A Novel Double-ball-bar With Two Spatial Linkages And One Spherical Joint

As a detecting instrument,double-ball-bar(DBB)has been widely used to measure the error of CNC.Because of the characteristics of simple structure,quick operation and high efficiency,DBB plays an important role in practical engineering application.However,due to the limited expansion length of DBB’s bar,the working efficiency of the DBB is greatly reduced.Different length bars are mostly used to realize different measurement ranges,resulting in discontinuous working range.If a novel DBB,which could detect most of the positions within machine’s measuring range,could be presented,it will be beneficial to extension and application of DBB.In this paper,a novel DBB with one spherical joint connecting two bars(J-DBB)was presented to implement a wide detection range and to simplify the operation.Through the theoretical modeling,numerical simulation and experimental study,the examination principle of DBB was researched and the feasibility of error detection was verified.The research work was supported by the Key Project of Zhejiang Provincial Natural Science Foundation of China(No.LZ16E050001),“Study on measuring method for multiple dimensional displacements of robotic spherical joint based on capacitive sensor”.Specific research contents in the thesis are summarized as following.(1)The background and significance of the study were firstly introduced.The current research situation on DBB were then reviewed.Finally,the main structure and contents of this thesis were proposed.(2)The CNC’s error causations were analyzed,and classified.The mechanical structure of the J-DBB was designed.The resolution of the J-DBB was calculated and discussed.The mechanical model was presented,and the mathematical model of error detection was established.(3)Base on the theoretical model,numerical simulation of the J-DBB was carried out.The examination principle,which used the angle changing of the spherical joint to test the error of CNC,was verified.The feasibility of error detection was verified.(4)The detection scheme of position and posture through mechanical decoupling was presented.Test rigs were constructed for verifying the feasibility of mechanical decoupling and the principle of J-DBB.The experimental prototype of the J-DBB was fabricated,installed on the CMM,and tested.