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Object Detection with TensorFlow Lite Model Maker

Overview

This project demonstrates the creation of a custom object detection model using TensorFlow Lite Model Maker with an EfficientDet-Lite2 backbone. Leveraging transfer learning, the model is fine-tuned on a novel dataset to detect two custom classes: rocks and bags. The model is trained in Google Colab using a custom Python environment and deployed to a Pixel 7a device for real-time inference.

The pipeline includes dataset preparation, hyperparameter configuration, and generating a TensorFlow Lite model (efficientdet-lite2.tflite) suitable for integration into an Android app for live object detection. While this project is not designed to interface directly with autonomous driving systems, it addresses challenges in autonomous systems where misidentification of objects, such as rocks and bags, can compromise safety.

  • Example Logic:
    • Detecting a rock prompts the vehicle to swerve, avoiding potential damage.
    • Detecting a bag minimizes unnecessary evasive maneuvers.

Object Detection App

Training Process

The EfficientDet-Lite2 model is trained using TensorFlow Lite Model Maker, a high-level library for efficient prototyping. Transfer learning reduces data and computation requirements, accelerating the training process.

Steps to Train the Model:

1. Setup and Environment

  • Upload the notebook_main.ipynb file to Google Colab.
  • The notebook initializes a custom Python environment with Miniconda to address Colab's limitations:
    • Installs Miniconda and sets up an isolated environment (myenv) with Python 3.9.
    • Ensures compatibility with the TensorFlow Lite Model Maker library in a CPU runtime.

Note: Training is CPU-bound, which may be slow for larger datasets. GPU support is currently unavailable due to compatibility constraints. Contributions to enable GPU acceleration are welcome.

2. Data Preparation

  • Images are downsampled to 256x256x3 for faster edge-device inference. For improved accuracy, downsampling of original images to 320x320x3 is recommended before annotation.
  • Bounding box annotations are created using LabelImg in PascalVOC format.
  • Dataset structure: 
    rockbag_figure.zip
└── rockbag_figure
    ├── train
    │   ├── IMG_001.jpg
    │   ├── IMG_001.xml
    └── validate
        ├── IMG_101.jpg
        ├── IMG_101.xml
  • Upload the dataset (rockbag_figure.zip) and an edited train.py script with configured hyperparameters (e.g., batch size, epochs).

3. Training Configuration

  • Execute the training pipeline in Colab:
    • COCO metrics are reported, including:
      • mAP (mean Average Precision): Detection accuracy.
      • Precision: Proportion of correct predictions.
      • Recall: Proportion of true objects detected.
    • A TensorFlow Lite model (efficientdet-lite2.tflite) is generated post-training.

4. Outputs

  • The efficientdet-lite2.tflite file is ready for deployment.

Android App Setup and Model Integration

Setup in Android Studio

  1. Download app files from this Dropbox link.
  2. Open the android folder in Android Studio.
  3. Options:
    • Run the app as-is.
    • Replace preloaded models with a custom TensorFlow Lite model.

Custom Model Integration

  1. Navigate to the /assets/ folder.
  2. Replace the existing model file (e.g., efficientdet-lite2.tflite) with your custom-trained model. Ensure the custom model filename matches the original model being replaced.
  3. Rebuild the app in Android Studio.

Version Tracking

Screenshots of tested software versions are stored in the version-checks/ directory, documenting:

  • Android Studio version
  • Gradle and JDK details

Future Work

Potential extensions include:

  • Expanding the dataset to cover diverse conditions (e.g., lighting variations).
  • Experimenting with alternative model architectures.
  • Optimizing inference for additional edge devices.

Acknowledgments

This project builds on the TensorFlow Lite Model Maker workaround shared by @tomkuzma. The Android app is based on the TensorFlow Lite Examples Repository.