What’s happening in batch automation these days?
The big thing in batch automation is to go small and to go fast. Batch automation systems follow the ISA 88 standard with a lot of success, but there has always been a concern that systems built to the standard are too big, expensive and slow for small jobs. The latest trends are to implement smaller unit-controllers; better integration between the controller programming system and the batch system; and support for faster batch step times.
Control vendors are addressing the size problem by providing complete unit level batch systems. These systems provide combined control code execution and recipe execution in a single box. Unit recipes are downloaded when needed and executed locally. This allows engineers to add batch capabilities to smaller systems without requiring the large investment required for complete batch automation. Unit level controllers also have the advantage of support for faster batch steps.
Because of communication delays and synchronization between the recipe execution server and the controller, most first generation batch systems were limited to a few seconds per batch step. Integrated recipe execution and control systems allow batch steps at the sub-second level. This allows the well defined ISA 88 structure to be applied to a wider number of projects.
Control vendors are also addressing the problems of integration of the recipe execution system to the controller code. First generation systems used a set of user-written controller code called a Phase Logic Interface (PLI) to handle to protocol between the recipe execution server and the controller. This code was often bigger and more complex than the actual control code.
Control vendors are now integrating the batch and control code development environments. With one click, an engineer can define a phase and have all of the associated controller code automatically generated and linked to the recipe execution system. Using conservative measures on new automation systems, this integration has reduced the implementation time for batch by more than 75%.
Basically, batch automation has become a “solved problem,” and second generation batch automation systems allow the well understood and proven ISA 88 models to be applied on smaller projects, where faster response is needed, and without extra control programming.
|Dennis Brandl is president of BR&L Consulting and ISA 88 committee chair.|