Research On Pose Optimization And Error Compensation Of Sample Operating Robot Based On Stiffness Characteristics Analysis

6-DOF robots have become an important component of neutron diffraction stress spectrometer due to its flexible freedom,high automation level and convenience.However,since the stiffness of the robot is slightly weak,there is a certain error in the positioning of the sample.This paper choose Staubli-TX90 sample operating robot as study object,focusing on the stiffness characteristics of robots,the main research contents are as follows:(1)The static stiffness model of the sample operating robot was established,ignoring the deformation of the robot link and assuming that the robot deformation occurs at its joints.According to the static stiffness model of the sample operating robot,the positioning error of the robot TCP is not only related to the stiffness value of the robot joints,but also related to the pose of the robot.The experimental platform were established with laser scan measuring arm and weights.And the joint stiffness values of the sample operating the robot were identified based on the least squares method.(2)Two scalar indexs to evaluate robot stiffness performance:displacement ellipsoid and displacement-force quotient,were proposed according to the nature of the Cartesian stiffness matrix.The stiffness performance of the sample operating robot within its workspace was analyzed with Monte Carlo method.The simulation results show that the main reason causing the robot TCP error is the effect of force on its line displacement.The positioning optimization model of the sample operating robot was established combining the positioning requirements of the neutron diffraction measurement.The optimization model was solved with genetic algorithm.The results show that the stiffness performance of the robot during sample position was optimized.The trajectory planning of the robot operated sample motion was carried out with quintic polynomials.And the simulation results show that the robot can move to the diffraction pose smoothly.(3)The robot joint torque when the robot operates samples was solved.A compensation solution for robot stiffness errors was proposed.The experimental platform for sample positioning robot was established.Coordinate systems in the neutron diffraction system were calibrated.Sample positioning with robot were performed by two different target joint angles: original target joints,joints with robot pose optimizaion and error compensation.Sample positioning errors of two type joints were measured,and the positioning error was compared and analyzed.The experimental results show that by robot pose optimization and stiffness error compensation,the error of sample positioning with robot is increased by about 42.35%.