Study On The Hydraulic Driving And Controlling System Of The Full Hydraulic Bulldozer

Since the eighties of the 20th century, the traditional machinery type, hydraulic-machinery type bulldozer are so close to even the same with the foreign corresponding products in terms of its manufacturing capacity, its production scale as well as its engineering level that our country has some capacity for the new products in the field by importing overseas technology and learning advanced technology from it. However, it is relatively late for our country to study full hydraulic bulldozer. Presently, in the domestic market there is a few full hydraulic bulldozer whose production and development are in the initial stage. Additionally, it falls behind the advanced international standards in the matching theories, appraising system, dependability, controlling algorithms and controlling scheme. The theoretical base, therefore, plays a realistically major role in the study of the full hydraulic bulldozer.In this paper, current situation of domestic and foreign research, development trend of bulldozer have been analyzed and synthesized. And the characteristic of each kind of hydraulic drive, and the characteristic of the electric-control method and the hydraulic-control method have been analyzed. Finally, the return circuit of hydraulic transmission system is designed on the basis of the drive device type and control scheme suitable for the bulldozer.The paper provides the match principles of pump-engine according to the analysis of the performance characteristics of hydraulic pump, motor and engine with systematic draught characteristic and economy economic characteristic, the full hydraulic bulldozer hydraulic driving systematic working pressure and working pace of amount operating mode are confirmed. Due to analysis of systematic efficiency and pace rigidity, the parameters matching of motor-pump are confirmed. And the parameter of the typical operating mode of the bulldozer is checked because of calculating formulae of the key parameters of the drive system.After having been carried on kinematics and dynamics analysis to the full hydraulic bulldozer, the characteristic equation of traction is set up where the specified slip ratio of the full hydraulic bulldozer is defined as 12%～15%,the force-to-weight ratio is 1.48KN/T and the power-to-weight ratio is 7.2KW/T with this value in reality equal to or larger than average.With transfer function of the variable displacement of pump and motor, transfer function of pump-motor system and transfer function of motor-walk system is set up. The dynamic characteristic mathematical model of the pump-controlled motor system is established with MATLAB software, simulation models of the regulate organization displacement of pump and motor are set up. Then its dynamic characteristic is simulated to know further its flow impulse response and satisfying dynamic characteristic.