OAenterprise and Automation Trends

Present day automation schemes have a number of general characteristics such as:

• They have been in the past based upon large quantities of directly connected inputs and outputs.
• The accumulated cost of the developed application is weighted heavily in favour of the engineering man hours.  The hardware is a very small part of the total cost particularly if you take into account the constant modification and upgrade that these systems undergo during their life.
• The various automation functions generally consist of a number of technologies from a number of suppliers.
• They have often grown in a haphazard manner with a variety of technologies.
• Growth or extension of the system can be difficult.
• There is quite often a disconnect between the business system that is based upon a relational database and the real time control system that runs the plant.

Real time control systems such as PLCs and DCSs were originally characterised by large quantities of inputs and outputs. The rapid growth of field bus systems means that the control processor is not an I/O scanner any more but is instead a command execution machine with I/O being handled via the network and serial connections. These systems are looking more like general purpose computers all the time.

In order to remain competitive manufacturers must make continuous improvement and apart from changes to the process itself the mechanism is often via the automation scheme. Either way the automation scheme requires constant tuning and modification in order to satisfy the requirement for improved manufacturing efficiency. Since hardware costs appear to be always decreasing and continuous engineering effort is required on these schemes the lifetime cost is predominantly man hours. Anything that can improve this situation is an advantage.

The overall plant automation scheme is often a multitude of systems combined together with interfaces between each and supported by very skilled people. A typical manufacturing plant can have multitudes of PLCs, DCS systems and sometimes Manufacturing Execution Systems (MES) or even SCADA systems. They are often from many suppliers and usually have operator interfaces from yet other suppliers. This multitude of systems is extremely complex, expensive to support and requires advanced engineering skills that are hard to find.

All manufacturing plants adapt and change over time. If nothing else factories are keen to exploit the advantages of higher production to reduce unit costs and further spread the overhead. Automation technology is being constantly added and modified and the same type of hardware is frequently not available. Perhaps this type of ad-hoc expansion is unavoidable but it adds to the problems of maintenance and support. It also means development of interfaces between systems and integration difficulties making extension difficult.

Control systems are time dependant devices and are by and large event driven. They are developed by engineers who are very mindful of the performance of the control system that is required in order to satisfactorily control the plant or process. Business systems on the other hand are transaction driven and are developed by IT people who are very mindful of the need to not lose data but are not so concerned how long it might take the processor to execute a transaction.  It is perhaps not surprising that it has taken so long to bridge this gap.

Most systems still today do not try to provide interfaces between these systems and manage this process by pen and paper.  The financial recording system (ERP) is often regarded as more critical than the production control system however the failure of either system can be catastrophic for the business and the failure to communicate between these systems causes problems.

OAenterprise is the next generation of system that can go a long way to solving these issues. OAenterprise is a highly integrated packaged that is built around reusable objects, is extensible and scalable and built on a Windows platform. Using the Windows platform means that all the interfaces you could possibly want are available at reasonable cost. This includes interfaces the low level plant transducer level and to the high level ERP systems.

Automation Design

A plant automation scheme requires many levels of control and monitoring in order to provide the required level of automation as well as the necessary integration into the organisations business systems.

Many customers have their own notion of ‘automation levels’ so we have used them as follows:

• Level 1 - The plant transducer level. These can be simple pressure and flow transmitters on an analogue link or alternatively sophisticated transmitters that use a field bus to send fault and statistical data as well as the measured value on a data link of some sort.
• Level 2 - The logic and real time control level. It traditionally consists of PLC and/or DCS systems. This is normally the first level where some control and intelligence is applied. It consists of logic for stop/start, open/close type actions and control loops for continuous control.  Operator displays are frequently added to this level.
• Level 3 - The plant supervisory level. For complex plant this can consist of sophisticated controls and modelling systems to ensure high level performance. More frequently it consists of the SCADA and recipe type level where job lots, batches and recipes are determined and handed down for the lower levels to execute.  This is sometimes also called a manufacturing execution system or MES.
• Level 4 - The business system. These are diverse and very complex systems because of the technology and their size.

There will always be variations on this theme and in some very large and very complex plant it is possible to identify as many as 6 distinct levels. Steel production and petrochemical plants are examples where there will, through necessity, be additional levels. Most however, fall within these guidelines.

OAenterprise by ObjectAutomation Inc is the first of the future generation control and supervisory systems where these two levels (levels 2 and 3) are integrated into one package and based upon standard operating system architectures.

Further more it is object based and thus allows designers to naturally break the design down into smaller and more easily understood portions as well as making it simpler and quicker to extend when required. Its use of DCOM means that the system is truly distributed and can be spread across as many physical processors as cost, performance and availability dictate.