作 者：
高原源;王秀;杨硕;赵学观;窦汉杰;赵春江
关键词：
精密播种;播种深度;下压力;监控;气动式;传感器
摘 要：
为保证播种机适宜的压实力和稳定的播种深度,提高种子出苗品质,促进后期生长发育,针对现有下压力测量方式灵敏度低、且缺少快速有效精准控制模型的问题,提出一种基于气囊压力和仿形四连杆倾角的播种下压力控制方法.采用一阶低通滤波的轴销传感器下压力监测方式,设计了气动式下压力监控系统,包括气压驱动装置、倾角传感器、数据采集控制卡及上位机控制软件等,轴销传感器和倾角传感器分别实时测量限深轮对地下压力和仿形四连杆倾角,并反馈给上位机,经过模型计算后控制数据采集控制卡发送信号调节气压驱动装置,保证限深轮对地下压力在设定范围内.室内建模和响应测试结果表明,在不同气囊压力和四连杆倾角设置下,建立的播种下压力控制模型校正决定系数为0. 974 3,均方根误差为49. 41 N,试验验证模型预测均方根误差为39. 51 N,对播种下压力具有较好的控制准确性;在0. 1~0. 6 MPa压力设定下,气囊充气阶跃响应平均超调量3. 83%,平均稳态误差0. 005 2 MPa,平均调节时间0. 42 s,满足作业需求.田间播种深度控制性能试验结果表明,在6~10 km/h作业速度范围内,气动式下压力控制系统对播种深度具有稳定可靠的控制性能,系统播种深度合格率不小于98. 91%,特别是在10 km/h高速作业时,播种深度标准差为3. 46 mm,变异系数为6. 97%,显著优于被动弹簧式下压力调节方式.
作 者：
GAO Yuanyuan;WANG Xiu;YANG Shuo;ZHAO Xueguan;DOU Hanjie;ZHAO Chunjiang;College of Information and Electrical Engineering,China Agricultural University;Beijing Research Center of Intelligent Equipment for Agriculture;National Engineering Research Center for Information Technology in Agriculture;
单 位：
GAO Yuanyuan%WANG Xiu%YANG Shuo%ZHAO Xueguan%DOU Hanjie%ZHAO Chunjiang%College of Information and Electrical Engineering,China Agricultural University%Beijing Research Center of Intelligent Equipment for Agriculture%National Engineering Research Center for Information Technology in Agriculture
关键词：
precision planting;;sowing depth;;downforce;;monitoring and control;;pneumatic;;sensor
摘 要：
An adequate and consistent depth positioning of seeds is vital for uniform crop germination to achieve the optimum yield of agricultural crops. However,the downforce variations from the row units will affect the stability of sowing depth because of the irregular and inconsistent soil resistance of the seedbed.Therefore,controlling the seeding downforce to compensate for changes in soil resistance can improve seeding quality. At present,most of the downforce control methods are driven by hydraulic pressure,which requires a high level for the tractor hydraulic system. In addition,previous studies have found that the existing downforce detection methods have problems of low sensitivity and lack of fast and precise control model,which can not achieve real-time accurate downforce control. To solve the problems,a new downforce control method based on the air-spring pressure and the four-link angle was proposed,and a corresponding pneumatic downforce control system was designed. The system consisted of pneumatic driving device,tilt sensor for profiling mechanism,pressure sensor for air-spring,downforce sensor for gauge-wheel,date acquisition and control module,and an upper computer. The pneumatic driving device,which mainly included air-spring,electric-gas proportional valve,air pump,gas tank and oil separation filter,was used to provide the necessary downforce on the profiling mechanism to ensure the optimum and consistency of sowing depth. The downforce sensor and tilt sensor were applied to generate downforce and the four-link angle signals in real time. After first-order low-pass filtering and model calculation by the upper computer,these actual downforce was displayed on the interface programmed by LabVIEW and the control signals were sent to the electrical-gas proportional valve through the date acquisition and control module based on RS485 communication. A modeling experiment was conducted to establish the relationship between the sensor values and the actual downforce under different air-spring pressures and four-link angles. Regression analysis showed that the model fitted the best,being 0. 974 3 in adjusted determination coefficient( R(Adj)~2_) and 49. 41 N in root mean square error( RMSE). The verification test showed that the predicted root mean square error( PRMSE) was 39. 51 N,which showed that the model had better control accuracy for downforce. Further,an air-spring response test and a field test were carried out respectively to test system control performance. The results showed that the airspring inflation step response average overshoot was 3. 83%, the average steady state error was 0. 005 2 MPa,and the average adjustment time was 0. 42 s when the pressure was set in the range of0. 1 ～ 0. 6 MPa. The field tests indicated that the system had stable and reliable control performance for sowing depth in the speed range of 6 ～ 10 km/h. Within the industry standard error range of 10 mm,the qualified rate of sowing depth of the system was not less than 98. 91%. Especially when the speed of the planter was over 10 km/h,the standard deviation( SD) of sowing depth was 3. 46 mm and the coefficient of variation( CV) was 6. 97%,which was significantly better than the passive downforce control system with the SD of 6. 70 mm and the CV of 13. 07% respectively.
