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Efficient small infrared (IR) maritime target detection in heavy waves is a key and challenging task in maritime distress target search and rescue systems. The current methods are struggling to enhance targets and suppress heavy waves because of the similar local contrast. In this letter, a weighted multidirectional gradient (WMDG) measure is presented. First, the candidate targets are extracted via facet model. Then multidirectional gradient and difference information are constructed to calculate average cumulative multidirectional gradient (ACMG) and achieve directional difference measure (DDM). Consequently, the final saliency is reconstructed via ACMG weighted by DDM. Finally, the actual targets are segmented through an adaptive threshold. Experimental results demonstrate that our method is superior to the state-of-the-art methods with regard to detection validity and robustness for small IR maritime target detection in heavy waves.

This paper addresses a problem on infrared maritime target detection robustly in various situations. Its main contribution is to improve the infrared maritime target detection accuracy in different backgrounds, for various targets, using multiple infrared wave bands. The accuracy and the computational time of traditional infrared maritime searching systems are improved by our proposed Local Peak Singularity Measurement (LPSM)-Based Image Enhancement and Grayscale Distribution Curve Shift Binarization (GDCSB)-Based Target Segmentation. The first part uses LPSM to quantize the local singularity of each peak. Additionally, an enhancement map (EM) is generated based on the quantitative local singularity. After multiplying the original image by the EM, targets can be enhanced and the background will be suppressed. The second part of GDCSB-Based Target Segmentation calculates the desired threshold by cyclic shift of the grayscale distribution curve (GDC) of the enhanced image. After binarizing the enhanced image, real targets can be segmented from the image background. To verify the proposed algorithm, experiments based on 13,625 infrared maritime images and five comparison algorithms were conducted. Results show that the proposed algorithm has solid performance in strong and weak background clutters, different wave bands, different maritime targets, etc.

A feedback-dominance based adaptive back-stepping (FDBAB) controller is designed to drive a container ship to follow a predefined path. In reality, current, wave and wind act on the ship and produce unwanted disturbances to the ship control system. The FDBAB controller has to compensate for such disturbances and steer the ship to track the predefined (or desired) path. The difference between the actual and the desired path along which the ship is to sail is defined as the tracking error. The FDBAB controller is built on the tracking error model which is developed based on Serret-Frenet frame transformation (SFFT). In additional to being affected by external disturbances, the ship has more outputs than inputs (under-actuated), and is inherently nonlinear. The back-stepping controller in FDBAB is used to compensate the nonlinearity. The adaptive algorithms in FDBAB is employed to approximate disturbances. Lyapunov's direct method is used to prove the stability of the control system. The FDBAB controlled system is implemented in Matlab/Simulink. The simulation results verify the effectiveness of the controller in terms of successful path tracking and disturbance rejection.

When detecting infrared maritime targets on sunny days, strong sun glitters can lower the detection accuracy tremendously. To this problem, we proposed a robust antijitter spatiotemporal saliency generation with parallel binarization (ASSGPB) method. Its main contribution is to facilitate to improve the infrared maritime target detection accuracy in this situation. The ASSGPB algorithm exploits the target’s spatial saliency and temporal consistency to separate real targets from clutter areas. The ASSGPB first corrects image intensity distribution with a central inhibition difference of Gaussian filter. Then, a self-defined spatiotemporal saliency map (STSM) generator is used to generate an STSM in five consecutive frames while compensating interframe jitters by a joint block matching. Finally, a parallel binarization method is adopted to segment real targets in STSM while keeping full target areas. To evaluate the performance of ASSGPB, we captured eight different image sequences (20420 frames in total) that were significantly contaminated by strong sun glitters. The ASSGPB realized 100% detection rate and 0.45% false alarm rate in these data sets, greatly outperforming four state-of-the-art algorithms. Thus, a great applicability of ASSGPB has been verified through our experiments.

