基于PID控制的电液耕深调节系统研究

发布时间：2018-07-14 07:37

【摘要】：耕作过程中保持耕深稳定是提高耕作质量的重要措施之一。目前耕作机械作业过程中耕深调节大多为力调节或位调节方式,其对耕深的控制效果较差,而且耕深测量也只能通过在耕后测量沟底到未耕地表的距离来实现,这种测量方式误差较大,且无法实时反馈耕深信息给机手,使机手无法根据耕作效果来实时调节耕深。随着耕作机械朝着自动化、智能化方向的发展,以及电控、液压等技术的逐渐成熟,实现耕深的自动调节已经成为一种发展趋势。为提高耕作机械作业过程中的耕作稳定性,本文研制了一种耕深自动调节系统,主要研究内容如下:以某款耕耘机的后悬挂旋耕部件为研究对象,设计了机电液一体化耕深控制系统,利用电控和液压技术实现对耕深的自动控制,同时加入PID控制算法优化控制效果。与传统的耕深调节方式相比,本系统采用双倾角传感器检测耕深,通过耕深设定电位器设定耕深,控制芯片采集目标耕深信号和传感器实时反馈信号,通过比较产生误差信号,误差信号经控制器计算处理后变为控制信号,控制电磁比例换向阀换向和开口大小,实现对液压系统的控制,从而达到控制耕深的目的。其中,电控系统采用AT89S52作为处理芯片,在硬件结构上设计了相应的模块电路,同时结合倾角传感器和执行阀进行接口电路设计,实现了信号采集和阀控PWM信号的输出。软件系统基于C语言开发,主要编写了主程序、采集程序、IIC通信程序、PWM输出程序等,其功能为接收耕深设定电位器和倾角传感器的实时信号,通过转换运算之后有选择的输出PWM波,其经过RC滤波处理后转换成模拟信号以控制电液比例换向阀的动作。在液压系统设计部分,根据耕耘机耕深调节的工作要求,设计了耕深调节液压系统及液压驱动旋耕回路;计算了旋耕部件作业的功率,根据功率匹配对液压系统进行了设计,确定工作压力为16MPa,油泵型号为PFE-31036,液压马达型号为1JMD-40,在此基础上完成了液压系统各个元器件和液压管道的设计和选用。耕深调节过程中控制系统的动态响应对耕深调节的即时性有重要影响,为研究电液控制系统动态响应特性,本文利用Simulink中的Sim Hydraulic模块对耕深控制系统进行动态仿真研究,搭建了闭环电液控制系统模型,根据各个元器件和模块的参数对仿真系统模型进行参数设定,对系统进行分工况仿真。仿真工况分为调节耕耘机耕深从0增加到100mm,和从175mm减小到100mm两个工况,用输入阶跃信号的方式表示设定耕深的动作,用SIMHydraulic中传感器模型来代替实际传感器检测相关数据,用阻尼模块代替悬臂给液压杆的反作用力,用摩擦力模块表示液压缸动作时活塞与缸体以及活塞杆与缸盖的摩擦力,液阻、机械惯性等其他影响因素在仿真模型中用相应的适当的模块表示。仿真结果显示,耕深控制系统存在约13%的耕深超调量,同时系统需要5.0s左右的振荡时间才能控制耕深达到稳态。为消除耕深超调现象,缩短调节耕深达到稳态所需的时间,本文采用在误差信号处理中使用积分分离PID控制算法的方法对耕深控制系统的动态响应特性进行优化。设定积分阈值为ε=0.08,当误差值较大时取消积分作用,加快调整速度,在耕深值迫近目标值时再加上积分作用,提高控制精度。采用经验试凑法整定PID参数,当Kp=0.08,Ki=1.2,Kd=0.001时,系统具有较好的动态响应,与未加入PID控制算法的仿真结果比较,几乎消除了系统的耕深超调现象,同时,将响应时间缩短到1.4s左右,使耕深控制系统的动态响应达到较好的效果。在此基础上,对耕耘机进行了耕深稳定性验证试验,耕耘机在10cm和16cm的预设耕深条件下作业时,耕深稳定性变异系数分别为6.05%和3.54%,达到了旋耕作业规定的农艺要求。
[Abstract]:Keeping the depth of tillage stability is one of the most important measures to improve the quality of Tillage in the process of tillage. At present, the cultivation depth regulation is mostly force regulation or position regulation, and its control effect on tillage depth is poor, and the depth measurement of tillage can only be realized by measuring the distance from the bottom to the untillage surface after the tillage. It has large error and can not feed back the deep information to the machine hand in real time, so that the hand can not adjust the depth of Tillage in real time according to the tillage effect. With the development of the farming machinery towards automation, the development of the direction of intelligence, and the gradual maturity of the electronic control and hydraulic technology, the automatic regulation of the depth of the tillage has become a trend of development. In this paper, a kind of automatic regulation system for tillage depth is developed in this paper. The main research contents are as follows: Based on the research object of the rear suspending rotary tillage part of a cultivator, the electromechanical hydraulic integrated tillage control system is designed. The automatic control of the depth of ploughing is realized by the electronic control and hydraulic technology, and the PID control algorithm is added to the control algorithm to optimize the control. Compared with the traditional tillage depth regulation mode, the system uses the dual tilt angle sensor to detect the depth of the tillage, set the tillage depth of the potentiometer through the depth of the tillage, and control the chip to collect the target ploughing depth signal and the real-time feedback signal of the sensor. The error signal is generated by comparison, and the error signal becomes the control signal after the controller calculation and processing, and the control electricity is controlled. The changing direction and opening size of the magnetic proportional directional valve realize the control of the hydraulic system, thus achieving the purpose of controlling the depth of the tillage. In the electronic control system, the AT89S52 is used as the processing chip, the corresponding module circuit is designed on the hardware structure, and the interface circuit is designed with