Advances in Mechanics Engineering

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Authors: Lei Fu, Min Xu, Xiao Min An, Xun Liang Yan
Abstract: A low-thrust guidance scheme, which is weighted combined by taking the optimum strategy of thrust allocation and the target deficits value into consideration for each orbital element, is developed. The presented guidance scheme is predictive in nature and does not rely on a stored reference trajectory or reference controls. The orbit transfer problem is converted into parametric optimization and utilizing a hybrid genetic algorithm. The minimum-time orbit transfer is considered. The influence of the Earth’s oblateness is taken into consideration in the simulation of minimum-time. A conclusion is drawn that the designed method presented here turns out to be an autonomous scheme because the information of target orbit is considered in the transfer process.
Authors: Zheng Ming Gao, Jun Bo Jia, Sheng Ping He, Bin Wang
Abstract: In order to analyze the structural characteristics or calculate the support force of large-scale complex systems with spherical joints, an approximated method was raised simplifying the force of inner bodies to contact pressure with a hypothesis that the contact zones is ideally spherical. The contact pressure distribution is obtained and normal force-displacement relationship is simulated with finite element methods (FEMs). Finally, the goodness of fit is calculated with statistical hypothetical test theory treating the FEM results as the sample data.
Authors: Pankaj N. Shrirao, Parvezalam I. Shaikh, Farazuddin Zafaruddin, A.N. Pawar
Abstract: Tests were performed on a single cylinder, four stroke, direct injection, diesel engine whose piston crown, cylinder head and valves were coated with a 0.5 mm thickness of 3Al2O3 .2SiO2 (mullite) (Al2O3= 60%, SiO2= 40%) over a 150 µm thickness of NiCrAlY bond coat. The working conditions for the conventional engine (without coating) and LHR (mullite coated) engine were kept exactly same to ensure a comparison between the two configurations of the engine. This paper is intended to emphasis on emission characteristics of diesel engine with and without mullite coating under identical conditions. Tests were carried out at same operational constraints i.e. air-fuel ratio and engine speed conditions for both conventional engine (without coating) and LHR (mullite coated) engines. The results showed that, there was as much as29.41% and 24.35% decreasing on CO and HC emissions respectively for LHR (mullite coated) engine compared to conventional engine (without coating) at full load. The average decrease in smoke density in the LHR engine compared with the conventional engine was 13.82 % for full engine load. However, there was as much as 20% increasing on NOx emission for LHR engine compared to conventional engine at full load. Also the results revealed that, there was as much as 22% increasing on exhaust gas temperature for LHR engine compared to conventional engine at full engine load.
Authors: Zong Sheng Wang, Jian Cheng Fang, Xiu Zhi Meng
Abstract: In order to suppress the impact of the friction torque and the magnetic levitation high-speed rotor system on the stability of gimbal servo system output angular rate, a self-adaption compensation method with no modeling for disturbance torque is presented. The interference suppressor calculates the disturbance compensation based on the torque motor current and the angular rate measured real-time by the current detection circuit and the frame angular detection circuit in the gimbal servo system, then feedbacks to the frame servo system controller to regulating the torque motor output current. 500Hz and 50Hz sinusoidal disturbance torque are introduced into the system to test the role of the interference suppressor. The result proves the interference suppressor has the same significant inhibition of effect for disturbance torque of different frequencies by MATLAB simulating framework output angular rate waveform.
Authors: Xing Wang, Dong Chen Qin, Jun Zhu
Abstract: The research of the dynamic performance is particularly important so as to improve the performance of electric vehicles. The method of computer modeling and simulation can be used to reduce the expense and shorten design cycle. The theory of dynamic performance standards of electric vehicle performance is introduced, and then, the main component of electric vehicle and the whole vehicle model are built up based on the advanced vehicle simulation software ADVISOR platform, which is developed by U.S. National Renewable Energy Laboratory. The curve results of the dynamic performance are obtained after the simulation of virtual electric vehicle, and it is consistent with the actual vehicle movement. At the same time, the simulation results can be served as essential reference for development and improvement of new vehicles.
Authors: Jian Ping Sun, Jian Xin Wang
Abstract: the columns of magnetostrictive transducer for the object, the establishment of a Radiant Panel in magnetostrictive rods through the spring of motion model, gives a method for solving first-order analysis and solutions, discusses the spring rate on radiation effect of amplitude. On reasonable determination of Radiant Panel structure, the size of the transducer, and optimization methods.
Authors: Tao Wang, Heng Zhou, Pan Zou
Abstract: A power network partitioning model based on the weighed local similarity measure is presented in this paper considering the regional decoupling characteristics of reactive power. A weighted graph model of reactive power network is established and a new measurement of local similarity based on weighed graph is defined. To utilize our measurement of similarity to partition reactive power network, a partitioning algorithm based on generalized ward hierarchical clustering method is proposed. The algorithm can ensure balance of the reactive power inside partition. Applying the proposed algorithm to IEEE 39-bus system, the results show that the proposed algorithm is feasible and effective.
Authors: Dong Jie Pei, Dong Chen Qin, Xing Wang, Jiu Shi Liu
Abstract: In order to improve the performance of the electric buses,composite power system is designed,which is analyzed and verified by the simulation using the software of Advisor. Advisor is secondary developed by updating assembly simulation models and vehicle models. The basic structure of composite energy storage system and the control strategy based on fuzzy theory are designed, and the simulation of vehicle performance is done under the road cycle of UDDS, and then compares with the bus with only batteries. The result shows that ultra-capacitor has a prominent "clipped peak and filled channel" protection for the battery, recovers energy commendably, and extends the battery’s life. The electric bus with composite power supply can meet the requirement of vehicle performance, and its indexes of all aspects are better than the electric bus with only batteries.
Authors: Wen Dan Xu, Ping Li Ma, Jian Guo Jiang, Yuan Tian
Abstract: Due to the high frequency, high density and high reliability requirements, as well as the difficulty of assembly, the lower qualified yield and the higher returning rate of the high density circuit module etc, a new testing method of high-density circuit module detection by electromagnetic scanning was present in order to realize comprehensive and efficient high-density PCB detection. Firstly, the standard board and tested board were scanned to get their electromagnetic information which was further used to compare and get their differences. Then the suspected faulty areas can be found according to the difference of the electromagnetic information. Finally, the suspected faulty components would be positioned referring to the high-density PCB design files. The simulation results show that the method based on electromagnetic information is feasible in high-density circuit module detection and has a higher detection rate.
Authors: Xiao Dan Wang, Li Xin Ma, Yue Xiao Wang, Shu Juan Yuan
Abstract: APF (Active Power Filter) is widely used in power system harmonic control and reactive power compensation, has been proven as an effective method to overcome various power quality issues such as unbalanced source current, large reactive power harmonic and neutral currents due to the proliferation of nonlinear loads. Optimizing the performance of APF using conventional ip-iq detection method based on instantaneous reactive power theory is quite difficult because of the complex coordinate conversion, what’s more, the presence of low-pass filter will cause a certain delay. This paper proposes the implementation of BP neural network to extract specific harmonic, it can optimize the APF performance for load compensation under distorted supply voltage condition and sudden load fluctuation. Weight adjustment using the BFGS quasi-Newton algorithm, which can accurately detect the fundamental and harmonic component of the phase amplitude . Matlab simulation results demonstrate that the performance of BP neural network algorithm is superior compared to conventional method, in terms of both convergence rate and solution quality.

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