Research On Assembly Robot Calibration And Hole Pose Reconstruction Based On Multivision~*

With the development of robots intelligentialize,more and more industrial robots are equipped with vision system.However,robot and vision deep fusing is still a major issue currently facing.In this paper,based on trinocular vision system consisted of eye to hand(ETH)and eye in hand(EIH),trinocular vision calibration,robot kinematic parameter calibration and arbitrary space hole pose reconstruction methods are proposed respectively for peg and hole auto assembly task by 6-DOF series intelligent robot.The experimental results verify the effectiveness of each method.The specific contents are as follows.(1)Trinocular machine vision system calibration.With a planar target images acquired,three camera internal and external parameters calibrated according to ZHANG calibration method.After that,the relation pose among tri-camera is optimized by trifocal tensor constraint.The unified coordinate system of tri-vision is established with benchmark of the left ETH.Lastly,chessboard horizontal and verical size are measured according to tri-vision loaction theory.The exprement shows the size relative error below 3.2%.(2)Robot kinematic calibration based on EIH.With robot every joint individual movement,EIH collects images of fixed plane target.According to ZHANG calibration method,the camera optic center position at every image shooting is obtained.By trajectory of the optical center fitting circle on each mono-joint rolling,the correspoding joint axis is gained.Whereafter,the every axis is optimized by trifocal tensor constraint consist of two images at its joint minimax rotation angle and the third image at middle,which joint screw is obtained by,then to establish exponential product model of robot.Finally,through two hessboard image achieved by EIH at different pose whose relative pose is calculated,hessboard horizontal and verical size are measured by principle of binocular reconstruction.The experiment shows the size relative error below 3%.(3)Space hole pose reconstruction based on directrix-generatrix.Firstly,hole directrix curve is fitted by marginal points in cross section of hole.With the same direction given of hole axis a generatrix drew through other point in cylinder of hole,the orientation of hole is gained by optimizing the minimun algebraic distance between the directrix and the crossover point between generatrix and cross section.The center of directrix curve can be used as hole location.The simulation experiment of pose reconstruction of inclined hole shows the results of relative error of 0.2%,and physical experiments also get higher reconstruction accuracy.Finally,a method of detecting the surface of the hole is presented based on vision.(4)Comprehensive experiment of target hole pose reconstruction based on the robot-vision system.By calibrating trinocular machine system and establishing the exponential product model of assembly robot,the ETH and EIH are used to reconstruct the workpiece hole pose respectively.Furthermore,the correctness of those methods proposed in this paper is further verified by the results.