Study On Vehicle-Liquid Coupling Dynamic Characteristics And Anti-Rollover Control Method For Tank Vehicles

Road tanker,the most widely used liquid dangerous goods transportation tool,tends to rollover easily due to its high mass center,large amplitude of liquid nonlinear violent sloshing within the tank and vehicle-liquid coupling motion.What's more,secondary accidents such as oil explosion and spill can easily occur,causing greater hazards and losses.Most studies focus on optimizing tank structure to improve the tank vehicle's stability and analyzing the influence of variables such as the tank structure and filling ratio on the dynamic characteristics o f tank trucks.However,the study of the vehicle-liquid coupling mechanism and the contribution of liquid sloshing to vehicle instability,which are the preconditions of applicable simplified models of tank vehicles and accurate and effective active safety control for tank vehicles,is insufficient.Furthermore,few researches focus on active rollover control that specifically considers the characteristics of liquid tank vehicles.Therefore,it is urgent to explore what characteristics should be taken into account and what methods should be used in tank vehicle roll stability control,and how to reduce the false alarm rate and improve the control effects.This subject is funded by the National Natural Science Foundation of China,"Study on Mechanism of Fluid-structure Interaction and Anti-roll Control for Road Liquid-filled Tractor-Semitrailers"(ID: 51575224),and Jilin Provincial Science and Technology Development Project "Stability control for Heavy Duty Vehicle base on Electronic Pneumatic Brake System"(ID: 20170414045GH)and "Heavy Duty Vehicle Electronic Pneumatic Brake System Development and Matching"(ID: 20150204066GX).Based on the research results of tank vehicle dynamics and active safety control methods,considering transient liquid sloshing in partially-filled tank vehicles,this article addresses the issue of unclear vehicle-liquid dynamics coupling mechanism and tank vehicle roll stability control,studies the vehicle-liquid coupling dynamic mechanism,and proposes a reasonable simplified basis for the dynamic model of liquid sloshing in tank vehicles.Based on the above research,an equivalent mechanical model of liquid nonlinear sloshing that can reasonably represent the liquid characteristics and its influence on the vehicle in actual working conditions is established herein.An active anti-rollover control algorithm for tank vehicle considering liquid slosh characteristics is developed.The main tasks include the following:(1)Establishment of a bi-directional coupling fine model for tank vehicles and analysis of vehicle-liquid coupling dynamic characteristicsSince the liquid sloshing characteristics and its influence on the response of the vehicle are not clear enough,it is necessary to simulate liquid transient slosh characteristics and vehicle dynamics as accurately as possible.Therefore,a liquid sloshing numerical model is established in FLUENT and a vehicle dynamic model is established in TruckSim.Then,a bi-directional coupling fine model for tank vehicles is established by creating timing information transfer platform for FLUENT and TruckSim.Besides,three simplified tank vehic le mode ls,rigid cargo model,Q-S liquid mode l and equiva lent pendulum model are developed respective ly.By comparing the simulation results from the above four tank vehicle models,the excitation degree of various liquid sloshing characteristics and the influence of various liquid sloshing characteristics on tank trucks dynamics under different types of actual conditions are discussed.This study provides guidance for the development of a more suitable simplified liquid slosh model.(2)Establishment of the nonlinear equivalent mechanical model for liquid sloshing in tank vehicleThe analysis of the vehicle-liquid coupling dynamics based on the tank vehicle fine model point out that,for the liquid lateral sloshing under handling manoeuvres,as the severity of the manoeuvres increases,the liquid slosh frequency increases and the impact amplification factor decreases.For the purpose,a trammel pendulum is utilized for equivalent liquid lateral nonlinear sloshing,and the parameters are identified using genetic algorithms.For the liquid longitudinal sloshing in braking manoeuvres,since tank vehicles are generally fitted with perforated diaphragms,it should be considered that the fundamental frequency changes with the severity of the manoeuvres,the inter-chamber mass transfer and the damping effect caused by the perforated diaphragm.Therefore,a trammel pendulum is utilized for equivalent liquid longitudinal nonlinear sloshing,and through Analog pipe flow,the relationship between inter-chamber mass flow rate and hole/plate area ratio,hole position and external acceleration excitation are analyzed.Based on the above,the longitudinal nonlinear sloshing equivalent mechanical model for porous diaphragm multi-chamber tank is achieved.The genetic algorithm is used to identify the parameters of the longitudinal trammel pendulum model,the parameters of the inter-chamber mass flow model and the total damping coefficient.The nonlinear equivalent mechanical model provides a model basis for the stability analysis of the tank vehicle system.