Biomedical Engineering Reference
In-Depth Information
Chapter 11
Adaptive Algorithms Based on Technical Vision
We have developed technology for the automatic microassembly of microfilters - a
description of the microfilters was presented in Chapter 8.
11.1 Microassembly Task
One problem with the microassembly process is that the workpiece sticks to the
micromanipulator gripper, and it is difficult to release the gripper from the work-
piece. To resolve this problem, we propose the following assembly process
sequence [
1
] (Fig.
11.1
). The gripper of the assembly device is the needle (1) in
the tube (2). The microring is put on the needle and is introduced with the needle
into the hole (Fig.
11.1a
,
b
). After that, the needle is removed, and the microring is
held in the hole with the tube (Fig.
11.1c
). In the next step, the tube with the needle
is moved aside, and the microring is held in the hole and cannot follow the tube
(Fig.
11.1d
). The tube then is moved up and liberates the end of the needle for the
next operation (Fig.
11.1e
).
Micromechanical device assembly requires the determination of the relative
position of microdetails (Fig.
11.2
). In the case of the pin-hole task, it is necessary
to determine the displacements
dX
,
dY
,
dZ
of the pin tip relative to the hole by using
the images obtained with a TV camera. It is possible to evaluate these displace-
ments with a stereovision system, which resolves 3D problems but demands two
TV cameras. To simplify the control system, we propose the transformation of 3D
into 2D images, preserving all the information about the mutual location of the pin
and the hole. This approach makes it possible to use only one TV camera.
Four light sources are used to obtain pin shadows (Fig.
11.3
). The mutual
location of these shadows and the hole contains all the information about displace-
ments of the pin relative to the hole. The displacements in the horizontal plane
(dX, dY)
can be obtained directly by displacements of the shadows' points relative
to the hole center. Vertical displacement of the pin may be obtained from the
