A Study for Shimmy Reduction using Theoretical Multi-body Model and Experimental Techniques

In this study, both theoretical linear model and numerical model are used to predict and optimize the frequencies of shimmy related modes and the level of the vibration for a vehicle. A theoretical multi-body linear model of 32-DOF were used for quasi-static analysis and modal analysis. The theoretical model was verified by comparing the results of modal analysis with those of modal test for front suspension system using CADA-X program. The quasi-static analysis results of the theoretical model were compared with those of ADAMS model. Also, full vehicle model using ADAMS was verified with the results of the modal test and chassis dynamometer tests for shimmy reproduction. From tests and simulations, we found wheel longitudinal vibration mode to be the most dominant source of shimmy vibration. Also, based on the test results, we selected 13 design parameters of the front suspension system, including compliance and geometric factors for reducing shimmy level. We performed 27 orthogonal simulations using Taguchi methodology and constructed an optimal combination of design parameters. Through modal analysis of theoretical model with optimized design parameters, we found that the wheel longitudinal vibration mode changed into two local vibration modes. Lastly, a simulation of the numerical model verified that the suggested design parameters resulted in reducing shimmy vibration.