05 February 2001
Ethernet in Motion Control
When UniWest of Pasco, Wash., wanted to network its motion control application, it connected its ETC-2000 three-axes scanner to a Parker Compumotor 6K4 controller via Ethernet. A leader in the nondestructive testing industry, UniWest began using the 6K4 and Ethernet connection in 1999, upgrading from an ISA-based controller. UniWest's ETC-2000 inspects jet engines, and it's now operating at full capacity.
Ethernet also adds the benefit of remote networking. Texas Instruments in Attleboro, Mass., for example, is using the 6K controller's Ethernet capability to remotely troubleshoot one of its machines in the U.K., eliminating the expense of sending a technician to Europe.
Dan Winebrenner of Fogg Filler, a bottle- and bag-filling equipment manufacturer in Holland, Mich., sees Ethernet as the option of choice over other protocols: "We use the Ethernet connectivity because it is a simple connection between the Compumotor 6K controller and the power station. The Ethernet was a better choice than the serial connection. It's worked great. I haven't had any problems with it, and I would use it again if I had a similar application."
So why have hundreds of motion control users chosen Ethernet over fieldbus and PCI? And what is so special about the 6K? As far as industrial motion control is concerned, Ethernet, fieldbus, and PCI are all capable of carrying the same information between a high-level machine controller and a motion controller. Ethernet is a networking protocol, PCI is a PC bus architecture, and fieldbus is used in industrial control. These three technologies are now competing for the same users, and while the playing field may be level, the technologies offer their own highs and lows. But Compumotor sees a definite advantage in Ethernet and has decided to base its single- and multiaxis motion technology on Ethernet communications. Its 6K controller is a technology-independent, stand-alone motion controller—an aggressive line of multiaxis controllers that drives down costs, eases programming tasks, and takes advantage of Ethernet field communication standards.
"The trend toward distributed, open digital drive networks and software-based motion programming is as plain as the nose on your face," said Compumotor's general manager, Roy Glassett, "and it's occurring in an Ethernet-dominated environment."
Motion and machine control has been center stage in the proprietary offerings of most factory and process automation firms. During the 1990s, these technologies began to adopt factory network communication strategies that themselves had proprietary roots. In an effort to open and decentralize motion control architecture, the pace of integration between motion- and machine-control platforms and sensor and fieldbus networks has reached a zenith. Compumotor had the choice of offering interfaces to a wide variety of networks but saw Ethernet as the most powerful network of all. Ethernet is as ubiquitous in automation and control as it is in computing in general. It has these important contemporary attributes:
- Software-based motion programming is easier to implement on Ethernet, at
lower cost, than any other communications network.
- Customers can openly choose programming packages. They won't be tied to
single vendor offerings.
- Customers for both new motion installations and upgrades are expressing
a higher priority for their network choice than for their motion solution.
- For a motion control leader such as Compumotor, porting software to a single
network enables engineers to concentrate on motion control functionality rather
than driver development.
- Each serious sensor and fieldbus network, no matter how proprietary, includes
Ethernet connectivity. This allows Compumotor to preserve fieldbus objects—device
descriptions and function blocks—that have already been developed by customers.
- World-class manufacturers are moving swiftly to implement Internet access
for customers via enterprise resource planning (ERP) software. By integrating
motion and machine control on Ethernet, direct connectivity with the ERP system
is easily established. Build-to-demand strategies can be automated.
- Motion control is swiftly shedding its "island of automation" image to become
an integral portion of the run-time system. Motion control component software
integrated with Windows NT is attractive because it offers seamless integration
with machine logic. Ethernet is the physical communications backbone for this
- Supplier independence requires network solutions and component software.
Systems integration and multivendor support are prime considerations, equal
to the choice of motion control components for machine control solutions.
- With Ethernet, there's simply no contest if openness, availability, and
costs are issues. While every other fieldbus and sensor network has supporters
and detractors, Ethernet has only supporters and a robust forward migration
path that will outlive many human generations.
- No fundamental engineering issues block the path to use of Ethernet in the
most demanding real-time, high-performance motion applications. Thanks to
readily available software that runs on Ethernet-enabled PCs, motion is far
easier to program.