SIEMENS

How can one of the world’s largest industrial machines fit into a room measuring only 15 m²? Just ask Dr. Thomas Baudisch. He and his team, which goes by the name of FINE (Functional and integrative engineering of mechatronic systems) deal with the development of systems in virtual space.
The team proceeds as though this lab — on the grounds of the Siemens Corporate Technology (CT) campus in the Neuperlach district of Munich — contains a bucket wheel excavator weighing as much as 14,000 t. Such steel colossi are some 90 m tall and about 200 m in length — almost as long as a bridge across the Rhine River. Nevertheless, the electronics required for the operation and control of such giant excavators fit into three rather modest control cabinets in Baudisch’s laboratory. There, scientists simulate the actions of the huge machine on a computer that’s connected to the electronics cabinets by a thick cable.
A large poster on the wall of the lab depicts such a bucket wheel excavator extracting brown coal. "The image constantly reminds us of what a monster we’re dealing with," jokes Baudisch. Since November 2008, Baudisch has been working with an interdisciplinary team of experts from the fields of mechanical engineering, information technology, mathematics, and electrical engineering to develop a simulation system that is customized for the bucket wheel excavators owned by the RWE power company. "Our excavators are between 15 and 50 years old," explains Thomas Nieß, who is responsible for the electrical engineering of conveyor systems at RWE. If the steel structure of a bucket wheel excavator is properly maintained, i.e. protected against corrosion, and its welding seams are repaired periodically, it is practically indestructible.
Not so with the electrical system that controls the machine. After 40 years at the latest, the electric cables have deteriorated so much from exposure to UV radiation and from wear that they must be completely replaced. "And the innovation cycles in electrical engineering have become so much shorter that we have to replace the system sooner and upgrade it at ever shorter intervals," says Nieß. That’s a trend in all sectors — even in the mining industry, which generally ranks on the conservative side.

New Technology — New Features. For RWE, the time has come to upgrade its bucket wheel giants to the latest state of technology. With this in mind, the company is working with Siemens in Cologne to develop a completely new automation system for 16 excavators it uses in open-pit brown coal mining in the Rhineland coal fields — a triangle between the cities of Aachen, Mönchengladbach, and Cologne.
"We have to pre-test the new automation programs in order to minimize excavator downtime during the implementation phase," explains Nieß. This is where the research team at Siemens comes in. It’s developing a simulator for testing the new automation system.
"The industrial use of simulation is increasing everywhere," says Roland Rosen, head of the Digital Product program within the Global Technology field of Modeling, Simulation and Optimization at CT. Rose explains that simulations are part of a larger trend toward digital products, which means that future products are increasingly being created entirely on computers, from concept and development to documentation and testing.
Siemens’ new software enables the excavators to perform many tasks automatically that the machine operator previously had to control. For example, electronic commands tell the excavator’s control system which portion of the terrain it must excavate, and they cause it to automatically position the boom accordingly. The control system checks via GPS whether the machine is positioned correctly. Sensors measure the distance to the slope and they actuate an alarm if the machine is too close. "That’s a very important part of providing machine operators with an assistance system for their daily work," explains Baudisch.
The control system also senses how much coal the excavator’s buckets pick up, and it regulates the angular velocity at which they dig through the material so that the quantity of material transported by the conveyor belt remains constant.
Many new functions are designed to ensure that the excavators operate as efficiently as possible and without stoppages. That’s because the impact of downtime can be quite severe. "An excavator mines up to 240,000 t of coal a day," says Nieß. The enormous machines are relatively robust, but they have some potential vulnerabilities that can be electronically guarded against.
One sensor, for instance, will monitor the current flow of the track drive for the crawler units. The current must conform to a specified profile. Any variation is indicative of a problem with the crawler drive. Should such a problem occur, the drive immediately stops in order to prevent damage.
"We use algorithms to simulate both the motor current and possible faults in order to test the operation of the control system," explains Baudisch. "Simulation means replication, analysis, and optimization of the physical and automation functions of a system within a specified timeframe," says Rosen. This can be achieved by using diverse mathematical modeling approaches, such as time-discrete models or equations. The data are evaluated using software, and any variance in the parameters, such as velocity or weight, is displayed on virtual measuring instruments.
But the simulator will be used for more than just testing the new automation systems. "We’ll also be using it to train new excavator operators," explains Nieß. Generally, these are people with an electrical or mechanical engineering background. But since they are new to this equipment, it is best not to have them practice on a real excavator right from the start, not only because such machines are in use almost all the time, but also because the equipment is expensive.
"But before our simulator can be used for training, it will need some additional functionalities," cautions Baudisch. For instance, he and his team plan to connect the simulator to a moving platform, so that future excavator trainees get to feel like they’re in a real excavator cab. "It’ll work exactly like a flight simulator," explains Baudisch.
Once the simulator is ready in the spring of 2011, excavator operators-to-be will be able to practice with particular emphasis on those functions that cannot be controlled automatically. For instance, the groundwater drainage holes that are commonly encountered in open-pit mining must be avoided with room to spare during excavation. They will also be able to learn how to plan the routes taken by excavators in open-pit mines.

Self-Assembling Simulation Models? The development of simulation models is still very costly and complex. To begin with, the required information must be gathered from engineering drawings, circuit diagrams, path-time diagrams and other sources. These data are augmented by process-specific know-how, such as material properties, digging process models, and control models.
Today, simulation engineers still have to perform extensive manual operations in order to create simulation models. But Siemens researchers are thinking ahead. "We expect to be able to develop methods that automatically search out the needed data and assemble them into a complete simulation model," Baudisch predicts.
"The first prototypes for the virtual commissioning of control systems already exist. It’s still difficult to predict how soon these methods can be widely used in the development process," says Rosen. At any rate, Siemens scientists are already focusing much of their attention on the future.