电动机驱动玉米气吸排种器总线控制系统设计与试验

Design and Experiment of Motor Driving Bus Control System for Corn Vacuum Seed Meter

车速对电动机驱动玉米气吸式排种器排种性能具有重要影响,为此设计了一种电动机驱动排种器CAN总线控制系统,采用CAN总线通讯的方法探究系统驱动排种器随车速的变化特性。该系统主要由人机交互设备、排种监测ECU、排种驱动ECU组成,参照ISO 11783协议,对播种机具总线系统进行了设计。以4行气吸式玉米排种器为对象,搭建试验台,对总线控制排种盘转速精度进行了试验。通过总线提取的排种盘转速闭环调控结果得出,排种盘转速位置PID控制调整过程中存在低速调节时间长、超调量大的问题。采用分段PID参数控制的方法,由试验结果将排种盘转速设定值分为低速(15～20 r/min)、中速(20～40 r/min)、高速(40～55 r/min) 3个阶段,分阶段赋予对应闭环调节参数,得出排种盘目标转速在低速阶段时平均响应时间、平均超调量分别为1. 84 s、38. 51%,与位置PID控制相比较,分别降低1. 63 s、34. 41%; 15～55 r/min时平均稳态误差绝对值为0. 97 r/min,标准差为0. 76 r/min,平均稳态误差绝对值减小0. 13 r/min。进行了总线系统落种监测精度试验,设定粒距20 cm,排种盘孔数为26个,车速4～12 km/h时,系统排种监测平均准确率为97. 53%,标准差为0. 48%。采用排种总线系统对车速影响排种器性能进行了试验,风机驱动轴转速为540 r/min,车速范围为4～8 km/h,测得风压范围为-6. 0～-5. 9 k Pa,播种合格指数平均为95. 68%,标准差为2. 29%;车速达到9 km/h时,合格指数降到90%以下,排种器漏播较严重。通过对播种总线系统车速和4行排种驱动电动机实时转速的监测,进行了车速阶跃变化播种系统响应试验,结果表明在车速4～12 km/h、2 km/h间隔递增过程中,系统对排种盘目标转速平均响应时间为2. 00 s,标准差为0. 34 s; 2 km/h间隔递减过程中,系统对排种盘目标转速平均响应时间为1. 83 s,标准差为1. 07 s,表明按照车速阶跃变化,该总线控制系统具有较好的响应性能。

The travel speed has great impact on motor driving planting performance.A motor driving planting system with CAN bus control was designed to explore the effect of travel speed on seed meter by using the method of CAN bus communication.The system mainly included an HMI,a planting monitoring ECU and a planting driving ECU,according to the ISO 11783 protocol,the planting machine bus system was designed.A four-channel air suction corn seed metering device was used as the test object,and a test platform was set up to test the bus control speed control accuracy of the seed plate.The problems of long regulation time at low speed and large overshoot in the traditional PID adjustment process were found from the bus extraction data.The piecewise PID parameter control method was adopted to optimize the control results.Based on the experimental results,the speeds of the seed plate were divided into three parts:the low rotation speed(15~20 r/min),the middle rotation speed(20~40 r/min)and the high rotation speed(40~55 r/min).In each part,the PID control set different parameter values.The optimizing system results showed that the average regulating time and the average overshoot were 1.84 s and 38.51%with 1.63 s and 34.41%decreases,respectively,at low rotation speed,when within the range of 15~55 r/min,the absolute value of steady-state error was 0.97 r/min on average,the variance was 0.76 r/min,and the absolute value of steady-state error was reduced by 0.13 r/min on average.In the monitoring planting accuracy test of the bus system,the seed space was 20 cm,the number of holes of the seed plate was 26,the travel speed was 4~12 km/h,the results showed that the average accuracy of system monitoring was 97.53%with standard deviation of 0.48%.According to the experimental results of the planting bus system performance influenced by travel speed,when the rotational speed of fan was 540 r/min and the travel speed was 4~8 km/h,the wind pressure was-6.0^-5.9 kPa and the mean qualified index of seeding was 95.68%with the standard deviation of 2.29%.When the travel speed reached 9 km/h,the qualified index dropped below 90%,and the miss-seeding index was high.The performance evaluation of planting bus system response performance influenced by a step change travel speed was done by monitoring the travel speed and four planting driving motors,when the travel speed was in the range of 4~12 km/h with an increment of 2 km/h,the average response time of the system to the speed of seed plate was 2.00 s with standard deviation of 0.34 s.When the travel speed was in the range of 4~12 km/h with a decrement of 2 km/h,the average response time of the system to the speed of seed plate was 1.83 s with standard deviation of 1.07 s,the planting bus control system had a short response time when influenced by travel speed step changing.