Xi Zhiqiang

Modeling and control simulation for farm tractors with hydro-mechanical CVT

To develop the control system of hydro-mechanical continuously variable transmission (HMCVT), a tractor power train model is built by using the principle of dynamics and modular method, which includes the engine, HMCVT, running system and driven implement. According to the characteristic of power split, HMCVT is separated as axes set, variable displacement pump-motor system, clutch set and control system. The control logic model of range shift process is developed by using the theory of finite state machine. It is realized that TCU continuously controls the process of speed change and range shift. The dynamic characteristic of automatic speed changing and ranges shifting is simulated. The result indicates that it is an effective method to improve the dynamic performances of HMCVT by using the variable parameters PID control method which use engine speed and throttle values as control parameters and the feedforward control method which use throttle change rate as control parameters. The model can be used conveniently for the analysis of tractor dynamic performance and the research of HMCVT control method.

Design of Powershift Transmission Control System for Tractor Based on DSP

An electro hydraulic gearshift control system was designed based on DSP for the purpose of realizing automatic control of tractors with power shift transmission. The hardware design principle of input module such as pulse signal, analog signal and switching value, and the output drive module of gearshift solenoid valve were investigated. Utilizing the method of modularizing design and the core of real-time and multitask handling system-DSP/BIOS, the operational control process of tractor such as starting, gear shift and braking was investigated, which guaranteed the extensibility of software program. To validate the design, a semi-physical simulation test was tried out. The testing results showed that the control system can realize the automatic shift control based on the tractor speed and the operation of driver, which effectively improved the operating efficiency of tractor.

Design of Virtual Terminal for Agriculture Machinery Based on ISO11783

According to the virtual terminal (VT) technology specification of ISO 11783 standard, a virtual terminal product is designed. Through analyzing the type, definition and relationship of objects in the object pool of working set, the data structure of VT’s object pool is created based on the software development principle of object-oriented method. The parsing algorithm of events and processing algorithm of message are developed. A multi-node ISOBUS network including VT is constructed, which can correctly transmit the object pool, activate and display the mask, process the messages from ISOBUS network. When electronic control farm implements connect with the tractor, the VT can be used as man-machine interface for parameters adjustment and work data display.