A Ride Comfort Design Sensitivity Analysis of a City Bus

A design sensitivity analysis, using concepts from design and analysis of experiments, of a city bus with respect to ride comfort is presented in this study. The response of the city bus, due to different types of road excitations, is calculated using a FE model of the complete bus. A global discomfort measure for the current bus design is thereafter calculated by evaluating the discomfort at three locations within the bus using the comfort standard ISO 2631:1997. Four different road excitation load cases are considered. In the first case prescribed vertical displacements, simulating a test-track road, are applied under all tires. In the second case vertical displacements, simulating the rear axle of the bus traversing a rectangular obstacle of full road-width, are equally prescribed under the left and right rear tires. In the third and fourth cases, the same obstacle shape is considered but now applied in turn to the rear tires. In total 26 design variables, such as dimensions and positions, in the wheel suspension, body structure and power unit insulation are defined. Design effects are calculated, using fractional factorial design, for each load case and compared in order to find the design variables, or combinations of variables, that most effectively affect the ride comfort characteristics of the bus.