双爪协同自动取投苗机构设计与试验

Design and Experiment of Dual-claw Collaborative Automatic Seedling Picking and Throwing Mechanism

摘要:

针对蔬菜自动移栽机苗盘不断移位送苗、多个取苗爪同时取苗投苗、分苗装置接苗分苗带来的工序多、结构复杂、协同控制难等问题,本文设计了一种苗盘固定不动、双模组纵横向驱动、双爪协调配合,集取苗、分苗、投苗于一体的双爪协同式自动取投苗机构。采用同步带直线模组纵向驱动左右取苗爪前后移动,正反牙滚珠丝杆模组驱动双取苗爪左右横向移动的设计方案,安装在滚珠丝杆左右滑块上的取苗爪采用主副气缸协调运动实现插夹拔取苗动作。基于取苗爪精确对穴取苗需要,对横向滚珠丝杆传动系统关键参数进行了仿真,建立滚珠丝杆进给系统动力学模型,确定了最优工作参数,对不同因素下滚珠丝杆振动特性进行了研究,确定了滚珠丝杆最优设计参数,保证了滚珠丝杆传动系统运动精度和工作性能;对双爪动态变距取投苗作业过程的运动控制方法开展了研究,以精准、可靠为目标,分析确定了取投苗最优运动路径和S形加减速运动控制策略,确定了纵向极限运动参数：速度v_max为1 m/s,加速度a_max为4 m/s^2,加加速度J_max为20 m/s^3。试验结果表明,机构取苗横向和纵向最大平均定位偏差分别为1.52、1.64 mm,投苗横向和纵向最大平均定位偏差分别为1.76、1.80 mm;当取苗速率为48株/min时,平均取苗成功率达95.83%,平均投苗成功率达97.10%,验证了该机构在运动稳定性和定位精准性方面的优越性能。

Abstract:

Aiming to address issues in vegetable automatic transplanters,such as continuous tray shifting for seedling feeding,simultaneous operation of multiple seedling claws,and the complex processes/structure and difficult coordinated control associated with separate seedling dividing devices,a dual-claw cooperative automatic seedling pick-up and planting mechanism was designed. This mechanism featured a stationary seedling tray,dual modules for longitudinal and transverse drive,and two claws working coordinately to integrate picking,dividing,and planting functions. The design employed synchronous belt linear modules to drive the left and right seedling claws longitudinally (front/back),and a ball screw module with right-hand and left-hand threads to drive the claws transversely (left/right). The seedling claws,mounted on the left and right sliders of the ball screw,utilize main and auxiliary cylinders for coordinated plugging,clamping,and pulling actions. To achieve precise cavity-aligned seedling picking,key parameters of the transverse ball screw transmission system were analyzed. A dynamic model of the ball screw feed system was established to determine optimal working parameters. The vibration characteristics under different factors were studied,finalizing the optimal design parameters to ensure motion accuracy and performance. The motion control strategy for the dual claws during dynamic pitch-varying operation was investigated. Aiming for non-damaging,precise,and reliable operation,the optimal pick/plant path and an S-curve acceleration/deceleration control strategy were determined. The longitudinal limits were set as: maximum velocity v_max=1 m/s,maximum acceleration a_max=4 m/s^2,and maximum jerk J_max=20 m/s^3. Test results indicated maximum average positioning deviations of 1.52 mm (transverse) and 1.64 mm (longitudinal) during picking,and 1.76 mm (transverse) and 1.80 mm (longitudinal) during planting. At a picking rate of 48 seedlings/minute,the success rates were 95.83% for picking and 97.10% for planting,demonstrating the mechanism's superior motion stability and positioning accuracy.