| Loader has the advantages of simple operation,flexibility and wide use,it plays an important role in infrastructure such as roads and bridges.As a loader with high power,high energy consumption and high social quantity,its energy-saving and consumption-reducing technology is the focus of current research.Loader is mainly composed of power transmission system and hydraulic system,the performance and operating efficiency of the loader are not only closely related to the performance of the system components themselves,but also largely dependent on the coordination and parameter configuration between the relevant components.Due to the complexity of loader operation process and frequent load change,today the research on dynamic load history and characteristics of loader under typical working conditions is not enough in-depth and detailed,which makes the main parts’ matching and optimization of power transmission system basically depend on the design experience and some static performance parameters,and the research on performance simulation and energy-saving mechanism of hydraulic system is difficult to carry out effectively and deeply.Engine power of loader is main-dynamically distributed between the power transmission system and hydraulic system in real time,only by integrating the power transmission system and hydraulic system and carrying out corresponding research can reflect the actual working process of loader,many scholars have done a lot of researches on the power transmission system and hydraulic system of loader,but most of them study the two systems separately,few people have integrates the two systems to carry out research,and in addition,a great deal of simplification has been done during the process of building simulation models of loader power transmission system and hydraulic system currently,which leads to the simulation results deviate too much from the real situation,and the value of engineering application is low.In view of the above problems,this paper takes ZL50 G wheel loader commonly used in China as an example to carry out relevant research,the main contents include:(1)The working characteristics of the main components of loader power transmission system and the operating forces of the vehicle are analyzed,and the corresponding mathematical models of engine,main components of the transmission system and the vehicle are established;Aiming at dynamic engine power split of hydraulic system,dynamic change of bucket resistance and four-wheel real-time full drive,the processing methods for power split of hydraulic system,shovel resistance and four-wheel drive and concrete implementation ways in the related modules are put forward,based on the established mathematical models of main components of loader power transmission system,and referring to the development method of vehicle performance simulation software ADVISOR,The performance simulation platform of power transmission system which is consistent with the working conditions of loader is developed.(2)Hydraulic system and working characteristics of its main components of the loader are analyzed,by applying AMESim,the simulation models of the work device hydraulic system,including the models of pilot valve and hydraulic control multi-way valve,and the steering hydraulic system,including the models of priority valve,full hydraulic load sensing steering device are established,after debugging the integrated simulation models of the work device hydraulic system and steering hydraulic system,the hydraulic system performance simulation platform of loader is developed.On this basis,MATLAB/Simulink interface module is applied to integrate the simulation models of the power transmission system and the hydraulic system,and a joint simulation platform for the vehicle performance of loader is built,which can realize the jointly dynamic simulation of the power transmission system and the hydraulic system.(3)The test parameters of loader are analyzed and determined,and a general scheme of parameter acquisition with the combination of wired test and short-range telemetry is designed,the sensors for parameter testing,telemetry system and data acquisition instrument are analyzed and selected,the torque sensor is constructed by using resistance strain gauge and full bridge circuit,the performance of torque and hydraulic sensors are calibrated by applying self-designed sensor calibration device,after connecting the signals of each sensor mounted on loader to the data acquisition instrument,the data acquisition system of loader work parameter is built;The typical test condition of loader is analyzed and determined,after carrying out actual vehicle tests,the first-hand test data are obtained.(4)The pretreatment method of loader load signal and the method of making simulation load spectrum of main components are studied,aiming at the characteristics of loader operation,in this paper,the methods of segmenting and merging,filtering and de-outlier,stationarity test and weighted average are proposed to analyze and process 180 sampled cyclic operation data,the simulation load spectrum of the main components and the typical driving cycle of the vehicle with typical working conditions of 87 s are made;The simulation test is carried out after the simulation load spectrum are applied to the developed loader vehicle performance simulation platform,by comparing with the test results of the real vehicle,it can be seen that: relative error of vehicle performance test data is less than 7%,the variation trend of hydraulic system parameters are comparatively consistent and the maximum value is basically close,the results show that the precision of the integrated vehicle simulation platform is high,and it can meet the need of loader performance simulation.(5)Based on the typical working conditions of loader and considering the different material operation proportion,the weighted torque value of engine actually consumed by hydraulic system is obtained,accordingly,a new matching scheme between engine and hydraulic torque converter is proposed,by means of integral mean calculation,the turbine shaft output power and engine fuel consumption rate of the new matching scheme in the high efficiency region of the torque converter are respectively 77.38 kW and 225.65g/(kW·h),it is better than the original matching scheme and partial power matching scheme.Statistical analysis is made on the usage of gear under typical working conditions of loader,and on the basis of gear utilization ratio under typical working conditions,an optimization method of transmission ratio is proposed,taking the highest utilization rate of output power in the high-efficiency region of the torque converter turbine as the objective function,and applying genetic algorithm to comprehensive optimization of loader transmission ratio,after optimization,the transmission ratios of forward gear Ⅰ and backward gear Ⅰ increase by 9.33% and 8.66% respectively,except for backward gear Ⅲ,the rest transmission ratios decrease,which is beneficial to improving the traction performance and working efficiency of the loader.The working energy consumption of the current hydraulic system of the loader is analyzed,the working efficiency of the system is calculated to be only 53.1%,and it is pointed out that the high energy consumption of the system is caused by the inability of output pressure and flow of the quantitative pump to automatically adapt to the load change;A new load sensitive control system is designed,its corresponding simulation model is established by using AMESim,and the structure and technical parameters of the system component are calculated and determined.The loader performance after system optimization and improvement is simulated by using the loader vehicle joint simulation platform.the results show that the operation efficiency of the improved hydraulic system is increased by 20.09%,the maximum traction force and maximum speed are increased by 5.27% and 7.63%,respectively than the existing systems,operating fuel consumption decreases by 5.93%,thus it can be seen that the methods of component matching and parameter optimization of power transmission system and the improvement measures of hydraulic system are feasible. |
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