| Off-road vehicles are important tools in rescue and relief work, nature exploration andmilitary transportation. With the development of science and technology progress, they playa more and more important role. Off-road vehicles’ working condition is unknown or notfully knowable. The terrain is complicated and difficult. So off-road vehicles should havehigh maneuverability and crossing ability. The running system of vehicles requires both agood climbing vehicle obstacle capability and a good driving stability. Wheeled vehicle hassimple structure. If off-road vehicles adopts walking wheel structure, it can realize the rapidand stable movement, and the energy utilization rate of the system is high. So it is widelyused in the field of mobile machinery.This paper comes from the National High-Technology Research and Development Pro-gram("863" project)―Wheeled Robot with Two Degrees of Freedom Articulated Vehicle forComplex Unstructured Terrain‖and university-enterprise cooperation projects―Developmentof an Articulated Wheeled Off-road Engineering Vehicle with tow DOF‖, a unique doublearticulated structure was designedin order to improve work efficiency. The vehicle uses amechanical–hydraulic compound transmission, utilization ratio of engine is high, the effi-ciency of the hydraulic drive system is high. The body of the vehicle consists of front frame,rear frame and double-articulated structure. Hydraulic cylinder drives the front and rearframe to make then relatively steering or swing Around the axis. The terrain adaptation ab-ilityof the vehicle is raised, and the off-road ability is enhanced. The vehicle can be driven inall terrain conditions, climbing, cross-country, wading, ice and snow.This paper analyzes the domestic and foreign development status of wheeled off-roadvehicle，designs a double articulated wheeled off-road vehicle. The frame has two degrees offreedom: rotation and swinging, which make the vehicle to adapt to the terrain better. Ac-cording to introduce the principle of mechanical–hydraulic compound driving systems andtheir components, theoretical analysis was combined with experimental study. The paper analyzes the characteristic of the mechanical–hydraulic compound driving systems by com-pared with simulation, research on walking system with steering system, and analyze drivingstability. The results provide the basis for the walking drive system to improve.The main contents are as follows:1. This paper discusses the significance of this study.It reviews the development historyof wheeled off-road vehicle at home and abroad, introduces the characteristics of variouswalking drive system and the control technology of hydraulic drive system in detail, ex-pounds the rational matching of engine and hydraulic pump and the relative content of stablerideability.2. Analysed the overall scheme and the system composition of the hydraulic drive sys-tem of the off-road vehicle, introduces the main components in the system and the controltechnology of the element. Introduces the working principle of variable pump in the constantpower control, load sensing control moded, function of multi-way valve and balance valve,and the control principle of displacement motor. Match parameters of hydraulic drive sys-tem.3. Establish mathematical model of the hydraulic components, analyzed the model,make theoretical analysis. Establish mathematical model of variable pump-controlvalve-displacement motor control system, while main hydraulic pump works in all wayscondition, and mathematical model of. variable pump,while it was controlled by balancevalve alone. Analysed characteristics of hydraulic drive system. Establish the relative posi-tion movement model of the front frame and rear frame, while the vehicle runs in Three di-mensional complex terrain. Analysed the driving stability while the vehicle wad in the dis-abled state. Introduction the steering principle of articulated vehicle. Establish mathematicalmodel of friction resistance moment and rolling resistance moment with two sides of thewheel in different rolling direction, according to the steering mechanics model. Introducedthe influence of tire mechanics performance on vehicle steering system, analyse the influ-ence of the stiffness of vehicle dynamic performance by establishing mathematical model oftire’s stiffness characteristics.4. According to theoretical analysis, a simulation model of travel drive system is estab- lished by using AMESim. Established the simulation model of main components respectively,analyse the simulation curve. For the vehicle having different load characteristic in differentworking condition, walking system performance analysis was carried out on the hydraulicdrive system simulation. Simulations on different working condition of variable pump areconducted. Establish simulations of steering system and its main components, Analyzechanges over time in the process of turning the steering hydraulic cylinder displacement andvelocity.5. Hydraulic drive system and vehicle stability are studied experimentally. The rela-tionship of the forward and reverse resistance is concluded by testing the resistance of me-chanical–hydraulic transmission system. the relationship ofulti-way valve inlet pressure andVariable pump control mode can also be get. Analyzes the role of balance valve in walkingdrive system by experiment. Static and dynamic obstacle stability are proved bycross-country performance test in the unstructured terrain.6. The system model of this vehicle is performed by Virtual.Lab Motion. According tothe known conditions, parameters of tire are setted. In order to analyse the system perfor-mance, Dynamic simulation of hydraulic system and steering system simulation model wascompleted by applying the AMESim and Virtual.Lab Motion. By analyzing the simulationcurve, the similarities and differences between the simulation results and experimental re-sults are known, the reason are also analysed. The main influencing factor of the systemperformance are found out by analysis, and good results are provides.7. The work and achievements of this thesis are summarized, and prospect the nextphase of work. |
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