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Ding J.B.,NanTong Shipping College | Li H.,Shanghai Zhenhua Heavy Industries Co. | Cao J.D.,NanTong Shipping College
Applied Mechanics and Materials | Year: 2014

A parametric model of a kind of low-voltage circuit breaker was set up by virtual prototyping technology software ADAMS, and the simulation of the low-voltage circuit breaker system's dynamic characteristics was successfully run to confirm the parametric model. Because it was easy for contact heads to produce arc during closing, the power spring system was designed and researched in order to obtain the parametric sensitivities. Based on the difference of parametric sensitivities, the rotational angular velocity of the moving contact heads was regarded as the objective function, and the optimization design of circuit breaker power system was completed. Optimized system ensured reliable contact and shortened the arc time of the static and dynamic contact heads during closing, avoiding phenomenon as rebound repeatedly beating of the contact heads, continued arcing and temperature sharp rising, etc. The analysis had guide significance for improving the safe reliability and operating life of the low-voltage circuit breaker, and provided a good platform for the further produce development and optimization design. © (2014) Trans Tech Publications, Switzerland. Source

Guo J.,Shanghai JiaoTong University | Zou Z.-J.,Shanghai JiaoTong University | Wang X.-F.,Shanghai Zhenhua Heavy Industries Co.
Chuan Bo Li Xue/Journal of Ship Mechanics | Year: 2013

Offshore platforms and many offshore operating ships are equipped with Dynamic Positioning systems in ocean engineering. It is of great importance to investigate the performance of ship DP system and its control issues. In this paper, two different filtering and state estimation techniques of Kalman filter and nonlinear passive observer are introduced to separate the Low Frequency (LF) motion from the ship motion measurements contaminated by the first-order wave-induced High Frequency (HF) motion. These two methods are applied to two DP control systems based on the linear and nonlinear models of ship kinematics and dynamics, respectively. PID control algorithm is used in both models for its simplicity and efficiency in application. Finally, to test the designed controllers and filtering methods and to validate the advantage of the nonlinear passive observer control model, simulation on a model of supply vessel for DP and tracking control is conducted and the performances of both control systems are analyzed and compared. Source

Fang Y.,Shanghai Zhenhua Heavy Industries Co. | Fang Y.,Shanghai JiaoTong University | Lu X.,East China University of Science and Technology
Information Processing Letters | Year: 2016

The online parallel-batch scheduling problem on single unbounded machine to minimize total weighted job completion time is studied. For the general case of processing time, we give an online algorithm with competitive ratio 5+1. When all jobs have identical processing times, we provide an optimal online algorithm. © 2016 Elsevier B.V. Source

Lan H.,Harbin University of Science and Technology | Zhang H.,Shanghai Zhenhua Heavy Industries Co. | Chen S.,Shanghai JiaoTong University | Sheng K.,Shanghai Zhenhua Heavy Industries Co. | Zhao D.,Shanghai Zhenhua Heavy Industries Co.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2014

The control of arc-sidewall distance is the key to ensure good sidewall fusion in the process of narrow gap metal active gas welding (NG-MAG) welding. Through pretreatment and analysis of arc sound in NG-MAG pulse vertical welding, it is found that there exists periodic “ringing” attenuation phenomenon in the time-domain waveform, and its frequency is equal to the pulse frequency of welding power. The frequency distribution of arc sound energy varies from 0.3 kHz to 12.0 kHz. And energy mainly concentrates in two bands, range of 0.3-3.0 kHz and 9.0-12.0 kHz. Spectrum distribution of arc sound is highly relevant to arc-sidewall distance. On this basis, noise reduction and time-frequency analysis of arc sound are achieved by use of wavelet transform (WT) and joint time-frequency analysis (JTFA). The results show that low-frequency energy distribution of arc sound is always present, show “intermittent-continuous-intermittent”, with gradually increasing of arc-sidewall distance. While high-frequency energy distribution of arc sound only present arc-sidewall distance more than 2.6 mm, show “intermittent-continuous”. The monitoring and early warning of arc-sidewall distance can be realized based on time-frequency distribution of arc sound in NG-MAG pulse vertical welding, which provides a new way for condition monitoring in the process of NG-MAG welding. © 2014 Journal of Mechanical Engineering. Source

Lan H.,Harbin University of Science and Technology | Zhang H.,Shanghai Zhenhua Heavy Industries Co. | Chen A.,Shanghai Zhenhua Heavy Industries Co. | Chen S.,Shanghai JiaoTong University
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2015

In the process of vertical narrow gap MAG (NG-MAG) welding, arc-swinging and time-independent fusion technology is the key to ensure good sidewall fusion. Through analyzing the change rule about velocity and direction of arc-swing, the dynamic heat source model of NG-MAG vertical welding was established by using the method of coordinate transformation based on the classical double ellipsoid heat source model. Temperature field simulation results show that the welding thermal curves are "multi-peak", weld surface shape is "building blocks" and cross section is "dumbbell", which are in consistent with the test result of NG-MAG welding. The "multi-peak" phenomenon is mainly caused by the arc heat source moves near and then away from the side wall, whiles the formation of "building blocks" and "dumbbell" are highly correlated to the periodic change of arc speed (heat input) and weld pool during arc-swing. The above-mentioned characteristics provide the technical support for further research on microstructure evolution of high strength low alloy (HSLA) steel in NG-MAG vertical welding process. ©, 2015, Harbin Research Institute of Welding. All right reserved. Source

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