CFC – PID-Controller

Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller Example of use PID-Controller CTRL_PID (PLS Siemens PCS 7): (Source: https://pcs.khe.siemens.com/index.asp?Nr=5844 - PCS 7 Library V6.0) Functionality: continuous PID-Controller (default control-ciruit) • Fixed comand control • Cascade controle (single-/multiple cascade) • Ratio control More possibilities of processing: • Switching between control mode: hand drive, automatic or tracking • Limit value monitoring of the variable, error signal and generating of messages • Disturbance variable compensation • Setpoint tracing • Valuation adjustment of setpoint and actual value (physical standardization) • Valuation adjustment of setpoint (physical De-standardization) • deadband (reaction point) in the sector of the actuating variable • Individual detachable and shiftable P-, I- and D-Part • P- and D-Part could be place in the refeed • Adjustment of the working point (P- rather PD-control operation) 1

Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Step response Step response:

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ER – error signal LMN – gate of control point LMN_HLM – Limit of the control point LMN_LLM – Lower limit of the control point GAIN – proprotional coefficient TN – reset time TV – derivate time TM_LAG – time lag D-Part SAMPLE_T – aperture time

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Setpoint creation – Structure

Setpoint creation:

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SP – active Setpoint SP_EXT – external setpoint SP_OP – control access for the setpoint PV_IN – actual value

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SP_TRK_ON – setpoint SP_OP tracking SPBUMPON – latitude impact for the setpoint Sollwert SPxRLM – maximal draft setpoint 3

Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Setpoint creation Setpoint creation: • Internal Setpoint – Handling and limitation of the internal setpoint SP_OP is founded about OP_A_LIM rather OP_A_RJC. • External Setpoint – The external setpoint SP_EXT can be connected and is limited in the range of (SPEXTLLM,SPEXTHLM). • Updated Setpoint – If SP_TRK_ON=1 then PV_IN is used as setpoint value. The tracking of the setpoint to the actual value is only active during the hand drive (with internal setpoint and if SPBUMPON = 1), and ist primary conduced for the switching between hand drive to automatic to find the right setpoint.

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Regler – PID-Kernel – Structure System deviation and PIDKernel: LMN_INT SP

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ER – system deviation PVx_ALM – actual value: alarm limit PVx_WRN – actual value: warning limit QPVxx_xxx – alarm/warning limit

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NM_PVxR – standardization of the measurement range INT_Hxxx – freezing I-Part LMN_INT – internal control point LMN_OFF – Working point

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Regler – System deviation System deviaton - Creation: • The system deviation ER is build with the active setpoint SP and the actual value PV_IN and is available on the exit ER after the dead zone DEADB_W.

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System deviation - Control – The system deviation ER is controlled with an collective hysteresis (ER_HYS) on the arlarm limits(ERL_ALM, ERH_ALM). Actual value - Control – The actual value PV_IN is controlled with an collective hysteresis (HYS) on the warning and alarm limits Alarmgrenzen (PVL_ALM, PVL_WRN, PVH_WRN, PVH_ALM). The inducation is shown of the outputs (QPVL_ALM, QPVL_WRN, QPVH_WRN, QPVH_ALM).

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – PID-Kernel Algorithm PID-Kernel : • Controller working with standardized Variables(-100 % - 100 %). • P-Part could be activated and deacitvated by P_SEL. • With PFDB_SEL and DFDB_SEL it‘s possible to add P- und D-Part to the refeeding independent of each other. – Pro: P- rather D-Part is not affected by the leaps of the setpoint, this means the control point does not change by leaps on leaps of the setpoint. • With TN = 0 (I-Anteil ist ausgeschaltet) the working point is given explicit by LMN_OFF. • With INT_HPOS = 1 and INT_HNEG = 1 you can freeze the P-Part – Pro: You can avoid that the Integrator integrates to endless high values, if the deviation is constant.

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – PD-Part in reduction PID-Controller in a standart structure: SP

ER

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PID

LM

Drift

PV

PID-Controller with a PD-Part in reduction: SP0=0

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PD + LM +

SP

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Drift

PV

I

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Controller algorithm Controller algorithm during „normal mode“:

Implementation of the Controller algorithm during „normal mode“: GAIN SAMPLE_T GAIN TV ⎛ ⎞ (ER(k) − ER(k − 1)) LMN_INT(k) = GAIN ER(k) + ⎜ LMN_INT_I(k − 1) + ER(k) ⎟ + TN ⎝ ⎠ TM_LAG + SAMPLE_T/2

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Standardization Physical standardization •

The actuating variable(ER) is standardized (in percent) by the physical measurement range of the actual value (NM_PVHR, NM_PVLR).

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Atfer the PID-Algorithm the actuacting variable is … (denormiert)… from percent to the physical measurement range of the control point(NM_LMNHR, NM_LMNLR).

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Internal rather external Setpoint, actual value such as associated parameter have to be entered in the physical measurement range of the actual value. Manual value, time of setpoint tracing of the actuating variable, circuit-entering of the disturbance variable such as associasted parameter have to be entered in the physical measurement range of the contol point. The amplification of thecontroller GAIN is shown in standardized form(without dimension).

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CFC – PID-Controller – Actuating variable – Structure

Linear, Nonlinear and Model Predictive Control

Actuating variable-creation: LMN_INT

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LMN – actuating variable (a.v.) DISV – circuit-entering of the disturbance

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NM_LMNxR – standardization of the actuating variable

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LMN_xLM – Limits of the actuating variable MAN_OP – ext. a.v. (Input Operator) LMN_TRK – external actuating variable QMAN_AUT – Output Manual/Automatic 11

Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Actuating variable – Choice Choice of the actuating variable:

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – circuit-entering of the disturbance variable circuit-entering of the disturbance variable : During the automatic mode the circuit-entering of the disturbance variable DISV is added on the output and after that the result is limited in the range from LMN_LLM to LMN_HLM.

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Parameter The Parameter of the Controller GAIN, TN(TI), TV(TD) and TM_LAG are usually not combinable. • In case they have to be connected , for example „Gain-Scheduling“,the attribute of the system s7_link has to be changed. • Changeover of the Parameter during the running automatic mode may lead to leaps of the actuating variable.

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Setpoint tracing mode Setpoint tracing mode: • In this situation (LMN_SEL=1) the acuating variable is taken by the comined setpoint tracing value LMN_TRK and put on the output. • The Outputs QLMN_HLM and QLMN_LLM are set on FALSE. • The mode „tracking" has priority against all other modes, so that via this input a security shutdown of the machine can be projected.

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Plugs (I)

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Plugs (II)

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Linear, Nonlinear and Model Predictive Control

CFC – PID-Controller – Plugs (III)

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