Abstract:In view of the development of cotton topping mechanization, it was found that in addition to cutting off the top branch, the highest lateral branch should also be cut off. Although the highest lateral branch will also produce cotton boll, the cotton boll bearing capacity is far lower than that of the lower lateral branch. The topping machine which can cut off the top branch and the highest lateral branch at the same time was designed by some scholars, but the auto-follow row problem was involved, which may result in the highest lateral branch being missed or over hit. Machine-harvested cotton planting patterns were combined, a set of auto-follow row device of cotton topping machine was designed by using sensor technology, motor control technology and PLC control technology. The device was mainly composed of testing mechanism, auto-follow row mechanism, motor control system, electronic control system and control software. RecurDyn software was used to simulate the motion of the testing organization, explore the law of motion, and provide a theoretical basis for the selection of angle sensor. The deviation of cotton plant was obtained by angle sensor, and the corresponding relationship between the rotation angle of detection rod and the stepping and rotation direction of stepper motor were established. The accurate topping of deviation cotton plant was realized by controlling the stepping and rotation direction of stepper motor. In order to improve the driver’s straightness, the control system was monitored in real time through the human machine interface. In order to avoid the disturbance of lateral branches, the position of the main stem was obtained by comparing the position information of the low lateral branches on both sides;for the case of single low side branch, the error can be ignored by field measurement. It was showed that the average deviation of the auto-follow row was reduced by 8.08cm, 56.62% and the rate of not auto-follow row was increased by 275% by field experiments. In the past, most of the topping machines only used the way of flat cutting to remove the top of the cotton plant, and the inhibition of the highest lateral branch was still controlled by chemical control. Therefore, only the topping machine was highly modeled. A device was designed to cut the top branch and the highest side branch at the same time. The intelligent control technology was integrated into the machine, and the auto-follow row device was designed, so the topping quality of the cotton topping machine was raised. The design had great innovation.