Development of a Tubing-grafting Robotic System for Fruit-bearing Vegetable Seedlings

Abstract

This research aims to develop an automatic tubing-grafting robotic system using soft rubber tubes as the grafting material that is suitable for the rootstock and scion of fruit-bearing vegetables having similar stem diameter, such as tomato, bitter melon and sweet pepper. Compared with grafting using grafting clips, the soft rubber tube approach is low-cost and minimizes water loss from the grafting wounds. Moreover, as the grafted seedlings grow, the soft rubber tubes automatically peel off from seedlings due to embrittlement and this saves recycling. The tubing-grafting robotic system is made up of six major units, namely the rootstock gripping, the rootstock cutting, the scion gripping, the scion cutting, the tube supplying, and the guiding units. A pneumatic mechanism with a programmable logic controller is used to process the sequential events needed. In the guiding unit, a pair of guiding sleeves ensures that the rootstock and scion are able to be inserted into the rubber tube smoothly even if the stem of either the rootstock or scion is deflective. The experimental results indicated that the average grafting success rate is over 93.8% and the system has a working capability of 327 seedlings per hour; the overall adhesion rate for the grafted seedlings kept in an acclimatization chamber is over 84.4%. Demonstrations were held and farmers were highly satisfied with the system performance.