Research And Design On The Nondestructive End-effector Of Kiwifruit Harvesting Robot

China is the largest amount of kiwifruit acreage country in the world. The kiwifruit arepicked mainly by hand, which is time-consuming and labor intensity. what’s more, the labourcost is higher and higher. With the development of economy and agriculture, the robot hasbeen applied in the agricultural production and showed a good result. Fruit nondestructivepicking method is one of the key technology of kiwifruit picking robot, which is theprecondition to ensure the quality of the fruit picking. So it is important for scientific researchand production practice of the study on the nondestructive end-effector of kiwifruit.Picking end-effector is installed on the end of the manipulator to achieve requirement ofharvesting movement and adjustment accurately, contacting with fruits and vegetablesdirectly. It is the key part to pick the fruit for the harvesting robot.In this paper, the variety of “Hayward” kiwifruit was chosen as the research object, theend-effector of kiwifruit harvesting robot was studied and designed. The main contents are asfollows:(1) The physical and mechanical properties of the kiwifruit were studied. Kiwifruitphysical parameters and mechanical characteristics provide the theoretical basis for thedetermination of the design parameters of end-effector. In this paper the kiwifruit (fruitvarieties:“Hayward”) physical parameters related with the design parameters of end-effectorand the compressive properties of the fruit and the influence factors were mainly studied. Theresults showed that: the shape of fruit was approximate spherical, the sphericity was0.84; thefruit damage pressure should not be greater than15N; the amount of compression was themost significanct effect to fruit damage.(2) The design project of kiwifruit nondestructive picking end-effector was determined.Fruit grabbed method and fruit stalk broken way were the main factors to the designing ofpicking end-effector. Firstly the method of fruit picking was proposed combined withpeduncle biological characteristics and artificial way of picking; Then simplified geometricmodel of fruit picking was put forward, the range of the end-effector rotation angle wasdetermined between25°to40°, the range of fruit stalk and fruit inertia axis angle wasdetermined between47°to60°; Fruit stalk broken test was carried on to certified thefeasibility of picking method, the broken force of fruit stalk was1.38N when the angle of fruit principal axis of inertia and peduncle was60°. Finally two kinds of different end-effectordesign project were put forward, and the project2was chosen as better one.(3) The nondestructive picking end-effector of kiwifruit was designed. In order toensure the quality of the fruit picking and realize nondestructive picking, an end-effectorcombining with mechanical structure and multi-sensor was designed, and the end-effectorprototype was manufactured. C51microcontroller was chosen as the controller of theend-effector, sensing system was consisted of the pressure sensors, hall position sensor andinfrared switch sensor. The terminal control principle was used to control the step motordrives to control the motions of the end-effccor.(4) Kiwifruit picking experiment to evaluate the performance of the end-effector wasresearched. In order to study the work performance and optimize the structure of theend-effector, firstly this paper had carried on the picking test used the end-effector only. Thefinger grasping force was collected through the grasping process to evaluate the performanceof the end-effector. Then the comprehensive picking test had carried on, combined with themachine vision and end-effector protype and in view of the error produced by the machinevision to identify fruits, the end-effector the adaptability was studied. The results showed that:the success rate of adjacent fruit separating was100%, the success rate of picking was96.0%,the average picking time was22s for one fruit.