Design of tomato fruit separation vibration generator with multi group non-circular planetary gear

Abstract: The processing tomato planting area is increasing year by year in Xinjiang, and mechanized harvesting has become an important mean of tomato harvesting. Fruit seedling separation device is one of the core working parts of processed tomato harvesting machine. At present, double eccentric block type of fruit seedling separating vibration generator is widely used. However, there are still some problems with this relatively matured technology, such as motion parameters are easily affected by load, device is easily blocked and so on, which strongly affect the performance of processing tomato harvesting machine. Some scholars proposed to apply non-circular planetary gear to the structure design of tomato fruit seedling vibration generator, but this type of tomato fruit seedling vibration generator has a problem that its transmission components load is imbalanced. To solve above problems, in this study, we put forward multiple-group non-circular planetary gear of tomato fruit seedling vibration generator. The research results published from other scholars about trajectories of separation roller and conditions of tomato harvesting vibration were used when we designed tomato fruit separation vibration generator base on multi-group non-circular planetary gear. Trigonometric function and MATLAB software were exploited to fit separate roller angular velocity and angular displacement scatter curve. Then fitting curve of angular displacement and angular velocity were obtained as well as input and output angular displacement fitting function type, which served as the objective function of tomato fruit separation vibration generator based on multi-group non-circular planetary gear. The fitting degree with no more than 0.85 of angular displacement and velocity were obtained. The OriginPro9.0 was used to obtain angular velocity and angular displacement fitting function. According to the method of theoretical mechanics and dynamics, the theoretical equation of dynamics and kinematics were established to obtain the transmission ratio and pitch-curve equation of the non-circular gear train. Non-circular gears based on three groups were designed and gear tooth profiles of non-circular gear were generated by using gear's pitch curve got from MATLAB. Then, the whole structure of fruit seedling vibration generator base on three group non-circular planetary gear was designed according to the selected type and corresponding parameters of gear train, which was mainly composed of input shaft assembly、tie rod assembly、shell and output shaft assembly. When this vibration generator working, power was input from the input shaft uniformly and transferred to the separation roller by transmission of this vibration generator. In this way, the uniform motion of input shaft was transformed into variable speed rotary motion of output shaft to drive the separation roller achieving the separation of fruit and stem seedlings. The model of vibration generator based on multi-group non-circular planetary gear was constructed, and this model was analyzed by simulating in the ADAMS at speeds of 111 revolutions per minute. The contrast figure of non-circular gear vibration generator and three groups non-circular gear vibration generator's tooth surface contact force diagram was obtained by analyzing the tooth surface contact force between the planet gear and the output shaft gear, which showed that the vibration generator possessed uniform stress, and small vibration and the correctness of the model were verified. Finally, the physical prototype of vibration generator based on multi-group non-circular planetary gear was developed, and then tomato fruit seedling separation test was conducted in the way that replacing double eccentric block vibration generator with vibration generator based on multi-group non-circular planetary gear on tomato fruit seedling separation test platform, in this test, the motion process of separating drum was tracked shot using CPL-MS70k high speed camera system, whose frame rate was set to 800. The test data were analyzed and we found that the actual motion curve of drum separation fitted better with simulation curve and objective motion curve, from which maximum error was less than 0.4 rad/s, showing that the mechanism design was reasonable. This study provides a new idea for the improvement of processing tomato fruit seedling separation device.