Edge AI with ML.NET Anomaly Detection Tutorial

Scripts → Tutorial | Concept | How-to Guide | Reference

Step 1: Create Monitoring Tags

1. Navigate to Unified Namespace → Tags
2. Create the following tags:
   • Tag.MixerVibration (Double) - Simulated sensor value
   • Tag.Anomalies (String) - Will hold the anomaly list
   • Tag.SimulatorSeed (Integer) - For simulation consistency

Step 2: Create ML Anomaly Detection Script Class

1. Navigate to Scripts → Classes
2. Click "Create new script"
3. Configure the new script:
   • Name: ML_Anomaly
   • Language: CSharp
   • Domain: Server
   • Select "Create new Code" → Methods (Default)
   • ? Check "Add ML.NET namespaces" (Required for ML functionality)
4. Click OK
5. Replace the default code with:

csharp

// HOW TO USE
// Create an expression or Task to run periodically with the code: 
// @Script.Class.ML_Anomaly.Check(@Tag.YourSensorValue);
// To retrieve anomalies: var list = @Script.Class.ML_Anomaly.GetAnomalies();

// Check if value is anomalous
public double Check(double currentValue) {
    // Initialize ML engine if needed
    if (_engine == null)
        Initialize();
    
    // Create data point
    var data = new SensorData {
        Timestamp = DateTime.Now,
        SensorValue = currentValue      };
    
    // Get prediction from ML model
    AnomalyPrediction prediction = _engine.Predict(data);
    
    // Store anomaly if detected
    if (prediction.Prediction[0] >= 1) {  // >= 1 means anomaly detected
        if (_anomalyBuffer.Count >= 10)
            _anomalyBuffer.Dequeue();
        _anomalyBuffer.Enqueue($"{DateTime.Now:yyyy-MM-dd HH:mm:ss}|{currentValue:F3}|{prediction.Prediction[1]:F2}");
    }
     return Prediction[0];
}

// Internal buffer to store last 10 anomalies
private static Queue<string> _anomalyBuffer = new Queue<string>(10);

// Method to retrieve anomalies and clear buffer
public string GetAnomalies() {
    if (_anomalyBuffer.Count == 0)
        return "No new anomalies detected";
    
    var anomalies = string.Join(Environment.NewLine, _anomalyBuffer);
    _anomalyBuffer.Clear();
    return anomalies;
}

//The following code is standard - no changes needed
public class SensorData {
    public DateTime Timestamp { get; set; }
    public double SensorValue { get; set; }
}

public class AnomalyPrediction {
    // SR-CNN returns an array with 3 doubles:
    // [0] = flag (0 or 1) - Binary indicator if anomaly detected  
    // [1] = score (0.0 to 1.0) - Confidence/severity of the anomaly
    // [2] = baseline - Expected normal value at this point
    // Note: This tutorial uses [0] for simplicity. Advanced users can leverage [1] and [2] for custom thresholds.
    [VectorType(3)]
    public double[] Prediction { get; set; }
}

private ITransformer _model;
private TimeSeriesPredictionEngine<SensorData, AnomalyPrediction> _engine;
private MLContext _mlContext;
List<SensorData> dataTrain;

private void Initialize() {
    _mlContext = new MLContext();
    
    if (dataTrain == null) {
        DateTime now = DateTime.Now;
        
        // Training data with clear normal pattern (wave-like)
        var trainingData = new List<(int minutesAgo, double value)> {
            (15, 0.20), (14, 0.25), (13, 0.30), (12, 0.25),  // Rising
            (11, 0.20), (10, 0.15), (9, 0.20), (8, 0.25),   // Valley to peak
            (7, 0.30), (6, 0.25), (5, 0.20), (4, 0.15),    // Falling
            (3, 0.20), (2, 0.25), (1, 0.30), (0, 0.25)     // Rising
        };
        
        dataTrain = new List<SensorData>();
        foreach (var item in trainingData) {
            dataTrain.Add(new SensorData {
                Timestamp = now.AddMinutes(-item.minutesAgo),
                SensorValue = item.value
            });
        }
    }
    
