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Modeling Multi-Position Actuators and Bi-Directional Drives Using PCS 7 APL VlvMotL

Modeling Multi-Position Actuators and Bi-Directional Drives Using PCS 7 APL VlvMotL

In SIMATIC PCS 7 Advanced Process Library (APL), modeling a bi-directional motorized actuator or positioning drive that travels in two directions (forward/reverse or open/close) and stops at multiple intermediate positions confirmed by inductive proximity switches is achieved using the standard APL block VlvMotL (Motor Valve / Motorized Actuator). VlvMotL provides dedicated bi-directional commands (Open/Close), intermediate stopping capability (StopAut / StopMan), travel time monitoring (MonTiDynamic), and interlocking inputs. In the Master Data Library, configure VlvMotL within a Control Module Type (CMT) paired with input drivers (Pcs7DiIn) for end limits and proximity sensors, enabling standardized instantiation across the plant hierarchy.

Table of Contents

Executive Summary

Process manufacturing skids, diverting chutes, sample collectors, and multi-port damper assemblies frequently require mechanical positioning mechanisms that travel in forward and reverse directions while stopping at discrete intermediate stations confirmed by proximity sensors (initiators). When engineering these devices within SIMATIC PCS 7 using the Type-Instance concept (Control Module Types - CMT), automation engineers often query whether a dedicated positioning template exists. While specialized servo blocks exist in motion control libraries, the standard PCS 7 Advanced Process Library provides VlvMotL (FB1899), an engineered block designed specifically for bi-directional motorized positioning. This technical guide outlines the CMT configuration, limit sensor interlocking, and faceplate control mechanics.

Architecture and Fundamental Mechanics

Control Module Type Architecture: VlvMotL Positioning Drive

+-------------------------------------------------------------------------+
|                   CONTROL MODULE TYPE (CMT): 'CMT_PosDrive_2Dir'        |
+-------------------------------------------------------------------------+
| Core APL Block: VlvMotL (FB1899 - Motorized Valve / Actuator)           |
|                                                                         |
| COMMAND INTERFACE:                                                      |
| - OpenAut / OpenMan:  Commands Travel in Direction 1 (Forward / Open)   |
| - CloseAut / CloseMan: Commands Travel in Direction 2 (Reverse / Close) |
| - StopAut / StopMan:  Halts Drive at Intermediate Positions             |
+-----------------------------------|-------------------------------------+
                                    |
   +--------------------------------+--------------------------------+   |
   | SUB-MODULE: End Limit Feedback | SUB-MODULE: Intermediate Limits|   |
   | - Pcs7DiIn (FbkOpen - 100%)    | - Pcs7DiIn (Pos1_Ini - 33%)    |   |
   | - Pcs7DiIn (FbkClose - 0%)     | - Pcs7DiIn (Pos2_Ini - 66%)    |   |
   +--------------------------------+--------------------------------+   |
                                    |
                                    v Positional Logic & Interlocks
+-------------------------------------------------------------------------+
| Operating Logic:                                                        |
| - Target Position Selected (e.g., Station 2):                           |
| - Command OpenAut = 1 (Drive starts moving forward)                     |
| - When Pos2_Ini triggers (Proximity switch closed):                     |
|   -> Asserts StopAut = 1 (Drive stops immediately at Station 2)         |
| - MonTiDynamic monitors transit between stations to detect jam faults   |
+-------------------------------------------------------------------------+

Functional Capabilities of VlvMotL

  1. Bi-Directional Output Commands: Generates independent digital output signals for opening (Open) and closing (Close), with built-in dead-time delays (IdleTime) to protect reversing contactors or motor starters from short-circuits during sudden direction reversals.
  2. Intermediate Stopping: Unlike standard open/close valves (VlvL), VlvMotL permits the actuator to stop in any intermediate position between end limits without flagging an error.
  3. Transit Time Supervision: Parameter MonTiDynamic supervises movement. If the drive is commanded to move toward an initiator and the sensor does not trigger within the timeout window, VlvMotL generates a runtime transit fault.

Step-by-Step Implementation Procedure

Step 1: Create the Control Module Type in Master Data Library

  1. In SIMATIC Manager, open the Master Data Library of your multiproject.
  2. In Component View, expand the Templates folder and locate Control Module Types.
  3. Right-click and select Insert New Object > Control Module Type.
  4. Name the CMT: CMT_PosDrive_2Dir.
  5. Open the CMT in the CFC editor.

