拖拉机电液转向系统的变论域两级模糊PID控制研究

[目的] 拖拉机在田间转向过程状态多变且环境恶劣,对转向系统控制精度和算法适应能力要求较高,故研究设计变论域两级模糊PID控制方法在拖拉机电液转向系统上的应用。[方法] 在分析了电液转向系统的结构原理的基础上,建立了其主要组成部分数学模型,然后将变论域两级模糊PID方法(VFFPID)引入到控制器设计中,进行蛇形跟随性、转向响应性仿真试验,并同时与模糊PID控制算法(FPID)和基于函数型变论域模糊PID算法(XFPID)作对比分析。[结果] 蛇形跟随性试验结果表明:拖拉机电液转向系统在VFFPID的控制下,转向油缸位移最大误差只有±1.43 mm,比FPID降低了49.5%,比XFPID降低了40.7%。响应性试验结果表明:在VFFPID控制下,转向油缸执行响应时间为0.123 1 s,比FPID缩短了17.8%;转向油缸位移平均误差为0.121 9 mm,是XFPID的28.3%。[结论] 拖拉机电液转向在VFFPID的控制下油缸位移最大误差、平均误差更小,执行响应时间更短,具有更好的跟随性和控制精度。
[Objectives] When driven on the farm road, the tractor has higher requirements for control precision of steering system and adaptable ability of control algorithm because of diverse condition and bad circumstance, and a method of variable universe two-stage fuzzy PID(VFFPID)was studied and designed in the application of tractor electro-hydraulic steering system. [Methods] Based on the analysis of the structure principle of new type electro-hydraulic steering system, transfer function was established and the experiments of serpentine following and steering response were conducted by introducing the method of variable universe two-stage fuzzy PID(VFFPID)into the controller design. [Results] Through comparing with fuzzy PID control algorithm(FPID)and variable universe fuzzy PID based on the functional algorithm(XFPID), the results of experiment of serpentine showed that the maximum error of VFFPID was reduced by 49.5% in comparison to FPID and was reduced by 40.7% in comparison to XFPID. The results of experiment of steering response illustrated that the response time of VFFPID was 0.123 1 s which was shorter by 17.8% than that of FPID, and the steering cylinder displacement average error of VFFPID was 0.121 9 mm which was 28.3% of XFPID. [Conclusions] The statistic demonstrated that VFFPID had smaller average error and response time, better stability and control accuracy