Protein fluid controlled by color camera.

Nowadays the need of vegetable proteins is increasing and will replace the animal proteins more and more. To produce vegetable proteins a special process is invented and patented by a Dutch firm. Very important in this process is a very accurate control of the fluid levels especially the fluid level containing the proteins.

The whole process takes place in a large RVS tank. On the bottom the vegetable pulp is pumped into the thank and a special designed pump out process pumps the protein into the next tank or container. A PLC controls the two pumps and three linear motors to position the camera and the pump out inlet.
Tank setup Camera setup To measure the fluid levels a programmable color camera is used. This camera detects the top level of light brown protein fluid and the top of the transparent water level above the protein level. This is theory, in practice the detection is more complex.
The color of the protein fluid is fluctuating between dark brown to very light brown. The pulp fluid level is dark brown to almost black and containing thin and thick vegetable fibers disturbing the transition of the pulp-protein level.

The transition of the top level of the protein to water is not always as clear as possible. The top of the water level is mainly a very small water-air meniscus, and the water is not always clear water. Sometimes on top of the water a white foam is visible so the detection is getting easy. But the foam changes from color, white to grey and even transparent grey. Actually a lot of color and structure changes during production.

To solve this problem a white frontlight is used to illuminate the protein and pulp fluid as the foam on the top of the water also. Very thin meniscus
A blue backlight is used to detect the transparent or semi transparent water level. The air is also transparent so it is difficult to distinguish between clear water and air.
As mentioned a small water-air meniscus is most of the time visible. When the water level increases this meniscus is getting thinner and thinner, finaly it disapears.
The transition water-air can not be detected. This is an extra difficulty in the measure and control strategy.

The camera is 90 degrees rotated so the maximum resolution is used. The images are also 90 degrees rotated. Left side of the image is the top in vertical direction. To decrease the overall dimensions of the camera set up a mirror in front of the camera is used.

Algorithm

After receiving a start measure signal from the PLC , the software starts detecting the different colors of the fluids. To create a reliable detection of the color several checks and special detections are developed.
On the image several marks show the transition of the fluids. Detection of the foam gives a clear water-air transition. The foam detection seems a simple task but it is also a complicated detection. The color and transparency of the foam changes so a double check is necessary. For the water-air meniscus detection a second image with other camera settings is taken. The thin meniscus requires special software and a quadruple check.
And of course only a certain fluid order is possible, air is always at the top and the dark fluid is always at the bottom. This order is of course incorporated in the software.
When the camera is positioned too low or the inlet pump boosts the fluid in the tank the water-air transition is outside the field of view.
Electrical set up Control room monitor
Every 10 minutes the measure area of the tank is cleaned by water. A lot of bubbles are visible in the water. This disturbs the water-air level. The software is insensible for this disturbance.
After detecting the fluid transition the position of every fluid transition is send to the PLC. The PLC knows the position of the camera with respect to the absolute reference of the tank and calculates the exact position of the levels. The PLC controls the pumps and the linear motors so the correct protein fluid layer can pumped out.
Via Ethernet the control room receives the live images of the four tanks on one monitor. So the operators can keep an eye on the fluid fluctuations in the thank.

Fluid images To adjust the detection algorithm the color scan of the camera can be send via Ethernet to the control room computer. For this purposes the PLC starts the measuring sequence by sending a special code to the programmable camera. Also the PLC can start and stop sending the images tot the control room.

The control room computer can save the images and data receiving from the camera for debugging and logging purposes. For adjusting the parameter settings special adjust software is added.

Full color incl foam 01 Protein and no water Water bubble 01 Water semi transparant