Design and test of double-roller clamping type cotton topping device

Topping has been one of the most important operations in cotton production. However, the existing topping machinery cannot fully meet the large-scale production in recent years, due to the low precision, high over-topping rate, and high labor intensity. Particularly, there is the serious pollution of the chemical topping agent to the environment. This study aims to design a new type of cotton topping device with double-roller clamping. Four components also consisted of the topping actuator, profiling motion mechanism, light curtain detection module, and control system. The high efficiency and precision of the cotton topping were then realized after mechanization and intelligence. The overall structure of the device and the parameters of the key components were also determined, according to the cotton fields and plants. The light curtain was combined to detect the cotton plants. The programmable logic controller (PLC) was also used to construct the accurate identification and automatic control system for the topping operation. Furthermore, the topping actuator was adopted as a double-roller clamping structure in the process of equipment design. The clamping and cutting of the cotton plant top were realized to adjust the opening and closing angle, as well as the rotational speed of the clamp. The light curtain module was used to detect the position of the cotton plant top in real time. The data was then transmitted to the control system of the topping actuator, in order to realize the precise control of the imitation height during topping. The control system took the PLC as the core. The sensors and actuators were combined to realize the automatic management in the whole process of topping operation. A series of experiments were carried out with the cotton plant tops during topping, including the cotton plant top identification, calibration compensation, and the performance of the topping actuator. The detection accuracy of the top position was significantly improved to calibrate and compensate for the light curtain module. The test results show that the average absolute value of the detected deviation was significantly reduced from 6.905 to 1.571 cm after calibration and compensation. It infers that the light curtain shared high accuracy and reliability in the identification of the cotton plant top. The topping performance test of the topping actuator demonstrated that there were great influences on the rotational speed of the clamping mechanism, the opening and closing angle of the gripper, and the nature of the material. A field test was conducted to further optimize the performance of the device. A single- and multi-factor optimization was carried out, taking the material nature, the rotational speed of the clamping mechanism, and the opening and closing angle of the gripper as the test factors, and the topping rate and over-topping rate as the evaluation indexes. An optimal combination of parameters was finally identified to determine the significance of the influence of each factor on the cotton topping performance. The average cotton topping and over-topping rates were 80.22% and 25.78%, respectively, when the machine was operated at the forward speed of 0.4 m/s, the rotational speed of the clamping mechanism of 60 r/min, and the opening and closing angle of the gripper of 85°. The better performance was achieved in the topping machinery. The cotton topping device with the double-roller clamping also improved the topping accuracy for a less over-topping rate.