The Impact of the Dynamic Tractor-Semitrailer Interaction on the Ride Behaviour of Fully-Laden and Unladen Trucks

In this paper, the effect of the dynamic interaction between tractor and semitrailer on the ride behaviour of heavy good vehicles is investigated. A multi-body model is constructed for a 4-axle tractor-semitrailer vehicle with flexible frames and excited by random road irregularities. The modal parameters of the connected frames are calculated using the FEM (Finite Element Method), as an integrated free vibrating structure, and incorporated with the equations of motion of the whole vehicle which are generated using the Lagrange energy approach.

Frequency response analysis is carried out for random road excitations to evaluate the vehicle ride dynamics. In order to give a broad overview of the vehicle ride quality, different loading conditions are considered in the computer simulation. The results showed that the acceleration levels of vehicle components are significantly increased when the effect of an empty semitrailer is considered within the vehicle model. This effect is suppressed by reducing the stiffness and damping coefficients of the suspension systems of the tractor and semitrailer. Practically, a change in the suspension stiffness can be achieved using conventional multi-stage leaf springs or adjustable air suspension systems in such a way so as to keep the static suspension deflections similar to those of the laden condition. At the same time, switchable dampers can be used to alter the damping coefficients. The results (root mean square values and power spectral density functions) showed that excellent improvements in ride behaviour of unladen vehicle can be achieved by using specific suspension parameters.