A study on the braking stability of articulated heavy vehicles

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A study on the braking stability of articulated heavy vehicles

Kaneko, T. / Kageyama, I.

The tractor-trailer combination provides high cost performance in the field of surface logistics and is one of the most important freight transportation systems in Japan. These vehicle systems have many problems including stability at high speeds and when braking. Many serious accidents continue to occur that result from the behaviour of articulated vehicles, chiefly involving jackknifing, which is unique to articulated vehicles. The paper describes the stability of a tractor-semitrailer combination while braking focusing on the coupling device (coupler, 5th wheel). Nowadays, the coupling devices adopted in Japan can be divided by degree of freedom into the 1-axis type and the 2-axis-type. In the paper, jackknifing on a long downslope such as on a highway during braking, is recreated by simulation. The authors report in the light of detailed vehicle dynamics, the influence of the coupling device on limit conditions and the mechanisms that cause jackknifing. The vehicle used in the simulation was a four-axle tractor semi-trailer, consisting of a tractor unit with a single drive axle, coupled by a fifth wheel coupling to a twin-axle trailer unit. Simulation study was carried out under several different road gradients and radius of curve conditions. The following conclusions were obtained from the study by numerical simulation: 1. Jackknifing, which occurs through different processes with different type of coupling devices, was recreated and its mechanism was clarified. 2. Since the roll motion of the tractor is not restrained by the trailer in the 2-axis-type coupling device, the behaviour of tractor was more influenced by transfer load than in the 1-axis croupling device.