1 / 55

   Achieving Target Control Performance Using                                 Fieldbus Devices

   Achieving Target Control Performance Using                                 Fieldbus Devices. Presenters. Terry Blevins Marcos Peluso Dan Christensen. Introduction. Overview – FF Block Applications that May be Addressed Single loop feedback control Feedforward control Cascade control

rhonda-morin
Download Presentation

   Achieving Target Control Performance Using                                 Fieldbus Devices

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1.    Achieving Target Control Performance Using                                Fieldbus Devices

  2. Presenters • Terry Blevins • Marcos Peluso • Dan Christensen

  3. Introduction • Overview – FF Block • Applications that May be Addressed • Single loop feedback control • Feedforward control • Cascade control • Interlock, Input selection, Flow integration, Calculations and characterization • Control Performance • Variation if Block Execution Time • Impact of Device Response Time and Slot Time • What determine Macrocycle • Example – Single Loop • Splitting Control Between Fieldbus and the Control System • Impact on delay on loop response, guidelines • Future – Assigning blocks to execute in DeltaV H1 card • Future – Viewing Execution Schedule • Summary • References

  4. FF Function Blocks Function Blocks Addressed by FF Interoperability Testing, v4.5 • AI – Analog Input • AO – Analog Output • PID – PID Control • DI – Discrete Input • DO – Discrete Output • ISEL – Input Selector • ARITH– Arithmetic • SC – Signal Characterizer • INT – Integrator • MAI – Multiple Analog Input • MAO – Multiple Analog Output • MDI – Multiple Discrete Input • MDO – Multiple Discrete Output

  5. Applications that may be addressed using FF function block capability • Single loop feedback control • Feedforward control • Cascade control • Interlock based on a discrete input • Input selection when redundant measurements are available • Flow integration • Calculations and signal characterization

  6. FC 101 Feed Tank Example: Single Loop FT 101 Feed

  7. Single Loop - Fieldbus

  8. FC 151 Example: Interlock Based on Status of Blocking Valve ZT 150 FT 151 Reactor 1 Feed

  9. Interlock Example: Use of Discrete Input From Upstream On-Off Valve

  10. AC 302 Example: Selection of Redundant Measurement AY 302 AT 302 AT 301 Static Mixer Feed A Reactor 1 Feed B

  11. Automatic Input Selection for Redundant Measurements

  12. TC 202 TC 201 Example: Cascade Control TT 202 RSP TT 201 Coolant Reactor 1 Discharge

  13. Cascades Loop - Fieldbus

  14. Arithmetic Block May be used to address a Variety of Calculations • Flow Compensation – Linear • Flow Compensation – Square root • Flow Compensation – Approximate • BTU Flow • Multiply and Divide • Average of inputs • Sum of inputs • Fourth order polynomial • Simple HTG compensate level

  15. FY 3-4 FY 3-4 Example: Calculation and Integration of Mass Flow Pressure & Temperature Compensation Totalized Mass Flow PT 3-4 TT 3-4 FT 3-4 Process Steam

  16. Example: Arithmetic and Integrator Function Blocks

  17. TE 801A TE 801B TE 801C TE 801D TE 801E Fieldbus enables Multi-sensor Applications Distillate Receiver Distillate TT 801 Feed Column Distillation Steam Bottoms

  18. Multi-sensor Applications (Cont) • Chemical Reactors Process In TT 901 TE 901 A-H Cooling Fluid In Cooling Fluid Out Process Out

  19. Example: Multiple Analog Input Block Supports a Maximum of 8 Inputs From a Fieldbus Device

  20. Other Function Blocks Are Defined by FF and Supported by Some Devices Blocks not included in device testing/registration ITK v4.5 , v5.0 • DC – Device Control (motor control) • OS – Output Splitter (split range control) • LL – Lead Lag (dynamic compensation of feedforward) • DT – Deadtime (dynamic compensation of feedforward) • SPG – Setpoint Ramp Generator (Program setpoint change) • AAL – Analog Alarm (alarming based on calculated value) • CS– Control Selector (override control for constraint handling) • B/G – Bias Gain (coordination of multiple loops) • RA – Ratio (blending to specified feed ratio)

  21. Control Performance Using Fieldbus The control performance that may be achieved is dependent on many factors: • Function block execution, maximum response time for compel data and slot time ( dependent of the device technology/design – specific to manufacturer) • Whether control is done in the field or in the control system (customer decision) • Scheduling of block execution and communications on the FF segment (dependent of control system design)

  22. AI Function Block Execution Time

  23. AO Function Block Execution Time

  24. PID Function Block Execution Time

  25. DI Function Block Execution Time

  26. DO Function Block Execution Time

  27. Calculation Block Execution Times

  28. Example*: Second GenerationThird Generation Improvement AI = 30ms AI = 20ms 33% PID = 45ms PID = 25ms 44% * Execution times based on Rosemount 3051 Third Generation Devices Offer Significant Improvement if Block Execution Time

