Research On Electronically Controlled Air Suspension Matching And Control Strategy For Bus

Vehicle suspension is an important part of the vehicle chassis, which canalleviate and whittle the vehicle vibration caused by uneven road, and it has asignificant influence on vehicle performance. Electronically controlled air suspension(ECAS) can improve comprehensive vehicle performance through adjusting itsparameters in real-time according to the changing travelling conditions, which hasbeen a development tendency of vehicle suspension. At present, our country is notable to develop ECAS independently so that we have been importing the products andtechnical services from foreign countries in high price for a long time. Therefore,researching on the key technology of ECAS contributes significantly to independentresearch and development.Based on the existing research on ECAS of our group, this dissertation analyzesthe development history and research status of ECAS technology at home and abroad.Then it researches on the ECAS matching and control strategy for bus, providingtheoretical support for promoting our country’s ECAS development. As a whole, thespecific work in this dissertation can be seen as follows:(1) In chapter one, this dissertation analyzes the development history and researchstatus of ECAS technology at home and abroad, and makes certain thatresearching on the key technology of ECAS has important practical significance.Then the concrete research content of this dissertation is put forward according tothe research needs.(2) In chapter two,1/4air suspension nonlinear mathematical model of vehicle isestablished, which is consisted of three parts. The first part is air springmathematical model applying thermodynamics, hydromechanics and Newtonianmechanics. The second part is pavement random input model established by filterwhite noise, which is suitable for the time domain simulation of nonlinear system.The third part is1/4mathematical model of vehicle. (3) In chapter three, the type of air spring is selected according to the designparameters of the target vehicle, and its three level working height is designedbased on the requirements of suspension natural frequency, air spring designingand absorber stroke. After that, Particle Swarm Optimization (PSO) is applied toanalyze the influence of pavement, driving speed and sprung mass on optimizingdamping coefficient. According to the analysis result, the vehicle runningconditions are divided into four modes. The damping coefficient is optimizedaccording different vehicle running conditions.(4) In chapter four, mode switching method based on vehicle traveling speedchanging is applied, and the problem of mode frequent switching is solvedthrough setting speed threshold and time threshold. Besides, ProportionDifferentiation (PD) control method is used to control the height of vehicle bodyeffectively.(5) In chapter five,1/4ECAS bench composed of suspension simulation system,hydraulic system, pneumatic system, test system and control system, isconstructed based on the rapid prototyping technology of Matlab/xPC Target. Theoverall design scheme of the bench and each individual subsystem are specified.Based on the bench experiments, the stiffness characteristic of the air spring istest, and effectiveness of the PD height control strategy is also proven.