A Hybrid Robotic System for Harvesting Heavy Produce

Certain agricultural work requires a very stiff robot arm to reduce vibration and damage to products. However, the structure of conventional articulated robots tends to be too weak to manipulate heavy objects, such as melons and watermelons. The Stewart platform is a typical parallel robotic mechanism with very high stiffness, but this advantage is balanced by a small workspace and large installation space. This research proposes a new type of agricultural robot arm constructed by combining a parallel and a serial mechanism. This robot consists of a hybrid manipulator, a robot controller and an end-effector. The hybrid manipulator has serial joints with two extra degrees of freedom, making the workspace wider. It was also designed to harvest heavy fruits such as melons, even from behind obstacles such as leaves or tree branches. Position control results of the developed hybrid robot showed that it could be controlled within a ±1 mm and ±0.2° range of error.