Aiming at the difficulty of unsupervised feature learning on defect vibration data of train running part, a method based on Compressed Sensing and Deep Wavelet Neural Network (CS-DWNN) was proposed. Firstly, the collected vibration data of train running part were compressed and sampled by Gauss random matrix. Secondly, a DWNN based on improved Wavelet Auto-Encoder (WAE) was constructed, and the compressed data were directly input into the network for automatic feature extraction layer by layer. Finally, the multi-layer features learned by DWNN were used to train multiple Deep Support Vector Machines (DSVMs) and Deep Forest (DF) classifiers respectively, and the recognition results were integrated. In this method DWNN was employed to automatically mine hidden fault information from compressed data, which was less affected by prior knowledge and subjective influence, and complicated artificial feature extraction process was avoided. The experimental results show that the CS-DWNN method achieves an average diagnostic accuracy of 99.16%, and can effectively identify three common faults in train running part. The fault recognition ability of the proposed method is superior to traditional methods such as Artificial Neural Network (ANN), Support Vector Machine (SVM) and deep learning models such as Deep Belief Network (DBN), Stack De-noised Auto-Encoder (SDAE).
In order to avoid transmission collisions and improve energy efficiency for periodic report Wireless Sensor Network (WSN), a Medium Access Control (MAC) protocol with network utility maximization and collision avoidance called UM-MAC was proposed. UM-MAC used Time Division Multiple Access (TDMA) scheduling mechanism and introduced the utility model into the slot assignment process. A utility maximization problem of joint link reliability and energy consumption optimization based on utility model was put forward. To handle it, a heuristic algorithm was proposed to make the network to quickly find out a slot scheduling strategy which maximize network utility and avoid transmission collisions. Comparison experiments among UM-MAC, S-MAC and CA(Collision Avoidance)-MAC protocols were conducted under networks with different nodes, where UM-MAC got larger network utility and higher average packet successful delivery ratio, the lifetime of UM-MAC was between S-MAC and CA-MAC, while its average transmission delay increased under networks with defferent loads. The simulation results show that UM-MAC can achieve collision avoidance and improve network performance in terms of packet successful delivery ratio and energy efficiency; meanwhile, the TDMA-based protocol is not better than competition-based protocol in low load networks.