Research On Stability Analysis And Anti-rollover Control Of Tank Semi-trailer

As the advantages of large loading capacity,high transportation efficiency and low economic cost,they have gradually become the main force of liquid cargo transportation in China.At the same time,due to its heavy load,high center of mass and the easily sloshing of the liquid in the tank,it is very easy to roll over under some external-excitation.In addition,most of the liquid cargoes have flammable,explosive,highly toxic and other dangerous properties.The consequences of secondary accidents such as liquid cargo leakage,combustion,and explosion caused by tanker rollover are even more serious.Most of the existing researches on tank vehicles are for small tank vehicles.From the research of liquid sloshing,the establishment of a liquid model,etc.,to analyze the impact of liquid sloshing on the vehicle roll stability,and propose to suppress the liquid by optimizing the tank structure.The magnitude of the shaking reduces the probability of the vehicle rolling over.However,the roll instability mechanism of large tank semi-trailers and the active prevention and control technology of vehicles have not been studied in depth.Most of the studies focus on liquid sloshing,and less research on vehicle-fluid coupling dynamics.Therefore,it is necessary to carry out a systematic and in-depth study on the rollover instability mechanism and anti-rollover control of a tank semi-trailer to reduce the probability of a vehicle rollover accident.Therefore,the thesis relies on the national key research and development plan sub-project "Technology and System for Actively Preventing and Controlling Rollover of Dangerous Goods Transport Tankers"(No.2017YFC0804804),aiming at the particularity and complexity of the dangerous goods tanker body structure(higher center of mass),Liquid disturbances easily cause centroid shift,etc.),study the instability mechanism and active prevention and control strategies of rollover accidents,the subject uses vehicle dynamics modeling and Trucksim virtual platform simulation,by establishing an mechanical model and multi-degree-of-freedom vehicle dynamics model,deeply investigate the roll instability mechanism of the tank semi-trailer,and build a vehicle anti-rollover controller based on the LQR control method,which will provide reference for the research on the integrated control technology of anti-rollover stability of the tank semi-trailer.Based on the existing research results,this paper has carried out the following research work:(1)Through accident investigation and tank force analysis,a complete roll stability model of tank semi-trailer was established.In view of the complex characteristics of fluid mechanics modeling and the difficulty of coupling with mechanical models,this article draws on the modeling ideas of mechanical vibration systems to describe the liquid sloshing.By mathematically describing the mass center of liquid in the tank,the Lagrangian method was used to establish an equivalent mechanical pendulum model that simulates the liquid sloshing in the tank;the functional relationship between the pendulum model and the roll angle of the vehicle was derived;through the real-time data interaction between the two,a complete roll stability model of the tank semi-trailer was established;meanwhile,considering the effect of liquid sloshing caused by the differential braking on the longitudinal motion of the vehicle,a longitudinal dynamic model of the liquid was established and compared with Trucksim.(2)The roll stability analysis of the tank semi-trailer under different working conditions was realized,and the rollover instability mechanism of the vehicle was analyzed.Based on the established vehicle roll stability model,the roll stability analysis of the tank semi-trailer was carried out under different working conditions and different filling ratios;the conclusion that the vehicle rollover threshold was the smallest at a filling ratio of about 0.6 was obtained;Through data fitting,the threshold curves of vehicle rollover under different working conditions and different filling ratios were obtained,which verified the accuracy of the built model,which laid the foundation for the subsequent establishment of the vehicle anti-rollover control strategy.(3)A seven-degree-of-freedom vehicle model of a semi-trailer was established based on the analysis of vehicle motion status.The key parameters of the model were identified and validated using different algorithms.By simplifying the actual tank vehicle,a seven-degree-of-freedom vehicle model of the tank semi-trailer was derived and established;the key parameters of the model were identified by the combination of genetic algorithm and optimization function;the final result of the identification was substituted into the model.The theoretical model output and Trucksim vehicle model output data were compared and verified under different operating conditions.The results show that the theoretical model output and the Trucksim model output have a good fit and can accurately characterize the basic kinematics of the vehicle.(4)Under the premise of considering the liquid sloshing,the anti-rollover control strategy of the tank semi-trailer was established based on the LQR method.The vehicle control architecture was determined for the anti-rollover control target of the vehicle,and the reference model of the vehicle was determined based on the seven-degree-of-freedom dynamic model;on this basis,a rollover warning system was established through a large number of simulation tests,the target threshold of each warning indicator was determined;a vehicle anti-rollover controller was built based on the LQR control method,the liquid weight sway correction coefficient was used to correct the obtained control weight coefficient;designed the decision rules and realized the decision and torque distribution of the target wheel;finally,the effectiveness of the control algorithm was verified under the double shift line and fishhook conditions in combination with the vehicle anti-lock control.