  29. Variation in Device Response Time of Different Fieldbus Devices

  30. Typical Slot Time for Different Devices

  31. Control Execution is Scheduled Based on the Segment Macrocycle A Macrocycle is determined by: - Function Block Execution times. - Transmission time of the cyclic messages. -Gaps between messages determined by the Network parameters. -Time reserved for acyclic messages

  32. AI=30 PID=45 TT AI=30 PID=45 Cascade Control Example FT AO=80 FCV Macrocycle • Function Block execution time depends on the type of block and on the hardware and software design. • In the time calculation, only blocks that must be executed consecutively are considered. • Block Execution Time = 30+45+45+80 = 200 ms • *Note that the AI in the flow device is executed in parallel.

  33. DATA CD DATA CD AI PID AO 0 250 Macro Cycle ms Bus Traffic 2.3 ms 5.4 ms Macro Cycle Macro Cycle Macro Cycle Macro Cycle Scheduled Control Execution

  34. DATA DATA DATA Macrocycle Some manufactures may by default assume conservative constant values for MRD and SLT. The user may change these values. MID MID CD FB FB (MRD+2xSLT) SLT - Slot time MRD - Maximum Response Delay MID - Minimum Inter PDU Delay

  35. Network Parameters • Network Parameters establish how the network operates. • The LAS must be set with the larger parameter values of the devices participating in the Network. Backup LAS LAS SLT =5 MRD=4 MID =8 10 4 12 SLT = 10 MRD= 3 MID = 12 SLT = 8 MRD= 3 MID = 10 SLT = 4 MRD= 4 MID = 8 Link Settings

  36. Impact of Network Parameters on Maximum Number of Communications/Second Ideal Max. CD DATA CD SLT= 16 MRD=10 MID= 12 20 / s 3.1 5.4 2.3 41 49.50ms Ideal Max. SLT= 8 MRD=3 MID=12 CD DATA CD 58 / s 2.3 6.14 5.4 3.1 17 ms Ideal Max. SLT= 1 MRD=1 MID= 1 CD DATA CD 125 / s 2.3 5.4 8 ms

  37. AI PID XFR AO XFR Minimum Execution Time With Only One(1) Control Loop on an H1 Segment 20ms 25ms 30ms 60ms 30ms Macrocycle = 165 ms Assumptions: 3rd Generation Transmitter, AI&PID executed in Transmitter, Second generation Valve executes AO

  38. Executing PID in the Valve Reduces the Number of Communications But Increases Loop Execution Time AI XFR AO PID 20ms 30ms 120ms 60ms Macrocycle = 230 ms Assumptions: 3rd Generation Transmitter, AI executed in Transmitter, Second generation Valve executes AO&PID

  39. AI PID XFR AO XFR Minimum Execution Time With Only Two(2) Control Loop on an H1 Segment AI PID XFR AO ACYCLIC XFR 20ms 25ms 30ms 30ms 60ms 30ms 55ms Macrocycle = 250 ms Assumptions: 3rd Generation Transmitter, AI&PID executed in Transmitter, Second generation Valve executes AO, 50ms for every 125ms of the execution schedule (for display update)

  40. Impact of Splitting Control Between Fieldbus and Control System • Execution in the control system is typically not synchronized with function block execution on fieldbus segments. • Lack of synchronization introduces a variable delay into the control loop as great as the segment macrocycle e.g. 1/2 sec loop may have up to 1/2 sec variable delay. • Added delay will increase variability in the control loop.

  41. PID 0 0 0 0 0 0 250 250 250 250 250 250 DATA DATA CD CD DATA DATA CD CD AI AI AO AO PID executed in the Control System PID Max Delay Minimum Delay PID PID Macrocycle Macrocycle

  42. Recommendation on Splitting Control Between Fieldbus and Control System • Oversampling of the fieldbus measurement to compensate for lack of synchronization i.e. setting macrocycle faster than control execution is often not practical if the loop execution is fast • Conclusion: Execute control loops in Fieldbus for better performance. • If target execution is ½ sec or faster, then limit the number of control loops to no more than two(2) per segment.

  43. Execution of Function Block in H1 Card • Capability is targeted of v9.x release of DeltaV • Will allow synchronization of block execution on the H1 card with those on the segment i.e. the H1 card acts as a FF device with function blocks. • Block execution time on H1 cards is significantly less and will allow a shorter macrocycle or more to be done within a given macrocycle.

  44. Auto-Assigned Execution to H1 – Module Property

  45. PID Execution in The Controller

  46. PID Assigned to Execute in H1 Card

  47. PID Assigned to Execute in the Device

  48. Viewing Execution Schedule

  49. Schedule – PID in Controller

  50. Schedule – PID in H1 Card Parameter show when cursor is over item

More Related