Research On Hydraulic Control System Design And Performance For Self-propelled Carrier-vehicle

The iron and steel industry is an intensive transportation industry. The logistics costsoccupies a higher proportion in the whole cost of production. Trackless transportation withits significant advantages such as less land occupation, flexibility, smooth operation, highefficiency can decrease effectively the cost of logistics compare with railwaytransportation. Because of that, in developed countries, the proportion of logistics costs isas low as8%~10%. But in China, the railway transportation is still the predominantmode of transport, and the proportation is up to30%. Hence, trackless transportation is thedeveloping trend in our country.Self-propelled carrier-vehicle has becoming one of the main trackless transportationsbecause of it can match with the basket to complete the tranfer of material, small landoccupied, high efficiency, large capacity and high performance, etc. The performance ofelectro-hydraulic control system is essential condition for the long-time operation of thevehicle in the condition of high speed and large load. In this paper, the objects of study arethe closed hydraulic driving system and suspending mechanism hydraulic system whichare the importance components in electro-hydraulic control system. Further studycombined with problems occurred on the operation, improves handling, safety, smoothoperation for the two systems are conducted. The main research contents are as follows:(1)According to the working requirements of high running speed and goodmaneuverability for self-propelled carrier-vehicle, a new closed hydraulic driving systemis designed, with the improved design of vehicle’s differential speed and force controlfunctions. To improve the vehicles’ operational safety furtherly, the vehicle’s hydraulicdelay warning control system and filter devices of the closed hydraulic driving system aredesigned.(2)A new composite control method-servo override control technology is used tooptimize the displacement control of variable pump and to manage the contradictions ofpower requirements among the closed hydraulic driving system, steering hydraulic systemand auxiliary systems, and dynamic characteristic of the control method is analyzed. (3)For meeting requirements of the height could be adjusted flexibly and four pointssupporting suspending mechanism has higher synchronous precision, the electro-hydrauliccontrol system with pressure sustaining and pressure loss protection has been designed.The constant pressure variable control system based on load sensing pump has beenproposed innovatively, which manages the contradiction between suspending mechanismand steering hydraulic systems on demand difference to oil source control form.(4)According to the characteristics of coupled, nonlinear and uncertainty of modelparameters existed in the synchronous lifting system, a fuzzy PID multi-cylindersynchronous driving control strategy based on multi-point output coupling has been putforward, and its effectiveness is verified through simulation and experimental analysis.(5)Whereas the characteristics of heavy rated load, fast running speed and largeimpact of ground excitation, a new suspending mechanism hydraulic system which meetsthe operational requirements of self-propelled carrier-vehicle is designed based on thetraditional constant stiffness hydraulic spring suspending mechanism. The evaluationindex of compliance of suspending mechanism hydraulic system has been put forward,and in the MATLAB/Simulink environment the compliance has been analyzedcontrastively in the simulation of random road input with the vehicle under two workingconditions. And validate effect of the developed suspending mechanism hydraulic systemon improving vehicles’ running compliance through on site contrast experiment finally.(6)The hardware acquisition system based on USB7360A data acquisition card andthe data processing system based on LabVIEW have been designed. Through this testdevice, the key parameters of vehicles’ systems (closed hydraulic driving system,suspending hydraulic system and steering hydraulic system) have been measured tovalidate the rationality of theoretical design.