Volume 2 Issue 2
Authors: Habib Dallagi; Chokri Mechmeche; Naceur Benhadj Braiek
Abstract: This paper presents a modelisation of a ship electric propulsion system and a design of residual generators in order to detect faults. The obtained system model belongs to the polynomial system class. Following some results in linear systems, a residual generator design method is developed, guaranteeing fault detection. The simulation results show how a fault detectability procedure can be made on the ship electric propulsion system.
Keywords: Ship electric propulsion system; Polynomial nonlinear system; Faults detection; Residual generator
Authors: A. Heckman; J. L. Rovey; K. Chandrashekhara; S. E. Watkins; D. S. Stutts; A. Banerjee; R. S. Mishra
Abstract: A health monitoring approach is investigated for hydrokinetic turbine blades. In-service monitoring is critical due to the difficult environment for blade inspection and the cost of inspection downtime. Composite blade designs provide a medium for embedding sensors into the blades for in-situ health monitoring. The major challenge with in-situ health monitoring is transmission of sensor signals from the remote rotating reference frame of the blade to the system monitoring station. In the presented work, a novel system for relaying in-situ blade health measurements in hydrokinetic systems is described and demonstrated. An ultrasonic communication system is used to transmit sensor data underwater from the rotating frame of the blade to a fixed relay station. Data are then broadcast via radio waves to a remote monitoring station. Results indicate that the assembled system can transmit simulated sensor data with an accuracy of ±5% at a maximum sampling rate of 500 samples/sec. A power investigation of the transmitter within the blade shows that continuous max-sampling operation is only possible for short durations (~days), and is limited due to the capacity of the battery power source. However, intermittent sampling, with long periods between samples, allows for the system to last for very long durations (~years). Finally, because the data transmission system can operate at a high sampling rate for short durations or at a lower sampling rate/higher duty cycle for long durations, it is well-suited for short-term prototype and environmental testing, as well as long-term commercially-deployed hydrokinetic machines.
Keywords: Marine Energy; Hydrokinetic Energy; Structural Health Monitoring; Acoustic Communication
Authors: Ren Xi; Zhao Jian-jun; Yang Li-bin
Abstract: Combining of the characteristics of grey prediction and Markov theory, an improved Grey Markov model is proposed, the sequence is disposed with moving average. The change trends system is fitted with unbiased GM (1,1) model, and thereby Markov prediction is done. During the prediction process, the original data are constantly updated. The result shows that, compared with the general grey prediction model, the prediction accuracy has been greatly improved, especially on medium-term and long-term prediction.
Keywords: Unbiased GM (1,1) Model; Spare Parts Prediction; Markov Process