Research On Travel System Of Skid-steer Loader

Within quite a few years, the national economic construction and the expansion of allkinds of infrastructure construction have accelerated the development of Constructionmachinery industry. As a rather important branch of Construction machinery industry,Multi-function mini construction machinery seems to have an impressive prospect.Skid-steer Loader is becoming more popular as one of the best kind of Multi-function miniconstruction machinery. However, the development and design of Skid-steer Loader in Chinastarted quite lately, and the core technology is needed to introduce from abroad. These twofactors limit the industrialization process of Skid-steer Loader greatly.As one core system of the Skid-steer Loader, the performance of travel system candirectly affect its overall performance. The level of travel system develops rapidly with thepromotion of the internal combustion engine technology, hydraulic technology and computercontrol technology. But the hydrostatic drive travel system still be the weak links of thewhole system. In addition, the relative theory is not perfect, and there has no enoughsystematic and integrated research. In order to improve the overall performance of theSkid-steer Loader, enhance its Market competitiveness, t he research in Skid-steer Loaderstravel system has important theoretical and practical significance.Referring to the School-enterprise cooperation project “The dynamic simulationanalysis and coMParison test of the loader hydraulic system and drive system “and”Thedynamic optimization simulation and experimental study of the loader hydraulic drivesystem”, depending on a certain type of Skid-steer Loader, combining engine, hydraulicdrive system, the wheel-ground load as a whole, using the methods of theoretical analysis,dynamic simulation and experimental study, this essay takes research for the travel system.There are many qualitative analysis on wheel load and hydraulic system performance inrespect of the system matches and the important parameters of the system, depending on thedevelopment of Engine-pump theoretical model, hydrostatic transmission mathematicalmodel, and Baker ground-based mechanical theory of traveling, slip steering tire-ground load model. The dynamic simulation research of the functional parameters of the keycomponents and the system are based on the AMESim and Virtual Lab Motion, and attaineda new method for dynamic optimization design. The travel system performance testingprogram is designed for testing straight-line driving, skid steering, joint shovel loading andsystem performance respectively. Experimental results reflect the performance of theexperimental prototype and verify the correctness of previous theoretical research andsimulation analysis. Finally, according to the engine flameout phenomenon in theexperimental procedure, the engine speed feedback power control system is developed, andthe correctness of this system is verified through simulation models. This dissertation hascertain reference value for the dynamic simulation design, optimizing analysis and systemperformance evaluation of the travel system of Skid-steer Loader. It also has importanttheoretical significance and practical value.The research contents are mainly as follows:Chapter1. This chapter is mainly about the purpose and significance of this paper; Itoverviews the domestic and overseas development and application status of Skid-steerLoader; it summarizes the development and research status of Skid-steer Loader travelsystem; the main contents of this paper is determined in this chapter.Chapter2. In this chapter, a detailed analysis of the composition and the operatingprinciple of the travel system is done according to a certain type of Skid-steer Loader. Themathematical models of Skid-steer Loader travel system (engine, hydraulic drive system,wheel-ground loader)are established from the point of view of the complete system.Moreover, in this chapter, the matching relationships of engine-variable displacement pump,the system performance of variable pump control quantitative motor, the control features ofthe close hydraulic system and wheel-ground interaction load characteristics based onBaker`s theory are analyzed and researched. Important parameters which affect the systemperformance are found here.Chapter3. It introduces the principle of skid steering and puts forward assumptions ofSkid-steer Loader travel system. Besides, according to the principle of skid steering, it raises the concept of transmission ratio and steering ratio of wheel slip vehicles, carrys out thequalitative analysis of the relationship between the steering force and steering power of twosides by establishing kinematics, dynamics mathematical models in the skid-steering process.All this is based on Baker ground-based mechanics theory. The simulation and experimentalresults show: relative to the straight-ahead driving, steering resistance moment is muchlarger than the rolling resistance torque and steering drag coefficient increases withdecreasing turning radius.Chapter4. In this chapter, according to the analysis of travel system, engine model,Half a physical change HCD model of variable displacement pump, Hydraulic drive systemmodel, Three dimensional dynamic model of wheel-ground interaction are built by usingAMESim Software and Virtual Lab Motion Multibody Dynamics Software. Then, simulationanalysis of engine and variable pump are carried out, as well as the joint simulation of thewhole travel system according to various travel system working conditions. Simulationresults show that: the model is built accurately and credibly, and the performance of thesystem is promoted greatly through matching spool control signal with the shape of the valveport combination reasonably. Component models are received and used in Skid-steer Loaderdesign and failure analysis after being packed modularly.Chapter5. In this chapter, Skid-steer Loader travel system performance testingprograms are developed. Depending on this, experimental test The experiment test andanalysis on straight-line driving, skid steering, joint shovel loading and system performanceare done. The analysis results verify the correctness of the theoretical model simulation.Chapter6. In this chapter, according to the engine flameout phenomenon of the testsample car, the speed feedback power control system of the Skid-steer Loader engine isdeveloped and designed. Simulation results show that: the system can maximize the use ofthe engine power corresponding to the throttle position, improve the power efficiency, andcan effectively prevent flameout occurring.Chapter7. The work and achievements of this thesis are summarized, and prospect thenext phase of work.