Implementing Mass Feedback Simulation for Motors and Valves in SIMATIC PCS 7 APL

In SIMATIC PCS 7 Advanced Process Library (APL), simulating feedback signals for hundreds of drives and valves during virtual commissioning should not be done by writing custom FCs in OB1, which disrupts CFC runtime execution groups. Instead, use native APL block simulation mechanisms or CFC loopbacks. For motors (MotL, FB1850), connect control output Start directly to feedback input FbkRun, or insert a TimerP block (FB1810) to emulate contactor pull-in delay. For valves (VlvL, FB1899), set parameters NoFbkOpen = 1 and NoFbkClose = 1 to disable feedback monitoring entirely. For comprehensive automated plant simulation without CFC modification, export the hardware configuration to SIMIT using the SIMIT Virtual Controller.

Executive Summary

During FAT (Factory Acceptance Testing) and virtual commissioning of PCS 7 projects, commissioning engineers frequently need to simulate feedback signals (such as run confirmation, limit switches, and torque status) for large numbers of motor and valve drives. Writing manual S7-SCL or STL logic in OB1 violates PCS 7 engineering standards, bypasses CFC chart execution sequences, and risks downloading unmanaged code to the controller. This guide outlines standard, scalable methods to simulate mass feedback using native APL block parameters, automated CFC loopback configurations, and external simulation platforms such as SIMIT.

Architecture and Fundamental Mechanics

The APL technological blocks MotL (FB1850) and VlvL (FB1899) evaluate field feedback to detect discrepancy faults (dynamic monitoring time MonTiDynamic and static monitoring time MonTiStatic):
1. MotL Feedback Logic:
When a start command is issued (Start.Value = 1), MotL starts the MonTiDynamic timer. If FbkRun.Value does not transition to 1 before the timer expires, the block trips with an alarm (FbkRunOut = 1). In steady-state running, if FbkRun.Value drops to 0, MonTiStatic detects the discrepancy and trips the drive.
2. Native Parameter Disabling (Valves):
VlvL provides dedicated configuration inputs: NoFbkOpen (no open feedback) and NoFbkClose (no close feedback). Setting these to 1 instructs the internal state machine to treat the drive as an unmonitored actuator, immediately assuming position upon command expiration without generating feedback alarms.
3. Native Simulation Mode:
Every APL core block incorporates internal simulation (SimOn = 1). When active, SimLiOp = 0 allows operator simulation from the OS faceplate, while SimLiOp = 1 enables programmatic simulation via SimOnLi. In simulation mode, the block internally substitutes the control command for the feedback signal and sets signal quality ST = 16#60 (Simulation).

Step-by-Step Implementation Procedure

Option A - Parameter Configuration for Valves (No Feedback Mode):
a. Open the CFC chart containing the valve instances (VlvL).
b. On each instance, set parameter NoFbkOpen = 1 and NoFbkClose = 1.
c. If modifying multiple instances, use the Process Object View (POV) under the 'Parameters' tab to bulk-set NoFbkOpen and NoFbkClose to 1 across all charts.
Option B - Native Block Simulation Mode (Motors and Valves):
a. Open Process Object View and navigate to the 'Parameters' tab.
b. Filter by Block Type MotL and locate column SimOn.
c. Set SimOn = 1 for all drives to activate simulation mode.
d. When activated, the block internally mirrors output commands to feedback inputs with simulated signal status (16#60).
Option C - CFC Loopback with Realistic Contactor Delay:
a. For realistic process dynamics, insert TimerP (FB1810) or PulseGen into the motor chart.
b. Connect MotL.Start to TimerP.In.
c. Set TimerP.Ti to the desired contactor pickup delay (e.g., 2.0s).
d. Connect TimerP.Out to MotL.FbkRun.
e. For dual-direction motors (MotRevL), replicate this logic for FbkRev using Rev.
Option D - Automated SIMIT Simulation Integration:
a. In SIMATIC Manager, export the station configuration using HW Config -> Station -> Export.
b. Open SIMIT, create a new project, and import the station XML or use SIMIT Virtual Controller (VC).
c. Instantiate SIMIT standard drive components (DRIVE, VALVE) which automatically couple with PCS 7 I/O addresses without modifying the CFC application logic.

Verification

In CFC Test Mode, turn on monitoring for MotL. Issue a manual start command via ManMod = 1 and StartMan = 1.
Observe FbkRun.Value transition to 1 within the configured dynamic monitoring window (MonTiDynamic).
Confirm that no feedback discrepancy alarm (FbkRunOut = 1) is generated.
Verify on the WinCC OS faceplate that the motor icon changes from gray (stopped) to green (running) without displaying a yellow warning triangle or blue maintenance lock.

Limitations and Operational Precautions

Direct CFC loopbacks and setting NoFbkOpen = 1 alter offline chart logic; these modifications must be meticulously reverted or tracked before cold commissioning with physical switchgear and field instruments. Always utilize Process Object View or SIMIT virtual coupling to ensure engineering safety and configuration integrity.

Engineer FAQ

Why is writing a custom FC in OB1 bad practice in PCS 7?

PCS 7 generates its runtime sequence automatically across cyclic interrupt organization blocks (OB30 to OB38). Inserting custom code directly into OB1 bypasses CFC execution groups and can lead to uncoordinated I/O cycle overruns.

How do I simulate valve limit switches without physical inputs?

Set NoFbkOpen = 1 and NoFbkClose = 1 on the VlvL block. This bypasses feedback monitoring, causing the block to transition immediately to open or closed states upon command.

What does the blue diamond symbol on the OS faceplate signify?

The blue diamond or wrench icon indicates that the technological block is currently operating in simulation mode (SimOn = 1).

Can I mass-enable simulation mode across hundreds of motors at once?

Yes. In SIMATIC Manager, open the Process Object View, select the 'Parameters' tab, filter by block type MotL, and set SimOn to 1 across all rows simultaneously.

Does SIMIT require changes to the PCS 7 CFC charts?

No. SIMIT couples at the hardware I/O image level or virtual controller interface, allowing complete FAT simulation without touching CFC charts or block parameters.