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Volume 26 Issue 8 - Publication Date: 1 August 2007
 
Contact Detection in Microrobotic Manipulation
 
W. H. Wang, X. Y. Liu, and Y. Sun Advanced Micro and Nanosystems Laboratory, University of Toronto,Canada
 
This paper presents a computer vision-based method for visually detecting the contact between an end-effector and a target surface under an optical microscope during microrobotic manipulation.Without using proximity or force/touch sensors, this method provides a submicrometer detection accuracy and possesses robustness. Fundamentally, after the establishment of contact in the world frame, further vertical motion of the end-effector (flexible or stiff) induces horizontal motion in the image plane. Contact between a micropipette tip and a glass slide in the scenario of microrobotic cell manipulation is used as an example to elaborate on the detection method. Experimental results demonstrate that the computer vision-based method is capable of achieving contact detection between the micropipette and the glass slide surface with an accuracy of 0.2 m. Furthermore, 1000 experimental trials reveal that the presented method is robust to variations in illumination intensity, microscopy magnification, and microrobot motion speed.
 
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Example 1: After the establishment of contact in the world frame, further vertical motion of the end-effector induces horizontal motion in the image plane. Detection of the contact between the end-effector and target surface is equivalent to locating the global minimum of x coordinates of the end-effector in the image plane with either a pixel resolution or sub-pixel resolution method. (3.5 MB) mpgi
 
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