Research On The Terminal Accuracy Of A High Speed Parallel Robot Driven By Parallel Cables

With the development of industry,robots have been widely used and become the main force of production automation.As an important member of robot,sorting robot is the core equipment in the field of sorting and packaging,and has a large demand.Cable parallel robot has the advantages of lightweight,high energy efficiency,low cost and high dynamic.In the previous research,the team proposed a new 3 translational DOF highspeed sorting robot with parallel cable drive structure,and showed great performance advantages and application potential.In the sorting system,it is necessary to grasp objects accurately,which puts forward higher requirements for the accuracy of the robot.In this paper,the pose accuracy of the high-speed parallel sorting robot with parallel cable is studied to ensure the accuracy of grasping,the main research contents are as follows:A high-precision kinematics model of cable parallel robot considering the kinematics of pulleys is established.Due to the influence of the swing of the pulley and the change of the wrap angle of the cable,the cable exit point of the pulley has a time-varying effect.Therefore,an accurate kinematic model considering the pulley is derived.Then,the sensitivity analysis of the parallel cable parallel robot is carried out on the basis of this model.The main structural errors that affect the accuracy of end effector and the influence size and relation of these errors are obtained.According to the results of sensitivity analysis,the kinematic model is simplified to lay the foundation for the follow-up research.The orientation accuracy assurance method of parallel cable parallel robot with two steps of precision design and initial position adjustment is established.Firstly,the application and characteristics of stochastic mathematics method and interval analysis method in precision analysis are compared.Then,assuming the initial cable length is accurate,the optimal tolerance of the pulley position and the cable connection point position on the end effector is obtained by accuracy synthesis based on the optimal manufacturing cost and interval analysis method.On this basis,we can obtained that the orientation error can be effectively reduced by adjusting the end effector at the initial position by the theoretical analysis,and the correctness of the above theoretical analysis is proved by simulation.A kinematic calibration method of the parallel cable parallel robot is proposed to improve its position accuracy.The error identification models of direct and indirect measurement of the end effector's position for identification of robot structure parameters and Z-coordinate for identification of initial cable length are derived respectively.Based on the minimum condition number of the identification matrix,the installation position of the distance sensor and the optimal measurement pose are obtained.The feasibility of calibration and the rationality of optimal pose are verified by simulation.The external calibration experiment of the parallel cable parallel robot based on laser tracking instrument is completed,and the experimental results show that the calibration is feasible and the optimal pose based on condition number is effective.The research results of this paper have engineering practical value for improving the accuracy of parallel cable parallel robot and promoting the application of related robots in the production line.