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Optimal Motion Planning for Differentially Flat Underactuated Mechanical Systems

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Chinese Journal of Mechanical Engineering 2009年第3期22卷 347-354页

作者： HE Guangping geng Zhiyong State Key Laboratory for Turbulence and Complex System Peking University Beijing 100871 China Department of Mechanical and Electrical Engineering North China University of Technology Beijing 100041 China

Underactuated mechanical system has less independent inputs than the degrees of freedom（DOF） of the mechanism. The energy efficiency of this class of mechanical systems is an essential problem in practice. On the basis of the sufficient and necessary condition that concludes a single input nonlinear system is differentially flat, it is shown that the flat output of the single input underactuated mechanical system can be obtained by finding a smooth output function such that the relative degree of the system equals to the dimension of the state space. If the flat output of the underactuated system can be solved explicitly, and by constructing a smooth curve with satisfying given boundary conditions in fiat output space, an energy efficiency optimization method is proposed for the motion planning of the differentially flat underactuated mechanical systems. The inertia wheel pendulum is used to verify the proposed optimization method, and some numerical simulations show that the presented optimal motion planning method can efficaciously reduce the energy cost for given control tasks.

关键词： differential flatness underactuated system motion planning optimization

Interaction of weak free-stream disturbance with an oblique shock： validation of the shock-capturing method

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Applied Mathematics and Mechanics(English Edition) 2017年第11期38卷 1601-1612页

作者： Caihong SU Jinlei geng Department of Mechanics Tianjin University Tianjin 300072 China

Transition prediction is of great importance for the design of long distance flying vehicles. It starts from the problem of receptivity, i.e., how external disturbances trigger instability waves in the boundary layer. For super/hypersonic boundary layers, the external disturbances first interact with the shock ahead of the flying vehicles before entering the boundary layer. Since direct numerical simulation （DNS） is the only available tool for its comprehensive and detailed investigation, an important problem arises whether the numerical scheme, especially the shock-capturing method, can faithfully reproduce the interaction of the external disturbances with the shock, which is so far unknown. This paper is aimed to provide the answer. The interaction of weak disturbances with an oblique shock is investigated, which has a known theoretical solution. Numerical simulation using the shock-capturing method is conducted, and results are compared with those given by theoretical analysis, which shows that the adopted numerical method can faithfully reproduce the interaction of weak external disturbances with the shock.

关键词： shock high speed flow free-stream disturbance shock-capturing

Boosting electrocatalytic nitrate reduction to ammonia via Cu_(2)O/Cu(OH)_(2)heterostructures promoting electron transfer

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Nano Research 2024年第6期17卷 4898-4907页

作者： Jing geng Sihan Ji Anhui Province International Research Center on Advanced Building Materials School of Materials Science and Chemical EngineeringAnhui Jianzhu UniversityHefei 230601China Anhui Province Key Laboratory of Advanced Building Materials Anhui Jianzhu UniversityHefei 230601China School of Energy Materials and Chemical Engineering Hefei UniversityHefei 230601China

Electrocatalytic nitrate(NO_(3)^(−))reduction to ammonia(NH_(3))offers a viable approach for sustainable NH_(3)production and environmental ***(Cu)possesses a distinctive electronic structure,which can augment the reaction kinetics of NO_(3)^(−)and impede hydrogen evolution reaction(HER),rendering it a promising contender for the electrosynthesis of NH_(3)from NO_(3)^(−).Nevertheless,the role of Cu_(2)O in copper-based catalysts still requires further investigation for a more comprehensive ***,the Cu_(2)O/Cu(OH)_(2)heterostructures are successfully fabricated through liquid laser irradiation using CuO nanoparticles as a *** and theoretical researches reveal that Cu_(2)O/Cu(OH)_(2)heterostructure exhibits enhanced electrocatalytic performance for NO_(3)^(−)to NH_(3)because Cu(OH)_(2)promotes electron transfer and reduces the valence state of Cu active site in Cu_(2)***−0.6 V(*** hydrogen electrode(RHE)),the NH_(3)yield reaches its maximum at 1630.66±29.72μg·h^(−1)·mgcat^(−1),while the maximum of Faraday efficiency(FE)is 76.95%±5.51%.This study expands the technical scope of copper-based catalyst preparation and enhances the understanding of the electrocatalytic mechanism of NO_(3)^(−)to NH_(3).

关键词： Cu_(2)O/Cu(OH)_(2)heterostructures electron transfer ammonia synthesis electrocatalysts nitrate

Investigation and measurement of old building response to the overlapped shield tunnel of multiple schemes in the sandy cobble stratum

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Underground Space 2024年第2期15卷 260-274页

作者： Xue Li Aopeng geng School of Geoscience and Technology Southwest Petroleum UniversityChengduSichuan 610500China China Railway Construction Bridge Engineering Bureau Group Co. Ltd.Tianjin 300300China

Ground movements due to tunneling are becoming increasingly critical as buildings are located around construction *** study proposes a new combined reinforcement method using a foundation grouting oblique pipe *** former improves the bearing capacity of the subsoil,and the latter blocks the transmission of soil deformation,which weakens the influence of construction during overlapped tunnel *** on this new method,a case study of the shield tunneling response to an old building in Line 6 of China’s Chengdu Metro is ***,three-dimensional numerical models without reinforcement,traditional foundation grouting reinforcement,and the new combined reinforcement schemes were *** numerical simulation performance was verified using a set of field instrumentation data,which demonstrated that the old building response to the overlapped tunnels was under control,and the maximum deformation,angular distortion,and principal tensile strain of the building were 5.25 mm,5.1010–6 rad/m,and 0.0081%,*** with the traditional reinforcement scheme,the deformation,angular distortion,and principal tensile strain in the combined reinforcement scheme were reduced by 54.78%,71.02%,and 70.22%,*** results have important implications for the design and construction of shield tunnels and their response to old buildings.

