C135 PCS 7 (PCS7)
6C
6 Cielo Ciencia y Tecnología
·Publicada en C135 PCS 7 (PCS7)

Implementing Process Modeling and Dynamic Skid Simulation in PCS 7 Using SIMIT

Implementing Process Modeling and Dynamic Skid Simulation in PCS 7 Using SIMIT

In SIMATIC PCS 7, creating dynamic process simulation models—such as pulp and paper skids, chemical batch reactors, or water treatment plants—to test automation logic and operator graphics without physical hardware requires pairing S7-PLCSIM or SIMIT Virtual Controllers with the Siemens SIMIT Simulation Platform. While S7-PLCSIM handles controller program execution, SIMIT provides real-time mathematical modeling of physical field behavior, including valve stroke times, pump head curves, pipeline flow dynamics, and sensor loop feedbacks. SIMIT couples directly to S7-PLCSIM via a high-performance shared memory API, cyclically reading controller outputs (such as motor run commands) and feeding back simulated process inputs (such as flow rates and limit switches) into the process image.

Table of Contents

Executive Summary

Testing complex technological processes (such as continuous pulp digestion, paper machine wet-ends, or multi-stage distillation) purely by manually toggling bits in S7-PLCSIM is labor-intensive, error-prone, and incapable of validating closed-loop PID control. The Siemens SIMIT Simulation Platform solves this challenge by providing modular, drag-and-drop physical component libraries. SIMIT automatically closes the loop between actuator outputs and sensor feedbacks in real time. Deploying SIMIT alongside PCS 7 allows engineering teams to conduct rigorous factory acceptance tests (FAT), optimize PID parameters, and train control room operators before actual plant commissioning.

Architecture and Fundamental Mechanics

The simulation architecture integrating Siemens SIMIT with SIMATIC PCS 7 operates across defined execution layers:

  1. The Behavioral Modeling Layer (SIMIT):
    * SIMIT provides graphical simulation diagrams where standard engineering components (actuators, pumps, heat exchangers, valves, piping nodes) are interconnected.
    * Each component executes real-time differential and algebraic equations representing physical conservation of mass, energy, and momentum.
  2. The Coupling and Memory Mapping Interface:
    * SIMIT establishes an inter-process communication (IPC) channel with the controller emulator.
    * SIMIT supports two primary simulation engines for PCS 7:
    • S7-PLCSIM Coupling: Couples directly to the standard desktop emulator, exchanging data over shared memory.
    • SIMIT Virtual Controller (VC): Executes the compiled controller code directly within the SIMIT simulation kernel, reproducing CPU 410-5H cycle execution with microsecond timing accuracy.
  3. Bidirectional Signal Synchronization:
    * In every simulation time slice (typically 10 ms to 100 ms):
    • SIMIT reads all digital and analog outputs from the controller (Q, PQW).
    • SIMIT updates its internal process models (e.g., motor accelerates to speed, pump develops head, fluid flows through pipe, tank level rises).
    • SIMIT writes the resulting process variables back to the controller's peripheral input image (PIW, I).
    • Downstream PCS 7 channel drivers (Pcs7AnIn, Pcs7DiIn) read these values seamlessly, enabling realistic, automated closed-loop testing.

Step-by-Step Implementation Procedure

Follow these procedures to set up a dynamic process simulation for PCS 7 using SIMIT and S7-PLCSIM:

  1. Export Station Data from SIMATIC Manager:
    * In SIMATIC Manager, ensure HW Config and CFC charts are compiled.
    * Export the Symbol Table or use the SIMIT PCS 7 project export assistant to generate the station variable mapping file.
  2. Create and Configure a SIMIT Simulation Project:
    * Launch Siemens SIMIT.
    * Create a new project (e.g., Pulp_Paper_Skid_Simulation).
    * In the Project Navigation tree, double-click Couplings and select New Coupling.
    * Select PLCSIM (or Virtual Controller) and import your exported station symbols.
    * Verify that the signals map to matching input and output addresses.
  3. Build the Physical Process Diagram in SIMIT:
    * Open a SIMIT diagram sheet.
    * From the Standard Components library, drag a drive component (e.g., Drive_Simple or Motor) onto the sheet.
    * Connect the motor run command from the PLCSIM coupling to the drive's start input.
    * Connect the drive's running feedback output to the digital input mapped to the controller's feedback pin.
    * For an analog tank: drag a Storage (reservoir) component; link its inlet flow from a simulated valve and its level output to an analog peripheral input (e.g., PIW 512).
  4. Launch Controller Simulation in S7-PLCSIM:
    * Open S7-PLCSIM from SIMATIC Manager and load the PCS 7 station hardware and CFC charts.
    * Set the virtual CPU to RUN-P.
  5. Start Simulation in SIMIT and WinCC Runtime:
    * In SIMIT, click the Start (Play) button in the top toolbar to begin dynamic modeling.
    * Launch WinCC Runtime on the Engineering Station.
    * Open the process graphic containing the pump and tank faceplates.

Verification

In WinCC Runtime, open the pump faceplate and command the pump to Start. Observe that SIMIT receives the digital output command, simulates realistic motor acceleration delay, and asserts the feedback bit. Confirm that the WinCC motor icon turns solid green without generating transit time alarms. Observe that the simulated tank level begins rising smoothly on the WinCC analog trend, and that the closed-loop PID controller adjusts its control valve output dynamically to maintain setpoint.

Limitations and Operational Precautions

Ensure that SIMIT simulation cycles are synchronized with the PLC cyclic interrupt OBs (e.g., OB35 100 ms); setting SIMIT time slices too coarse introduces numerical integration instability in fast hydraulic models. SIMIT component libraries require adequate capacity licensing based on active simulation tag counts.

Engineer FAQ

What is the primary benefit of using SIMIT over manual S7-PLCSIM testing?

SIMIT automates dynamic process feedback (e.g., valve travel time, tank filling, temperature curves), enabling automated closed-loop PID testing without manual bit forcing.

Can SIMIT simulate chemical reactions and thermodynamics?

Yes. SIMIT offers specialized add-on libraries (such as SIMIT FLOWNET and CHEM-BASIC) that model thermodynamic fluid dynamics and chemical enthalpy.

Do I need physical controller hardware to run SIMIT?

No. SIMIT couples directly to software-based controllers (S7-PLCSIM or SIMIT Virtual Controller) running entirely on a single PC or virtual machine.

Can SIMIT be connected to 3D virtual reality models?

Yes. SIMIT can interface with Siemens NX Mechatronics Concept Designer (MCD) or 3D visualization tools via shared memory or OPC UA.

Technical References

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Related Tags

  • SIMIT V10.2
  • Process Simulation
  • Virtual Commissioning
  • Closed-Loop Testing
  • S7-PLCSIM
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