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Future Perspectives of PID Control

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Panel presentation by Dr. Willy Wojsznis, Emerson Process Management, given at the IFAC PID'12 conferenced in Brescia, Italy on March 29th, 2012

Panel presentation by Dr. Willy Wojsznis, Emerson Process Management, given at the IFAC PID'12 conferenced in Brescia, Italy on March 29th, 2012

Published in: Education, Technology, Business

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  • 1. Future Perspectives of PID Controllers (industrial process control) IFAC Conference on Advances in PID Control Brescia, 28-30 March 2012 Willy WojsznisSlide 1 IFAC - PID’12 – Brescia Italy
  • 2. Thoughts • Where PID is? • Why PID ? • Direction for evolution • Examples of PID evolution • ConclusionSlide 2 IFAC - PID’12 – Brescia Italy
  • 3. Where PID is?  PID proved it can compete in many applications with new promising techniques, like  Fuzzy Logic  Model based controllers  MPC  Slogans “replace all PID” is not used as10-20 years agoSlide 3 IFAC - PID’12 – Brescia Italy
  • 4. Where PID is ? • PID “found” its favorite spot, where it is doing the better than other techniques  This is the low and intermediate level control in process industry where PID is absolutely dominant control  MPC reign in multivariable control and optimization. PID provide good control at the lower level  Instead of competition – good cooperationSlide 4 IFAC - PID’12 – Brescia Italy
  • 5. Why PID ? • Feedback is universal control • Intuitive for the human, appreciated by operators • P I D - the most natural rules • PID like control used in nature on various levels and time scale (molecular level - seconds, species – thousand of years)Slide 5 IFAC - PID’12 – Brescia Italy
  • 6. PID – direction for evolution  Enhanced PID for dealing with special conditions or applications with added logic and calculations  Examples: saturated conditions, wireless, event driven, non-linear ….  Robust adaptive tuning and control  Performance monitoring and reporting  Valve diagnostics – mechanical failure can nullify all gains achieved from improved tuning or control strategySlide 6 IFAC - PID’12 – Brescia Italy
  • 7. PID at saturated conditions • A better response to major upsets can be achieved through the use of a dynamic pre-load and reducing the filtering that is applied in the positive feedback path when the output limitedSlide 7 IFAC - PID’12 – Brescia Italy
  • 8. PID – model based adaptive tuning  Why model based adaptation?  Model validation for model switching adaptation with parameter interpolation is performed in parallel with parameter evaluation  Ratio of maximum to minimum errors signifies how fast is conversion  If the model with the middle parameter value has smallest error it indicates the optimum is  Well established, intuitive tuning rules – Lambda, IMC, SIMC within adaptation range  Model can be used for other purposes – loop diagnostics,  Statistical validation – recent model quality, performance monitoring…. parameters standard deviation, number of adaptationsSlide 8 IFAC - PID’12 – Brescia Italy
  • 9. PID – model free adaptation  There are number of smart techniques model free techniques PVi(t SPi(t)  Fictitious set point ) + + OUTi(t )  Controller switching  Balancing controller terms P P   Pk ; and I   I k ;  k k I 1  Ti (k )   Ti (k )   1  Slide 9 IFAC - PID’12 – Brescia Italy
  • 10. PID – loop diagnostics  Valve diagnostics features – mechanical failure can nullify all gains achieved from improved tuning or control strategySlide 10 IFAC - PID’12 – Brescia Italy
  • 11. PID – loop diagnostics  Simple valve diagnostics can detect valve dead band and hysteresis h  2 A(out ) 2 Ampl ( PV )  Kr r  2 Ampl ( PV ) b  hr KSlide 11 IFAC - PID’12 – Brescia Italy
  • 12. PID future - conclusion  PID will continue to be main control on the basic level in the process industry  PID evolution as discussed will enhance PID competitiveness  Model free adaptive tuning can be useful in special applicationsSlide 12 IFAC - PID’12 – Brescia Italy