关键词： Overlapped tunnels Reinforcement schemes Under-crossing Old building Numerical simulation

Simulated annealing algorithm for detecting graph isomorphism

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Journal of Systems Engineering and Electronics 2008年第5期19卷 1047-1052页

作者： geng Xiutang Zhang Kai Dept. of Control Science and Engineering Huazhong Univ. of Science and Technology Wuhan 430074 P. R. China

Evolutionary computation techniques have mostly been used to solve various optimization problems, and it is well known that graph isomorphism problem （GIP） is a nondeterministic polynomial problem. A simulated annealing （SA） algorithm for detecting graph isomorphism is proposed, and the proposed SA algorithm is well suited to deal with random graphs with large size. To verify the validity of the proposed SA algorithm, simulations are performed on three pairs of small graphs and four pairs of large random graphs with edge densities 0.5, 0.1, and 0.01, respectively. The simulation results show that the proposed SA algorithm can detect graph isomorphism with a high probability.

关键词： graph isomorphism problem simulated annealing algorithm nondeterministic polynomial problem,local search.

Coalescence of pore columns by domain switching

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Acta Mechanica Sinica 2006年第3期22卷 207-216页

作者： Liming geng Wei Yang Department of Engineering Mechanics Tsinghua University Beijing 100084 China

The present paper studies the coalescence of pore columns in ferroelectric ceramics driven by back and forth domain switching under cyclic electric field. A finite element method that incorporates mass transfer capacity is formulated to simulate the evolution of point defects subjected to the kinetics of pore surface diffusion and domain wall migration. The merge of point defects provides a mechanism for the vacancy agglomeration that leads to the formation of large pores or microcracks.

关键词： Point defect Ferroelectrics Domain switch Coalescence Structural evolution Finite element

Super twisting controller for on-orbit servicing to non-cooperative target

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Chinese Journal of Aeronautics 2015年第1期28卷 285-293页

作者： Chen Binglong geng Yunhai Research Center of Satellite Technology Harbin Institute of Technology

A relative position and attitude coupled controller is proposed for rendezvous and docking between two docking ports located in different spacecraft. It is concerned with servicing to a tumbling non-cooperative target spacecraft in arbitrary orbit subjected to external *** considering both kinematic and dynamical coupled effects of relative rotation on relative translation, a coupled dynamic model is established to represent the relative motion of docking port on target spacecraft with respect to another on the service spacecraft. The spacecraft control is based on the second order sliding mode algorithm of super twisting（ST）. It is schemed to manipulate the relative position and attitude synchronously. A formal proof of the finite time convergence property of the closed-loop system is derived theoretically by the second method of Lyapunov. Numerical simulations with the designed ST controller are presented to validate the analytic analysis by contrast with the twisting control algorithm. Simulation results demonstrate that the proposed relative position and attitude integrated controller is characterized by high precision, strong robustness and high reliability.

关键词： spacecraft orbit cooperative attitude robustness kinematic sliding dynamical rotation concerned

Beam-based optimization of SwissFEL low-level RF system

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Nuclear Science and Techniques 2018年第9期29卷 171-178页

作者： Zhe-Qiao geng Paul Scherrer Institut(PSI) 5232 VilligenSwitzerland

Swiss FEL is a free electron laser(FEL) under commissioning at the Paul Scherrer Institut(PSI) in Switzerland. Digital low-level RF(LLRF) systems are used in Swiss FEL to control more than 30 RF stations with either standing wave cavities(e.g. RF gun) or travelling wave structures working at different frequencies. After conditioned to desired power levels, the RF stations need to be setup for beam operation and the LLRF parameters need to be optimized for maximizing the beam stability. Several beam-based algorithms were developed to facilitate the setup, calibration and optimization of the Swiss FEL RF stations for beam operation. The algorithms were implemented as automation procedures in the framework of Experimental Physics and Industrial Control System(EPICS) and were used in commissioning and daily operation of Swiss FEL. In this paper, the algorithms and the implementation will be introduced together with the test results during the commissioning of SwissFEL.

关键词： SwissFEL LLRF optimization Beam-based calibration

Effect of Thermal Cycles on the Thermal Expansion Behavior of T700 Carbon Fiber Bundles

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Chemical Research in Chinese Universities 2018年第3期34卷 451-456页

作者： geng Guohang MA Xiaofei geng Hongbin WU Yiyong School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 P. R. China CAST-Xi 'an Institute of Space Radio Technology Xi 'an 710100 P. R. China

The relationships between the coefficient of thermal expansion（CTE） of T700 carbon fiber bundles（CFBs） and the thermal cycles were investigated. The microstructure of T700 CFBs was analyzed with Raman spectra and XRD before and after the thermomechanical test. The results indicated that the T700 CFBs exhibited negative expansion in the direction of parallel fibers in the temperature range of-150-150 ℃ The thermal strain that occurred during the heating and the cooling thermal cycle had an unclosed curve that served as the loop. When the experimental load was the same, the position of strain loop tended to move upward, and the length of the specimen increased continuously with the thermal cycles increasing. The microstructural analysis suggested that the degree of structural order and the degree of orientation along the fiber axis were improved with the increase of thermal cycles. The change of microstructure parameters could be the primary cause of the negative CTE＇s variation within the T700 CFBs.

关键词： T700 carbon fiber bundle Thermal cycle Coefficient of thermal expansion Microstructural analysis