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Advanced Process Control for the Refining and Petrochemical Industry
  Aptitude software tunes multiple PID loops at the touch of a button


Cambridge UK , May 14 th 2007

The new AptiTune™ multivariable PID tuning software package, to be launched at European Refining Technology Conference in Rome next week, is the first ever software solution that enables control engineers to simultaneously optimise the tuning of several interacting PID loops.

One of the most important challenges facing the process industry is optimizing the operation of complex oil refining and chemical processes, without compromising the safety and integrity of the process equipment. Process complexity has increased significantly over the past two decades due to ever increasing levels of heat integration aimed at reducing operating costs. With ever more sophisticated control systems, engineers have to contend with optimising a large number of strongle interacting PID control loops – a difficult and often very time consuming task.


AptiTune TM has been designed to provide a comprehensive PID tuning solution for complex process units where interactions between the various PID loops are significant. It is easy to use and integrates simply into the standard APC workflow. Control engineers can easily and reliably tune several PID loops simultaneously that ‘fight' each other. Given a model, the optimiser can try several thousand different values for the PID tuning in a matter of seconds on a desktop PC and produce a good tuning solution in minutes, rather than the days or weeks taken by traditional methods.


Easy to use

The software uses an n x n OP to PV model matrix, so it understands all the interactions between the different loops. The control engineer picks the DCS specific PID equation and the type of controller (P, PI, PID, or I-only), and then enters the instrument ranges. The possibly noisy FIR model is then smoothed by fitting a high order state space model with explicit dead time, to approximate the FIR model. The resulting state space model is usually very smooth and reflects a high degree of process realism. The calculated tuning can withstand significant changes in process dynamics as the unit moves to different operating points, without the PID loops going unstable. Using this approach, AptiTune TM produces reliable tuning, even if the test data set was noisy or relatively short.


Process-specific tuning

Control engineers often need to achieve closed loop behaviour precisely tailored to the specific requirements of a process. AptiTune TM uses specific soft and hard tradeoffs as part of the design process so the user has complete and accurate control over competing design objectives like setpoint tracking and disturbance rejection. Key parameters can be precisely controlled. For example, limits can be placed on the maximum PV overshoot or on peak OP value for specified step changes in the setpoints. Loops can be made faster or slower at the expense of others, and so on.


And if the process dynamics change in the future?

AptiTune TM uses a sophisticated robust control approach and explicitly takes into account worst case changes in process gain and dead time to ensure all interacting loops remain stable and well-damped, even if the process dynamics change dramatically in the future.


This is the first PID loop tuner of its kind on the market and is long overdue ” commented Michael Harmse, Aptitude director. “ AptiTune TM will become an indispensible tool for control engineers helping them to achieve in minutes what used to take days or even weeks. The productivity improvements that AptiTune TM can deliver are enormous ”.

For full details about AptiTune TM and to download a demo, please visit www.aptitudegroup.com or email info@aptitudegroup.com


About Aptitude:

Aptitude Ltd specialises in providing software implementation services for the fast deployment of Advanced Process Control (APC) and realtime optimisation applications in the oil, gas and chemicals industries. These include APC, process operation analysis, benefit studies and application maintenance and APC training services. Its teams have significant experience managing large, complex projects and multiple stakeholders. Aptitude's unique business model has contributed to the success of many leading plants and refineries worldwide. Aptitude has offices in the UK and India .


For further details visit www.aptitudegroup.com or contact us at info@aptitudegroup.com



(c) 2007 Aptitude Ltd.