the inclination sensor and the execution valve, and the signal acquisition and valve control are realized. The output of the PWM signal. The software system is developed based on the C language. The main program, the acquisition program, the IIC communication program and the PWM output program are mainly written. The function of the software system is to receive the real-time signal of the potentiometer and the tilt sensor for receiving the depth of the tillage. After the conversion operation, the selected output PWM wave has been converted to the analog signal after the RC filter processing. In the design part of the hydraulic system, the hydraulic system and the hydraulic driven rotary tillage loop are designed according to the working requirements of the cultivation depth regulation. The power of the working of the rotary tillage parts is calculated and the power matching hydraulic system is designed. The working pressure is 16MPa and the model of the oil pump is PFE-3 1036, the model of the hydraulic motor is 1JMD-40. On this basis, the design and selection of the components and the hydraulic pipes of the hydraulic system are completed. The dynamic response of the control system has an important influence on the immediacy of the ploughing depth regulation. In order to study the dynamic response characteristics of the electro-hydraulic control system, this paper uses the Sim Hydraulic model in the Simulink. The closed loop electro-hydraulic control system model is built by the dynamic simulation of the block to the tillage depth control system. According to the parameters of each component and module, the parameters of the simulation system are set, and the simulation system is simulated. The simulation conditions are divided into two conditions, which are to adjust the plough depth from 0 to 100mm, and to decrease from 175mm to 100mm. The input step signal means the action of setting up the depth of the tillage, using the sensor model in the SIMHydraulic to replace the actual sensor to detect the relevant data. The damping module is used to replace the reaction force of the cantilever to the hydraulic rod. The friction force, the hydraulic resistance and the mechanical inertia of the piston and the cylinder body, the piston rod and the cylinder head are expressed by the friction module. The simulation results show that the tillage depth control system has about 13% deep overshoot in the tillage control system, and the system needs about 5.0s oscillation time to control the tillage depth to reach the steady state. In the error signal processing, the integral separation PID control algorithm is used to optimize the dynamic response characteristics of the tillage depth control system. The integral threshold is set to be epsilon =0.08. When the error value is large, the integral action is cancelled and the adjusting speed is accelerated. The integral action is added to the value of the depth of the ploughing to improve the control precision. The experience test is adopted. In the case of Kp=0.08, Ki=1.2 and Kd=0.001, the system has better dynamic response. Compared with the simulation results without PID control algorithm, the system has almost eliminated the deep overshoot of the system. At the same time, the response time is shortened to about 1.4s, and the dynamic response of the control system of the ploughing depth control system is better. On the basis of this, the dynamic response of the PID is achieved. The tillage depth stability test was carried out by the cultivator. The variation coefficient of the tillage depth was 6.05% and 3.54% respectively when the cultivator was working under the presupposition tillage condition of 10cm and 16cm, which reached the agronomic requirements stipulated by the rotary tillage operation.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S222

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