Reduce communication, raise industrial quality
By using wireless networks, and at the same time by reducing communications by 90 percent, Swedish process industry can produce a higher quality at a lower cost. This is what the doctoral student Erik Henriksson, who has put a new method to the test, predicts will happen.
By using wireless networks, and at the same time by reducing communications by 90 percent, Swedish process industry can produce a higher quality at a lower cost. This is what the doctoral student Erik Henriksson, who has put a new method to the test, predicts will happen.
"Together with Holmen Paper, we have controlled a paper machine, and our tests indicate that wireless communication with so-called event-based measurement techniques have reduced communication needs by 90 per cent, with no deterioration in the quality of the paper," says Erik Henriksson, doctoral student of Automatic Control and ACCESS Linnaeus Centre.
In the modern wired paper industry, a control system receives several hundred readings every second: when the blocks of wood are ground into sawdust, when the lignin is removed and the chips are made into pulp and finally when it comes out the other side as different grades of paper, writing paper, cardboard, paper for envelopes, etc. These readings are then used to calculate how the production process should be adapted to achieve the best quality. The more readings, the better the quality.
To replace the nearly two kilometres of cable in a paper mill with a wireless network has many advantages. Production becomes more flexible and it becomes cheaper to improve quality, because wireless networks will allow you to measure more things at a much lower cost. The marginal cost of adding one more measurement value is also much lower and things can easily be changed.
"You might have an idea that you think may produce better quality. With wireless it is easy to test this theory because you do not have to connect a cable, it is sufficient to place a radio transmitter on the machine. Wireless makes it possible to measure completely new activities as well. A wireless sensor can easily be attached to a machine despite the fact that the machine moves or rotates. This was not possible before, as the cable would have broken,” explains Erik Henriksson.
But the transition to a wireless networks in the process industry will still have to wait. The challenges are still many. With an increasing number of measuring points in the wireless network, the network traffic can easily become congested. There are also problems associated with the use of radio equipment. The radio waves transmitted from the wireless equipment in the factory can easily be impeded as they hit the large paper rolls, the walls and the machinery or get absorbed by the metal equipment.
"Today the situation is such that the systems report every little incident. It's a bit like having to ring your boss every time there is some activity, regardless of the type of activity. This can easily become too much for him with the result that he does not react when something important happens. Similarly, the networks become congested the more measuring points there are. So to be able to take advantage of the greater intelligence of the wireless networks and improve quality, the readings must be more flexible.
Thanks to the fact that Erik Henriksson and his research colleagues were able to conduct their research in a real industrial environment in various projects, both in conjunction with ABB, Uppsala University and Holmen Paper, they have been able to make use of their measurements and the identify problems.
It is through these experiences that Erik Henriksson in his doctoral thesis has been able to expand upon a new measurement technique that frees the networks from unnecessary communication. The method only measures values when it has to measure, it is interactive and adapts to the surrounding environment.
Imagine you are walking through central Stockholm. There are people everywhere. You look up to plan your route and then walk straight ahead. But people suddenly appear in your path, and you have to look up and replan your route. If the pavements are free, you can safely walk ahead looking down at your mobile phone in your hand, says Erik Henriksson.
"It is the same with this new measurement method in an industrial environment. This method ensures that the equipment measures often when the activity is high, and less when there is less activity. With less information there may be more findings and this may improve the quality of the paper.
For more information, contact Erik Henriksson, erik.henriksson@ee.kth.se, +46-8-790 74 23.
