科研之友
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摘要
The vacuum sucking and pulling operation is being increasingly employed for isolating a target fruit from other fruits of the same cluster, performing initial attachment of the end-effector to the target fruit, and preventing the fruit's movement during the cutting operation in robotic harvesting. Studies on the mechanical interaction between the suction pad and the fruit and of the corresponding response of the fruit-stem system are essential for optimizing control strategies for this operation. However, no study has thus far been conducted on these basic rules. We therefore performed mechanical and kinematic modeling of the vacuum sucking and pulling of tomato fruits on the basis of the physical and mechanical properties of both the fruit-stem system and the suction pad, and established the relation among the vacuum suction, motion of the suction pad, and response of the fruit-stem system to the sucking effect. The obtained results indicated that the tensile force and required degree of vacuum are related to the physical and mechanical properties of the fruit-stem system and the suction pad. A difference exists between the movement distances of the fruit and the suction pad that is attributed to the deformation of the suction pad, and the permissible movement distance of the fruit is decided by both geometrical and mechanical factors. Furthermore, a much higher degree of vacuum is necessary in the initial phase of high-speed fruit pulling with a suction pad. The modeling and findings of this study are valuable for both the optimal selection of the suction pad and the optimization of control strategies for realizing a precise, high-speed, and energy-saving operation.
