| In recent years,Chinese commercial vehicle production has consistently ranked first in the world.The construction of highways and development of automobile technology has led to continuous increase of vehicle speed,and public requirements on vehicles' performance are increasing correspondingly.The key which ensures the safety of commercial vehicles mainly depends on pneumatic brake system.The pressure response characteristics during braking directly affect the vehicle's safety status.Accurately acquiring dynamic characteristics and influence factors of pneumatic brake system's pressure response is essential for developing and testing of brake control system,designing and matching of pneumatic brake system,as well as predicting and analyzing of vehicle brake performance.Establishing precise and comprehensive pressure response simulation model for pneumatic brake system in commercial vehicles can provide not only technical basis for performance analysis,structural design and control algorithm development,but also an effective means for ensuring excellent performance.In this dissertation,the theoretical analysis,modeling and simulation,as well as experimental verification were adopted to systematically investigate the construction and integration of pneumatic brake system's pressure response model.Main work of the dissertation is as follows.(1)The pneumatic brake system was divided into gas storage tank,brake chamber,relay valve,series double chamber brake valve,quick release valve and pneumatic pipeline according to the structural composition and working principle of the commercial vehicle pneumatic brake system firstly,then theoretical models of the basic pneumatic units such as orifice and gas volume were established.The distributed parameter theoretical model for pneumatic pipelines was established.On the basis of basic pneumatic units' theoretical models,combined with working mechanism of each key component and its connection mode with the pipeline,theoretical model of each key component of the commercial vehicle pneumatic brake system was established.(2)According to theoretical models,framework and connection rules for orifice and gas volume's simulation model were proposed.And orifice and gas volume's modular simulation model were established.The distributed parameter theoretical model of the pneumatic pipeline was solved with Cubic Interpolation Profile method,and the pipeline calculation boundary was set.The pipeline's modular simulation model was established.On the basis of the orifice and gas volume simulation model,the simulation model which reflects characteristics of the structural parameters of each key component was established with reference to the object-oriented programming paradigm.The simulation model of each key component was packaged and integrated to form a simulation model library.Pressure response simulation model of the pneumatic brake system was constructed by adopting the simulation model library.(3)A pneumatic brake pressure response test bench was set up with real vehicle pneumatic brake components and LabVIEW data acquisition software.Modeling method and correctness of each component's simulation model were verified through the pressure response experiments,which were conducted on brake chamber,series double chamber brake valve and relay valve.Correctness of the pneumatic brake system's simulation model was verified through the pressure response experiment of pneumatic brake system.Moreover,pressure response characteristics of different pipelines in pneumatic brake system were analyzed.In this dissertation,the pressure response simulation model of commercial vehicle pneumatic brake system considering the influence of pipeline was established.The simulation model is flexible,and the simulation results owns high degree of confidence.The modeling method of pneumatic brake system and the treat mode of pipeline model can provide reference for modeling commercial vehicle pneumatic brake system.The integrated pressure response simulation model can be applied to structural design,parameter optimization and control algorithm development of commercial vehicle pneumatic brake systems. |
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