MAN vs MACHINE THE CONTROL SYSTEM CONUNDRUM

Just where that boundary lies depends on the relationships between man in the form of the crane driver, and machine in the form of the increasingly clever control systems the customer can choose from. Nick Elliott reports.

Taking part in the debate are the manufacturers, the port planning consultants advising terminals on layout, dimensioning, equipment concepts and specification, the terminal’s own engineers and of course the accountants. The terminal’s management, as always, stands as the final arbiter.

At the heart of the debate lies the question: what is the point of fitting expensive positioning, anti-sway, profiling and other control systems when crane drivers invariably switch them off? And why is it that despite this, customer specifications have become more and more precise as to cycle times, sway control, accuracy of the final position above the deck, provision for the driver to select the cell on the ship or the lane on the terminal, and so on? And of course the technology keeps getting smarter: “Technology is often the driving force for the application and not the other way round, ” admits Rene Kleiss, vice-president of Kalmar ship-to-shore cranes.

INFLUENCE OF TIDE AND WIND Profile-scanning for example will, when the trolley travels above the ship, detect the containers, their height and their number, so with every cycle the form of the stack can be updated. And with such intelligent sensor systems it is also possible to consider the influence of tidal movements. Another variable to take account of is the list that can develop if the ship’s ballasting is not precise. Then there’s the effect of the wind.

So today manufacturers consider not just the mathematical model of the swaying of the load, but the boundary condition too. But is it all worthwhile if the crane driver prefers to feel the operation for himself rather than “fly by wire”?

Norbert Schilling, head of project engineering, heavy equipment, at Noell Crane Systems sums up the conundrum: “All cranes we’ve delivered in recent years were equipped with semi-automatic control and anti-sway systems for positioning of containers. But most crane drivers switch off these systems because, due to their experience and feel for the job, they can work more efficiently without the support of the computer. From our point of view it’s very difficult to handle this situation. Port equipment consultants around the world and the terminals’ technical management specify such modern systems but after commissioning, during the first shift, they are switched off. So getting feedback as to time-savings and the other benefits these control systems are supposed to bring, is very difficult.”

Rene Kleiss concurs. Kalmar recently won an order to deliver ten super post-Panamax quay cranes to the MSC Home Terminal in Antwerp, a joint-venture between MSC and PSA Corp’s Hesse Nord Natie (HNN). “Whilst HNN specified state-of-the art drive systems with high-powered AC motors and PLC*, in automation terms the specification was very down-to-earth. Their philosophy is keep it simple, and with that keep it reliable. Their aim is to have a workhorse crane working 24/7. The order had an option for the anti-sway system which was not taken up. It costs money and the users don’t use it. The driver wants to feel the characteristics of the crane in his own hands.”

There are a number of factors at work here and terminal operators PS spoke to agreed that the situation is not black and white. On the human side drivers have a genuine case for not using the control systems particularly when to do so, in the short term at least, often slows down the cycle time. Also there is a fear that it is one more step towards an automated future where at best the driver’s role is subordinated to mere computer operator, and at worst, there is no job because one computer operator will work multiple cranes.

However, even though a well-trained and experienced crane driver can handle more containers over two hours by controlling the crane himself, what about after four or more hours? Meanwhile, the control system will deliver a smooth, consistent throughput over a longer period. Notwithstanding which, when the spreader stops half a metre above the top of the container, the rest of the task must still be done manually.

Whatever the role of man in the future, the technology march continues and the introduction of the second trolley was a stepchange in that march. The original idea behind it was to improve safety on the ground. A lashing platform was developed so all handling around the container by means of inserting/removing twistlocks, checking seals, tallying and so forth, was no longer performed on the ground but on the platform on the crane. “Then we thought, we have the main trolley on top of the crane running along the boom and bridge girder, ” says Noell’s Schilling. “This picks up the container, sets it down on the lashing platform and you wait 30 seconds while the job is done, then the box is lifted again and set down on the backreach.

It made no sense so the idea of converting the lashing platform into a second trolley was borne thus dividing the cycle into two.

SENSORS TO DETECT PATHS OF MANNED EQUIPMENT “Then we thought, ” he continues, “the second trolley’s operation could be fully automated. This was first achieved at a terminal using manned strad carriers. We had difficulty with the statutory bodies to get approval to use this second trolley in combination with manned equipment on the terminal. And many interfaces had to be considered. Sensors had to be installed to detect the paths of the manned equipment, to detect containers and stackers.”

Schilling says: “But if there is a fully automated system on the landside using AGVs for example, then you can think about a completely different crane system. We have built cranes with a second trolley which have been successful from the technical viewpoint, but from the investment position, when considering what has to be done to adapt a terminal which already exists, then it is a more difficult decision. But if you are planning a completely new terminal, HHLA’s Container Terminal Altenwerder (CTA) for example, with completely automated terminal operations with automated RMGs, and with AGVs for connecting the quayside to the stack, plus quay cranes with a second trolley, then it makes sense. And that is the best a crane can do to optimise cycle times at the shipside at the terminals of the future.”

Kalmar’s (formerly Nelcon) Kleiss describes another branch of the evolutionary process: “A few years ago we developed a crane where the operator’s cab was stationary and separate from the trolley. The idea was that the operator had a fixed position over the ship and the total cycle of the trolley after lifting the container from the ship would be automatic. You need infrared scanning devices and so on if you have automated landside systems as well. Otherwise it doesn’t make much sense. It costs a lot of money. It makes the cranes a little bit slower and it doesn’t help the total cycle time or performance on the ship. It only makes sense if you automate the total cycle behind it.”

Schilling makes the same point: “In the end the cycle time is not determined by the speed of the machinery but by bottlenecks on the terminal. At present we are at 180 metres/minute for the hoist machinery with an empty spreader and 90 metres/minute lifting and lowering speed for a fully loaded container. It makes no sense to increase speed to reduce cycle time when the trolley then has to wait on the landside.”

So what’s the next step?

Disconnecting the driver from the fast accelerating trolley says Kleiss. “What you see on ASC’s (Automatic Stacking Cranes) is already a very common sight in Rotterdam. You have them in Singapore too: a driver sitting at a screen. He switches from crane number 1 to 74 then to 36. 80% of the total cycle is automated. Only lifting from or landing onto a truck is manual. With STS cranes at modern terminals, I foresee the same thing happening: the crane driver will still handle the manual interface above the ship but as soon as the container is lifted from the ship the rest of the cycle will be automated.”

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PLC: Programmable Logic Control connects the input and output of all the cranes drives, in effect an intelligent relay cubicle.