Jiawang Chen

Depth control of ROVs using time delay estimation with nonsingular terminal sliding mode

In this paper, a nonsingular terminal sliding mode (NTSM) control method based on time delay estimation (TDE) is proposed and investigated for the depth control of remotely operated vehicles (ROVs). The complex dynamics is approximately compensated by TDE leading to an attractive model-free nature, which is more suitable for practical applications than other model-based methods. Furthermore, the NTSM manifold based on nonlinear error dynamics can ensure better control performance than the traditional sliding mode (SM) manifold with linear error dynamics. Stability of the closed-loop system is analyzed using Lyapunov theory. Finally, the faster convergence and higher tracking accuracy compared with traditional TDE method with linear error dynamics are verified through simulation.

Effects of inlet flow rate and concentration fluctuations on the separation performance of a novel dynamic hydrocyclone

In this paper, a computational fluid dynamics (CFD) calculation was used to evaluate the effects of the inlet feed flow rate and concentration fluctuations on the hydrocyclones separation performance. A mixture model was used to model the multiphase flows, while the Reynolds stress model (RSM) modeled the turbulence in the inner field of the dynamic hydrocyclone. After a numerical investigation, it is found that when the flow rate at the inlet was below a certain value, favorable separation efficiency was obtained with some fluctuations that most likely resulted from the influence of the wall at the high rotary speed. When the flow rate at the inlet was too large, the separation efficiency would dramatically decrease. When the inlet concentration was below a certain range, it would have little influence over the separation efficiency; however, when it became too large, the separation efficiency would rapidly decline. The simulation results agreed with the theoretical results.

Study of a Novel Underwater Cable With Whole Cable Monitoring

This paper describes a novel concept for detecting and tracking underwater cables that differs from common detection methods, including visual, acoustic and magnetic detection, which are based on a survey platform, such as remotely operated vehicles and autonomous underwater vehicles, and have high costs and require long-time monitoring. The proposed detection method can be performed in locations that are difficult to observe using cameras without the use of magnetic fields. The concept relies on low-cost flex sensors that provide underwater, real-time, whole cable detection. Building off of this concept, a detection system and an error analysis system were incorporated, which includes the characteristics of the flex sensors, the mounting structure for the flex sensors, and the underwater cable as well as the 2-D cable bend model and a water tank test. The detected data set, which was rendered on an observation monitor, provided visual feedback regarding any bending or warping problems. To evaluate the detection accuracy, mean absolute error and similarity analyses were performed using the observational data and sensor data obtained from the water tank test. The results of these analyses showed strong agreement between the fitted curve to the detected data and the observational curve, indicating acceptable error. These results demonstrate the feasibility of the proposed system for effective underwater cable detection. Thus, the results of this investigation clearly reveal the potential of the novel sensing technique for practical underwater cable detection and monitoring applications. However, the 2-D cable bending detection model is not suitable for 3-D bending or torsion, which will be considered in future research.

Review of Underwater Cable Shape Detection

AbstractUnderwater cables play vital roles in marine engineering because they provide power and communication connections from the shore to an increasing number of sea installations. To ensure the system is operating reliably and continuously, it is necessary to detect the shapes of underwater cables in real time. However, this task is difficult to accomplish because the underwater cables are located in a dynamic and complicated subsea environment, which can cause changes in position, depth, and visibility.In this report, the current development of underwater cable shape detection methods, including visual, acoustic, magnetic detection, and multisensor fusion detection, and the advantages and disadvantages are described and analyzed. Furthermore, the disadvantages of these methods are addressed, which, based on survey platforms with high cost, include a long detection period and the failure to reveal emergencies. Then, the need to construct a simple and reliable system to detect the shapes of underwater c...

