Abstract
With the development of agricultural science and technology，the utilization of crop straw has become more diversified，and its demand has also increased. This paper aims to solve the disadvantages of small round baler in hills and mountainous areas，such as easy scattering of bales，unadjustable number of net layers and low degree of automation. The net-wrapping device was modularized，including the design of the net feeding mechanism，the net cutting mechanism，the detection mechanism and the control circuit，and the mechanical analysis of the net feeding mechanism was carried out. The operation parameters of the device are detected by the detection device，and send to corresponding execution instructions to the feeding mechanism and cutting mechanism after processing by the controller，thus realizing the automatic operation of feeding，winding and cutting，and realizing the adjustable number of winding layers. When the net is wrapped，the friction torque limit component exerts tension on the net，so that the net is more tightly wound，the mechanical analysis found that the net tension depends on the compression spring elasticity，and the corresponding adjustment method is provided. The performance test results show that the device has stable performance and reliable operation. It can automatically wrap the hay bale of Φ 500 mm×700 mm. The wire net covers the side of the bale without leakage and entangling. When the number of layers is 3，the success rate is 95% and the anti-fall rate is 83.3%. When the number of layers is 4，the success rate of wrapping is 100%，and the anti-fall rate is 90%. When the number of net layers is 5，the success rate of net-wrapping and the anti-fall rate of bale are 100%. This paper designed a small automatic net-wrapping mechanism for small round baler in hills and mountains areas，the test verified that the performance of the machine is stable and reliable，meet the design requirements. When the number of layers is 3，the cost performance of flat operation is the highest，and when the operation is hilly and mountainonous areas，it needs to be adjusted to 4-5 layers to the slope of the operation.
