Presentation on theme: "DeltaV Tune for Fieldbus PID Support in DeltaV v7.2 and v7.3."— Presentation transcript:
DeltaV Tune for Fieldbus PID Support in DeltaV v7.2 and v7.3
Implementation Options with Fieldbus à DeltaV allows all elements of the control loop to be assigned to fieldbus à The loop PID may be assigned to the transmitter or the valve. à Portions of the control loop, such as the PID, may be assigned to the DeltaV controller and the remaining functions such as AI and AO done in fieldbus devices. Where will PID be Assigned??
Control Performance Achieve Using Fieldbus à Function block execution, maximum response time for compel data and slot time ( dependent of the device technology/design – specific to manufacturer) - see ISA2002 Fieldbus Tutorial à Whether control is done in the field or in the control system (customer decision) à Scheduling of block execution and communications on the FF segment.
Scheduled Control Execution With Fieldbus 0250 ms AIPIDAO CD DAT A Macro Cycle 2.3 ms 5.4 ms Bus Traffic
Minimum Execution Time With Only One(1) Control Loop on an H1 Segment AIPIDXFR AO 20ms 25ms 30ms 60ms 30ms Macrocycle = 165 ms Assumptions: 3 rd Generation Transmitter, AI&PID executed in Transmitter, Second generation Valve executes AO
Executing PID in the Valve Reduces the Number of Communications But Increases Loop Execution Time AIXFR PID 20ms 30ms 120ms 60ms Macrocycle = 230 ms Assumptions: 3 rd Generation Transmitter, AI executed in Transmitter, Second generation Valve executes AO&PID AO
Minimum Execution Time With Only Two(2) Control Loop on an H1 Segment AIPIDXFR AO 20ms 25ms 30ms 30ms 60ms 30ms 55ms Macrocycle = 250 ms Assumptions: 3 rd Generation Transmitter, AI&PID executed in Transmitter, Second generation Valve executes AO, 50ms for every 125ms of the execution schedule (for display update) AIPIDXFR AO ACYCLIC
Impact of Splitting Control Between Fieldbus and Control System à DeltaV module execution is not synchronized with function block execution on fieldbus segments. à 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 of added variable delay when control is split between fieldbus device and the DeltaV controller. à Added delay will impact control loop tuning and result in increase variability in fast control loop.
PID executed in the Control System 0250 AIAO CD DAT A 0250 PID Minimum Delay Max Delay Macrocycle 0250 PID 0250 AIAO CD DAT A Macrocycle 0250 PID 0250 PID
Recommendation on Splitting Control Between Fieldbus and Control System à Execute control loops in Fieldbus for better performance when the process dynamics are fast e.g. liquid pressure or flow. à If target loop execution is ½ sec or faster, then implement the control in fieldbus and limit the number of control loops to no more than two(2) per segment.
Original DeltaV Tune Capability à Only supported PID/ Fuzzy Blocks in DeltaV Controller à Dynamics are captured by a (hidden) Autotuner Modifier so no error is introduced by communications delay/jitter.
DeltaV v7.2 Tuning Support for all Manufacturers FF Devices à DeltaV Tune appears and operates the same. à The PID mode changing to Man (rather than LO) during the Test phase à Tuning of fast loops may be conservative because of deadtime introduced by fieldbus communications. à Patent pending. Shadow PID with Autotune Modifier
Launching DeltaV Tune à The DeltaV Tune application may be launched in context by right clicking on the module or fieldbus block
Testing the Process à When test is selected, the PID Autotune modifier changes the PID output by the amount specified and captures the process response.
Select Tuning Rule à The default ( normal user ) tuning rules be used with fieldbus PID. à The normal rules apply to all process dynamics
DeltaV v7.3 Tuning Support for Emerson Fieldbus Devices à All new Emerson fieldbus devices will include the Autotune modifier as part of the PID. Initially available on 3244, 3051, 3144 à DeltaV Tune looks and operates the same. à No communications delay or jitter in identifed dynamics. à Patent pending In Emerson fieldbus devices
ConclusionConclusion à Tuning of PID in any fieldbus devices is supported in v7.2. Conservative tuning will be obtained for fast loops. à An improved tuning capabilty is provided in v7.3 for Emerson fieldbus devices. Even the fastest loop may be accurately tuned. à DeltaV Tune support of fieldbus devices enables utilizing control in the field. This can lead to reduced control variability for fast process dynamics.