Abstract:To measure micromanipulator depth motion,a gray variance-based focus measure operator is utilized to compute its defocus image features.The defocus feature curve is theoretically distributed with only one peak,which represents depth position of the microscopic focal plane.The extracted defocus features usually include lots of random noises.A nonlinear tracking differentiator is developed to suppress noises and smoothly track the features and their differential values without oscillation.Based on the differential defocus signals,a coarse-tofine self-optimizing vision controller is presented for the micromanipulator to precisely locate assembly plane along the depth way.Experimental results of microassembly depth motion demonstrate the validity of the proposed approach with a depth servoing error of 7.5 μm.
[1] Pentland A P.A new sense for depth of field[J].IEEE Transactions on Pattern Analysis and Machine Intelligence,1987,9(4):523 -531. [2] Xiong Y,Shafer S A.Depth from focusing and defocusing[A].Proceedings of the IEEE Conference on Computer Vision and Pa-.ttern Recognition[C].Los Alamitos,CA,USA:IEEE Computer Society,1993.68-73. [3] Sun Y,Duthaler S,Nelson B J.Autofocusing algorithm selection in computer microscopy[A].Proceedings of the IEEE/RSJ International Conference on Iutelligent Robots and Systems[C].Piscataway,NJ,USA:IEEE,2005.70-76. [4] Yang G,Nelson B J.Micromanipulation contact transition control by selective focusing and microforce control[A].Proceedings of the IEEE International Conference on Robotics and Automation[C].Piscataway,NJ,USA:IEEE,2003.3200-3206. [5] 韩京清.跟踪-微分器的离散形式[J].系统科学与数学,1999,19(3):268-273. [6] 黄一,张文革.自抗扰控制器的发展[J].控制理论与应用,2002,19(4):485-492. [7] Subbarao M.Parallel depth recovery by changing camera parameters[A].Proceedings of the IEEE International Conference on Computer Vision[C].Washington DC,USA:IEEE Computer Society,1988.149-155. [8] Huang X H,Lv X D,Wang M.Development of a robotic microassembly system with multi-manipulator ooperation[A].Proceedings of the IEEE International Conference on Mechatronics and Automation[C].Piscataway,NJ,USA:IEEE,2006.1197-1201. [9] 康宗明,张利,谢攀.一种基于能量和熵的自动聚焦算法[J].电子学报,2003,31(4):552-555.