Step 2: Insert and Parameterize VlvMotL

  1. From the APL library, drag VlvMotL (FB1899) into the CMT chart.
  2. Parameterize reversing interlocks:
    - Set IdleTime := 1.0 (1-second pause when changing direction to prevent contactor arc flashover).
    - Configure transit monitoring time: MonTiDynamic := 15.0 s.
  3. Configure Feature Bits:
    - Feature Bit 0: Set to 1 for full operator mode flexibility.
    - Feature Bit 12: Set to 1 if stop command should be evaluated with highest priority.

Step 3: Insert Proximity Switch Drivers and Intermediate Stop Logic

  1. Insert input driver blocks (Pcs7DiIn) for:
    - DI_EndOpen: Fully open/forward limit switch.
    - DI_EndClose: Fully closed/reverse limit switch.
    - DI_IniPos1: Intermediate position 1 proximity switch.
    - DI_IniPos2: Intermediate position 2 proximity switch.
  2. Connect DI_EndOpen.Out to VlvMotL.FbkOpen and DI_EndClose.Out to VlvMotL.FbkClose.
  3. Create intermediate stop evaluation logic:
    - When target position matches active initiator, assert VlvMotL.StopAut := 1.
  4. Connect motor safety interlocks to VlvMotL.Permit, Intlock, and Protect.

Step 4: Configure CMT Parameters and Signals in Process Object View

  1. Open Options > Process Object View.
  2. Open the Control Modules tab.
  3. Select CMT_PosDrive_2Dir and declare the external I/O signals, setpoint targets, and operator control attributes.
  4. Instantiate the CMT across target plant hierarchy folders.
  5. Perform a Changes Only compilation of CFC charts and OS.

Verification

  1. Bi-Directional Travel Test: In WinCC Runtime, open the VlvMotL faceplate. In Manual mode, click Open. Verify that the forward output energizes. Click Stop; verify that the motor halts immediately in mid-travel.
  2. Intermediate Position Stop Test: Select an intermediate position in the supervisory sequence. Command the drive to advance. Verify that upon reaching the inductive proximity switch, StopAut trips and the drive holds position cleanly.
  3. Transit Timeout Alarm Test: Command travel with the initiator sensor disconnected. Confirm that after MonTiDynamic expires, the block generates an 'Actuator Transit Fault' alarm and halts.

Limitations and Operational Precautions

  1. Closed-Loop Continuous Servo Positioning: VlvMotL is designed for discrete positioning with fixed sensors; continuous analog position control (e.g. 0.0% to 100.0% modulating control) requires VlvAnL (Analog Valve) coupled with position feedback transducers.
  2. Mechanical Inertia Coasting: Proximity switch placement must account for mechanical brake lag and motor coast-down distance to ensure precise stopping at the target point.

Engineer FAQ

Which APL block handles bi-directional motor positioning with stopping?

The block VlvMotL (FB1899 - Motorized Valve / Actuator).

Can VlvMotL stop between end positions without alarming?

Yes. Unlike VlvL, VlvMotL is explicitly designed to permit stopping and holding at intermediate travel positions.

What does IdleTime do on VlvMotL?

It enforces a minimum pause duration when reversing direction to prevent mechanical drive stress and electrical contactor short-circuits.

Can I create a Control Module Type (CMT) using VlvMotL?

Yes, VlvMotL can be placed inside a CMT in the Master Data Library and mass-instantiated via Process Object View.

What is the difference between VlvMotL and MotRevL?

MotRevL is a reversing motor with no valve/damper semantics; VlvMotL incorporates end-position limit monitoring, intermediate stops, and standard valve faceplates.

How do I supervise intermediate transit times?

The parameter MonTiDynamic sets the maximum allowable transit duration before an operational fault alarm is triggered.

Can operators manually jog the drive from the faceplate?

Yes, the VlvMotL faceplate provides Open, Close, and Stop operator buttons in Manual mode.

What block input commands an automatic stop?

The boolean input StopAut commands an immediate halt during automatic sequence execution.

Can multiple proximity switches be connected to one VlvMotL?

Yes, by aggregating proximity sensors into stop logic that commands StopAut when the target sensor triggers.

Does VlvMotL support rapid traverse and creep speed?

For two-speed positioning, pair VlvMotL with an auxiliary speed selection block or use MotSpdCL.

Technical References

Related Articles

Related Tags

  • VlvMotL
  • CMT
  • Motor Valve
  • Bi-Directional Drive
  • Proximity Switch
  • APL
  • Positioning
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