YM:PID Temperature Control

1 Description

Author: FRH / EEC (Date: 21.03.2023)

2 Definitions

Since the end of 2022 all new lines will be equiped with a new temperature controlling system, that is not done via external system anymore (PSG) but via a Siemens function block (PID_Temp) directly inside the line PLC.

3 Comparison to previous system

New controllers are running directly on line PLC

• no external system
• no separate communication bus
• no additional parameterization tool

File:PIDTEMP system comparison.png

Separate link structure for controller specific part

File:PIDTEMP explanation link.png

Each controller consists out of three objects

File:PIDTEMP 3 objects.png

Input scaling via _SEN_ACT- object

File:PIDTEMP input scaling.png

Temperature ramp

• RamMax = 0 -> no ramp
• RamMax > 0 -> only positive ramp
• RamMax < 0 -> positive and negative ramp

File:PIDTEMP ramp.png

• Used for Extrusion
• Used for MDO (Rotary Heads)

Sensor monitoring

• Temperature change needs to be at least 4°C at maximum output within monitoring time

File:PIDTEMP sensor monitoring 1.png

• Evaluation:

File:PIDTEMP sensor monitoring 2.png

Feed forward control

• Maximum offset can be enterd at “General“ page
• Actual offset can be seen at “Specific“ page

File:PIDTEMP feed forward control.png

• Extrusion Cylinder: Influence linear from MpuStaSpd to MpuSpdSetMax
• MDO Preheating: Influence linear from 0.0 to ChrDrvSpdMax

4 Output Type

Puls / Pause

File:PIDTEMP output typ 1.png

• Originally used for SSR, now very seldom -> problem: low sample time = bad resolution, high sample time = possible temperature oscillation, replaced by Mode 3

Position Valve

File:PIDTEMP output typ 2.png

• Now “Valve Reference“- function is available
• Revers connected feedback is working now (RawMin > RawMax)
• Important is that both Raw Values are not too close to overflow (>500 / <13000)

Puls Modulation

File:PIDTEMP output typ 3.png

• Very common now for most heating with SSR but also digital valve and fan cooling
• mode is a feature of PID_Temp -> not useable in combination with CONT_C (e.g. ChnLubSwbHtg)
• Advantage is to set a minimum output time

Fast Pulse

File:PIDTEMP output typ 4.png

• Application for digital auctors, mostly cooling
• Possibility to also create output pulses at Y = 0.0 (e.g. Single Screw Feeding Zone)
• Function is basically an imitation of typ 5 for digital outputs with lower switching frequency

Fast Pulse Hardware

File:PIDTEMP output typ 5.png

• Major use for evaporative cooling at twin screw cylinder zones
• Can be recongized by periperhie output word

Exceptions

In some cases Y is directly assignet to peripherie -> no output type selected -> Yfactor needs to be set accordingly:

File:PIDTEMP output typ exceptions 1.png

• MDO Low Load Cooling Controller -> Yfactor = 27648
• Die Bolt Heating -> Yfactor = 1000

File:PIDTEMP output typ exceptions 2.png

Setting at output card for die bolt heating

5 Controller Tuning

General Information

• Tuning is not applicable at all zones -> check individually (most Ext: Yes, Str: No -> Standard Settings)
• Fine Tuning does can take very long time and delivers very “optimistic“ results -> prefer Pretuning
• Tuning cooling is only working after tuning heating -> so no tuning possible for some zones at all
• Do Pre Tuning to thermal linked zones simultaneously but Fine Tuning individually

Pre Tuning Heating:

• Temperature jump condition 1: TmpSet > (AlaMax – AlaMin) x 0.3
• Temperature jump condition 2: TmpSet > TmpAct x 2.0

Pre Tuning Cooling:

• Temperature jump condition: TmpSet < TmpAct x 0.95

Pre Tuning

• Rule 0: Fast PID
• Rule 1: PI
• Rule 2: Slow PID

File:PIDTEMP pretune.png

At pre tuning a fixed output degree is applied for certain time and response of zone is recorded during a temperature jump. As zones are linked thermally this type of tuning should be done simoultaneously as the later heatup szenario would be also like that.

Checklist Pre Tuning:

• Pre Tuning needed / allowed?
• Temperature Ramp = 0?
• Output Type correct and auctor function is tested and working / zone supplies are in specified range?
• Controller off and target setpoint according to temperature jump rules? (in case limits can be lowered to reduce temperature jump)

Fine Tuning

• Rule 0: PID automatic
• Rule 1: PID fast
• Rule 2: PID slow
• Rule 3: ZN PID
• Rule 4: ZN PI
• Rule 5: ZN P

File:PIDTEMP finetune 1.png

At fine tuning a certain oscillation of the controller output is applied and zone response is recorded. Expierience has shown that during this process temperature deviation from setpoint is quite significat so that this should not be done during production. If temperature reaction is sluggish, fine tuning can take very long time or end without result, in care cases temperature can exceed (maximum) alert limit.

Checklist Fine Tuning:

• Pre Tuneing done?
• Controller on / “stable“?

File:PIDTEMP finetune 2.png

As zones are linked thermally this type of tuning should not be done simoultaneously to neighbored zones as they would disturb each other.

Block Mode

File:PIDTEMP block mode.png

• Ensure all tuning conditions for all zones are fulfilled
• Set filter accordingly
• Enable required optimization type (Heating, Cooling, Heating + Cooling)
• Set Mode: 1 = Pre Tuningune, 2 = Fine Tune
• Start zones (for Pre Tuning simultaneously -> All Zones)

Verify Tuning Result

File:PIDTEMP verify tuning result.png

• AlaMax > SetLimMax / AlaMin < SetLimMax
• Ti ∿ 10 x Td (if Td > 0.0)
• CtlZon >> 0.0
• Puls Modulation:
• Ts min. 10 x On_TimMin
• Position Valve:
• Hys > 0.0 min. 0.2%
• Td = 0.0 / Kp < 8.5 / Ts > 5.0s
• In case only cooling function is used also heating parameters need to be set -> Standard
• In case of cascade control zone controller (outside) needs to be slower that Htu- controller (inside)

6 Standard Parameters

Please find the actual standard parameters under the following link:

PID_Temp_Parameters-Excel

If you have a new zone to which there is no suitable application yet please create a reasonable one, eighter by tuning or manual, and fill out the following template:

PID_Temp_Parameters_Template-Excel

Please send this template for verification and implementation to:

IBN ESC
Franz Hoeller