Development of a Vision Guided Robot Manipulator for Packing Horticultural Produce

Abstract The use of robots in horticulture is discussed and it is concluded that industrial manipulators are not well suited to potential horticultural applications. In general they are over specified, especially with respect to accuracy and as a result, too expensive. The commercial uptake of robotic technology would be facilitated by the availability of low cost manipulators with appropriate specifications. In most cases horticultural manipulators require only modest positional accuracy of a few millimetres under the guidance of a vision system. They should be robust, tolerant to dirty and humid environments and be capable of meeting hygiene requirements. A low cost pneumatically activated manipulator incorporating flexible inflatable elements has been developed to meet this specification. The characteristics of the patented flexible actuator (trade name 'Flexator') are examined and modifications made so that they better suit this application. An experimental two degree-of-freedom manipulator has been constructed and its dynamic performance evaluated. A package consisting of a vision system, high level controller, end-effector and the new manipulator have been put together in a demonstration system. Experimentally, error has been recorded as 2·1 mm in the X coordinate and 2·0mm in the Y coordinate with standard deviations of 0·7 and 0·6mm respectively. Vision-guided packing of loose tomatoes into plastic trays of eight has been chosen as the application. This task is performed reliably in about 21s. Although 2·5% of tomatoes were not picked successfully, the system automatically recovered, resulting in all 20 trial packs being correctly filled.