Abstract
Agricultural robots, which harvest tomato, cucumber, orange and so on by their manipulators, have been studied in recent years in Japan. But the manipulators which were used in the studies have almost ordinary mechanisms, so that their operational space of manipulator could not include the range of the positions of all the fruits, and the manipulatability of the posture of manipulator might happen to be very low even when the manipulator moved to a fruit whose position was included in its operational space.
In this paper, it is reported that basic mechanism manipulator to work in tomato plant field was studied. At first, physical properties of tomato plant were studied such as phyllotaxis, positions of fruit, lengths of stems and leaves, width between ridges and so on. Secondly, operational space, measure of manipulatability, space for obstacle avoidance, redundant space and posture diversity were contrived and used as evaluation indexes in order to investigate the basic mechanisms of several manipulators with 5 to 7 degrees of freedom.
From the result of evaluation, the manipulator with 7 degrees of freedom which consisted of 2 prismatic joints and 5 rotational joints was selected. It was considered that the manipulator which was adapted to the physical properties of tomato plant could work efficiently not passing through singular points and that the mechanism greatly should depend on the training of object.
