Upload
emerson-exchange
View
130
Download
1
Tags:
Embed Size (px)
DESCRIPTION
Panel presentation by Dr. Willy Wojsznis, Emerson Process Management, given at the IFAC PID'12 conferenced in Brescia, Italy on March 29th, 2012
Citation preview
Slide 1
Future Perspectives of PID Controllers
(industrial process control)
Future Perspectives of PID Controllers
(industrial process control)
Willy Wojsznis
IFAC - PID’12 – Brescia Italy
IFAC Conference on Advances in PID Control
Brescia, 28-30 March 2012
Slide 2
Thoughts Thoughts • Where PID is?
• Why PID ?
• Direction for evolution
• Examples of PID evolution
• Conclusion
IFAC - PID’12 – Brescia Italy
Slide 3
Where PID is? 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 ago
IFAC - PID’12 – Brescia Italy
Slide 4
Where PID is ? Where PID is ?
IFAC - PID’12 – Brescia Italy
• 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 cooperation
Slide 5
Why PID ? Why PID ?
IFAC - PID’12 – Brescia Italy
• 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 6
PID – direction for evolution PID – direction for evolution
IFAC - PID’12 – Brescia Italy
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 strategy
Slide 7
PID at saturated conditions PID at saturated conditions
IFAC - PID’12 – Brescia Italy
• 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 limited
Slide 8
PID – model based adaptive tuning PID – model based adaptive tuning
IFAC - PID’12 – Brescia Italy
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
within adaptation range
Statistical validation – recent model quality,
parameters standard deviation, number
of adaptations
Well established, intuitive tuning rules – Lambda, IMC, SIMC
Model can be used for other purposes – loop diagnostics, performance monitoring….
Slide 9
PID – model free adaptation PID – model free adaptation
IFAC - PID’12 – Brescia Italy
There are number of smart techniques model free techniques
Fictitious set point
Controller switching
Balancing controller terms
+ SPi(t)
+ PVi(t
)
OUTi(t
)
; and ; k k
k k
PP P I I
I
1( ) ( ) 1i iT k T k
Slide 10
PID – loop diagnostics PID – loop diagnostics
IFAC - PID’12 – Brescia Italy
Valve diagnostics features – mechanical failure can nullify all gains achieved from improved tuning or control strategy
Slide 11
PID – loop diagnostics PID – loop diagnostics
IFAC - PID’12 – Brescia Italy
Simple valve diagnostics can detect valve dead band and hysteresis
2 ( )h A out 2 ( )Ampl PV Kr
2 ( )Ampl PVr
K b h r
Slide 12
PID future - conclusion PID future - conclusion
IFAC - PID’12 – Brescia Italy
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 applications