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Soft controller combines motion and logic functions
Published:  01 October, 2000

Soft controller combines motion and logic functions

A software package that performs both motion and sequential control functions, and a hardware controller that cuts the cost of distributed control, are the latest members of Rockwell Automation`s Logix family of industrial controllers that share a common "engine" and programming technique.

The expanding Logix family now includes process controllers, and integrated as well as distributed sequential controllers. All use the same programming techniques, leading to savings in training, designing, implementation, and maintenance, according to Rockwell.

The company has also released preliminary details of further Logix products, still in the pipeline. These include a drive - called DriveLogix - that will be able to control both PM and standard induction motors, will accept inputs from high-resolution encoders and will offer a choice of control strategies.

The PC-based implementation of Logix - called SoftLogix 5800 - incorporates a "virtual chassis" that replicates the functions of a traditional PLC and an HMI. Using a monitoring tool, users can create, configure, and control processors and communication cards in the PC.

The package can perform multi-axis motion control in software and generate complex cam profiles in a fraction of the time needed for hardware-based systems. John Pritchard, Rockwell`s motion control business manager for the UK, gives the example of a system running on a 300MHz PC which, he says, can generate a profile from a few points in just 1ms, compared to the 30ms typically needed by a PLC.

Pritchard says that unlike some other "soft" motion controllers which perform their calculations on a card plugged into a PC, SoftLogix 5800 uses the PC`s own processor. The advantage, he says, is that it will become even more powerful as faster processors emerge.

Initially, SoftLogix 5800 is available for Windows NT and 2000, but other versions are planned including one for the portable Windows CE operating system. Also in the pipeline is a SERCOS interface.

The latest hardware implementation of the Logix engine is a distributed control system called FlexLogix, which combines Logix with Allen-Bradley`s Flex I/O to create a controller that can be mounted on a DIN rail close to the point of application. It can handle up to 256 local I/O points and a further 256 via a network.

Next year, this will be joined by an all-in-one controller called CompactLogix. Richard Sturt, Rockwell`s control and information group business manager, expects users to choose between the distributed or centralised versions according to their wiring preferences. Although the CompactLogix controller will be 15-20% cheaper than a similar FlexLogix system, its wiring costs will be higher.

Also due next year is a variable speed drive, based on Rockwell`s Powerflex family, but incorporating the Logix engine to give it extra power. Details of DriveLogix are still sketchy, but it will offer: a 50µs update rate; a choice of networking topologies; a motion planner that can control permanent magnet motors; and inputs for 4 million pulse/revolution dual encoders. The drives will provide a variety of control options including open-loop, vector and brushless AC, and each will have its own IP address to link it into the Internet.

Rockwell`s UK marketing manager Steve Darnell says that the DriveLogic will replace not only PLCs but also mechanical linkages. He cites the example of the flying knife cutters used in paper-making which have traditionally used gears to co-ordinate the movements of two rotating cylinders. "You will be able to replace the gears with DriveLogix," he says, "producing a 25-30% reduction in implementation costs". DriveLogix is expected to go on sale in the UK next summer.

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