Research On Control Of Reversing For Tractor-semitrailer Combination

Tractor and semitrailer combination is composed of a tractor and a semitrailer, which has many advantages such as large capacity, high efficiency and low cost of transportation. This is the reason why it becomes the main parts of road transport vehicles. When the tractor-semitrailer is driving forward, the dynamic state is open-loop stable. As the factors that nonlinear, instability and uncertainty, when the tractor-semitrailer is reversing, the dynamic state is open-loop unstable, so it is easy to jackknife and collision. In addition, the body of the tractor-semitrailer is longer than other vehicles and the installation limit of rear-view and side-view mirrors on the vehicle caused poor visibility, these reasons lead to the reverse process is totally dependent on driving experience and driving skills. In order to reduce the driving difficulty and enhance the driver working efficiency, it is necessary to research the backing-up control of tractor-semitrailer, as well as provides a powerful technical support for the research of the driving assistance system of tractor-semitrailer.In view to research the problem of jackknife and collision in the process of backward, based on the nonlinear kinematic relationship, the aim of this paper is to design differential flatness controller and angle feedback controller respectively and put forward the control strategy accordingly, so that the problem of jackknife and collision in the process of backward can be solved.Specific contents are as following:According to nonlinear kinematic relationship, tractor and semi-trailer kinematics models were set up respectively, and found out a flat output of tractor and semi-trailer system to solve the flat prime problem, so that the tractor and semi-trailer system was proved to be a differential flat system. Based on differential flat theory, differential flat controller was derived and plan desire backer-upper trajectory.Through building the tractor and semi-trailer kinematics models, nonlinear kinematic model was linearized approximately. To prove the unstable reversing state of tractor and semi-trailer, it is necessary to analyze the system stability. In order to design angle tracking feedback controller, including heading angle and centroid orientation angle, it is necessary to transferring the approximate linear kinematics model into Laplace Transform.Applying simulation test, the suitable gain of flat differential controller and angle tracking feedback controller were found respectively. To verify tracking and feedback condition of desire backward trajectory and angle, two simulation tests were proceeding. One simulation was tractor and semi-trailer reversing along the expected trajectory that had been planned based on flat differential controller. The other one simulation was tractor and semi-trailer reversing along straight line based on angle tracking feedback controller, including heading angle and centroid orientation angle. Through simulation test, the tracking condition of backing up trajectory and angle feedback of each controller was verified.