    // SR-CNN in ML.NET - use these default values for most applications
    SrCnnAnomalyEstimator pipeline = _mlContext.Transforms
        .DetectAnomalyBySrCnn(
            outputColumnName: nameof(AnomalyPrediction.Prediction),
            inputColumnName: nameof(SensorData.SensorValue),
            windowSize: 32,
            backAddWindowSize: 32,
            lookaheadWindowSize: 16,
            averagingWindowSize: 16,
            judgementWindowSize: 16,
            threshold: 0.15);
    
    IDataView dataView = _mlContext.Data.LoadFromEnumerable(dataTrain);
    _model = pipeline.Fit(dataView);
    _engine = _model.CreateTimeSeriesEngine<SensorData, AnomalyPrediction>(_mlContext);
    
    // Train the model with initial data
    foreach (var row in dataTrain) {
        _engine.Predict(row);
    }
}

Step 3: Create Value Simulator

1. Go to Scripts → Tasks
2. Create task: SimulateVibration
3. Set trigger: Period = 500ms
4. Add code:

csharp

// Simulate normal sensor data with occasional anomalies
if (@Tag.SimulatorSeed == 0)
    @Tag.SimulatorSeed = Environment.TickCount;

Random rand = new Random(@Tag.SimulatorSeed + DateTime.Now.Millisecond);

// Base vibration level with sine wave pattern
double time = DateTime.Now.Ticks / 10000000.0;
double baseValue = 0.25 + 0.05 * Math.Sin(time);
double noise = (rand.NextDouble() - 0.5) * 0.02;

// 5% chance of anomaly
if (rand.NextDouble() < 0.05) {
    @Tag.MixerVibration = baseValue + (rand.NextDouble() * 0.5 + 0.3); // Spike
} else {
    @Tag.MixerVibration = baseValue + noise; // Normal
}

Step 4: Create Monitoring Task

1. Go to Scripts → Tasks
2. Create task: MonitorVibration
3. Set trigger: Period = 1000ms (1 second)
4. Add code:

csharp

// Call the ML anomaly detection
@Script.Class.ML_Anomaly.Check(@Tag.MixerVibration);

Alternatively:

1. Go to Scripts → Expressions
2. Add the same expression and trigger

Step 5: Create Display Components

1. Open Displays → Create New Display
2. Add a TextBox for Results:
   • Add a TextBox control
   • Configure in Settings tab:
     • Label Text: Last 10 anomalies
     • Linked Value: Tag.Anomalies
     • Binding: OutputOnly
     • ? Enable Multiline
3. Add a Refresh Button:
   • Add a Button control
   • Label: Refresh
   • In the Dynamics tab, add an Action:
     • Event: MouseLeftButtonDown
     • Action: RunExpressions
     • Result (optional): Tag.Anomalies
     • Expression: Script.Class.ML_Anomaly.GetAnomalies()

Step 6: Test the System

1. Start Runtime (F5)
2. Open your display
3. Observe the simulated vibration values
4. Click "Refresh" button periodically
5. The TextBox will display:
   • "No new anomalies detected" when buffer is empty
   • List of anomalies with format: timestamp|value|severity

Example output:

2025-01-15 10:23:45|0.895|0.82
2025-01-15 10:24:12|0.756|0.91
2025-01-15 10:25:33|0.923|0.75

How It Works

1. SimulateVibration generates realistic sensor data with 5% anomalies
2. MonitorVibration checks each value using ML model
3. ML_Anomaly class uses SR-CNN algorithm to detect spikes
4. Anomalies are buffered internally (max 10)
5. Refresh button retrieves and clears the buffer

Key Learning Points

? ML.NET Integration: Must enable ML.NET namespaces when creating script class
? Simple API: Single method call Check() for detection
? Self-contained: No external tags needed for ML state
? Production Ready: Can replace simulator with real sensor tags

Next Steps

• Connect real sensor data instead of simulator
• Adjust SR-CNN threshold (0.15) for sensitivity
• Crate alarms for critical anomalies
• Store anomaly history in Historian
• Create trending displays for pattern analysis

This completes the ML.NET anomaly detection implementation in FrameworX!

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