Opening up controls architecture

Manufacturing Engineering, Nov 1995 by Owen, Jean V

Open architecture is good; proprietary architecture bad. Though some machine tool builders admit open architecture will work but aren't sure they want it to, others see a chance to ride the PC technology wave rather than always playing catch-up. That explains the traditional proprietary systems with a PC look touted as "open."

Allen-Bradley calls its 10/Series CNCs "open" because they have an ISA-compatible bus that accepts thirdparty hardware and software, common components, and modular hardware and software. Cincinnati Milacron's Acramatic 1200 CNC is built on two PC motherboards and looks like a PC at the operator interface. Siemens' "open-system" 840 D digital CNC features access to NC kernel software for customizing the control for specific machine functions and "man-machine modules:--PCs with integrated hard drivesthat allow the builder to add proprietary technologies for the operator interface.

Robomatix (Wixom, MI), which builds large robotic systems for companies like Boeing, "preserves the concept of an open system quite fanatical," according to Benny Granot, system software department manager, because connectivity of the system to the rest of its world is all-important. The front end of its proprietary CNC control--operator interface, VO handler, and application programming environment--stays intact, while the rear end, from the machine axis configuration to the motor drivers, changes with the application.

In a full-body laser cutting system installed at GM, for example, the robot controllers are proprietary, but the equipment around them--the PLC, which runs the four robots and vision system at the operational level, the network server, and the vision computer--can be any type. "The data link configuration lets the plant use the same algorithms whatever equipment the user picks," says Granot.

Wizdom Controls (Naperville, IL) says its Paradym-31 lets users "custom-build a control system using the most popular PC-based motion and logic control components," thanks to a Delta Tau PMAC board. (For more on the PC-CNC connection, see "The PC's CNC Transformation," ME, August 1995.)

When you get away from product-specific definitions, it's easier. "Open architecture is a series of black boxes that talk to each other," says Donald Adrian, who heads the Icon Industrial Controls Group (Shreveport, LA) industry-government consortium. "It's the Silicon Valley model the PC followed."

Defining "open" is simple, says Granot. Can you run your code on different computer controls under different operating systems with few modifications to the source code! Can you establish information flow between system components easily, while maintaining reliable data transfer and a friendly operating interface! If so, you have an open system.

Steven K. Sorensen, vice president, Cimetrix Inc. (Provo, UT), Motorola's partner in the development of an open-architecture, standards-based robot controller, says an open-architecture control must meet four requirements:

* It must use standard computing architectures like VME or ISA bus and standard processors like Motorola 680 x 0, PowerPC, or Intel 1x86/Pentium-based systems;

* It must be based on standard operating systems like Unix or Windows NT;

* It must be programmable in standard languages like Microsoft Visual Basic and Visual C or C/C and X-Windows/Motif; and

* Its control software must be open and extendable to let the OEM or user integrate custom control algorithms.

Engineering staff from eight GM, six Ford, and two Chrysler units recently produced a document stating that proprietary control technology--with prices dictated. by vendors, noncommon interfaces, higher integration costs, and special training requirements--is no longer acceptable. For future auto applications, controllers must be open, economical, maintainable, modular, and scalable.

Open means "allowing the integration of off-the-shelf hardware and software into a controller infrastructure that supports a de-facto standard environment."

Economical means low life-cycle cost, not low purchase price (the document goes on to list the- costs of opportunities lost because proprietary equipment could not be upgraded and the costs incurred because available hardware and software and tools could not be reused).

Maintainable means maximum uptime, fast repairs, easy maintenance, extensive support from controller suppliers, integrated self-diagnosis and help functions, and minimal spare parts inventory.

Modular means permitting plug-and-play of a limited number of components for selected functions.

Scalable means "easy and efficient reconfiguration."

At GM's Manufacturing Controls Dept., where an open-architecture program called OMAC is under way, C. Jerry Yen, one of the authors of the document, says definitions are changing. "No controller today is truly open, by our OMAC definition, which calls for open on the hardware side, modular on the software side, and with defined APIs [Application Programming Interfaces] for each module," he says. "Today, when we ask for 'open architecture' for the next major program at Powertrain, we mean a PC-based user interface and a SERCOS interface to drive the motors."