Study of an Underwater retrievable cabin manufactured by hand layup process

Underwater surveillance network (UWSN) has been widely used in various scenarios, which is constructed by several single nodes composed of two parts: triangle bracing frame and retrievable spherical cabin fixed on top of it. This paper mainly presents the study of the cabin made of glass reinforced plastic material (GRP) manufactured by hand layup process. Then the strength and stability of the cabin was analyzed using finite element analysis software named ABAQUS. In addition, many influences were researched affecting the strength of the GRP product in hand layup processing. Especially, effects of resin content (resin weight fraction) were studied. Finally, the results of hyperbaric chamber experiment show that the designed retrievable cabin manufactured by hand layup process can properly work under ocean water of 200 meter.

Research on a Nonlinear Robust Adaptive Control Method of the Elbow Joint of a Seven-Function Hydraulic Manipulator Based on Double-Screw-Pair Transmission

A robust adaptive control method with full-state feedback is proposed based on the fact that the elbow joint of a seven-function hydraulic manipulator with double-screw-pair transmission features the following control characteristics: a strongly nonlinear hydraulic system, parameter uncertainties susceptible to temperature and pressure changes of the external environment, and unknown outer disturbances. Combined with the design method of the back-stepping controller, the asymptotic stability of the control system in the presence of disturbances from uncertain systematic parameters and unknown external disturbances was demonstrated using Lyapunov stability theory. Based on the elbow joint of the seven-function master-slave hydraulic manipulator for the 4500 m Deep-Sea Working System as the research subject, a comparative study was conducted using the control method presented in this paper for unknown external disturbances. Simulations and experiments of different unknown outer disturbances showed that (1) the proposed controller could robustly track the desired reference trajectory with satisfactory dynamic performance and steady accuracy and that (2) the modified parameter adaptive laws could also guarantee that the estimated parameters are bounded.

Hydrodynamic simulation on swing wings of vertical underwater glider

This paper introduces a new kind of vertical underwater glider with swing wings, combining Argo float and underwater glider together to achieve the goal of operating in the ocean automatically. The paper analyses the rectilinear motion and force of this new kind of underwater glider. The calculated and simulated results are shown in this paper.

Underwater cable shape detection using ShapeTape

This paper describes a method for detecting and tracking underwater cables using ShapeTape (Measurand Inc., Canada). ShapeTape is a light weight, flexible ribbon which senses the bend and twist along its length. The ability of ShapeTape to detect underwater cables was carried out in a water tank. A mean absolute error and similarity analysis were performed to evaluate the detection accuracy. The results of analysis indicated that the errors between fitting curve of detected data and the observational curve were acceptable. And these results demonstrate the feasibility of ShapeTape for underwater cable detection.

Experimental and analytical investigations of wave-induced artificial upwelling

Artificial upwelling is supposed to be a general technique to enhance the marine primary productivity and fishery resources by means of pumping the nutrient-rich deep ocean water (DOW) to the euphotic layer. The wave energy is the most conspicuous form of ocean energy, the extraction of energy from the waves can be a viable economic solution to the power requirements of artificial upwelling. To extract the wave energy, a structure which responds to the input wave motion is required. This paper presents our latest investigation on the wave-induced artificial upwelling device by a fixed rigid pipe submerged in the water. In this study, we improve the theoretical methods, and the calculated results are verified by the wave-tank experiments. It turns out that the upwelling rate was affected of the wave height H, the wave period H, the water depth ft, the length of the pipe L and diameter of the pipe d, etc. Based on the theoretical calculations and experimental results, we can estimate the upwelling flow rate of the wave-induced artificial upwelling device applied in the open sea.

Development of one pressure core transfer device for one long gravity-piston pressure-retained corer

A transfer device, which can subsample cores and subsequently transfer subsamples into specialized chambers under pressure for further measurements, is under development for investigating methane hydrate sediments in the South China Sea. The transfer device is designed to be a robust and efficient equipment, which is compatible with the long gravity-piston pressure-retained corer. The corer has been applied in the SCS for dozens of times and proved convenient and efficient. This paper mainly introduces the structural form of the pressure core transfer device, illustrates working principles of the transfer device, and demonstrates details of the catcher, key to the transfer device.