Effect of chassis frame compliance on heavy truck ride quality

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Effect of chassis frame compliance on heavy truck ride quality

Ledesma, R.H.

This paper presents the prediction of ride quality for a heavy truck through the use of time-domain (transient and steady-state) analysis within a multibody dynamics formulation. Two models of the heavy truck are developed. In the first model, the chassis is assumed to be infinitely rigid so that the multibody system consists only of rigid bodies that are interconnected through mechanical constraints or user-defined force elements. In the second model, the compliance of the chassis frame is considered in the formulation. This is done through the assumed modes method wherein the selected modes of chassis frame deformation are coupled with the nonlinear equations of motion associated with the large rigid body displacements of the sprung and unsprung masses. The two vehicle models are validated by simulating a heavy truck traveling along a highway with vertical force inputs. Ride quality is then quantified through the root mean square (RMS) vertical acceleration of a specified critical location in the heavy truck. Comparison of the simulation results with test results indicate that chassis frame compliance plays an important role in predicting ride quality, especially when the natural frequency of the chassis frame is within the frequency range of the suspension modes. Design sensitivity studies are then conducted in order to determine which suspension design parameter has the most significant effect on the ride quality of the subject vehicle.