The early release from wetlands and shallow ponds could provide extra water storage during heavy rainfall, thus mitigating floods. In this paper, a remotely operated integrated siphon system intended to release water from wetlands/shallow ponds ahead of (a few hours or a few days before) a heavy rainfall that is forecasted to produce flooding is proposed. Siphons work under the pull of gravity and are limited to pond berm heights below about 6 m. An array (e.g. hundreds) of the proposed siphon system can be controlled remotely by an operator or by a Decision Support System. A self-operating and remotely controlled siphon system could open the doors for managing wetlands and shallow ponds for multiple purposes, including flood control and improvement of aquatic habitat. Laboratory tests using 4 and 15 cm-diameter siphons were performed in this study. The results showed that the integrated control system is technically feasible and economically viable.

For the study of dark adaptation at the entrance section of a tunnel, the effects of photopigments in rod cells and luminance can be disregarded because the luminance of this section is in the range of photopic vision. Instead, light color characteristics can be considered. This paper focused on the impact of light color, including correlated color temperature (CCT), color rendering, and spectrum, on dark adaptation at the entrance section of a tunnel. An experiment was performed based on seven kinds of high-power LEDs with different CCTs (3000-6500 K). The experimental results showed that the light color characteristics of LEDs significantly affected dark adaptation. Specifically, the better the color rendering and the lower the absence of blue light, the shorter the dark adaptation time. Among various LEDs with different CCTs, the 4000 K-4500 K LEDs have better light color characteristics and can shorten dark adaptation times. Therefore, LEDs with CCTs of 4000 K-4500 K are preferable for lighting tunnel entrances.

Aiming at the chattering problem of conventional sliding mode control systems for dc-dc converters, a quasi-continuous second-order sliding mode (QSOSM) control scheme for buck converters has been presented in the paper. It will be shown that the QSOSM controller is practically a continuous function of the states everywhere except the origin. And thus the chattering problem existing in conventional sliding mode can be practically solved due to the fact that the states cannot be stabilized to the origin from engineering point of view. Theoretical analysis also shows that the closed loop system of the buck converter is globally finite-time stable. Finally, the theoretical considerations have been verified by simulation and experimentation. Specifically, the comparisons between QSOSM controller and PID controller show that the former one provides a better robustness.

It has always been a great challenge to efficiently detect small infrared targets from complex image backgrounds without any prior knowledge. This is especially true when both strong and weak targets appear in the same image or when the weak targets come up on image borders. The main contribution of this paper is to design a robust infrared maritime target detection method, in which a visual attention and pipeline-filtering model is proposed by integrating a revised visual attention model (VAM) and the antivibration pipeline-filtering algorithm. The revised VAM, a single-frame target detection strategy, will first compute a saliency map (SM) from a specific modality, which is automatically selected according to image background smoothness. Then, an automatic strategy for extracting suspected targets from an SM is also proposed here, which highlights targets and suppresses background clutters in SMs through local saliency singularity evaluation. Moreover, contrary to the original VAM, we adopt border saliency preservation in center-surround difference so that robust detection can be guaranteed for targets on image borders. Finally, to eliminate the interference of sea glints and confirm real targets, we adopt the antivibration pipeline-filtering algorithm, a multiframe-based clutter removal method. Compared with the original VAM and two other existing target detection algorithms, experimental results have proven that our strategy can detect infrared maritime targets much better under different environmental conditions. This research can significantly improve the success rate and efficiency of searching maritime targets in different weathers using infrared imager, especially in heavy sea fog and strong ocean waves.

This paper presents a novel control circuitry design for both vibrating axes (drive and sense) of vibrational gyroscopes, and a new sensing method for time-varying rotation rates. The control design is motivated to address the challenges posed by manufacturing imperfection and environment vibrations that are particularly pronounced in microelectromechanical systems (MEMS) gyroscopes. The method of choice is active disturbance rejection control that, unlike most existing control design methods, does not depend on an accurate model of the plant. The task of control design is simplified when the internal dynamics, such as mechanical cross coupling between the drive and sense axes, and external vibrating forces are estimated and cancelled in real time. In both simulation and hardware tests on a vibrational piezoelectric beam gyroscope, the proposed controller proves to be robust against structural uncertainties; it also facilitates accurate sensing of time-varying rotation rates. The results demonstrate a simple, economic, control solution for compensating the manufacturing imperfections and improving sensing performance of the MEMS gyroscopes.