| Tractor-semitrailer has become the main vehicle model of transportation because of large load capacity and low transportation costs. The tenth five-year plan of the automotive industry pointed out that the proportion of heavy vehicles and special vehicles (including tractor-semitrailer) in the structure of truck product is increased. Tractor-semitrailer has low roll stability when turning because of the special nature of high center of gravity and tread too narrow in relation to body height. That the sudden turning and changing lanes operation will make rapidly increase of lateral load transfer of tractor-semitrailer leads to rollover.It is a hot issue that how to prevent rollover of tractor-semitrailer and further improve the stability of tractor-semitrailer. At present, anti-rollover research of tractor-semitrailer mainly involves two aspects: (1)optimizing the structural parameters and the use parameters to improve the anti-rollover capacity of tractor-semitrailer;(2)researching the advanced control devices to control rollover of tractor-semitrailer. The first method for enhancing the anti-rollover capacity of tractor-semitrailer is limited. So the second method will be the main directions of development of anti-rollover control of tractor-semitrailer. Abroad, the anti-rollover technology of tractor-semitrailer through impose braking has very sophisticated and sophisticated products have appeared, such as Roll Stability Control System,Roll Stability Support System and Electronic Stability Control System,but the research of the area in China is still in its early stages, so carrying out research in the area has important practical significance and broad application prospects.The paper researchs mainly about anti-rollover control of tractor-semitrailer, three-axle tractor-semitrailer as the research target, the lateral acceleration of semi-trailer as the control variable, through impose braking on the outside wheels of tractor to prevent rollover of tractor-semitrailer. The paper is completed on the following aspects:(1) Tractor-semitrailer is composed of tractor and semi-trailer through the connections of the fifth wheel,tractor and semi-trailer will be interaction when tractor-semitrailer is traveling. Therefore, the movement characteristics of tractor-semitrailer compared with ordinary commercial vehicles will be some differences. The paper applies dynamic simulation software-Arcsim to analyse the movement characteristics of tractor-semitrailer when the steering wheel angle input is sinusoidal and find out the movement characteristics of tractor-semitrailer that is different from ordinary commercial vehicles. At the same time the paper applies dynamic simulation software-Arcsim to analyze the influence that the structural parameters and the use parameters impacted on the tractor-semitrailer roll stability, reveals the intrinsic relationship between roll stability of tractor-semitrailer and these parameters,provides the reference for designning anti-rollover control system.(2) The paper proposes a set of anti-rollover control algorithm of tractor-semitrailer that prevents rollover of tractor-semitrailer through imposing braking on the outside wheels of tractor, and the lateral acceleration of semi-trailer is be as the controlled variable. The algorithm includes four parts ,such as identification of turning and turning type,anti-rollover control threshold settings,anti-rollover control identification to determine the beginning and the end,anti-rollover control strategy. The maneuver induced rollover is usually accompanied by the curve movement, so identification of turning and turning type is necessary. The identification is identified through lateral acceleration,vehicle speed and angular velocity of the steering wheel. Turning types can generally be classified into two types of one-way turning and no one-way turning, the control threshold of the beginning and end should also be different according to turning type. The control algorithm can be made more precisely because of identification of turning type. When the lateral acceleration of semi-trailer is beyond the control threshold of the beginning, the braking pressure of tractor is changed through the pressurized,keeping pressure and decompression to control rollover of tractor-semitrailer.(3) In this paper, the tractor-semitrailer researched is three-axles, tractor has two axles, the front axle is the steering shaft which includes two tires, the rear axle is driving shaft which includes four tires. Semi-trailer is one-axle, the only axle of semi-trailer includes four tires. Engine is in the front of tractor and the rear axle of tractor is driving shaft, all axles adopt non-independent suspension. The model of tractor-semitrailer will be divided into the sprung mass of tractor,the unsprung mass of tractor,the sprung mass of semi-trailer,the unsprung mass of semi-trailer and wheels in accordance with these characteristics of tractor-semitrailer.Setting up simulation model of tractor-semitrailer is essential in order to validate the algorithm of anti-rollover when the algorithm of anti-rollover has been set up.The paper has set up 21-DOF nonlinear vehicle model of tractor-semitrailer in Matlab/Simulink environment, these models include brake model,suspension model,tire model,driver model,the fifth wheel bound model and dynamic model of vehicle. These models can effectively verify the algorithm of anti-rollover.(4)The paper structures the controller model in Matlab/Simulink environment, simulates verification in the open-loop conditions of steering wheel angle step input and steering wheel angle hook input and in the closed-loop conditions of double-lane change, and evaluates the effect of anti-rollover control. The simulation results show that the algorithms of anti-rollover can a certain extent be up to prevent rollover of tractor-semitrailer effectively.
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