Joint Stiffness Identification And Trajectory Planning Of Heavy-duty Robot

Compared with the traditional light-load robot,the heavy-duty robot is high-load,especially in high-speed motion,the flexibility of the robot joint leads to the problems of low precision of the trajectory positioning and poor robot motion performance.With the increase of load-to-weight ratio of heavy-duty robots,the problem of joint flexibility of heavy-duty robots will become more prominent.Relying on the Jiangsu Province Science and Technology Achievements Special Fund Project “Research,Development and Industrialization of High-speed Heavy-duty Industrial Robot Core Technology”,based on the 150 kg heavy-duty robot developed by enterprise cooperation,the joint stiffness parameter identification and the trajectory planning of heavy-duty robot are studied in the dissertation.The main contents are as follows:Aiming at the problem of joint stiffness modeling and joint stiffness parameter identification for heavy-duty robots,an accurate method for identifying the joint stiffness parameters of heavy-duty robot is proposed.Firstly,the Cartesian stiffness and the joint stiffness of the robot are defined respectively,and the mathematical model of the deformation angle from the end to the joint is constructed.On this basis,a method of calculating the stiffness of the robot based on the offset plate is proposed.By designing the bias plate mounted at the end of the flange and deriving the kinematic model from the plate to the end of the flange and the force and torque conversion model,the force of the heavy-duty industrial robot flange is calculated more effectively;finally using the laser tracker to measure the data deviation,combined with the least squares method,the heavy-duty robot joint stiffness parameters is identified.In the case of heavy-duty robot,the flexibility of the robot joint leads to the large deviation of the position and posture of the motion trajectory.A deviation compensation method based on the flexible joint stiffness of the heavy-duty robot is adopted in this paper.Firstly,based on the joint flexibility of heavy-duty robots,the identification of the joint stiffness parameters of heavy-duty robots,considering the dynamics and load factors of heavy-duty robots,the deviation compensation model based on robot dynamics and the load-based compensation model are established respectively.Then comprehensively consider the robot body dynamics and load deviation compensation model,a heavy load robot deviation compensation model is proposed.The trajectory deviation compensation model can effectively reduce the position and orientation deviation of heavy-duty robots and significantly improve the pose accuracy of heavy-duty robots.In order to solve the problem of large start and stop shocks and robot jitter in typical industrial applications of heavy-duty robots,a mathematical model of polynomial 7-7-7 trajectory interpolation was proposed in this paper.Firstly,the trajectory interpolation model for heavy-duty robots is established.On this basis,the performance criteria such as number of trajectory conditions,end-to-end deviation and total running time of heavy-duty robots are established.Then the multi-variable multi-objective mathematical model trajectory planning for heavy-duty robots is proposed.In addition,the multi-objective NSGA-II algorithm is used in this dissertation to solve and optimize multi-variable multi-objective trajectory planning mathematical model.Finally,the heavy-duty robot can start quickly under large load conditions and has little jitter during start-up and stop section.The robot runs fast during the whole movement,and the transition is smooth and stable.For the typical industrial applications of heavy-duty robot handling,this dissertation takes SolidWorks as the development platform,VC++/MFC as the development environment,and completes the heavy-duty robot handling software package based on the ROBOLP,a general robot off-line programming and simulation platform developed in the laboratory.According to the identification of the stiffness parameters of heavy-duty robot joints,this dissertation proposes the functional modules of heavy-duty robot deviation and heavy-duty robot transportation trajectory planning.At the same time,the software package also developed a heavy-duty robot handling parameter setting module,robot dynamics module,heavy-duty robot motion simulation module,robot collision detection module,robot post-processing module and other functional modules.In this dissertation,the 150 kg heavy-duty robot in cooperation with the company,is used to study the research content of the joint stiffness parameter identification,the trajectory error compensation of heavy-duty robot,and the trajectory planning of heavy-duty robot.The experimental results show the validity and correctness of methods proposed in this dissertation.