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2. Hardware of the system.
When designing the system, the hardware was given priority
because of the special requirements of the system.
To make it possible to measure the teatcup liner inside the
milking machine without disturbing the process, an adapter with
a window to the teatcup had to be designed. The vacuum
process should remain intact while measurements are taken.
Limited space and limited budget were other constraints in the
system consideration.
The hardware solution was a mono-camera system with a
mirror arrangement in front of the camera to create stereoscopic
split images. In general, one-camera designs have some obvious
advantages in price, calibration, etc. (El-Hakim 1990), and in
this set-up factors like size, data quantity and synchronization
also play decisive roles.
The aim was also to use a "bottom to top" strategy in the
design and start with uncomplicated solutions.
The selected camera has a remote miniature head sized 17x55
mm with resolution better than 360 (horizontal x 420
(vertical). Since the simultaneous images are recorded on the
same frame, no synchronization or pairing problems occur.
Figure 2 shows two cross-sections of the teatcup and the
camera adapter.
The glass plate separate the mirrors and camera from the
teatcup where varying vacuum occurs. Illumination is by
external light sources through a diffusive window to avoid
disturbing reflections. The prototype adapter is made of brass,
but, the next version will be of a lighter composite material to
keep down the additional weight of the adapter.
3. Functions of the system.
To get the required results of the system, solutions from
different parts of the subject area had to be adapted and
adjusted to the tasks. The accuracy requirements of the results
were the most important factors for the choices of methods of
measurement, data handling, estimation, etc. The system
overview is shown by data flow diagram (DFD) (Gane and
Sarson, 1979) in figure 3, and the more detailed decompositions
are shown in the following subsections.
In this article the processes of calibration and measurement are
emphasized, both because they are the two most decisive parts
of any system and because of the special solutions in our
system.
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Section B-B
|
| camera
| housing
| E ;
i BI mirrors
glass plate
teatcup liner
A 1 1 L 1 — CM
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Section A-A
Figure 2. Teatcup with adapter.