Research On End-effector Of Apple Picking Based On Flexible Pneumatic Actuator FPA

Apple is one of the most popular fruits, the planting area and yield of apple is increasing year by year. But the manual picking of the operation, the long period of operation and big labor intensity restrict the apple industrialization greatly. With the aging population and agricultural workforce reduction, it is necessary to develop apple harvesting robot to execute the process of harvesting, instead of human. However, due to apple's own characteristics and forms of restrictions, the roboticized level of picking apples at home and abroad is still very low. In order to resolve the problem, a kind of end-effector which is suitable for apple-picking is proposed in this thesis.As final executing manipulator for robot to interact with outside environment, the end-effector has been paid much attention. Besides the traditional rigid driving and executing devices, the new type flexible pneumatic actuator FPA, developed by our researching group, is a kind of actuator as well as manipulator. Different joints can be designed using FPA. Because of the high deformability of rubber, the bent joint in the load direction will produce distortion. In this thesis, the lateral stiffness is enhanced based on the original bending joint structure. The end-effector formed by the three bending joints, not only maintains certain flexibility, but also takes into account the stiffness. Inflating compressed gas into the FPA achieves the end-effector movement. The whole work is as follows:(1) Researching the basic mechanical characteristics of the apple, using universal electronic testing machine, the completion of apple compression and apple stems shear test, discussed the characteristics of their relationship;(2) A new type of bending joints was developed based on flexible pneumatic actuator. The relationship between pressure and bending capacity was analyzed. The experimental platform was built to complete the joint angle bending and output force experiments, whose results show that experimental curve matches with the theoretical curve well;(3) A new type of end-effector was developed based on flexible pneumatic actuator. The grasping apple's mathematical model of end-effector was established. And the grasping apple model was compared and analyzed.(4) The grinding, rotary shearing and linear cutting fruit-branch separating models are analyzed and the experimental results show that the rotary shearing model has virtues of simply structure and easy to be controlled. The rotary shearing model was taken as the fruit-branch separating structure for the end-effector.(5) Building experimental platforms for the end-effector. The force of the end-effector is quite strong, and the actuator can grasp apples perfectly and flexibly. Designing the integrated control system, and analyzing the controlling process of the entire apple picking robot.In this dissertation, the end-effector and its controlling system was developed based on flexible pneumatic actuator, bending joint and rotary shearing fruit-branch separating structure. Experiments show that the end-effector can be a good completion of apple's grasping and fruit-branch separating task.