Proceedings of COBEM 2005 18th International Congress of Mechanical Engineering Copyright ' 2005 by ABCM November 6-11, 2005, Ouro Preto, MG DYNAMICAL PERFORMANCE OF A BUS UNDER DIRECTIONAL MANEUVERNS Nilson Barbieri Pontifcia Universidade Catlica do ParanÆ  PUCPR  Rua Imaculada Conceiªo, 1155  CEP: 80215-901  Curitiba  PR nilson.barbieri@pucpr.br Renato Barbieri Pontifcia Universidade Catlica do ParanÆ  PUCPR  Rua Imaculada Conceiªo, 1155  CEP: 80215-901  Curitiba  PR nilson.barbieri@pucpr.br Claœdio Carreirªo Volvo do Brasil Veculos Ltda claudio.carreirao@volvo.com Abstract. The dynamical performance of a bus, under directional maneuver over a flat road is analyzed through a physical model with eight degrees of freedom. Non linearities coming from the brake and side forces developed on the tire contact patch are considered for the vehicle under directional maneuvers. The mathematical models are validated by comparisons between the experimental and simulated data. The experimental data are obtained through an accelerometer placed in the gravitational center at lateral direction and four displacement sensors placed in the vehicle suspensions. The parameters analyzed are lateral acceleration and roll angle. Keywords directional maneuver, bus, lateral acceleration, roll angle 1. Introduction The behavior of the vehicle under the directional point of view was analyzed by Nardello, BenincÆ and Vargas (2000). The focus is directed to the experimental investigation, considering the effect of the use of the stabilizers bars and suspension dampers in different buses. Allen et. al. (2002), created and validated experimentally, a computational model to preview the directional behavior of bus. Brach (1991), developed a simple and flexible computational model capable to generate simulations of articulated and non articulated vehicles. This work uses the BNP model for the simulation of the tire lateral and brake forces. Allen, Rosenthal and Szostak (1987), developed a complex model considering the parameters that influence the generation of lateral and longitudinal force by the tire. A complex tire model was presented with details. Shiller (1995) and Ramanata (1998) studied an intermediary area between control and directional dynamics. Both authors developed optimal vehicle path generator using directional control of the bicycle model for the vehicle with the Dugoff and Segel tire models. Smith and Starkey (1995) presented eight degrees of freedom vehicle model using the Dugoff’s tire model. In the area of directional control, Lee, Lee and Han (2001) and Lee and Han (2001), explored the effect of the control of the kinematics of the suspension, especially the roll center position. Kwak and Park (2002) and Kwak and Park (2001), starting from a computational nonlinear model with 15 degrees of freedom, showed the benefits of a control system using traditional traction and variables of directional control. Mangliardi and Mantriota (2001) analyzed possible conditions of instability that can be induced by the presence of oscillating cargo. Diaz et. all (2004) introduced a new method based on a theoretical model and dynamics test establishing the rollover limit that a vehicle can reach without rolling. The equations of the model represent the vehicle dynamical behaviour when the bus is being driven on a curve. The results of the tests allow to characterise the behaviour, for real conditions on a turn, of many parameters involved in the model. The dynamic tests on the road and the mathematical model predict a reliable rollover limit of a bus. The knowledge of this value will increase the safety of these vehicles. The main objective of this work is to analyze the lateral acceleration and the roll angle of a bus through eight degrees of freedom model. To analyze the dynamical performance of vehicle the forward speed was varied between 20 and 60 km/h. The experimental data was acquired through an accelerometer placed at the gravitational center in lateral direction and four displacement sensors placed in the suspensions in vertical direction. The simulated and experimental data are confronted to validate the mathematical model. Virtual design of new bus can be obtained through the computational simulations using the reliable mathematical model.