基于弹齿轨迹的滚筒式牧草捡拾器遗漏率及工作参数优化

该文基于弹齿的运动轨迹,建立了遗漏率理论模型并进行了仿真,利用MATLAB编程实现捡拾器凸轮机构的参数化设计。对凸轮轨道为正弦加速度规律运动的捡拾器进行遗漏率理论分析,并利用高速摄像系统进行试验,理论与试验的漏捡区高度线性拟合调整R~2为0.998 8,漏捡区面积线性拟合调整R~2为0.960 4。在捡拾器机器前进速度4~6 km/h,滚筒转速40~90 r/min时,应用遗漏率理论模型进行中心组合响应曲面法分析和目标优化,得到的理论工作参数最佳组合为前进速度4.0 km/h,滚筒转速54.299 r/min,此时,漏捡区高度0.796 cm,漏捡区面积6.369 cm~2。在前进速度4 km/h和滚筒转速55 r/min的条件下进行不同含水率牧草的捡拾试验,遗漏率均低于国家标准要求的25%。该研究为捡拾器设计提供了理论基础,且能更好地指导实际生产。

Leakage rate and optimization of working parameters for cylinder pickup collector based on spring-finger trajectory

Abstract: The leakage rate is a very important pickup performance indexer of a grass collector machine. It is critical to determine mechanical structural and performance parameters of a grass collector so that its leakage rate is lower than national standard. The overlap area of two adjacent bullet teeth trajectory profile is called pickup leakage area. A lower leakage rate requires a smaller pickup leakage area and lower height of pickup leakage area. Leakage rate of a collector could be well represented by total pickup leakage area and height of pickup leakage area. In this study, a program named "Parametric design system of spring-finger cylinder pickup collector" was developed using MATLAB 2016b based on kinematics analysis of spring-finger cylinder pickup collector. An innovated spring-finger cylinder pickup collector was designed based on sinusoid accelerated cam mechanism at Inner Mongolia Agricultural University. In order to optimize and minimize leakage rate of this spring-finger cylinder pickup collector machine, a simulation model was established using its mechanical structural and performance parameters. This mathematical simulation model contained five kinds of follower movement law, it provided spring-finger teeth to teeth trajectory profile, spring-finger teeth speed profile and spring-finger teeth acceleration profile. These data were used to check mechanical structural parameters and boundary condition of the spring-finger cylinder pickup collector; and they were also used to calculate total pickup leakage area and height of pickup leakage area of the collector. Central composite response surface method test was taken on the new type of the pickup collector test bench developed by Inner Mongolia Agricultural University. Under conditions of forward speed of 4 - 6 km/h and cylinder rotation speed of 40 - 90r/min, high - speed camera system was used to track the moving trajectory of the bullet teeth end, the end displacement fitting curves of spring finger were got by using three-time sample insertion method for interpolation, experimental leakage area height and leakage area were calculated. The theoretical leakage area height and leakage area were analyzed by the program. Test results are basically consistent with the theoretical results of the program. Correctness of simulation mathematical model of the program is verified. The study showed the correlation coefficient of height of pickup leakage area between theoretical model and tested result was R2=0.960 4; the correlation coefficient of pickup leakage area between theoretical model and tested result was R2=0.998 8. Response surface based analysis and test result showed that when forward speed was set as constant, the leakage rate decreased if the drum rotation speed was increased; and when drum speed was set as constant, the leakage rate increased if the forward speed was increased. After increasing the boundary condition of collector, the leakage rate optimization showed that the lowest leakage rate happened when moving forward speed was 4.0 km/h and a drum rotating speed was 54.299 r/min, at which point that the leakage area height was 0.796 cm, and total leakage area was 6.369 cm2. The tests were conducted for Alfalfa grass with different moisture content, when the forward speed was 4.0 km/h and drum rotation speed was 55 r/min, leakage area rate of the spring-finger cylinder pickup collector were all lower than 25% national standard.