With control choices expanding daily, some users are confused about what type of control to specify: soft control, PLCs, hybrid controllers, or new architectures. To assist users, Rockwell Automation (West Allis, Wis.) plans to provide a control engine (the services that implement control tasks) that will be common throughout company's platforms and devices.

Along with multiplying choices, control is spreading to all parts of the automation landscape. No longer constrained by limited vendor offerings, desired control type is defined by application requirements. Some solutions require modular control with maximum flexibility in the smallest space; some must be distributed close to the process in sensors or actuators; and others require open, packaged, or embedded control. Control type is dictated by application needs, rather than the "box" where the control resides.

Rockwell Automation's "Logix" engine delivers common control services across multiple requested platforms. It has three core characteristics: portable, contemporary, and fast.

Regardless of size, type, or position, the same Logix engine can be used in a range of devices. Logix's services are also the same when implementing a process application, a discrete manufacturing line, or a drive system. Since all Logix applications use common development tools, developer and operator training is minimized after the first installation. A common data model ensures consistent information exchanges among various Logix-based controllers.

Reflecting current software tools, Logix's object-based design offers an intuitive environment for design, development, and troubleshooting. Logix also uses native symbolic programming, which allows symbols to be part of the run-time environment. This becomes a self-documenting feature, permitting future users to understand the program faster. Human-machine interface and production control systems use the same native symbols without need for translation. Standard control programming chooses symbols within the programming tool to represent devices, such as floor I/O devices (sensors, valves, etc.). However, when the programming tool is removed, addressing be-comes an arcane set of letters, numbers, and punctuation.

Logix is about three times faster than Allen-Bradley's PLC-5 programmable controller. This speed allows efficient multi-tasking-multiple control tasks to run simultaneously. For example, separate sequential, motion, and process tasks can run concurrently on a single Logix engine implementation.

Rockwell Automation has been developing its Logix strategy for several years, and implementation will be phased in gradually. The first product with the Logix engine is the Allen-Bradley Logix 5550 controller, part of the ControlLogix system. The engine is part of Allen-Bradley's ProcessLogix system and will soon be included in the SoftLogix 5 Controller. The company also plans to launch several subsequent products based on users' distributed, embedded, and packaged control needs.