Visual loop closure detection based on binary generative adversarial network

In view of the problem that the existing loop closure detection models are mostly trained based on supervised learning and require a large amount of labeled data, this paper proposes a new method for visual loop closure detection. The idea of the generative adversarial network is adopted, and thus, a deep neural network is designed and trained through unsupervised learning methods to extract more discriminative binary feature descriptors with low dimensions. The distance propagation loss function and a binarized representation entropy loss function are introduced into the neural network. The first loss function can help spread the Hamming distance relationship of the high-dimensional feature space to the low-dimensional feature space, and the second one increases the diversity of the low-dimensional feature representation. The extracted local features are fused into global features by using the BoVW model for further loop closure detection. Experimental results show that the proposed method has better performance than feature extraction algorithms such as SIFT and ORB in complex scenes that have a strong viewpoint and appearance changes, and its performance is comparable with that of supervised deep networks such as AlexNet and AMOSNet. It is especially suitable for loop closure detection in large-scale open scenes because the time-consuming and tedious process of supervised data annotation is completely avoided with the use of unsupervised learning. Moreover, the binary feature descriptors can greatly save storage space and computing resources.