| Recently, HST(Heavy S emi-Trailer) is becoming one of t he m ost i mportant transport tools due to its large capacity, high effici ency and l ow cost. However, HST al so m akes the i ncreasing ratio of its acci dents among seri ous traffic accidents. This paper aims to i mprove HST’s path foll owi ng performance and latera l stabilit y and mainly focus on active trailer steering system, meaning to im prove road safety through steering the trailer actively.Firstly, the curre nt trailer steering sys tems are analyze d. And then focus on active trailer steering sys tem. The s tructure, principle and characteristics of which are then researched. Trucks im is used to build up the nonlinear vehicle model of HST of CHNTC ZZ4257V33247NIB/ V2 PC tractor and TAZ94000 TJZ semi-trail er, as the studi ed object in next chapters.Secondl y, considering t he complex working conditions for HS T, in order to make the optimal control under al l conditions, and develop t he full potential of active trailer steering sys tem, this paper propose a path fol lowing control(PFC) strategy and a roll stabili ty control(RSC) strategy. P FC’s principle is trailer rear end following the 5th wheel. Due to the difference of calcula tion of the 5th wheel’s si de-slip angle, PFC is divided into low speed and high speed P FC. And then com bined into t he combined cont rol strategy wi th feedforward and feedback control. RSC is used for high speed working condit ions and mean to im prove the roll stability of HS T. With the trailer ’s lateral acceleration as the controlled object, R SC i s designe d us ing LQ R optimal cont rol technique.At last, based on co-simulation of Trucksim-Simulink, simulation research of PFC and RSC is conducted. Because of low speed and bi g steering angle of low speed cornering condit ion, HST is difficult to control. Low speed PFC achieve s good path follow and t ire wear. From low s peed t o high speed, loaded or unloaded, st eady- state or t ransient state, active trail er s teering system is able to achieve the optim al control of path follow under all kinds of worki ng conditions. What’s more, res earc h showsthat the transient roll st abil ity of it is also better than other trailer steering m anners.Simulation compari son under SAE J2179 condi tion make it clear t hat PFC has better perform ance of off-tracking, CoG s ideslip angle and yaw; while R S C has bet ter perform ance of roll angle, lateral acce lera tion and rearwar d ampl ification. Because of this, this paper proposes that using PFC under st eady-state condition to control path follow and using RSC under dangerous condition to control rollover, which can achieve the goal to make full use of di fferent control strategies. At last, active trailer steering system is able to control HS T from rollover, and signifi cantly improve its road safety abilit y. |
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