播种机开沟深度控制系统的设计与室内试验

针对播种机开沟深度稳定性影响播种质量、开沟深度难以精确控制、仿形滞后等问题,该文设计了开沟深度控制系统,系统包括地表高度检测机构、四连杆仿形机构、PLC控制系统和液压系统。通过建立开沟深度数学模型,确定了开沟深度闭环控制方案,实现了开沟深度的精确和实时控制;采用补偿延迟时间的方法,实现了开沟深度的同步仿形;对系统进行了试验。试验结果表明,系统的响应时间为0.12 s;开沟器上升和下降的平均速度为78.7、102.8 mm/s;前进速度5 km/h条件下,开沟深度在30、50、70 mm时,系统理论开沟深度稳定性系数分别为90.98%、91.45%、92.32%,测量开沟深度稳定性系数分别为90.66%、91.33%、91.82%,系统测量误差≤0.54%,满足开沟深度稳定性要求。该控制系统的研究为播种机播种单体和开沟深度控制机构设计提供了参考。

Design and laboratory test of control system for depth of furrow opening

Abstract: Seeding depth is one of the indicators required by agricultural seeding technology. Seeding depth too large, too small or not consistent will cause low germination rate, slow seedling growth and other problems. It will affect late crop growth and finally reduce yield. In China, conventional tillage is widely used. But with the development of modern agricultural science and technology, the quality of soil in conventional tillage can not meet the requirements of the crop growth. Under the circumstances, conservation tillage arises in china, but the residues on surface of conservation tillage and the surface roughness is larger than conventional tillage. So working depth control is one of the keys for planter design. In order to control working depth constantly, profiling mechanism was adopted in planter for furrow opener, which was one of the most important ways to control working depth. Profiling mechanism mainly included whole profile modeling and unit profile modeling, of which whole profile modeling was simple, but the stability of its working depth was poorer. So whole profile modeling and unit profile modeling were adopted in most planter to keep working depth constantly. At present, the passive regulating mode was more used to control working depth in domestic, such as adjusting spring and parallelogram linkage. In other countries, in order to control working depth, besides the passive regulating mode, the active regulating mode was also adopted, which was controlled by electro-hydraulic technology and could realize the accurate control of working depth. Therefore, in order to improve the stability of no-till planter seeding depth, a depth of furrow opening control system was designed. The system included a surface height detection mechanism, four-connecting-rod profiling mechanism, PLC control system and hydraulic system. In the system, working depth was controlled by feedback and synchronization of profiling in real-time, the surface height by checking could reach 200 mm, and the capacity of profile modeling was 370 mm. In hydraulic system, through analyzing the work load and the speed of the system, it was determined that the rated system pressure was 10 MPa and the rated flow was 40 L/min. The average speeds of rise and fall of furrow opener were 78.7 and 102.8 mm/s, respectively. Through various tests on the depth control system, the working parameters of the control system were obtained. The system response time was 0.12 s, and working depth stability was more than 90%. In the speed of 5 km/h and working depths of 30, 50 and 70 mm, the stabilities of working depth were 90.98%, 91.45% and 92.32%, respectively, and the measurement error of the system was less than or equal to 0.54%. Therefore, it can meet the requirements of the standard on working depth stability. The research of the depth of furrow opening control system provides the reference for designing planter and understanding its furrow opening depth control mechanism.