Development Of High-Power Tractor Hydro-Mechanical Continuously Variable Transmission Controller

Hydro-mechanical Continuously Variable Transmission (HMCVT) is a kind of transmission device combining hydraulic stepless transmission with mechanical transmission. HMCVT overcomes the disadvantages about the complex of mechanical transmission structure and the inefficiency of hydraulic stepless variable speed, and has a large transmission power, high transmission efficiency etc.. So HMCVT, apparently, belongs to the new stepless variable speed drive system. And, the research of HMCVT controller is the basic of studying on HMCVT power characteristics, dynamic characteristics, the minimum feature of engine fuel consumption and the control strategy.In this paper, based on the high-power tractor hydro-mechanical continuously variable transmission test bench, we designed a controller. The functions of the controller include the speed control for a pump-motor system, the control of a wet clutch shifting, and the data collection of gearbox related parameters. The main research contents are as follows:1. The overall scheme of the controller has been designed. Based on the hydro-mechanical continuously variable transmission test bench, and according to the speed ratio control form, the transmission structure form, the speed characteristic, the torque characteristic, and the power characteristics, the controller general scheme is presented. The controller uses a master to control two slaves. One of two slaves is used to collect data and the other is used to control the hydraulic system. PC as the master plays a role in the policy decision.2. The controller hardware has been designed and has been manufactured. The controller used the two single chip microcomputers, called STC12C5A60S2, as the two slaves. Controller hardware includes the data collecting circuit, the hydraulic system control circuit, the power supply and communication circuit. The data collecting circuit includes the pulse signal gathering circuit, the analog acquisition circuit, the switch signal acquisition circuit and the torque signal gathering circuit. The hydraulic system control circuit contains the speed regulation control circuit of variable pump-motor system, the electromagnetic directional valve control circuit about a wet clutch shifting.3. The controller of software system has been designed. After all circuits has been designed, we built an available environment on the implementation of control theory, including:building communication protocol between the PC master and two slaves, writing the communication command, writing the program of the master serial port data reception and sending by VB6.0, writing the interrupt receiving program,writing data acquisition program, the program of the speed regulation control circuit of variable pump-motor system and the wet clutch shifting program etc. by Keil-uVision4.4. The HMCVT controller test has been carried on. And, the result shows that this controller, basically, meets the demand of the data collection about gearbox related parameters and the hydraulic system control circuit.