| In recent years,with the worldwide upsurge of the "Industrial 4.0",various countries have focused on the transformation and upgrading of manufacturing industry and it is the general trend to improve the level of manufacturing industry and automation.Robot is the symbol of the era of automation and also the cornerstone of the era of intelligence.Industrial robotics appeared in intelligent production lines will receive more and more attention.Three degrees of freedom Delta robot(3-DoF Delta)has been widely used in packaging sorting,3D print,medical surgery,micro-motion and other fields because of its high precision,high stiffness and high load-to-weight ratio.This paper focuses on the research of the Delta-like 3-PUU Parallel robot and takes the motion control as the main line,studies on several aspects such as the kinematics analysis,the whole workspace performance,the dynamic modeling and simplification and the dynamic control strategy,which lays a foundation for further improving the dynamical operation performance of Delta robot.The concrete research contents of this paper include:(1)Based on its structural characteristics,the geometric model of 3-PUU Parallel robot is established.The inverse kinematics is obtained by using closed-loop vector equation on the basis of the geometric constraint of the rod length.The velocity model and the acceleration model are obtained from its derivation.On the basis of Jacobean matrix,the dimensionless stiffness performance index and global dexterity index are proposed and the comparison of the performance in the whole reachable workspace between two parallel robots is proposed via limit boundary search method.(2)The generalized force of each part of the robot is analyzed and the complete dynamic model of 3-PUU Parallel robot is deduced by virtual work principle.The weightiness of each component of motor driving moment is also analyzed.In order to solve the problems of large amount of calculation and poor real-time performance of the complete dynamic model,a simplified model is established based on the principle of neglecting secondary factors.Then,based on the static equivalent principle,the mass of the driven rod is proportionally distributed to the slider and the platform at both ends,and another simplified dynamic model is established.Finally,the computational efficiency and accuracy of the two simplified models are compared,the final simplified scheme is determined and the dynamic equation in joint space is deduced.(3)On the basis of inverse kinematics and dynamic model,the three closed-loop PID controller based on kinematics model,the computational moment PD controller based on dynamics model and the nonsingular terminal sliding mode controller based on dynamics model are designed respectively and the stability analysis is carried out via Lyapunov principle.Taking trajectory tracking accuracy and system robustness as objectives,it is indicated that the nonsingular terminal sliding mode controller has better tracking accuracy and robustness with the simulation in MATLAB/Simulink.(4)The inverse kinematics model,the dynamic model and the designed nonsingular terminal sliding mode controller is validated with the comparison of the theoretical formula and co-simulation results in MATLAB/ADAMS.Then the experiment of scanning the workspace of 3-PUU Parallel robot is conducted with the help of laser tracker,and the comparison and verification between the experimental workspace and the solved workspace by the limit boundary search method is carried out.Finally the test of the self-developed control system is conducted to verify of the feasibility of the three closed-loop PID controller based on kinematics model. |
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