28 July 2010
In 1996, KUKA launched a Windows based control solution for industry robots. The standardised, computer-based concept offered simple handling and flexibility. With its new control generation the company says its has replaced system limiting hardware with intelligent software functions.
This means that the new systems requires 35 per cent less hardware and 50 per cent less plug connections and cables compared to its predecessor. The complete safety control has been integrated into the control system without the need for proprietary hardware. Thus, Kuka has developed computer-based robot control with integrated safety soft PLC.
“By omitting restrictive hardware components in favour of nearly unlimited extensibility of the software-based security interfaces, completely new safety concepts in automation can be realised,” explained Manfred Gundel, CEO of Kuka Roboter GmbH. The KR C4 architecture also gives flexibility to integrate new sensors, which will be used in future to enable close co-operation between humans and robots.
Conventional interfaces have been replaced with intelligently connected data streams, allowing for direct communication between the single modules of the KR C4. This does not only save material cost, but also improves performance and availability. The new robot control is based on open industry standards like multi-core and Ethernet. While the previous version KR C2 communicated over seven partly proprietary technologies, now only one is needed: with the KR C4, the whole communication is done over real-time Ethernet.
Choosing the mainboards
In choosing the mainboards, Kuka relied on the same manufacturer that has been delivering the boards for the KR C2 control since 2005. Back then, Fujitsu Technology Solutions had replaced an Asian manufacturer as mainboard supplier: As the mainboard is the central component of a control, very high requirements had to be fulfilled. Beside the guaranteed availability of all single components, it is also indispensible that all system functions are reliable and extremely stable even under rough and demanding conditions. “Our control systems have to stand 24/7 operation at an ambient temperature of up to 45 °C,” explains Heinrich Munz, senior software developer at KUKA.
Munz, who has been significantly involved in the development of the new control generation, sees a decisive advantage in the close proximity to the partner, a factor that had a positive effect on the KR C4 development: “Like our company, Fujitsu’s development department and production are located in Augsburg. This makes it easy to be in regular contact with our motherboard manufacturer when preparing an upgrade of our control.”
The preceding version worked with a single-core processor. For the new control generation, a multi-core processor with more computing power and independent operating cores has become necessary as the previously implemented external components for safety control, automation control etc. have now been replaced with software functions. The most important requirements for the mainboard included multi-core support, durability, high quality and reliability under challenging industrial circumstances (continuous operation, higher temperatures). Additionally, the mainboard provider should have good platform know-how and be able to deal flexibly with special customer requests regarding layout, features and BIOS.
Mainboard Adjustments due to Special Requirements
For Kuka, the mainboard D2608-K employed in the new robot control was derived from the Fujitsu standard product D2608-A, which has already been used in several thousand of Fujitsu’s Celsius workstations. “KUKA profits from the mass production of the base version. The fact that we are using it in our own systems testifies to the high degree of product maturity. Due to a high output volume, cost can be kept down, and availability of the materials has also been secured in the long run,” explains Peter Hoser, director of OEM Sales at Fujitsu Technology Solutions in Augsburg, who is responsible for the distribution of industrial mainboards.
The D2608-A is a workstation mainboard based on Intel’s X3 Express chip set for Core2 Duo and Core2 Quad processors. The six-layer construction ensures highest signal quality and reliability in operation. It was at the very beginning of Kuka’s new robot control design phase that Fujitsu initiated some necessary board adjustments, for example in the voltage monitoring or the system management micro-controller. In addition, customised functions for KUKA were implemented in the BIOS.
There have been further special requirements to the mainboard since the safety control for the emergency stop in the KR C4 was implemented as safety PLC on the mainboard which now communicates via “Safety over Ethernet”. “However, Kuka has communicated its adjustment requests early enough, so we were able to integrate all desired functionalities into the board,” Peter Hoser explains. During the KR C4’s three-year development time, the robot control developers were in regular contact with the motherboard provider. The realisation of these safety functions in “safe technology” over dual software created by two compilers on two CPU cores meant an enormous effort for software development, documentation and certification of the Technical Inspection Authority (TÜV). “Eventually this additional effort meant the technology leadership for KUKA regarding the realisation of a safe and nonetheless cost-efficient robot control, which nearly revolutionised the interaction of men and robot,” says Hoser.
In addition to the D2608-K, Fujitsu has developed a durable Dual Gigabit Ethernet card for KUKA, which together with the D2608-K’s onboard Gigabit Ethernet controller are the essential interfaces of the control computer as the KR C4 communicates with the outside world only via these three default Ethernet controllers.
Green Automation
Thanks to the exclusive concentration on Ethernet, other functions, among them energy-saving procedures, can also be realised with the KR C4. Although production in the majority of cases is down on weekends, control systems have hardly ever been shut down so far, because a complete reboot of the production equipment on Monday mornings takes too long, leading to very high and unnecessary energy consumption. With the “wake on LAN” function of the Ethernet controller, it is now possible to send all systems into sleep-mode via telegram from a central hub on Friday evenings. The centrally controlled wake-up call on Monday morning puts all controls into the same state they were left in on Friday.
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