Design and experiment of a human-machine cooperative Chinese wolfberry harvester

Against the background of large-scale and high-quality development of the Chinese wolfberry industry, vibration-based mechanized harvesting methods still face challenges in achieving both low-damage and precise harvesting of fresh wolfberries in the short term. Human-machine collaborative harvesting provides a feasible approach to improving the adaptability of mechanized fresh wolfberry harvesting under current conditions. To overcome the problems of inclined trunks, ground-hugging fruiting branches, and complex field environments in traditional wolfberry cultivation, a human-machine collaborative wolfberry harvester was developed to address the issues of insufficient field trafficability, low fruit-catching efficiency, and high fruit damage rate. The bilateral fruit-catching devices were designed with adjustable width and height to adapt to field conditions and improve inter-row operational performance. The adjustable width enabled the catching devices to close around the trunk center, thereby reducing fruit loss during catching. Collision kinematics analysis and simulation were conducted considering fruit falling height, catching plate inclination angle, and cushioning material selection. Under the constraint of non-destructive fruit catching, a flexible catching plate was designed to achieve low-damage fruit collection. Furthermore, the conveying and pneumatic separation mechanisms were optimized to establish an integrated “catching-conveying-separation” technology scheme for fruit collection and impurity removal. A portable vibration harvesting device was developed, and a spring-balanced auxiliary suspension structure was adopted to reduce operator holding load and improve human-machine collaborative operation comfort. Finite element analysis was performed to verify the strength and stiffness of the machine frame structure, and field performance tests were conducted to evaluate the travelling stability and harvesting performance of the prototype. The results showed that the prototype met the design requirements under sandy loam and soft-ground conditions, achieving stable travelling performance and completing operations such as in-situ turning. Under typical operating conditions, the fruit damage rate during harvesting was approximately 2.27%, and the actual damage rate after 24 h storage was 4.07%. The impurity removal rate of the pneumatic separation device reached 97.5%, with a fruit loss rate of 0.3% during separation. In conclusion, the developed human-machine collaborative wolfberry harvester can meet the harvesting requirements of fresh wolfberries and provide an effective solution for alleviating labor shortages.