Error Compensation And Vibration Reduction Optimization Of High Speed Delta Parallel Robot

Parallel robot is one of the important members in robot family, compared with serial robot, it has the characteristics of high speed and high precision, and widely used in food packaging, manufacturing, aerospace and other fields, with the development of industry, higher working speed and precision required, parallel robot is moving toward the direction of high speed and lightweight, the factors affecting the dynamic performance and vibration characteristics of parallel robot are more and more complex. In the view of elastic dynamic, high speed leads to the increase of inertial force excitation frequency; lightweight leads to increase the flexibility of rod, and derease the natural frequency. These factors are easy to cause the system’s motion error and elastic vibration, and affect it’s working performance seriously. How to improve the accuracy of position and attitude of parallel robot, reduce the vibration of system in the condition of high-speed operation, has become the frontier in the field of parallel robot already. In this paper, take one of the most widely used parallel robot-Delta robot as research object, on the basis of theoretical modeling, software simulation and experimental analysis, elastic dynamics, integrated position error, system vibration characteristics, scale synthesis, trajectory planning and control, error compensation of Delta robot are studied deeply. The experimental results show that the position error of moving platform is compensated, and the vibration characteristics improved as well. The main contents of this paper as follows:1. The establishment of dynamic model. Considering the characteristics of high speed and light weight Delta robot, on the basis of dynamic model of rigid body, finite element theory and Lagrange equation, the elastic dynamic model of Delta robot system is established;2. Comprehensive error model. Taking fully consideration of the error sources that influence the position accuracy of Delta robot, mechanism error model and joint clearance error model are established respectively, take the mechanism error and joint clearance into elastic dynamic model, the integrated elastic dynamic model of Delta robot is established, and then obtain the Delta robot’s comprehensive error model, the vibration coupling characteristics of error sources is analyzed, finally, it shows the relationship between the position error of each direction and the coordinate axes of system’s global system.3. Scale synthesis. Scale synthesis is a complex task with multiple constraints and multiple objectives, in order to improve the efficiency of Delta robot’s scale optimization, in the view of rigid dynamics and elastic dynamics, the Scale synthesis is conducted step by step. According to the optimized scale parameters, the Delta robot physical prototype is manufactured;4. Trajectory planning and control. Definiting the comprehensive dynamic dexterity, various constraints are considered, trajectory planning based on modified trapezoidal mode is carried out in the trajectory lattice; combinating fuzzy PID controller and traditional PID controller in parallel form to control Delta robot, using genetic algorithm to optimize the range of fuzzy PID control’s control parameters, to improve it’s real-time and accuracy.5. Error compensation. A scheme is proposed to compensate the position error of moving platform and reduce the vibration of system by adjusting the actual value of the active arm’s input angle.In order to verify the correctness and validity of this paper’s study, the experimental verification and analysis are carried out on the Delta robot physical prototype. Finally, the PS2 wireless game handle is modified to a hand held device for teaching and controlling the Delta robot.