SELF-STEERING BEHAVIOUR OF HIGH-SPEED TRACTOR-SEMITRAILER AND ITS CONTROL

The loss of the stability of heavy highway tractor-semitrailer combinations is the usual cause of several serious traffic accidents. One of the reasons is the different behaviour of the vehicle under changed conditions (e.g. different loading conditions, abrupt side wind gust acting on the vehicle, etc.) which is not expected by the driver or it differs from the usual one. The authors of the paper study the behaviour of the articulated vehicle from the point of view of the steerability and define the conditions of self-steering characteristics of articulated vehicles. In the paper, linear model of the articulated vehicle is used, but the simulations are carried out for more realistic non-linear two-track model including real tyre model. On the basis of the results of the above written examination, the authors deal with the improvement of the lateral stability of the tractor-semi trailer combination using controlled elements in the vehicle chassis, namely the steering of the rear axle of the tractor is examined, however, the practical realization is complicated. Possible solution is proposed instead of the steering of the rear wheels of the tractor based on control of their side slip angles. Results are shown on controlled steering of the wheels on the axle(s) of the trailer. In both mentioned cases, new method of the robust control design is used called Robust LQR (RLQR). Design of the anti-jackknifing device is demonstrated, which means the semi-active control of the switchable damper in the joint.