Abstract:With the rapid development of artificial intelligence technology,open set recognition has been widely studied as an emerging field of classification problems. This study designed an open set recognition task for the FLSMDD sonar dataset, aiming to evaluate the ability of the Openmax algorithm to handle unknown class samples,then we compare it with traditional Softmax and its thresholded variants. By combining residual networks and transfer learning techniques, the study tested the performance of different algorithms in terms of classification accuracy and robustness. The results show that the Openmax algorithm has an overall accuracy improvement of 5% compared to Softmax, a macro-F1 improvement of 7%, and a weighted Macro-F1 increase of 6%, indicating that it has significant advantages in adaptability and robustness in handling unknown categories. Future research will explore optimizing algorithm to further improve recognition accuracy and processing efficiency. This study provides strong evidence for the development of open set recognition technology and lays a theoretical and experimental foundation for the application of deep learning in a wider range of classification problems.