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棉田回收膜杂风选机自动清堵系统设计与试验

Design and test of automatic plugging control system for membrane miscellaneous winnowing machine

  • 摘要: 针对滚筒筛式膜杂风选机筛孔堵塞后人工清理劳动成本高、效率低等问题,该研究提出了一种多区域对列清堵方法,搭建了多区域对列清堵系统,实现自动清堵作业。通过对YOLOv8s模型剪枝得到YOLOv8s-prune模型,实现筛孔的识别与定位,结合YOLOv8s-prune识别堵塞筛孔坐标信息,利用单片机(STM32F103C8T6)控制运动模块完成喷头与堵塞筛孔的对列定位。识别试验结果表明:相较于其他目标检测算法,YOLOv8s-prune模型保持高精度的同时,模型参数量、计算量、模型大小均明显减少,在测试集上准确率P、召回率R和平均精确度mAP0.5均大于98%,在筛分环境下堵塞筛孔的平均识别率大于94%;对列定位试验结果表明:定位偏差绝对值最大为25.6 mm,最小为7 mm,合格率大于94%,满足循环作业需求;整机正交试验表明:各因素对清堵率的影响次序为:清堵风速、作业距离和清堵角度,圆整后的最优参数组合为:清堵风速5 m/s,清堵角度11°,作业距离120 mm,该参数下的验证试验得到平均清堵率为90.56%,满足膜杂风选机的作业需求。研究结果可为膜杂风选机自动清堵系统的研发和作业参数设置提供参考。

     

    Abstract: A winnowing machine has been used to screen the residual film and impurities for resource utilization as post cotton harvesting. However, the manual cleaning hinders its further development after screen hole clogging, due mainly to the high labor costs and low efficiency. In this study, a multi-region dual-column unclogging system was proposed to realize the automatic cleaning operations. Firstly, the YOLOv8s model was selected for the identification after the comparative experiments on the YOLO series. Then, the pruning experiments were conducted to determine a pruning rate of 40% followed by 200 epochs of fine-tuning. The YOLOv8s-prune model was also established after verification. Finally, the identification performance of the YOLOv8s-prune was evaluated to compare with the various object detection. The results showed that the YOLOv8s model achieved the optimal performance on the validation set: precision (P) of 99.4%, recall (R) of 99.2%, mAP@0.5 of 99.5%, mAP@0.5-0.95 of 94.7%, and a model size of 21.4 MB. After that, the YOLOv8s-prune model was achieved in a precision (P) of 99.3%, recall (R) of 99%, mAP@0.5 of 99.5%, mAP@0.5-0.95 of 92.1%, and a model size of 10.9 MB. There was a decrease of 0.1, 0.2, 0, and 2.6 percentage points, respectively, while the model size was reduced by 50%, compared with the YOLOv8s before optimization. The YOLOv8s-prune model significantly reduced the number of parameters, computational load, and model size, compared with the rest object detection. On the test set, it was achieved in a precision (P) of 98.9%, a recall (R) of 99%, and mAP@0.5 of 99.4%. The coordinate information was also identified by YOLOv8s-prune. An identification control system was constructed to take a microcontroller (STM32F103C8T6) as the controller. The coordinate information was also divided into four intervals corresponding to four nozzles. The motion module traveled 360 mm per cycle was realized in the queue-based positioning between the nozzles and screen holes. Positional accuracy compensation was implemented for the motion module, according to the difference between the identified X-axis coordinate value of the leftmost screen hole and its actual coordinate value. The performance tests showed that the average recognition rate of the model was 98.3% within 0-10 min, 95.4% within 10-20 min, and 92.7% within 20-30 min, respectively, during sieving operations. The average recognition rate also exceeded 94% for the screen holes. The queue positioning test indicated that the absolute positioning deviation of the motion module ranged from a maximum of 25.6 mm to a minimum of 7 mm, with a qualification rate exceeding 94%, thus fully meeting the requirements for the cyclic operations. Orthogonal experiments on the whole machine revealed that the influencing factors on the unblocking rate were ranked in the descending order of: unblocking wind speed, operating distance, and unblocking angle. The maximum unblocking rate of 93.535% was achieved under the optimal conditions. Furthermore, the optimal combination of the rounded parameter was: unblocking wind speed of 5 m/s, unblocking angle of 11°, and operating distance of 120 mm. The average unblocking rate was 90.56% with an error of 2.975 percentage points, compared with the theoretical prediction, thus meeting the operational requirements of the film residue winnower. The findings can also provide a strong reference to develop the automatic unblocking for the film residue winnowers.

     

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