Research On Simulation And Control Of Differential-Braking-Based Stability Of Tractor Semi-trailer

Now the active safety and stability of tractor-trailer have become big concern among the Road Transportation Industry. The purpose of this investigation is to specify the research object, set up the accurate and reliable dynamic vehicle model for computer simulation, and design the control block to improve the active safety and stability of tractor trailer.In developed country, such as Germany, USA, this kind of investigation has been carried on early in the 1960s. In China, however, it is still in the beginning stage. By tracing the international trend, the researcher focuses on this field, and make some accomplishment as following:In chapter 2, by reviewing the previous research, we put the stability of tractor trailer into two categories, roll stability and yaw stability, and identify the indicators of two kinds of stability. Further we came up with three normal stability loss situations. They are roll-over, jack-knife and trailer swing. This work extends previous tractor trailer stability research from roll stability to roll/yaw stability, moreover, we set up the object of our investigation, that is'enhance the tracto-trailer stability by reducing the occurrence of three stability loss.Based on the tractor semi-trailer model built in MATLAB, we made research on how the vehicle parameters affect the entire vehicle dynamic stability. In this section, we modified the model by changing a more sophisticated tire model. This work will benefit the commercial vehicle designer in the early stage of vehicle designing. In chapter 3, we investigate the means on how to build the tractor semi-trailer dynamic model under the environment of ADAMS/Car. According to the parameter presented by Sampson, we built the vehicle dynamic model of tractor semi-trailer. This model includes two major parts, tractor and semi-trailer. Multiple axle and dual tire are taken into account.After the foundation of vehicle model, we do the extreme course simulation to testify the model. The simulation results proved that the ADAMS/Car model can simulate three stability loss situations of tractor semi-trailer. And two important conclusions areeduced:1. On the road of high adhesive coefficient, it is more relevant for us to pay attention to the roll stability, because the vehicle has roll over before it lose the yaw stability. In this case, we can brake the whole vehicle to lower down the vehicle speed. This is proven as the effective way to prevent the occurrence of roll-over.2. On the road of low adhesive coefficient, the yaw stability is the key issue. We can improve the vehicle dynamic stability by correct the over-steer and under-steer of the tractor. Braking the whole vehicle doesn't make any sense, we are supposed to apply'brake the individual wheel'in order to pull the vehicle back to desired path.These two conclusions are regarded as the basic principle when we solve the tractor trailer stability issue.In chapter 4, we introduce the active control system to enhance the stability of tractor semi-trailer. Firstly, We illustrate the principle and the operation process of ADAMS/MATLAB co-simulation. Then, we use this way to do the control job. We chose the low adhesive coefficient, ISO double lane change as the test path. By applying the'brake individual wheel'we want to improve the vehicle dynamic performance during the extreme course. In the section, we analyze the principle of'brake individual wheel', and identify the desired vehicle yaw rate which is calculated by 2 DOF vehicle model as the tracing object. By controlling the vehicle actual yaw rate following the desired yaw rate, we can put the vehicle under the controllable stability situation. Here PID controller is applied to accomplish this target.We got the conclusion that'brake individual wheel'can actually improve the vehicle roll/ yaw stability during the dangerous situation, and release the driving tension of driver. The asset of this report is that it extends the tractor-trailer stability investigation from roll stability to roll and yaw stability. And set up the ADAMS model. Innovatively, we implement the'brake individual wheel'to enhance the full stability.