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Sensor Networking Software and Architectures
Published in John R. Vacca, Handbook of Sensor Networking, 2015
SAS imaging is the acoustic equivalent of synthetic-aperture radar (SAR) imaging. The applications cover a wide range of oceanic search, surveys, and mapping. It normally functions in the reflection mode with a multielement array. The field experiment was conducted in the San Diego Bay with a linear 10-element sonar array operating in the side-looking linear-scan model. The use of a multielement array is to produce the redundancy for the estimation of platform motion. The platform motion consists of six parameters, of which three are associated with the translational vector and another three associated with the rotation matrix in three dimensions. The synthetic aperture is 1D, and thus, the final image is 2D. Figure 16.6a is the reconstructed image of a sunken airplane, and Figure 16.6b is the enlarged version.
Robust self-organising fuzzy sliding mode-based path-following control for autonomous underwater vehicles
Published in Journal of Marine Engineering & Technology, 2023
G. V. Lakhekar, L. M. Waghmare
The coordinated path-following problems of multiple underactuated AUVs described in Ghommam et al. (2008) are based on the convergence of geometric errors at the origin of each vehicle. Bo et al. (2009) resolved the path-planning problem through the fast marching algorithm, assuming the AUV manoeuvres at a fixed depth. The control algorithm for the path following an AUV suggested in Subudhi and Datta (2009) uses vehicle dynamics to generate the reference orientation, body-fixed velocities and error dynamics. Then it stabilised using an inverse dynamics control strategy, forcing the tracking error to an arbitrarily small neighbourhood of zero. Williams (2010) discusses the utilisation of synthetic aperture sonar (SAS) data collected at sea surface level to perform mine counter measure (MCM) operations. Zhao and Zhu (2011) found a solution to the path following a problem based on the design of a control algorithm from biological agents. Xiang et al. (2011) developed a novel bioinspired model in the horizontal plane to generate forward and angular velocities smoothly and in real time. Lyapunov's direct method has devised a backstepping strategy to solve the path-following and trajectory tracking problems and then extended to resolve the dynamic problem.
Enhancement signal detection in underwater acoustic noise using level dependent estimation time-frequency de-noising technique
Published in Journal of Marine Engineering & Technology, 2020
Yasin Yousif Al-Aboosi, Ahmad Zuri Sha’ameri, Adheed Hasan Sallomi
Many techniques for detection in presence of non-Gaussian noise were reported, such as neural detectors are presented in (Gandhi and Ramamurti 1997) under several non-Gaussian noise environments and are compared with those of matched filter and locally optimum detectors. A threshold-system-based detector (TD) for detecting a known deterministic signal in an independent non-Gaussian noise is proposed in (Guo et al. 2012). subspace-based detection method for multichannel (high frequency and broadband) synthetic aperture sonar (SAS) imagery is addressed in (Azimi-Sadjadi et al. 2017). Noise-enhanced signal detection that used in this paper is a method used for non-Gaussian detection, and it was initiated by Kay (Kay 2000). A suboptimal threshold-system-based detector was shown to have an improved detection probability by adding AWGN. In (Nason 2006), the pdf equal to the sum of a Gaussian random variable and a Student’s t distribution on odd degrees of freedom greater than or equal to three is derived. The tail of the resulting pdf is heavier than that of the Gaussian distribution but lighter than that of the Student’s t distribution, indicating that the pdf is nearly Gaussian.