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Since the kinematic characteristics of a vehicle suspension are very complex and difficult to understand, CAE techniques must be applied to perform the suspension analysis. In this study, the influences of rear suspension geometry on the handling performances of a large-sized bus are investigated. The bus involved in this study has air spring type rigid axle suspensions with four links. Quasi-static analyses are performed to evaluate the roll characteristics of the front and rear suspension. The quasi-static responses of suspensions are evaluated in terms of roll center height and roll steer. Roll center height is mainly dependent on the vertical displacement of a panhard rod, and the vertical displacements of lower control links affect chiefly the roll steer. The parameter study with the change of rear suspension geometry is conducted to investigate the vehicle handling performance.

The air distribution duct with multiple outlets is an essential part of the automotive air-conditioning system in a bus. The estimation of airflow rate in an automotive air-conditioning duct is typically very complicated due to large variations in cross-sectional area and abrupt changes in flow direction, as well as unbalanced distribution of the flow. This paper describes numerical simulations performed for two simplified air conditioning ducts used in a medium bus. The three dimensional Navier-Stokes code was used to evaluate the overall pressure, velocity field, and distribution rate at each diffuser according to the change of cross-sectional duct area and diffuser area. In addition, a one-dimensional program based on the Bernoulli equation was developed to obtain the optimum diffuser area required to equalize discharge flow rate at each outlet. The results of this analysis were compared to the results obtained from experimental measurement and CFD simulation.

This paper presents the CAE technique to estimate the dynamic stress in a vehicle structure at an early stage in the vehicle design process, using modal stress superposition. Dynamic joint reaction forces are obtained by flexible multibody dynamics simulation using DADS. Stress influence coefficients are computed through the inertia relief analysis using MSC/NASTRAN. A test vehicle was run over a zigzag bump course with a constant speed of 40km/hr, and the results of the numerical analysis were compared to those of the test.

At the initial design stage of a new vehicle, chassis layout has the most important influence on overall vehicle performance. Most chassis designers have achieved target performances by trial and error as well as by individual know-how. Accordingly, a general procedure for automatically determining the optimum location of suspension hard points with respect to the kinematic characteristics needs to be created. In this paper, a method to optimize the toe angle in the double wishbone-type front suspension of a four-wheel-drive vehicle is presented using design of experiments, multibody dynamic simulation, and an optimum design program. The handling performances of two full vehicle models having the initial and the optimized toe angle are compared using a simulation of a single lane change maneuver. Front and rear suspensions are modeled as rigid bodies connected by kinematic joints using DADS.

For the three-cylinder engine whose crankshaft has a phase of 120 degrees, the total sum of unbalanced inertia forces occurring in each cylinder will be counterbalanced among the three cylinders. However, parts of inertia forces generated at the No.1 and No.3 cylinders will cause a primary moment about the No.2 cylinder. In order to eliminate this out-of-balance moment, a single balance shaft has been attached to the cylinder block so that engine durability and ride comfort may be further improved. Accordingly, the forced vibration analysis of the three-cylinder engine must be implemented to meet the required targets at an early design stage. In this paper, a method to reduce noise and vibration in the 800cc, three-cylinder LPG engine is suggested using the multibody dynamics simulation. The static and dynamic balances of the three-cylinder engine are investigated analytically.