm to a toy example in up to 20 dimensions and to an industrially relevant flowsheet simulation.

关键词： machine learning flowsheet simulations constraints exploration

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Wolfe-Type Duality for Mathematical Programs with Equilibrium constraints

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Acta Mathematicae Applicatae Sinica 2019年第3期35卷 532-540页

作者： Lei GUO Gui-hua LIN Jing ZHAO Sino-US Global Logistics Institute Shanghai Jiao Tong UniversityShanghai 200030China School of Management Shanghai UniversityShanghai 200444China School of Mathematical Sciences Dalian University of TechnologyDalian 116024China

This paper considers the mathematical programs with equilibrium constraints(MPEC).It is well-known that,due to the existence of equilibrium constraints,the Mangasarian-Fromovitz constraint qualification does not hold at any feasible point of MPEC and hence,in general,the developed numerical algorithms for standard nonlinear programming problems can not be applied to solve MPEC *** the past two decades,much research has been done to develop numerical algorithms and study optimality,stability,and sensitivity for ***,there are very few results on duality for MPEC in the *** this paper,we present a Wolfe-type duality for MPEC and,under some suitable conditions,we establish various duality theorems such as the weak duality,direct duality,converse duality,and strict converse duality *** further show that a linear MPEC is equivalent to a linear programming problem in some sense.

关键词： mathematical program with equilibrium constraints Wolfe-type duality duality theorem

An improved heuristic for one-machine scheduling with delays constraints

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Science China Mathematics 1997年第7期40卷 680-686页

作者：杜东雷韩继业陈礴 Institute of Applied Mathematics Chinese Academy of SciencesBeijing 100080China Warwick Business School University of WarwickCV4 7ALU.K.

An improved heuristic is proposed for one-machine scheduling problem with delay constraints,thus an open problem raised by Wikum et *** *** heuristic solves the corresponding unit-execution-time problem optimally.

关键词： scheduling precedence constraints heuristic worst-case performance ratio.