| In recent years, the process of industrial automation is accelerating with aging population, increasing labor cost and the development of manufacturing industry. And the manufacturing industry of China is gradually transforming and upgading to intelligent manufacturing. Industrial robot has become the focus of the world’s manufacturing as one of the key technologies of intelligent manufacturing. In the "Made in China 2025" issued by the State Council, our country has put high-end CNC machine tools and robotics as one of the ten key development areas. And the application of industrial robots will have a great impact on the development of the world’s manufacturing industry, and also will reshape the world’s modern industry.As a kind of automatic welding equipments, welding robot has been widely used in automobile, ship, bridge and other fields due to its advantages such as improving the welding quality, improving production efficiency and decreasing the labor intensity of workers. Combining with robots and seam tracking technology, a small mobile welding robot system is developed to solve the problem of automatic welding of large steel structure which has the characteristics of large operation range and small space in welding. And the welding robot mechanism, sensor system, control system and welding process are also designed and optimized for the system.Firstly, according to the characteristics of large steel structure welding condition, a kind of small mobile robot mechanisms is designed by utilizing the large movement range of wheeled mobile platform and the fast response speed of manipulator. And a system for the recognition of welding seams and conditions is also designed which based on the rotating arc sensor, ultrasonic sensors and photoelectric sensors. And the control system of the small industrial computer based on PC 104 bus is also designed, which is mounted on the robot body for reducing the control cables and the volume of robot. And in the WinXP environment, the software of control system is developed with VC, which realizes the arc signal acquisition and processing, the deviation identification, the setting of welding parameters and the monitoring of the running state data in the process of welding.Secondly, the unified kinematic equation of the welding robot mechanism which has redundancy and non-holonomic is established by the motion analysis. At the same time, the unified dynamic model of the welding robot is also established by using the Routh equation and Lagrange method for the coordinated control of welding robot.In the arc signal processing, according to the structural characteristics of the original current data, a combined filtering method is proposed which includes limiting, multi-cycle mean and Kalman Filtering methods. And it can effectively suppress the noise and improve the signal to noise ratio. the characteristic harmonic method and the average current method are also proposed for the lateral and height offset identification of the fillet welding seam in the large steel structure. At the same time, the experiments are also carried out and the results shows that the test results are in line with the actual situation, and the accuracy of the welding seam recognition is in accordance with the requirements.A new intelligent control method based on sliding mode control and fuzzy control is proposed by analyzing the mathematical model and the dynamic characteristics of the wheeled mobile platform and the manipulator. And the coordination control of wheeled mobile platform and manipulator is realized by fuzzy and sliding mode controller. At the same time, the test platform of the small mobile robot is also built, and the tracking test and the factory application of different forms of welding seam are carried out. The experimental results show that the design of the small mobile robot system is feasible and reliable, and can meet the requirements of large steel structure.In the end, the droplet transfer behavior of the rotating arc GMAW welding process is analyzed theoretically, and the real-time observation of the weld pool is carried out using high-speed cameras. And the effects of different welding processes and sensor performance parameters on the droplet transfer and weld pool shape were studied, and the optimized parameters of rotating arc GMAW welding process were determined for the establishment and application of the welding process database based on the rotating arc sensor.Through the research of this subject, the small automatic welding equipment is developed, which has the independent intellectual property rights, and has improved the welding automation level of our country in the field of ships, containers, bridges and storage tanks, and has good economic benefits and applications. |
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