Configuring PID Autotuning from HMI in TIA Portal V14 SP1

Configuring PID Autotuning from HMI in TIA Portal V14 SP1 on S7-1200

1. Overview

Pressure-control loops drift as process gain, dead time, and load profile change. A controller tuned once at commissioning rarely stays optimal for the life of the line, so the operator must be able to re-trigger PID autotuning from the HMI without a programmer present. On a SIMATIC S7-1200 CPU 1212C running TIA Portal V14 SP1 Update 8 with a TP900 Comfort panel, the closed-loop regulator block PID_Compact (FB 1139, DB 1139 instance) ships with an integrated pretuning and fine-tuning routine that can be started from a single mode-select input. Wiring that input to a tag and exposing the tag to a TP900 button is the cleanest, most supportable path.

The official Siemens sample project "PID Control with PID_Compact V13 SP1" (entry ID 100746401) demonstrates exactly this HMI-driven autotuning flow. The V13 SP1 project is the lowest revision that will upgrade into V14, so it remains a useful starting template even when the active engineering station is V14 SP1 Update 8.

2. Prerequisites

Confirm the TIA Portal installation includes the optional package "STEP 7 Basic" and that the device catalog under Controllers > SIMATIC S7-1200 > CPU > CPU 1212C resolves a hardware version that matches the actual PLC. Mismatched firmware warnings will block download.

3. Converting the V13 SP1 Sample Project to V14 SP1

The 100746401 sample is published as a TIA Portal V13 SP1 archive. TIA Portal performs forward conversion on open. The conversion path is unambiguous: there is no need to obtain a re-archived copy from a third party.

1. Launch TIA Portal V14 SP1 Update 8.
2. Click Open existing project on the start page or use Project > Open (Ctrl+O).
3. Browse to the unzipped .ap13 / .ap13_1 project file. TIA Portal recognizes the V13 SP1 archive by its file version header.
4. Click Open. A dialog asks whether to upgrade the project. Confirm with Upgrade.
5. TIA Portal rewrites the project database in place. A conversion report is appended to the project tree under Common data > Logs.
6. After upgrade, recompile the project (Project tree > CPU_1 > Compile > Software (rebuild all)). Watch for unresolved device versions; pin the device versions to those available on the engineering station if the catalog is missing the original revision.

Once compiled cleanly, save the project as a TIA Portal V14 SP1 archive (Project > Archive > Name.iap14) to lock in the new format.

4. PID_Compact Block Architecture

PID_Compact is the standard closed-loop controller for S7-1200. The block combines continuous PID, output scaling, and an integrated identification routine. The interface relevant to HMI-triggered autotuning is summarized below.

The Mode input is the HMI trigger. Valid values:

• 0 – Inactive (block executes but does not control)
• 1 – Manual (operator drives output via ManualValue)
• 2 – Automatic (closed-loop control with current PID parameters)
• 3 – Automatic with pretuning request
• 4 – Automatic with fine-tuning request
• 5 – Automatic with fine-tuning request, then closed-loop

5. PLC Program Skeleton for HMI-Triggered Tuning

Wrap the mode change in a one-shot so a button press does not repeatedly request tuning while held.

// FB instance: "PID_Pressure" of type PID_Compact (DB1139)
// HMI tags (HMI side): "bStartPretune", "bStartFinetune", "iMode", "bManual", "rManVal", "rSP", "rPV", "rOutput"

// Edge detection for tuning buttons
"bStartPretune_Old" := "bStartPretune";
IF "bStartPretune" AND NOT "bStartPretune_Old" THEN
    "PID_Pressure".Retain.Mode := 3;  // Pretuning request
END_IF;

"bStartFinetune_Old" := "bStartFinetune";
IF "bStartFinetune" AND NOT "bStartFinetune_Old" THEN
    "PID_Pressure".Retain.Mode := 4;  // Fine-tuning request
END_IF;

// Mode = 2 holds the loop in automatic after tuning completes
IF "bAutoMode" THEN
    "PID_Pressure".Mode := 2;
END_IF;

// Manual / automatic toggle
IF "bManual" THEN
    "PID_Pressure".ManualEnable := TRUE;
    "PID_Pressure".ManualValue  := "rManVal";
ELSE
    "PID_Pressure".ManualEnable := FALSE;
END_IF;

// Wire analog IO
"PID_Pressure".Input     := "rPV_scaled";   // scaled via NORM_X / SCALE_X
"PID_Pressure".Input_PER := "iwAI_Pressure"; // raw 0-27648
"PID_Pressure".Setpoint  := "rSP";

6. TP900 HMI Screen Design

On the TP900 Comfort, build a faceplate with five controls and four readouts.

Define a tag table HMI_Tags_PID on the TP900 with the data type of each tag matching the PLC tag exactly. Use the TP900 connection "HMI_1 > Connections > S7_1200_1" pointing to the CPU 1212C. Tags must be configured with acquisition mode Cyclic in operation for the mode state and Cyclic continuous for PV / SP / output, with a 1 s update cycle. Mode-toggle tags use On demand acquisition to avoid PLC-side floods.

