Applied Mechanics and Materials Vols. 97-98

Abstract: Large eddy simulation (LES) was made to solve the flow around two simplified CRH2 high speed trains passing by each other at the same speed base on the finite volume method and dynamic layering mesh method and three dimensional incompressible Navier-Stokes equations. Wind tunnel experimental method of resting train with relative flowing air and dynamic mesh method of moving train were compared. The results of numerical simulation show that the flow field structure around train is completely different between wind tunnel experiment and factual running. Two opposite moving couple of point source and point sink constitute the whole flow field structure during the high speed trains passing by each other. All of streamlines originate from point source (nose) and finish with the closer point sink (tail). The flow field structure around train is similar with different vehicle speed.

Abstract: The misfire of one or more diesel cylinder and the abnormal clearance in the intake valve train of cylinder are common faults which affect the safety and the performance of the engine seriously. A new fault diagnosis method based on EEMD and instantaneous energy density spectrum is proposed here. The IMFs generated by EEMD can alleviate the problem of mode mixing and approach the reality IMFs. The instantaneous energy density of these IMFs can distinguish the faulty impacts clearly. The effectiveness of this method was demonstrated by analysis the vibration signals of misfire fault and abnormal clearance in the intake valve train of 3110 diesel.

Abstract: Taking example of a four-cylinder inline diesel engine that used in vehicle, this paper makes an assembly engine of three-dimensional that based on virtual prototype technology. While using the flexible-body dynamics simulation, the main bearing load that effect engine’s vibration will be gained. And the key point vibration response will be gained when the support part constrained. The experimental results coincide with the simulation results shows the correction of the simulation analysis. The initial stage of the vibration can be predicted by using the method of multi-body system analysis, and this guide the designer to identify the engine vibration.

Abstract: The air flow around the high-speed train passing through a tunnel is three dimensional, compressible and unsteady in nature. This paper carried out the numerical simulation of it and evaluated the effect of nose shapes of high-speed trains on tunnel entry/exit waves radiated directly from tunnel entrance or exit. The elliptical, parabolic and conical nose shapes were analyzed. A commercial CFD code STAR-CD based on the finite volume method was used applying the SIMPLE algorithm and a moving grid technology. The comparison study shows that though the patterns of tunnel entry waves or exit waves induced by high-speed trains with above three nose shapes are similar, the amplitudes of them are different. The wave amplitude of elliptical shape is the highest, and that of conical shape is the lowest, which implies that with the nose shape be more streamlined and slender, it might be more likely to reduce the amplitudes of tunnel entry/exit waves.

Abstract: Actuator is the key to vehicle active suspension. Based on the analyses of traditional passive suspension and active suspension system, a novel vehicle active suspension with Electro-Hydrostatic Actuator (EHA) is put forward. The system consists of two parts: spring and actuator with variable control force. The actuator is made up of hydraulic cylinder, hydraulic pump, controller and BLDCM. According to bond graph principles, bond graph model of 2 DOF passive suspensions and bond graph model of EHA active suspension are built. Moreover, fuzzy logic controller is designed and fuzzy control active suspension is simulated using MATLAB tools. The prototype and test rig of EHA active suspension are developed and bench tests are carried out. The simulation and experimental results show that fuzzy control active suspension with EHA provides better ride comfort, handling and stability than passive suspension.

Abstract: The dynamic tension of synchronous belt and pulleys forces are obtained by analyzing the dynamic characteristics of timing drive system of a diesel based on muti-body dynamics. The effects of crankshaft speed fluctuation and other excitations on the dynamics characteristics of synchronous belt are illustrated. After the analysis, it is found that crankshaft speed fluctuation has a great influence on the linear and transversal vibrations of synchronous belt. Comparing the simulation results of the original timing system and the one optimized, it is found that the modal frequency of synchronous belt depends on its span. Therefore it is important to control the span of belt and arrange the tensioner pulley properly for timing system design.

Abstract: Hydro-Mechanical Transmission System has six basic schemes when the planetary train for power conflux connects to other mechanism with different ways. The paper divides the six basic schemes into two kinds of positive phase and negative phase according to the relationship of output speed and motor speed. If the positive phase planetary train and negative phase planetary train are combined to used as power conflux mechanism, Multi-Range Hydro-Mechanical Transmission System can be realized that has a wide range of infinitely spItalic texteed variable. The paper analyzes the kinematics characteristic and the reasonable value of parameters of planetary train of the eight combined schemes, when the output speed of all ranges follows arithmetic or geometric law. According to the results, the best combined scheme of planetary train for vehicle transmission is determined at last.

Abstract: In order to resolve matching optimization between EPS and mechanical steering system of vehicle, the difference and rate between operating torque and ideal torque of steering wheel is set as the control target. Fuzzy controller would be adopted to change parameter of PD controller. Through these, real-time assistant voltage is dynamically adjusted and ideal assistant torque is gained; further operating torque of steering wheel, vehicle yaw rate and slip angle as performance indicators, selecting retarding mechanism parameter and PD controller as optimal objects, utilizing genetic algorithm, electric power assistant system (EPS) would be dynamically multi objects optimized; finally utilizing EPS testing system controller is online simulated and verified, test proves that fuzzy PD controller via multi objects optimization could effectively increase vehicles steering portability and stability.

Abstract: Based on two freedom degrees of vehicle model, control method which takes yaw rate and sideslip angle as system state, and front wheel corner and direct yaw moment as control input is put forward. Considering uncertainty of velocity and direct yaw moment, feedforward-feedback controllers are designed. Four wheel drive force are allocated by using feedforward compensation and yaw moment which is formed by driving force difference value. It makes yaw rate and sideslip well of tracking the desirable model when the vehicle drive steering. Finally, vehicle handling stability is studied on conditions of step input and sine input by simulation.

Abstract: A new fault diagnosis method for rolling bearing based on ensemble empirical mode decomposition (EEMD) and instantaneous energy density spectrum is proposed here. The intrinsic mode functions (IMFs) generated by EEMD can alleviate the problem of mode mixing and approach the reality IMFs. The characteristic frequencies were found in the instantaneous energy density of Hilbert spectrum. The effectiveness of this method was demonstrated by analysis the vibration signals of a rolling bearing with inner-race fault.