Pictures of the Future     Spring 2005

Five Decades of Automation

About 50 years ago, Siemens introduced microelectronics to automation technology. Suddenly, transistors were being used to control enormous steam turbine sets. It was an advance that marked the beginning of solid-state industrial automation.

Erlangen, 1956. A small team of experts is gathered at the Siemens-Schuckert plant. Their job is to find out what the recently invented transistor can do for the electric power industry. The team is given free rein and develops something entirely new. At the Paris machine tool fair in 1959, Siemens proudly presents the first generation of its "Building-Block System for Solid-State Controls": the SIMATIC G. These controls performed many functions, from summoning elevators when the "up" and "down" buttons were pushed, to directing machine tools to perform work according to a programmed sequence. Switching elements in that era’s conventional electromechanical systems were relays and contactors. But in the SIMATIC G, transistors performed these functions. Their advantage was that they were smaller and not subject to wear and tear. That’s why SIMATIC G was at first mainly used where highly reliable control elements were needed: in transformer substations and power plants.

In the ensuing decades, SIMATIC G has been succeeded by five generations of controls with an ever-expanding range of functions. While the first generation was designed entirely for programmed control functions, today’s SIMATIC-S7 system, as the core of Totally Integrated Automation (TIA), performs virtually any conceivable industrial automation task, from managing electric power generation to waste treatment, and from controlling transportation systems to manufacturing plants.

Worldwide Leadership. The SIMATIC platform continues to make Siemens a world leader in automation technology. "A key to our success is the fact that individual SIMATIC components have always interacted flawlessly," says Thomas Hahn, head of software development at Siemens Automation & Drives in Nuremberg. Another factor driving SIMATIC’s success was that Siemens tended to swiftly include innovations in semiconductor technology. But that also caused problems. In the development of SIMATIC G, for instance, several transistors proved useless for industrial applications. Their properties would gradually change until they disintegrated at elevated temperatures. But develop­ment engineers devised a method for identifying unsuitable transistors.

Another problem was that insulating properties were first tested with older methods that had been developed for robust contactor systems. Factory engineers would expose transistors to peak voltages in the kilovolt range—much more than a transistor can take. According to one early assembly report: "The failure rate of SIMATIC components was far worse than if entire control consoles had caught fire."

On the other hand, a factor that helped SIMATIC gain ground was the very positive response to the arc control system developed in the early 1960s. Siemens equipped many transformer substations with this system, because these facilities often suffered short circuits caused by arcs resulting from operator errors in using the switchgear, or from voltage surges due to lightning. The resulting damage was enormous and caused prolonged power blackouts. Arc extinction systems had to convert an arc into a harmless short circuit in a matter of milliseconds, which SIMATIC G could do thanks to its fast switching times.

The era of programmable logic controls (PLCs) began in the early 1970s. Their functions were not determined by hardware connections but by software, which made programming a lot easier. "In addition to the programming functions, SIMATIC has been able to accomplish more and more higher-level tasks," notes Hahn. A key requirement for making this possible was the continuing increase in device computing power: In 1965, a SIMATIC N module could perform 20 transistor functions and consequently 15 instructions per second. In the S5 module of 1988, the numbers had soared to about four million transistor functions and 32,000 instructions per second.

The S5 module, which was introduced in 1979, performed automation, pro­gramming and documentation tasks. Soon thereafter, the first bus systems were introduced. This technology was essential for data communication and commands. Bus systems integrated multiple individual controls into a single, powerful data network. During the 1990s, these advances enabled SIMATIC to develop into the core of a process control and management system that handles all automation tasks from the signal level to the control console.

Though on many occasions SIMATIC is still equated with programmable controls, that association has long been incorrect, explains Hermann Richter, product manager for SIMATIC PCS 7: "SIMATIC stands for Totally Integrated Automation, and consequently for a new way of implementing automation tasks." Take a brewery. A SIMATIC platform, Richter explains, makes end-to-end automation feasible. All of the fermentation, brewing, bottling and sales processes are controlled by a higher-order control level. "The advantage is that this will virtually eliminate costly system incompatibilities and discontinuities," explains Richter.

Platform for Control Systems. A prerequisite for such integration is uniform data networks that connect all levels of automation, much like a nervous system. Equally crucial is to structure the system landscape according to hierarchical and, as far as possible, autonomous levels. The advantage is, if a fault occurs, only the function of the affected process segment is lost; the rest of the system continues to operate, though with limitations. This approach also makes it possible to expand the system step by step. "The trend is clearly in the direction of open systems architecture," Richter says. He adds that this is necessary to protect the customer’s investment. "Such a system shouldn’t be scrapped early; it should continue to serve the customer’s needs."

As automation systems move toward open architectures, Siemens is focusing on implementing a uniform architecture for all the control technologies it makes. Some 40 different control systems are used in Siemens products, from telephone systems to control systems for building management and power plants.

A uniform platform would be a great advantage for Siemens and its customers, explains Werner Schlieker, product development manager at Siemens A&D AS in Nuremberg. Schlieker is coordinating the company’s platform project as part of the top⁺ Innovation business excellence program. A uniform platform, he adds, would yield great savings from R&D synergies. Investments of tens and even hundreds of millions of euros have gone into the development of each of these control systems. And customers would benefit mainly from simplified operation due to uniform interfaces. "Training expenses would also be cut sharply," adds Schlieker.
                                                                                                        Luitgard Marschall