| The riveting and windshield installation processes in the aircraft cockpit cover manufacturing and assembly process require a large number of holes.At present,the holes are mainly made by manual drilling,but the quality and efficiency of manual drilling cannot achieve the desired results,the urgent requirement to use advanced robot automatic hole making technology to improve the quality and efficiency of hole making.However,this technology cannot be implemented because the absolute positioning accuracy of the robot in the actual hole making is insufficient to meet the accuracy requirements of the cockpit cover hole making.To solve this problem,this paper investigates the most important factor affecting the absolute positioning accuracy of the robot: the kinematic parameter errors and their compensation,in order to obtain the true values of the robot kinematic parameters and achieve the purpose of improving the absolute positioning accuracy of the robot.The details of the study are as follows.(1)The kinematics analysis and error modeling of the robot are carried out,and the kinematics model of the KUKA KR16-2 industrial robot is established by using the D-H modeling method,and the forward and inverse kinematics equations of the robot are deduced.On this basis,the improved MD-H model is used to eliminate the influence of parallel or approximately parallel axes of adjacent joints of the robot.The mathematical model of the robot’s positioning error is established by using the matrix method and the principle of differential transformation,and the parameters to be identified are determined according to the error model.(2)A joint algorithm based on genetic algorithm and quasi-Newton method is proposed to realize the identification of robot kinematic parameters.The initial population pattern of the generation algorithm between cells is established,which improves the accuracy of the algorithm parameter identification.In order to overcome the shortcomings of premature convergence of traditional genetic algorithms,the quasi-Newton operator is creatively introduced.The quasi-Newton operator performs the quasi-Newton operation on the identified parameters,which not only retains the global fast search characteristics of the genetic algorithm,but also gives full play to the local precise search characteristics of the quasi-Newton method.The joint algorithm is implemented by using MATLAB programming software.(3)The principle,structure and operation process of the robotic hole-making system are described.According to the working conditions of the developed hole-making system in the actual hole-making process,the main error sources,distribution rules and characteristics of the hole-making errors are studied,and qualitative analysis is made.The analysis shows that the main reason for the unqualified hole quality is the insufficient absolute positioning accuracy of the robot under the load state.(4)The FARO laser tracker and KUKA KR16-2 industrial robot are used to build an experimental bench to verify the correctness of the algorithm.The positioning error of the robot in the initial state,the positioning error after identification and compensation by traditional genetic algorithm,and the positioning error after identification and compensation by joint algorithm are measured and compared.At the same time,according to the three-dimensional model of the cockpit cover,two kinds of hole-making path points,straight line and arc surface,are generated,so that the robot with load runs the program according to these two kinds of hole-making path points,and the compensation of the robot with load in the actual hole-making state is measured.Absolute positioning accuracy.The experimental results show that the use of the joint algorithm to compensate the kinematic parameter error of the loaded robot greatly improves the absolute positioning accuracy of the robot,which can meet the technological requirements of automatic canopy making. |
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