Abstract
Interest in vehicle safety with respect to rollover is at an all time high. This has been fuelled by recent government legislation and also the acceptance within the industry of the "fishhook" manoeuvre as a means to quantify the rollover propensity of a vehicle.
From a vehicle manufacturer´s perspective, it is now essential to consider the rollover characteristics of a vehicle at an early stage in the design process. When examined from first principles in a quasi-static analysis, the mechanism for vehicle rollover appears relatively simple. However when a test is observed, it is clear that as the vehicle approaches roll over, the behaviour becomes very erratic. The purpose of this study was therefore to increase knowledge of how certain attributes contribute to rollover propensity and then examine ways to minimise their effect.
In doing this, a multi-body vehicle model of an SUV was generated and simulations conducted to predict rollover performance. To lead and guide this process, an extensive test programme was undertaken on the real vehicle, starting at static and dynamic K&C testing, through to full vehicle handling tests and culminating in a series of rollover tests. The process was constructed in such a way as to provide the greatest level of understanding of how the vehicle behaved during rollover and in doing so, utilised state of the art techniques in both testing and simulation. Wheel force transducers in conjunction with wheel positioning systems allowed all forces and displacements to be measured simultaneously. Detailed models of the vehicle´s suspension, steering and body were developed to increase frequency content and predict cornering forces at high camber angles.
This paper summarises the process followed, the challenges faced and how the results were used to offer guidance on the next design of vehicle to improve rollover performance and ultimately improve vehicle safety.
Keywords - Rollover propensity, handling simulation, Kinematics and Compliance, wheel lift, tyre characteristics