Design Of Distant-close View Vision System For Strawberry Picking Robot

The research of picking robots to assist or replace artificial picking is not only an important way to solve the problems of labor intensity,low efficiency,and high cost for picking fresh fruits and vegetables,but also a research hot spot in the field of smart agricultural machinery.China is a large country for the cultivation and consumption of fresh strawberries.Its relatively standardized cultivation mode and operating environment provide favorable conditions for automated picking.The postures or slender handles are not same for different strawberries.It is difficult to accurately identify the position of picking and cutting points by using long-distance image information.This paper studied the combination of remote and near-view positioning methods and devices,at the same time,made the innovative design and applied research of end-effector and picking visual positioning system.The main work completed and conclusions are as follows:(1)To reduce the damage to strawberry fruit and plants during strawberry harvesting and collection,a single-acting,dual-clip type strawberry picking end effector was designed.The end effector sheared and clamped the strawberry stem with power source from the cylinder.Through the experimental study on the mechanical parameters of the strawberry fruit and stalks of the "Christmas Red" variety elevated,the design parameters of the end effector were obtained and a prototype machine was manufactured.The end effector had a simple structure and small size.(2)To improve the positioning accuracy of strawberry picking,this paper proposed a method of combination of far-and-close perspectives for strawberry picking and established a visual positioning system for strawberry picking robot.The system included a long-range positioning binocular vision system and a second close-range fine-tuning vision.Based on this,combined with the actual planting environment of strawberry under elevated cultivation,the design of the structural parameters of the binocular vision system and the close-range fine-tuned vision system were respectively completed.In order to improve the positioning accuracy of strawberry picking process,this paper proposed a positioning method of combination of far-and-near views,and a visual positioning system of strawberry picking robot was built.The system included a long-range positioning binocular vision system and second-time close-range fine-tuning visual system.On this basis,the structural parameters of the binocular vision system and the close-range fine-tuning vision system were respectively designed in conjunction with the cultivation environment of the elevated cultivation strawberry.The spatial imaging method of the visual positioning system is further analyzed,and the method of obtaining the spatial point three-dimensional coordinate expression from the spatial imaging coordinate equation is specified.(3)To obtain the angles of the joints of the manipulator after fine-tuning of the close-range,and realize the combination of far-and-close views,the camera was calibrated separately,and the camera internal and external parameters were obtained;the remote camera and close-range camera were respectively obtained by calibrating the two sets of different eye hands in the far and near eyes.The conversion relationship between the camera coordinate system and the robot coordinate system and the relationship between the adjacent links of the VS-6556 GM manipulator was established using the DH method,combined with the end-effector integration parameters,the adjusting angles of the arm base and the arm are obtained,and the close-range compensation positioning is realized,and finally the coordinates of the picking point are obtained.(4)To evaluate the long-range and short-range combination positioning accuracy and the success rate of picking the end-effector,a prototype of the robot was selected based on the tomato picking robot,and the remote and near-view combined positioning system and the structural parameters of the end-effector were used to assemble the strawberry picking robot test prototype.Elevated "Christmas red" varieties of strawberries were tested in the greenhouse.The test results showed that the average error of the far-and-close combination positioning in the X-Y plane was 3.43 mm,and the average error in the space was 4.82 mm.The end effector picked on the strawberry after positioning,the success rate was 95%.The test results verified that the designed strawberry picking end effector and the remote-close-view combination visual positioning system can satisfy the picking operation of the "Christmas red" strawberry which was elevated.It accords with the accuracy of the strawberry picking operation and the quality requirements of the picking.