| With the rapid development of China’s economy,the pace of modernization and urban construction is accelerating,the market demand for engineering vehicles is constantly improving.The traditional single transmission mode can no longer meet the contradiction requirements of engineering vehicles that require both low-speed stable operation capability and high-speed transfer capacity.However,the mechanical hydraulic composite transmission combines the advantages of high efficiency of mechanical transmission and the advantages of hydraulic transmission with stepless speed regulation.It has good low speed stability,high transmission efficiency,good power and high energy efficiency,and it has been widely developed and applied in the field of engineering machinery.Firstly,through the analysis and research on the advantages and disadvantages of the existing mechanical hydraulic composite transmission technology,this paper proposes a new driving scheme of installing a mechanical-hydraulic compound transmission box between the original engine and the mechanical gearbox on the basis of maintaining the original vehicle chassis.That is,under the transitional conditions,the vehicle adopts pure mechanical transmission to transfer at high speed,and under the working condition,it adopts mechanical hydraulic composite transmission to operate at low speed.And taking the chassis of SX1254BM434 produced by Shaanxi Automobile Group as the research object,and the specifications and models of major components such as engines,hydraulic motors,hydraulic pumps and transmissions in the transmission system were selected.Next,with DSP TMS320F28335 as the core,the hardware interface circuit is designed,including the minimum system circuit,signal conversion and conditioning circuit,power drive circuit and communication interface circuit.On the basis of this,according to the control requirements,the software design of the function modules such as working mode switching,engine management and vehicle speed control was completed,and the software and hardware design of the mechanical hydraulic composite transmission control system was completed.Then,in order to improve the stability of vehicle operation,improve the automation degree and ensure the quality of operation,a fuzzy PID controller is designed.The fuzzy PID control strategy is adopted to control the vehicle working speed,so that the system has stronger working condition adaptability and anti-interference ability.Finally,Finally,the mathematical model of the walking system is established,and its simulation model is built in the MATLAB/Simulink environment.The low-speed performance and control performance of the vehicle are simulated and analyzed.The results show that the composite transmission scheme and its control strategy are reasonable and feasible,and have a good application prospect. |
