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Machinery General

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Numerical modeling of journal bearing considering both elastohydrodynamic lubrication and multi-flexible-body dynamic

Numerical modeling of journal bearing considering both elastohydrodynamic lubrication and multi-flexible-body dynamic

J. Choi, S.S. Kim, S.S. Rhim, J.H. Choi, International Journal of Automotive Technology, February 2012, Volume 13, Issue 2, pp 255-261.

Abstract

This study uses an elastohydrodynamic lubrication model coupled with multi-flexible-body dynamics (MFBD) to analyze dynamic bearing lubrication characteristics, such as pressure distribution and oil film thickness. To solve the coupled fluid-structure interaction system, this study uses an MFBD solver and an elastohydrodynamics module. The elastohydrodynamics module passes its force and torque data to the MFBD solver, which can solve general dynamic systems that include rigid and flexible bodies, joints, forces, and contact elements. The MFBD solver analyzes the positions, velocities, and accelerations of the multi-flexible-body system while incorporating the pressure distribution results of the elastohydrodynamics module. The MFBD solver then passes the position and velocity information back to the elastohydrodynamics solver, which reanalyzes the force, torque, and pressure distribution. This iteration is continued throughout the analysis time period. Other functions, such as mesh grid control and oil hole and groove effects, are also implemented. Numerical examples for bearing lubrication systems are demonstrated.

How Multibody Dynamics Simulation Technology is Used

RecurDyn is coupled with an elastohydrodynamic module to analyze dynamic bearing lubrication characteristics, such as pressure distribution and oil film thickness. The elastohydrodynamic module transmits pressure, force, and torque data into RecurDyn. The FFlex module in RecurDyn allows for compliance effects to be analyzed while solving the dynamics of the system. These results agreed with experimental results and can now be used to improve the design.

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In Machinery, Machinery General, Research

Coupled simulation of gas flow and dynamic analysis for stroke calculation in circuit breaker

Coupled simulation of gas flow and dynamic analysis for stroke calculation in circuit breaker

Y.S. Lee, H.S. Ahn, S.W. Park, J.H. Lee, 1st International Conference on Electric Power Equipment – Switching Technology (ICEPE-ST), Xi’an, October 2011, pp 203-206.

Abstract

Electrical energy transmission and distribution devices are becoming more sophisticated and diversified in design, and also higher in its capacity due to rising in electricity usage. In direct response to demands of more reliable GIS (Gas Insulated Switchgear) from customers, computer simulations such as dynamics, structural, and fluid dynamics analysis are becoming more incorporated into the design process. Among the many types of simulations in GIS are low current interruption, SLF interruption, and BTF interruption. In the simulations, a stroke profile measured under loaded condition is required, and it leads to reduction in time and cost required towards the product development. In the paper, first, the actuator and interrupter of GIS is modeled using dynamics simulation program called RecurDyn. Second, SF6 gas pressure change in the interrupting chamber is made into a sub-routine using house code. Finally, with consideration of ODP (Oil Dash Pot) and friction forces of actuator, stroke profile under actual loaded condition is calculated.

How Multibody Dynamics Simulation Technology is Used

The actuator and interrupter of a gas insulated switchgear are modeled using RecurDyn. The results of this study are expected to be helpful to improve the efficiency and structural reliability of ultrahigh-voltage GIS circuit breakers early in development. This is expected to shorten the period of research and development and reduce test costs.

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Optimal Control of passive Locking Mechanism for Battery Exchange Using Pontryagin’s minium principle

Optimal Control of passive Locking Mechanism for Battery Exchange Using Pontryagin’s minium principle

Wonsuk Jung, Jongwon Park, Seungho Lee, Kyungsoo Kim, Soohyun Kim, 8th Asian Control Conference (ASCC), Kaohsiung, May 2011, pp 1227-1232.

Abstract

Mobile robot market and its importance are rapidly increasing. Mobile robots usually mount batteries to extend operating time and workspace. For that, robot has to charge the battery while stopping at a station or exchange the battery. Charging battery is too slow to restart robots. Therefore, battery exchanging method is encouraged. Until now, this method needs expensive sensors such as laser range finder and vision sensors to align and is very complex mechanism which including battery removal from robot, moving to the station, docking mechanism and exchange mechanism. Thus, we proposed a new complete passive battery docking and exchange mechanism. This mechanism uses no actuators at whole actions. And it simplifies the process that unifies the docking and exchange mechanism using key and housing system. This system reduces the docking and exchange operating time and compensates wide range of offset between battery and charge station. But this mechanism needs optimal control of robot moving, because this system is composed of springs and dampers which are passive modules that should be controlled accurately. This paper proposes optimal control of robot moving at passive docking mechanism in battery system for reducing docking time, rebounding force and stable docking using Pontryagin’s minimum principle. Also this paper verifies proposed optimal control using dynamic analysis program, Recurdyn and Matlab Simulink.

How Multibody Dynamics Simulation Technology is Used

An efficient method to dock and exchange batteries for a mobile robot was verified using RecurDyn. RecurDyn was able to evaluate the dynamics of the system with a specific control method without experimentally testing each case.

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