E-Servo for e-motion

Monday, October 30, 2000

Rocklin, CA--E-Series Motion Controllers from Galil Motion Control Inc. are designed specifically for Ethernet-based distributed control systems. To realize the shorter wiring of a distributed control system and the low cost and simple programming of centralized control, E-Series firmware allows the controller to be configured as a master or a slave. As a master, one controller commands all the other slaves via Ethernet, and appears as a "virtual multi-axis" controller to the host PC.

According to Galil, benefits include:

*Simpler code. It off-loads programming from the host to the controller.

*Efficient communication. The host only needs to communicate with one controller instead of many.

*Lower cost. 2-axis capability allows grouping motors in pairs for coordinating motion instead of using two separate single-axis controllers.

One of the first decisions a motion system designer must make is between central or distributed control. Centrally controlled systems use one motion controller to control all of the motors. That motion controller is often implemented in a host PC with ISA-, PCI-, or PC104-based motion cards. But in some instances, it's accomplished using a standalone controller communicating serially by RS-232 or other form with the host computer.

Either way, according to Galil President Jacob Tal, the advantage is simpler programming because the host only needs to communicate with a single device. The biggest drawback is wiring complexity, since all the various I/O devices such as motors and encoders must be connected to the controller. "Such long wiring may be cost prohibitive, and may produce noise levels that degrade performance--especially in larger systems," says Tal.

That's why distributed systems are used. With a single-axis controller near each motor, the wires are shorter. "But because each controller deals with a single motor," Tal explains, "system designers must coordinate between the various controllers, making the host computer program much more complex."

To meet the objective of short localized wiring, simplified programming, low-cost components, and efficient communications, Galil developed a new design approach that Tal calls the E-Servo. The DMC-3425 is the first controller in the series and sells for $695 in single quantity, which lowers to $445 in quantities of 100.

"The technology combines all the benefits of the two approaches," Tal says. To work, the motion controllers and the host communicate through an Ethernet LAN hub. Controllers placed near the motors and the I/O signals reduce wiring. But Galil went an extra step to simplify the programming. By making one controller a master that communicates with the other controllers, it becomes a virtual central controller to the host.

"This means the host needs to communicate with only one controller," says Tal. In an effort to reduce the cost, Galil allows each controller to control two motors. "Because coordinating axes require motors to operate in pairs," explains Tal, "using a single controller to control both motors can significantly reduce the cost, and the wire length is not increased much."

For more information visit www.galilmc.com.