Achievable roll stability of heavy road vehicles

A general purpose numerical model, suitable for simulating the yaw—roll behaviour of torsionally flexible heavy goods vehicles with an arbitrary arrangement of vehicle units, is presented. A controllability analysis is then performed to examine the fundamental limitations in achievable roll stability of heavy vehicles with active roll control systems. It is established that it is not possible to control simultaneously and independently all axle load transfers and body roll angles. The best achievable control objective for maximizing roll stability is shown to be setting the normalized load transfers at all critical axles to be equal, while taking the largest inward suspension roll angle to the maximum allowable angle. The results of a simulation of a tractor—semitrailer vehicle with a full—state feedback active roll control system are presented. It is shown that the roll stability of the vehicle can be increased by 30-40 per cent for steady state and transient manoeuvres and that the handling performance improves significantly.