Research Of Force-Position Combined Control For Tractor Hydraulic Hitch System Baesd On Can Bus

Because of the atrocious working environment, fluky work status and many influencing factors, it is difficult to describe the tractor with a precise mathematical model. In recent years, with the rapid development of computers, electronic control, artificial intelligence, network communications, and so on, especially their applications in tractors, the amount of tractor electronic control units become more and more. In this paper, the tractor suspension system and its tools supporting units acted as the object of study, carried out with a research in comprehensive adjustment of tractor hydraulic suspension system using the BP neural network and CAN bus.In order to facilitate research, firstly, this article has designed a new electro-hydraulic suspension system on the basis of the traditional hydraulic suspension system. According to the operation habit and CAN bus transmission requirements, it choosed the product with CAN bus as the intelligent node of the operator panel. And for the hydraulic circuit, electro-hydraulic proportional directional valve was used to replace the traditional mechanical splitter, which was combined with pressure relief valve, shuttle valves to achieve bi-directional and precise flow control. At the same time, for the convenience of indoor research, designed an electro-hydraulic loading system. The system also installed a draft sensor, a position sensor and two speed sensors. And the sensor signals acted as feedback signals, which were used to achieve true time control. In addition, it also analyzed the traditional tilling depth control method, proposed a new comprehensive of the force-position combined control, and introducted the concept of the comprehensive coefficient.And then BP neural network is selected as its control strategy after analyzing the limitations of the traditional control strategy, in view of nonlinear, hysteresis quality and uncertainty of influencing factors of the system. And discoursed on the basis of ideology, structure, mathematical description and characteristics of BP network. It also established a comprehensive coefficient model based on BP neural network, and trained the models. When simulation experiments were Carried out, the results showed that the application of BP neural network owns very application values.Finally, it designed the hardware and software for the control units of the tractor electronic hydraulic hitch system. According to the system requirements, selected TMS320F2812as the processing chip, and designed the DSP2812minimum hardware system. Combined with the sensors and actuator, designed interface circuit and CAN modules, enabling some features such as real-time sampling, control based on BP neural network, PWM output and CAN communication. Selected the CCS software, it completed the entire system’s programming using C language.By doing the PWM signal testing, it has proved the reliability of programs. It also has completed the driving control of electro-hydraulic proportional directional valve, and has tested the whole system, received the comprehensive adjustment curves. After the comparative and analysis, it can be proved that the properties of this control system basically meet the design requirements.