Customer Marin has that much confidence in the chosen route that the first working day after the planned commissioning has been fully booked. By using extensive virtual testing in advance, now commissioning will require only two weeks instead of six. That's pure time saving. And that's just one aspect of the added value.
We have written about it earlier, if time is money, and you can save a lot of time by doing part of the tests virtually, then the choice is fairly obvious. VSE and Controllab carried out HIL tests, Hardware In the Loop, in which the machine - the trailer car at Marin - is simulated by a computer and all the controls are linked to the simulation. Does the control do what it is supposed to do? Under standard conditions, but also under special conditions?
That part's over and done. Succesfully! At Marin, the entire towing station and all the periphery have been stripped and rebuilt. The safety features have been adapted to the latest requirements, the controls have been built in and the first live tests have been successful. On the last day of commissioning, we are allowed to watch. And ride along, of course!
"At Marin, we are dealing with critical users. They have to be, because the interests are huge. Then it's nice to find that they have a lot of confidence in the quality and in the delivery of our work. So much so that immediately after the planned commissioning, they do indeed have the agenda full of assignments". Jan van Vuuren, project leader of VSE, has the floor. "In this project, every little detail matters. Even the lighting can be a determining parameter, it's a combination of many factors".
At Marin, ship models are tested in the enormous Seaway and Manoeuvre basin. Above that basin a tow unit moves very accurately, following the movements of a ship model in the water. The tow unit consists of a station intended for the researchers and a seating platform intended for the client, ordering the test. Cameras and sensors are aimed at the model from every conceivable angle and the model itself is also heavilly equipped with measuring instruments. The basin can simulate all possible waves at sea and the tow unit follows the model up to hair, which requires real sea legs in case of extreme waves. And that accuracy, combined with high acceleration and braking power, are basically the real challenges. Challenges at which the manufacturer of the control unit scratched his head and said: "If anyone can do this, it's VSE". And so it turned out to be. This is now the fifth basin of which VSE was responsible for the conversion.
Time for renewal
Jan de Boer of Marin: "After having been in operation for sixteen years, it was time to renew the technology. When we started with the first basin, Siemens sent us to VSE for the execution. They were able to give us a picture that we also felt was feasible. By now, we have already done four basins together with VSE, but this is the most difficult one. If we manage to deliver on time, on budget and with the intended quality, then you can only be satisfied". De Boer first learned about virtual testing last year. "Given the enormous time pressure on this project, we really wanted to get to work on it. In the end it surprised me how quick and smooth the testing went, it's really going incredibly well".
The project had a very clear separation, VSE took care of the electrical controls and the software. The brakes, hardware and safety doors were Marin's responsibility. The entire system - up untill the brakes - was therefore validated by VSE.
Van Vuuren: "When you start up any system, you have saved the most exciting thing for last. You start by putting the voltage on the system and then test it while it's on blocks. After a manual run and testing the emergency systems, you arrive at the most exciting part, the speed and the accuracy."
The first physical tests have been carried out on location, we get to see the start of the definitive fine-tuning. Users, working in different shifts - and having therefore experienced different tests - have made their wishes known on the basis of those first physical tests. "Based on these wishes we add an acoustic signal, at a desired point in the process, and we can make a choice to put the settings on manual or auto. But there's much more to it than that."
"The main thing that users have to get used to is the smoothness of the acceleration. During testing we hardly notice that the car starts to drive, and how fast and silent it goes. Marin employee Peter Geurts jokes to his colleagues: "They have made it far too good, I miss that nostalgic bumpy and noisy feeling of before." But 'far too good' is also a plus for him. "Because everything runs and reacts much smoother, the measuring signals will show much less disturbance and the whole will have a much longer lifespan. We will continue to work with the same maintenance intervals, but that's purely for the safety system."
A year has passed between the start of the assignment and the final delivery. Van Vuuren: "We made a completely new design of the controls, based on the required performance. For this we used a Motion Controller from Siemens from the Simotion line. This gives us the freedom to build and connect the various controls that Marin needs. In addition, we completely renewed the safety system. But the exciting thing was the accuracy of the controls."
The car is controlled at a position at a moment in time. That fact determines the speed. A camera shows the position of the measuring trolley, which is calculated back to the position in the basin, then back to the trolley position and from there to the model position." Sounds complicated but it turns out to be crystal clear.
Nine weeks was the time span the team was granted for the entire conversion. "At times we were working on site with ten VSE colleguaes at the same time. Time really is money here." And the customer? He tells all his fellow institutes about the smooth running.
The main car, that is the car that drives alongside the basin, weighs 94,000 kilos, is powered by eight 40kW asynchronous servomotors, has a top speed of 6m/s and a maximum acceleration of 0.8m/s2.
The subcar, this is the car that moves at right angles to the main car and 'hangs' underneath it, weighs 28,000 kilos, is driven by four 17.5kW asynchronous servomotors, has a top speed of 4m/s and a maximum acceleration of 0.8m/s2.
At those weights and speeds a positioning accuracy of no less than +/- 0.001m is achieved.