Research And Design On Fruit Picking Robot Control System

Fruit picking robot is an integrated system, which can implement environmental awareness, dynamic decision-making and planning, movement control. Researching on the key technology of fruit picking robot can not only meet the demand of the market and reduce labor intensity, but also keep up with the pace of the new developing agricultural technology in the modern world and improve economic efficiency.At the same time, it is important for improving Chinese agricultural modernization. Our study plan is supported by the National High Technology Research and Development Program of China (863Program, No.2006AA10Z254). This work do some research on a prototype of the fruit picking robot, such as modeling of the picking robot, control method, real-time obstacle avoidance algorithm and the design of Control system software and hardware. The main work is as follows:1. Kinematics simulation modeling of the fruit picking robot. Through analysing the robot's mechanical structure, we have finished building the camera model and the mobile platform model.In the meantime, we have adopted the geometric structure algorithm to establish forward and inverse kinematics equations of the fruit picking robot. Thus we have laid basic theoretical foundation for the robot control.2. We have conducted research on control methods of the picking robot based on the characteristics of the robot's mechanical structure. Meanwhile, We have designed an image-based visual servoing controller and adopted controlling algorithms of small step approximation to guide the robot's end-effector to orientate the target fruit exactly. We have designed a fuzzy-PID controller according to the nonlinear and strong coupling characteristics of the servo control system and put it in use to the servo motion control of the robot's manipulator joints.3. Design of picking robot's control system.In terms of openess and real-time principle, we finished building the open software and hardware platform for the fruit picking robot's control systems. In the hardware design, we have focused mostly on the selection for the following key modules that compose the control system, such as industrial personal computer, serial communication interface converter, joint drive motor.We have selected sensor in conformity with its working characteristics and designed corresponding signal acquisition circuit ,thereby equipping it with such abilities as image acquisition, target localization, perception of the obstacles, position limiting protection and so on.As a result, the robot get better in intelligence and perception of the environmental information on the external.As for the software design, mainly from the perspective of real-time, we applied the technology of VFW to achieve real-time image acquisition and worked out a real-time obstacle avoidance search algorithm.On the basis of VC ++ language, we utilized multi-threading technology to accomplish the whole control system software, which is capable of serial communications, image capture and target recognition, real-time obstacle avoidance control and limit protection.4. Carry on experiments with the fruit picking robot platform in both laboratory and orchard environment. In the laboratory environment, the picking robot can finish the work automatically and continuously with a relatively high rate of successfully picking.Whereas, it could only preliminary complete picking operations in the complex orchard environment and showed general effect with a certain gap from the expected outcomes. These results demonstrate that the fruit picking robot's control system developed in our subject has relatively good reliability and a certain degree of adaptability. However, the picking robot's control system is necessary to be further optimized if we want to achieve the goal of continuous harvesting operations in orchard environment.