Estágio realizado na Critical Software e orientado pelo Eng.º Ricardo Barbosa / Tese de mestrado integrado. Engenharia Informática e Computação. Faculdade de Engenharia. Universidade do Porto. 2009

The focus of this study was deep learning. A small, autonomous robot car was used for obstacle avoidance experiments. The robot car used a camera for taking images of its surroundings. A convolutional neural network used the images for obstacle detection. The available dataset of 31 022 images was trained with the Xception model. We compared two different implementations for making the robot car avoid obstacles. Mapping image classes to steering commands was used as a reference implementation. The main implementation of this study was to separate obstacle detection and steering logic in different modules. The former reached an obstacle avoidance ratio of 80 %, the latter reached 88 %. Different hyperparameters were looked at during training. We found that frozen layers and number of epochs were important to optimize. Weights were loaded from ImageNet before training. Frozen layers decided how many layers that were trainable after that. Training all layers (no frozen layers) was proven to work best. Number of epochs decided how many epochs a model trained. We found that it was important to train between 10-25 epochs. The best model used no frozen layers and trained for 21 epochs. It reached a test accuracy of 85.2 %.

Under de senaste året har modeller för djupinlärning använts inom nästa alla områden, från industri till akademi, särskilt för bildklassifikation. Dessa modeller är dock enorma i storlek, med miljontals parametrar, vilket gör det svårt att distribuera till mindre enheter med begränsade resurser såsom mobiltelefoner. Denna studie tar upp små modeller av faltningsnätverk som är toppmoderna inom djupinlärning och vars storlek är lämplig för mobilapplikation. Syftet med denna studie är att utvärdera prestanda på faltningsnätverken Xception, InceptionV3 och MobilNetV2 för att underlätta vid valbeslut av faltningsnätverk som bas vid utveckling av mobila applikation inom bildklassificering. För att uppnå syftet har dessa faltningsnätverk implementeras med hjälp av överföringsinlärning metod samt utformas för att skilja på bilder av nätpaneler från företaget Troax. Studien tar upp metoden som möjliggör att överföra kunskap från befintliga förtränade modeller till nya modeller. Studien förklarar även hur träningsprocessen och testprocessen gick till samt analys kring resultatet.   Resultat visade att Xception hade 86 % noggrannhet med en processtid på 10 minuter på 2000 träningsbilder och 1000st testbilder. Xceptions prestation var bäst bland alla dessa modeller. Skillnaden mellan Xception och Inception var på 10 % noggrannhet och 2 minuter processtid. Mellan Xception och MobilNetV2 var skillnaden på 23 % noggrannhet och 3 minuter processtid. Experimentet visade att dessa modeller presterade mindre bra vid mindre träningsbilder under 800st. Över 800st bilder började respektive modell att utföra prediktering över 70 % noggrannhet. / In recent years, deep learning models have been used in almost all areas, from industry to academia, specifically for image classification. However, these models are huge in size, with millions of parameters, making it difficult to distribute to smaller devices with limited resources such as mobile phones. This study addresses lightweight pre-trained models of convolutional neural networks which is state of art in deep learning and their size is suitable as a base model for mobile application development. The purpose of this study is to evaluate the performance of Xception, InceptionV3 and MobilNetV2 in order to facilitate selection decisions of a lightweight convolutional networks as base for the development of mobile applications in image classification. In order to achieve their purpose, these models have been implemented using the Transfer Learning method and are designed to distinguish images on mesh panels from the company Troax. The study takes up the method that allows transfer of knowledge from an existing model to a new model, explain how the training process and the test process went, as well as analysis of results. Results showed that Xception had 86% accuracy and had 10 minutes processing time on 2000 training images and 1000 test images. Exception’s performance was the best among all these models. The difference between Xception and InceptionV3 was 10% accuracy and 2 minutes process time. Between Xception and MobilNetV2 there was a difference of 23% in accuracy and 3 minutes in process time. Experiments showed that these models performed less well with smaller training images below 800 images. Over 800 images, each model began to perform prediction over 70% accuracy.