7. Step-by-Step Commissioning Procedure

1. Wire the pressure transmitter to AI0 of the CPU 1212C. Calibrate the transmitter zero and span against a reference gauge. Verify the engineering-unit conversion in a watch table: PEW96 should read 0 at 0 bar and 27648 at full scale.
2. Download the hardware configuration to the CPU. The CPU reports the configured AI range back in the online diagnostics; confirm "Measuring range: 0-10 V" or "4-20 mA" matches the wiring.
3. Add a PID_Compact instance (DB) to the program blocks. Open the configuration editor and assign Input_PER to %IW96, Setpoint to a default of 0 bar, and Output_PER to %QW96 if the actuator is on the onboard AQ.
4. In the PID_Compact commissioning window (called from the block properties or by right-clicking the DB), open the online preview. Set the controller to Manual with output = 0 % and verify the actuator responds (valve closes, pump idles).
5. Establish a stable manual baseline. Drive the output to the expected operating point (e.g., 50 % valve opening) and let PV settle. Note the steady-state PV value.
6. Switch the controller to Automatic. Tune the loop using the operator HMI: tap Start Fine Tuning. The TP900 should display "Tuning" in the mode field. PID_Compact will perturb the setpoint by a small step and identify the process response.
7. When the mode returns to "Auto" and the block reports Retain.CtrlParams.Gain, TI, and TD are non-zero, the loop is tuned. Verify disturbance response by injecting a small setpoint step from the HMI IO field.
8. Save the project. Back up the tuned parameters by reading the DB online and writing the values to a recipe on the TP900 (Recipe view > Recipe_1) so the parameters can be reloaded after a CPU stop / restart with retain cleared.

8. Verification Checks

After tuning completes, perform the following quantitative checks before releasing the loop to production:

• Closed-loop error: Steady-state deviation between Setpoint and Process value should be < 1 % of sensor span.
• Overshoot: Step response from 0 to 50 % SP should overshoot by no more than 10 % of the step. PID_Compact fine-tuning aims for a damping factor of 0.8 by default; reduce Retain.CtrlParams.Gain by 10 % if overshoot is excessive.
• Integral windup: With output saturated at 100 %, verify that the integral component does not grow indefinitely. PID_Compact implements anti-windup internally; confirm by reducing SP and watching the loop recover within the expected time constant.
• Mode tag sync: Press the HMI Manual button. The PLC Retain.Mode should read 1, and the HMI mode display should show "Manual". If only one side updates, the tag acquisition cycle is mismatched.
• Retain behavior: Power-cycle the CPU. The loop should resume in the tuned state (not as defaults). If not, the DB was generated as non-retain; right-click the DB instance and toggle Retain for the CtrlParams and Mode structures.

9. Using the TIA Portal Openness API for Diagnostic Automation

For installations that retune many loops, manually driving the HMI is impractical. TIA Portal exposes a public scripting interface, the TIA Portal Openness API, that can read controller state, trigger a project build, and compare the running configuration against the offline project. Diagnostic information from a live TIA Portal instance – including currently opened projects, active sessions, and log-level events – can be retrieved through a static method on the diagnostic interface. The reference page is in the official TIA Portal Openness documentation at Diagnostic interfaces on TIA Portal.

A minimal C# snippet (Visual Studio, .NET 4.8, references Siemens.Engineering.dll and Siemens.Engineering.Hmi.dll) that reads the TIA Portal session diagnostics to confirm the V14 SP1 Update 8 project is open and unmodified looks like this:

using Siemens.Engineering;
using TiaPortal.Openness.Diagnostics;   // public static accessor

class Program
{
    static void Main()
    {
        var tia = TiaPortal.GetFromLocalProcess();
        var diag = TiaPortalDiagnostic.GetDiagnostics(tia);

        foreach (var entry in diag)
        {
            System.Console.WriteLine($"{entry.Timestamp} {entry.Severity} {entry.Source} {entry.Message}");
        }

        // Walk every PID_Compact instance and dump tuning state
        var project = tia.Projects[0];
        foreach (var device in project.Devices)
        {
            foreach (var blockGroup in device.DeviceItems[0].Software.PlcSoftware.BlockGroups)
            {
                foreach (var block in blockGroup.Blocks)
                {
                    if (block.Type == BlockType.FB && block.Name.StartsWith("PID_"))
                    {
                        System.Console.WriteLine($"Found {block.Name} on {device.Name}");
                    }
                }
            }
        }
    }
}

Note that the Openness API is read-only with respect to online PID values – it cannot write to the live controller. For online writes, the engineering station must use a connected TIA Portal in TIA Portal mode, or the HMI path described above. Openness is most useful for documentation, audit logs, and verifying that the offline project matches the deployed controller configuration after a tuning campaign.

10. PID Lean as an Open-Source Alternative

The standard PID_Compact block is general-purpose. When the process is dominated by first-order lag with measurable dead time (typical for pressure loops with long pipe runs), a lighter controller is often adequate. Siemens' community-published "PID Lean" library provides a smaller code footprint, an explicit auto-tuning step, and a quicker commissioning dialog. PID Lean is distributed as a global library for TIA Portal and can be imported into a V14 SP1 project via Options > Global libraries > Open library.

11. Troubleshooting Matrix

12. Field-Proven Caveats

• The CPU 1212C has only two onboard analog inputs and two onboard analog outputs. If the pressure loop is one of several on the same PLC, plan to add an SM 1231 AI4 and SM 1232 AQ2 to avoid contention.
• TP900 Comfort panel projects compiled with TIA Portal V14 SP1 Update 8 cannot be opened on an older V14 SP1 Update 5 or earlier runtime image on the panel. Keep HMI images and engineering versions aligned.
• Comfort panel faceplates can be re-used across multiple S7-1200 controllers, but each instance must have its own tag-prefix space. A single global PID faceplate with a tag prefix interface is more maintainable than per-loop copies.
• PID_Compact autotuning assumes the process is stable at the current operating point. If the loop is in manual with output saturated, switch to automatic with a realistic setpoint first, then trigger fine tuning.
• Retain behavior in S7-1200 is byte-granular and only applies to bit memory (M), DBs, and some I/O. If the DB instance containing PID_Compact is not flagged as retain, all tuning parameters are lost on power cycle.

13. HMI-to-PLC Tag Reference Summary