Control Delay Of Delta Robot Based On EtherCAT Bus Dynamic Characteristics And Motion Planning

With the coming of industry 4.0 era,industrial robots with IOT connectivity are being researched and developed,and applied to the production field.An important carrier of information transmission and everything interconnection is industrial Ethernet,with which PLCopen controller or related motion control card has been widely concerned and applied in the control system of delta parallel robot.Based on the development background of the industry technology,this paper studies the performance improvement requirements of the three DOF Delta Parallel Robot Based on the Ether CAT control bus.Focusing on the contradiction between the high speed of delta robot operation and the delay of Ether CAT bus transmission,the influence of control delay on the high-speed pick-up performance of delta robot is evaluated through simulation model construction and influence factor analysis.Furthermore,a motion planning method considering the dynamic characteristics and specific scenes is proposed,and the relevant experiments are completed by building a delta robot control and experiment platform based on the Ether CAT bus transmission.The research work of this paper is summarized as follows:(1)Research on the influence of Ether CAT bus control delay on the high-speed movement of delta robot.Based on the inverse dynamics' analysis of virtual work principle,the equivalent rotor inertia and the Coriolis force of interference force source needed in the motor model are calculated.Then,the motor control model with position loop,speed loop and current loop PID control using Ether CAT servo drive / servo motor is established in MATLAB Simulink environment,and the PID parameters are adjusted by the method based on NCD and optimization function.Finally,the motor drive simulation control model of delta robot with time delay is established.According to the Simulink control model with time delay,the influence of time delay on the stability of the system is analyzed by using Bode diagram and root locus method.Furthermore,the joint simulation system of MATLAB and Adams is established by inputting the motion track and considering the interference force in the control simulation model.Based on this,the influence of the control delay on the motion performance of the end door trajectory of the robot is evaluated under the three speeds of low,medium and high.(2)Research on the combined motion planning of delta robot considering dynamic characteristics and specific scene.According to the requirements of delta robot's practical application,a path / trajectory motion planning method for delta robot considering dynamic characteristics and specific scenes is proposed.For the part of path planning,different displacement functions are used to get the new combined path function.The trajectory planning combines the advantages of modifying trapezoid motion law and polynomial motion law,and combines the asymmetrical acceleration law,proposes a new method of robot end trajectory combination.According to the proposed combined motion planning method and the path planning obtained from the traditional motion planning method,the motion simulation is carried out,and the indexes such as angular acceleration and jump of the robot end motion are compared.The simulation results verify the effectiveness of the proposed motion planning method,and ensure the motion speed and stability of the robot in a specific scene.(3)Experimental platform construction and experimental research.Based on the Ether CAT control bus specification,two sets of experimental platforms were built,including PC + motion control card control architecture and PLCopen-based soft motion control architecture.The basic motion accuracy of the two control architectures is compared by using segmented linear and circular trajectories.Using the original and planned gate-shaped path,through the measurement of the vibration characteristics of the robot end,and using the adaptive Chirplet transform method based on matching tracking to perform signal analysis,the effect of control delay on the dynamic characteristics of the Delta robot and the proposed combined motion planning are verified Effective for improving the dynamic characteristics of the robot end.