June 10, 2005 |
Highlights | Sponsored by FCI |
Choosing the best machine controller for an application can be a confusing process. Knowing the pros and cons of key motion control products—such as intelligent drives, intelligent motors, and intelligent bus-based motion controllers, as well as serial, centralized, and decentralized options—can help you make the best decision. |
Motion Control Options
Manufacturers and machine designers having a range of motion control options to select from. However, choosing the best controller for a specific application is often confusing. The following reviews the various choices for motion control and presents the pros and cons of each. Intelligent drives They offer cost and space savings for single-axis projects by often eliminating the need for a separate controller. Intelligent drives can also be used for multi-axis, distributed control applications where each amplifier is placed in close proximity to each motor. The advantages of the distributed approach is that the designer has the flexibility to match specific drives to individual axes and eliminate the long wires that connect to a multi-axis, central controller.
Intelligent motors Many users find the intelligent motor solution convenient since all components come from one supplier and work together seamlessly. The disadvantage of using one supplier, however, is that users cannot mix-and-match components from different vendors and, therefore, cannot pick the best-in-class for each component. Also, the intelligent motor solution becomes more costly and complex for multi-axis applications requiring motion coordination. As with intelligent drives, the intelligent motor solution puts the burden of axis synchronization and coordination on the host computer.
Intelligent controllers The main disadvantage of bus-based, central controllers is the connectivity and wiring complexity required for interfacing to various drives and motors. For example, the computer that contains the central control card may not reside close to the motors and drives. This results in long wires. Also, the bus architectures are at the mercy of PC vendors, as there may be a limited number of bus slots available. There is also the issue of the format perhaps becoming obsolete, like the ISA bus.
Serial multi-axis intelligent controllers Like other central controllers, a serial, multi-axis controller will relieve the host computer and programmer from the time-intensive and complex task of motion coordination. Also, the designer can mix-and-match motor types and choose the best drives and motors for the application. Unlike distributed control systems, central controllers tend to have more complex and longer wires going from the central controller to the various drives and motors.
Centralized intelligent controller/drive However, multi-axis amplifiers are less flexible for applications that require a different drive style for each axis.
Distributed intelligent controller/drive For example, the user might design a 16-axis system using four 4-axis controllers, two 8-axis controllers or eight 2-axis controllers. These are then distributed on a single network such as Ethernet. One controller can even be designated as the master over the other controllers. The master would receive commands from the host computer and then distribute appropriate commands to each controller in the network. This provides the advantage of reducing the communication burden for the host computer. Another advantage is that multi-axis controller/drives are typically more economical than multiple single-axis products. Further cost and complexity reductions are achieved because the controller and drive are combined as a single unit.
This article was supplied by Galil Motion Control Inc., www.galilmc.com |