Research On Tomato Harvesting Dual-arm Robot And Its Control System

Most of the greenhouse high-value crops are still harvested by human labor nowadays.However labor costs would rise with China's population aging fast.It is urgent to find a new automatic harvesting solution.The robot technology has proved its great effect in the field of industrial automation,and it would do the same in the field of agriculture.This project focus on the automatic harvesting of the greenhouse fresh tomato and has designed a tomato harvesting dual-arm robot.The research results covered by this article mainly includes the following aspects.1)For the mechanism design problem considering constraints on workspace,size and loading,completed the design of the dual-arm robot's mechanical structure and the robot's virtual assembly using SolidWorks.The strength of the key structures got checked by finite element technique.The whole coordinate frames were described using D-H parameters.The forward kinematics and the inverse kinematics of the 5R serial robot arm were analyzed.During solving the inverse kinematics,knowledge about parameter equation of the space circle and extreme value point of the function was used.2)For the real-time synchronous control problem of the serial robot arm,used a multi-axes synchronous servo control system based on EtherCAT bus,while the end-effector was controlled by a single chip connected using serial port.Then solutions were designed to improve the repeated positioning accuracy and the absolute positioning accuracy of the robot arm.Machine vision was used to get data to rectify the offsets in the nominal model,and eventually the positioning accuracy was improved.3)For the problem that a multitasking program structure for an agricultural robot with many functions would be too complex to complete,built the upper computer software system of the robot based on the robot operating system.Software included functions such as showing the 3D virtual model,machine vision and motion plan of the robot arm.Proposed a new method to get the accurate fruit pose which combined the binocular camera and two cameras placed on two arms.Then wrote slave computer programs for the multi-axis controller and the end-effector controller.Program for the multi-axis controller used the structure of state machine,and program for the end-effector controller used timer to realize time-shared control.