Active Roll Control Of Tractor Semi-trailer

Tractor semi-trailer has high-efficient and economic characteristics, which is the most ideal style of "section transportation", "swing-hang transportation", and "rolling transportation ", which is the widest transport vehicle used in the domestic market at present. The economy of the tractor semi-trailer is favored by people, but the design of its many axles is less than satisfactory. There are roll danger and handling instability. The roll over of heavy vehicles is an important highway safety problem of world-wide.The main purpose of this paper is to design an active roll control systems consisting of active anti-roll bars to regulate vehicle lateral load transfer and roll motion, in order to improve the roll stability of single unit vehicle and tractor semi-trailer; The typical handling conditions are simulated and the simulation results verified that the adopting of active anti-roll control systems significantly increase roll stability.This paper research work and conclusion are as follows:First, Anti-roll bars, also known as lateral stabilizer bars.Vehicle body roll it happens during almost every turn only occurs when one side of the suspension is compressed while the other extends. Therefore, we can limit body roll by making it harder for the driver-side and passenger-side suspensions to move in opposite directions. Anti-roll bars both ends are connected to the suspension directly, its torsion stiffness determines its ability to reduce body roll.Bars are connected to vehicle frame by a pair of hydraulic actuators. By extending one actuator and retracting the other, apply a roll moment to the sprung mass and tilt the vehicle body into corners.Second, tractor semi-trailer has many degrees of freedom; a preferable approach is build up simplified dynamic models, only including the important roll and yaw dynamics, used for simulation the handling and roll performance. At the modeling, start with by a single unit vehicle, build up five degree offreedom model, then build up the simulation model of eight degree of freedom of tractor semi-trailer, the models are written in the form of the state-space;The design techniques of the modern control system put emphasize on the use of state-space methods, the state-space model can totally express all states and performance of the system. And SIMULINK is the most advanced tool of control system calculates and simulation, so simulation goes on under the environment of SIMULINK;Third, comment on the mechanics of the roll-over process. As net restoring moment is not enough to balance destabilizing overturning moment, the vehicle will roll over. It might not imply a loss of roll stability of the entire vehicle that wheel lift off at a particular axle.Vehicle with passive suspension lean toward the outside of the turn when it is steering, lateral load transfer is destabilizing moment; And with active roll bar, can rolling the vehicle body into corners, reduce the lateral load transfer thus increasing roll stability;Fourth, controllability refers to the ability to use control torque generated by active anti-roll bars to regulate lateral load transfer and roll motions.The inputs of active control system are that the roll moment generated by each active anti-roll bar, the outputs are that roll angle of vehicle body and lateral load transfer of every axle. By controlled analyzing, the number of system inputs is little than of outputs, thereby, it is not possible to control all outputs at the same time independently by bars alone, that is to say, the achieved roll stability is limited;The control objective of maximizing roll stability is balancing the load transfers at all critical axles while taking the largest inward suspension roll angle to the maximum allowable angle;Fifth, active roll control is a problem of optimal disturbance rejection, which is an extension of the standard LQR problem. The optimal control of the control system goes on with LQR method, sets up a full-state feedback controller, and has simulation test only to typical maneuver on single unit vehicle and tractor semi-trailer;...