| Ultrasonic detection technology is one of the most frequently used methods of workpiece defect detection in modern industry.In recent years,robot technology in intelligence has a fast advancement.Hence,the use of ultrasonic detection robot for automatic detection has become the mainstream trend.The contact force between the end detection probe and the workpiece is particularly critical to the whole operation when the robot is in contact with the workpiece.This paper takes ROKAE XB7 robot as the main research object and combines the current impedance control method to design a force/position control system of ultrasonic detection robot with high force tracking accuracy,strong stability and good real-time performance.The main research work is as follows:Firstly,the kinematics of the robot is studied.The kinematics model of XB7 robot is established by the improved D-H parameter method.The forward kinematics equation of the robot is deduced by the transformation relationship between the adjacent links.The workspace range of the robot is analyzed by Monte Carlo method.To solve the problems of complex design and unsatisfactory accuracy of the inverse solution algorithm for 6R robot,an analytical inverse solution optimization algorithm based on the separation of position and attitude is proposed.The simulation results show that the improved algorithm not only has higher solving accuracy,but also greatly simplifies the solving process and improves the operation efficiency compared with the existing analytic optimization algorithm.Based on the research results of kinematics,MATLAB software platform is used to design an intuitive and convenient human-computer interaction interface.Secondly,the research on robot manpower/position control technology is carried out.The principle of impedance control technology and three common impedance models are introduced.The influence of different impedance parameters on the performance of the control system is studied by single variable method.The application of impedance control in the axial direction of the robot end is analyzed.The working principles of force-based impedance control and position-based impedance control are summarized,and the two methods are compared from multiple angles.The working process of ultrasonic inspection robot is analyzed.Based on the conventional impedance control technology,the manpower/position control system of ultrasonic inspection machine is designed based on the unique advantages of PID,and the working principle of the designed system is described in detail.Thirdly,the simulation experiment of robot manpower/position control technology is carried out.The robot CAD model is assembled by Solid Works software,and the visualization 3D physical model of the robot is generated by Simscape Multibody.The robot manpower/position control system of ultrasonic detection is built by Simulink,and the simulation environment of robot plane detection is created.Based on the MATLAB software,the contact force tracking experiment,the expected contact force change experiment and the comparison experiment are carried out.The simulation results show that the force control accuracy of the system designed in this paper is in the order of magnitude10-2,and has a good constant expected force control function.Compared with the conventional impedance control,the impact force of the robot end at the moment of contact with the environment is greatly reduced,effectively avoiding the serious consequences of excessive contact force on the robot and the measured workpiece damage.At the same time,compared with the conventional impedance control system,the force/position control system designed in this paper can significantly reduce the number of fluctuations and reduce the adjustment time by about 10%in the process of contact force tracking,which has better stability and real-time performance. |
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