Crane reaction

An intelligent control system devised as part of an EU project could revitalise European manufacturers’ ageing armies of overhead cranes. Christopher Sell reports.

Overhead travelling cranes, the stalwarts of many large manufacturing operations, have remained pretty much unchanged for the last century. However, with around half of these estimated to be nearing the end of their useful lives, and investment in new engineering infrastructure at something of a low point, manufacturers are faced with a pressing problem.

In response to this, Prof Janusz Szpytko of the AGH University of Science and Technology in Poland has led the development of an intelligent control system that can be applied to existing cranes and could, he claimed, both revolutionise operational performance and improve safety and reliability.

The RobCrane project (an EU Eureka initiative) has drawn on expertise from Poland, France, UK and the Czech Republic, in order to adapt overhead travelling cranes for the factories of the future.

Szpytko explained that much of the impetus for the project also lies in the lack of investment in manufacturing infrastructure throughout Europe.

Officially there are 35,000 cranes in Poland, while in countries such as Italy and Germany, that number rises to 45-50,000. Szyptko claimed that in 50 per cent or more of these cases, the cranes are well past their prime and are coming to the end of their lives.

He explained that the big challenge is to re-engineer old constructions and introduce an element of automation into the process. ‘When you are in your 20s and 30s, you learn, educate, take on skills and experience. When you are 35-50, you are powerful. But once you are in your 60s, your lifecycle goes down and your potential becomes less and less. It is the same with devices — you have to replace something or do something in a beneficial way that will make it useful.’

Overhead cranes are found traditionally in shipyards, container ports, aircraft factories and other heavy industrial plants. The crane operates at ceiling height moving along rails that run the length of the factory floor. Currently there are two basic operating systems; older installations have a man positioned above the crane at ceiling level, looking down at the procedure while in contact with someone at ground level.

The alternative approach is either through radio control or a dropped cable with a control box so an operator can stand just a few feet away from the crane and operate it. These both have the advantage of enabling a better view of the procedure from the ground rather than being positioned above the crane where line of sight can sometimes be impaired.

Two French companies, Predict SAS and Nancy, were responsible for designing and developing software-based monitoring and diagnosis processes, while the technical development work, rapid prototyping and testing of the concept took place in Poland, where the team had access to cranes at the Sendzimir Steelworks and other metallurgical plants. UK participation came in the form of consultants from the Scottish Maintenance Centre at Glasgow Caledonian University.

Essentially the project is aimed at making the overhead travelling crane more intelligent. The target, according to Szyptko is ‘to manage intelligent systems, lower operation and maintenance costs, improve safety and reliability of the device, while achieving better movement accuracy and reduced human error.’

Glasgow Caledonian University’s Prof David Harrison, a project consultant and adviser, echoed this. The aim of the project, he explained, was to modernise and automate the overhead travelling crane through a built-in intelligent control system that is sensitive to track and crane performance as well as different environmental conditions. ‘It’s about control accuracy, making sure you are getting an accurate position. These cranes are fairly large and are used to position large items, for example in the steel industry when molten steel or rolls of steel are being moving around,’ he said.

But working with such heavy materials can place stress upon the crane which can in time affect it. As a crane moves back and forth along its rails, it can distort due both to the extreme loads it is carrying and because the weight is transferring from one part of the crane to the other. Any distortion can of course affect accuracy. ‘we are only talking millimetres here, but it all makes a difference,’ said Harrison. As an example, he used the wing of the Airbus A380.

‘Some of the wing’s components are up to 42m long, so while you must have complete control over lifting awkward units, it has to be completely controlled and accurate to ensure no damage occurs to individual pieces,’ he said.

RobCrane has made things more accurate and more articulate claimed Harrison who added that the technology will be most beneficial to industries best described as ‘dirty’. On a steel site, for instance, sparks from molten steel become small metal dust particles which, in time cover everything, including the rails. If grit gets into the rails or crane wheels it can adversely affect the performance of the crane.

Using intelligent computer-aided monitoring systems to acquire data fed back from motor drives, strain gauges and other measuring devices it can ensure the crane achieves optimum performance, ensuring it is not operating outside prescribed tolerance levels.

Harrison detailed the four distinct software applications that have been developed through the project.

1. A Maintenance management system, which prompts regular maintenance checks, ensures that parts remain in good working order and therefore minimise breakdowns.

2. A monitoring and data acquisition system which, as the name suggests, monitors the performance of individual elements of the crane, detects any machine failure or human error and raises the alarm before a major failure occurs.

3. Predictive displacement, a stress analysis package that monitors the stresses and strains that a carriage moving across a crane would induce.

4. A Supervision system that monitors the condition of the track.Marketability of the project (PPHU EkoEnergia of Poland is responsible for this) is a driving factor in its development and, as Szyptko points out, with the lack of major investment throughout Europe, and the increasing desire for full automation (or at least some) RobCrane has global potential.

With installations already up and running in Poland and France, Szyptko said that the project could save an estimated $8,500 (£ 4, 748) per unit in running costs each year.

Every country has a heavy industry base and the chances are, he said, that the RobCrane project could play a major part in the modernising and automation of heavy industry factories around the world.