Power And Energy-saving Shift Shedule Based On3Parameters For Construction Vehicle

The working conditions for the construction vehicles (wheel loader, bulldozer,etc.) are very complicated and the operating loads change frequently and sharply. Inorder to adapt to the rapid changing loads and improve the ability to overcome heavyloads at a low speed, the powertrain of a construction vehicle generally consists of ahydraulic torque converter and a power shift transmission. As a result, the efficiencyof the hydraulic powertrain system decreases when the torque converter works withlarge loads. Multi-gear transmission can improve the powertrain efficiency and fueleconomy. However, for vehicles equipped with manual transmission, frequent shiftingincreases the driver’s labor intensity and reduces the operating efficiency too. Inaddition, there is a great deal of subjectivity and arbitrariness for the manual shift andthe different levels of driving skills will make a tremendous impact on the vehiclepower, fuel economy, riding comfort, etc. The goal of the powertrain control forconstruction vehicle is always to improve the operating efficiency and make full useof the petroleum energy. Consequently, the technologies of automatic transmissioncontrol for construction vehicles appear at the base of this background.At present, the major international construction machinery companies, includingVolvo, Caterpillar, Kawasaki, Komatsu, ZF and other companies have been usedautomatic transmission technology on their construction vehicles. The automatictransmission strategies that most of these companies adopted are the two parameters(vehicle speed and throttle) strategies which commonly used for cars. However, theworking characteristics between the construction vehicles and the car are verydifferent. For construction vehicles, the hydraulic pump which does not exist inconventional vehicles, drives the main hydraulic system. It takes up a great deal of theengine power (up to40%-60%), while a construction vehicle is operating (shoveling,bulldozing, etc.). With the changes in operating loads, the engine output power hasbeen in a volatile state. The current application of the shift control principle does notconsidered the changes in operating loads affect the shifting process (or simplyassuming the operating load to be a fixed value) and therefore it can not get the bestshifting effect.The works in this paper were supported by the Specialized Research Fund for theDoctoral Program of Higher Education of China under Grant (200801830028)“New3parameters of the automatic transmission technology for construction vehicles”. Thetheory and experiment of the automatic transmission technology are in-depthresearched for the purpose of improving the economic and power of the constructionvehicles. Include the following contents: 1. In this paper, the operating load factor was used for describing the operatingload of the construction vehicle. The largest traction output and optimal torqueconverter efficiency wre choosed as control objectives and the throttle opening,vehicle speed and operating load factor are the shift control parameters. As a result,the power shift schedule, energy-saving shift schedule and comprehensive shiftschedule were developed. The depth and systematic study of the impact of theoperating load factor on the optimal shift point was made. The application of thethree-parameter shift schedule can further enhance and improve the economic andpower of the construction vehicles.2. The ZL50wheel loader was selected as prototype in this paper, and based onthe composition of its transmission system, the dynamic models of the constructionvehicle driveline were established, including the diesel engine, hydraulic pump group,torque converter and gearbox mathmodels. Multivariate polynomial regressionmethod was used for solving the functional relation of the proposed shift schedule.The three-parameter decision diagrams of energy-saving, power and comprehensiveshift schedule on the basis of the functional relation. As the kinetic models, the shiftschedules and the performance parameters of the vehicle drive system were obtained,the computer simulation model of automatic transmission system for constructionvehicles was established on the software platform of MATLAB/Simulink. Simulationexperiments on the shift schedule proposed in this paper were carried out for analysis.3. The automatic transmission controller of construction vehicle was developed,and confirmatory tests were maded on the transmission test bed. The test results showthat the vehicle driveline efficiency is always maintained at the higher range (η≥0.75)by the application of three-parameter energy-saving shift schedule; the power shiftschedule enables the vehicle to obtain a continuous and stable power output; Thepower and economy indexs of the comprehensive shift schedule are between thepower and the energy-saving shift schedule. The shift control system was reliable andaccurate during the tests, and the phenomenon of frequent shift, cyclic shift or errorshift did not appear at the same time. to verify the reliability and feasibility of theautomatic shift controller developed in this paper. The results demonstrate thereliability and feasibility of the automatic shift controller developed in this paper.The work done in this paper can provide a theoretical basis and practicalexperience of accomplishing the operating tasks more energy efficient forconstruction vehicles.