(3)Roll stability analysis for tank vehicleThe tank vehicle roll dynamic model is established by combining the lateral nonlinear sloshing equivalent mechanical model and the vehicle roll dynamics considering wheel lift-off.Then,in order to understand in depth of the liquid roll motion-liquid lateral sloshing coupling mechanism of liquid tank vehicles,phase space analysis is used for the influence analysis of the initial value of state variables and the system input(lateral acceleration)on roll dynamic characteristics of tank vehicles.The main characteristics and reasons of the roll phase space of tank vehicles are clarified,which provides theoretical guidance for the anti-rollover control of tank vehicles.(4)Development of integrated control strategy for slosh-suppression & yaw & anti-rollover of tank vehicleIn order to improve the yaw and roll stability of the tank vehicles and reduce transient liquid sloshing,the slosh-suppression & yaw & anti-rollover optimal control system for tank vehicle is developed based on the ESC system.For the transition condition where the vehicle's handling performance is not stable but has not yet entered roll instability,the LQR based yaw & slosh-suppression control strategy is developed to delay the entry of anti-rollover control timing,and the control objective is to follow the expected value of the yaw rate,the side-slip angle and the liquid equivalent swing angle of the tank vehicle.For rollover hazardous manoeuvres,a LQ R output optimal roll control method is developed,and the control objective is to minimize the lateral transfer rate LTR of the tank vehicle.In order to dynamically distinguish the degree of urgency of the rollover and prevent the control system from triggering too early or too late,a time-to-rollover(TTR)warning algorithm considering liquid sloshing is developed.Finally,integrated control strategy for slosh-suppression & yaw & anti-rollover of tank vehicle is developed using TTR as the switching index of the yaw & slosh-suppression control mode and the anti-rollover control mode.(5)Establishment of the modeled tank vehicle experimental system and vehicle experiment studyA vehicle experiment system with scaled tank is built,for the experimental study of the vehicle-liquid coupling characteristics and the verification platform of the liquid slosh numerical model and the tank vehicle dynamic model.An appropriate scaling ratio is first chosen according to the similarity principle,then an experimental vehicle with a scaled tank that can be visually observed and measure liquid sloshing forces and vehicle motion is built.Finally,through vehicle tests,the liquid slosh numerical model and the tank vehicle dynamic model are validated,and the vehicle-liquid coupling characteristics are studied.The innovations in this article are reflected in the following three aspects:(1)The main features of the vehicle-liquid coupling dynamics are explored.Based on a bi-directional coupling fine model for tank vehicles,the vehicle-liquid coupling dynamics are analyzed thoroughly and guidance for the development of a more suitable simplified liquid slosh model is provided,by discussing the excitation degree of various liquid sloshing characteristics and their influence on tank trucks dynamics under different manoeuvres.(2)The longitudinal and lateral nonlinear sloshing equivalent mechanical models that describe the main vehicle-liquid coupling characteristics are established.Considering the vehicle-liquid coupling dynamics characteristics,a trammel pendulum is utilized for equivalent liquid lateral nonlinear sloshing,besides,the longitudinal nonlinear sloshing equivalent mechanical model for porous diaphragm multi-chamber tank is established by combining a longitudinal nonlinear equivalent trammel pendulum and a function of inter-chamber mass flow rate about hole/plate area ratio,hole position and external acceleration excitation.(3)An integrated control strategy for the slosh-suppression & yaw & anti-rollover of tank vehicle is proposed.In view of the problem that the liquid sloshing will reduce the roll stability of tank vehicle,the control of liquid sloshing,yaw stability and roll stability of tank vehicle are considered comprehensively and a time-to-rollover(TTR)warning algorithm considering liquid sloshing is developed as the switching index of different control modes,to prevent triggering too early or too late.