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Front. Inform. Technol. Electron. Eng.  2016, Vol. 17 Issue (5): 458-464    DOI: 10.1631/FITEE.1500172
    
Proportional directional valve based automatic steering system for tractors
Jin-yi Liu, Jing-quan Tan, En-rong Mao, Zheng-he Song, Zhong-xiang Zhu
Beijing Key Laboratory of Optimized Design for Modern Agricultural Equipment, China Agricultural University, Beijing 100083, China
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Abstract  Most automatic steering systems for large tractors are designed with hydraulic systems that run on either constant flow or constant pressure. Such designs are limited in adaptability and applicability. Moreover, their control valves can unload in the neutral position and eventually lead to serious hydraulic leakage over long operation periods. In response to the problems noted above, a multifunctional automatic hydraulic steering circuit is presented. The system design is composed of a 5-way-3-position proportional directional valve, two pilot-controlled check valves, a pressure-compensated directional valve, a pressure-compensated flow regulator valve, a load shuttle valve, and a check valve, among other components. It is adaptable to most open-center systems with constant flow supply and closed-center systems with load feedback. The design maintains the lowest pressure under load feedback and stays at the neutral position during unloading, thus meeting the requirements for steering. The steering controller is based on proportional-integral-derivative (PID) running on a 51-microcontroller-unit master control chip. An experimental platform is developed to establish the basic characteristics of the system subject to stepwise inputs and sinusoidal tracking. Test results show that the system design demonstrates excellent control accuracy, fast response, and negligible leak during long operation periods.

Key wordsAutomatic steering system      Hydraulic circuit      Proportional directional valve      Proportional-integral-derivative (PID) control     
Received: 30 May 2015      Published: 04 May 2016
CLC:  TP273  
  TH137.52  
Cite this article:

Jin-yi Liu, Jing-quan Tan, En-rong Mao, Zheng-he Song, Zhong-xiang Zhu. Proportional directional valve based automatic steering system for tractors. Front. Inform. Technol. Electron. Eng., 2016, 17(5): 458-464.

URL:

http://www.zjujournals.com/xueshu/fitee/10.1631/FITEE.1500172     OR     http://www.zjujournals.com/xueshu/fitee/Y2016/V17/I5/458


基于比例控制的农业机械自动转向系统研究

目的:就现有农业机械面临的自动转向系统发热、适用车型受限、未实现产品化等问题,对农业机械的自动转向系统做了深入研究。开发了一种采用螺纹插装阀的多功能比例集成控制阀块。该阀块适用于具有开心式、闭心式或负载压力传感式全液压转向器的液压转向系统。
创新点:开发了一种采用螺纹插装阀的多功能比例集成控制阀块。该阀块适用于多种转向液压系统。通过简单的增量型PID算法控制即得到了良好的控制效果。
方法:根据大多数农业机械液压转向系统的特点,结合自动转向系统设计原则,提出了一种以三位五通比例换向阀为核心的农业机械自动转向集成阀块(图2)。选择宏晶科技的STC90C516RD单片机为控制器,增量型PID算法为控制算法,将自动转向比例集成控制阀块与福田雷沃TG1254拖拉机的原有液压系统并联(图9),进行实车跟踪试验,以测试阀块对自动转向控制系统的响应特性和跟随特性。
结论:本文所设计的自动转向比例集成控制阀块以福田雷沃TG1254拖拉机为试验平台进行实车跟踪试验。通过直线信号跟踪(图10)和正弦信号跟踪(图11),可以看出自动转向系统有快速的响应性能和良好的跟随性能,能够适应农业机械导航控制的需求。

关键词: 自动转向系统,  液压回路,  比例换向阀,  PID算法 
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