Underwater Towed Vehicle Research Articles

Numerical analysis of dynamic behaviors of underwater towed system with hydrofoil manipulations

This paper addresses the dynamic characteristics of an underwater towed system under manipulations of synchronous hydrofoils, considering the coupling of instantaneous fluid forces on the complete systems and hydrofoil control, which is usually difficult to solve with existing methods. A hydrodynamic model coupled with hydrofoil control algorithms is presented, wherein the hydrodynamic forces on the hydrofoils and Underwater Towed Vehicle (UTV) are simulated using the Computational Fluid Dynamics (CFD) method, and the fluid forces on the Towing Cable (TC) are described using a flexible cable dynamic model. The dynamic behaviors of the underwater towed system under depth-undulating, depth-tracking, and depth-keeping controls of hydrofoils are analyzed using the proposed model. The results show that the towing speed has a significant effect on the control efficiency of the hydrofoils. The dynamic responses of the underwater towed system increase or decrease more significantly in submerged depth control operations than in freely towing operations. The hydrofoils can achieve satisfactory effects in submerged depth control for the UTV at an appropriate towing speed, whereas it fails at a lower towing speed and noticeable dynamic response oscillations occur simultaneously. This study is expected to provide guidance on both hydrodynamic and control issues of underwater towed systems.

Simultaneously Tracking and Pitch Control of Underwater Towed Vehicle with Multiple Elevators: A Finite-Time Fuzzy Approach

Simultaneously Tracking and Pitch Control of Underwater Towed Vehicle with Multiple Elevators: A Finite-Time Fuzzy Approach

Research into the integrated navigation of a deep-sea towed vehicle with USBL/DVL and pressure gauge

Underwater Towed Vehicle navigation and localization in deep sea environments are particularly challenging without high-precision inertial sensors. In this paper, the multi-sensors navigation fusion method of a towed underwater vehicle based on the ultrashort baseline (USBL) system, Dopplervelocitylog (DVL) and a pressure gauge in the deep sea is investigated. Combined with GPS real-time tide detection technology, the positioning principle of the USBL based on the depth constraint is given, and a straight-line model be proposed to estimate the position of the vehicle used the average heading when underwater towed vehicle is working normally in deep sea without DVL. The interacting multiple model (IMM) algorithm based on smoothing algorithm is proposed to improve the positioning accuracy in the deep sea, and the nonlinearity of the model, precision and stability of filtering are considered simultaneously using the adaptive robust square root cubature Kalman filter. The results of the simulated and practical experiments at 4800 m verify that the new algorithm can take full use of high-precision observation information and greatly improve the positioning accuracy and robustness of a deep sea underwater towed system.

Calculation the total resistance and squat of underwater towed vehicle based on CFD

CFD method is used to calculate drag and sinking force of underwater towed body. Using cubic spline curve interpolation and finite difference method are used to calculate the tangential force and normal force of towing cable. Finally, the squat of underwater towed vehicle in the water and the total force at the end of towing cable are obtained.

Multi-dimensional water quality assessment of an urban drinking water source elucidated by high resolution underwater towed vehicle mapping

Spatial surveys of Ramsey Lake, Sudbury, Ontario water quality were conducted using an innovative underwater towed vehicle (UTV) equipped with a multi-parameter probe providing real-time water quality data. The UTV revealed underwater vent sites through high resolution monitoring of different spatial chemical characteristics using common sensors (turbidity, chloride, dissolved oxygen, and oxidation/reduction sensors) that would not be feasible with traditional water sampling methods. Multi-parameter probe vent site identification is supported by elevated alkalinity and silica concentrations at these sites. The identified groundwater vent sites appear to be controlled by bedrock fractures that transport water from different sources with different contaminants of concern. Elevated contaminants, such as, arsenic and nickel and/or nutrient concentrations are evident at the vent sites, illustrating the potential of these sources to degrade water quality.

Parametric Study for the Steady-State Equilibrium of a Towfish

The dynamic equilibrium in steady-state conditions is of great importance for the attitude control of an underwater towed vehicle. The paper aims to investigate which parameters allow to maintain a given horizontal attitude at a desired depth. Some simplifications as constant speed of the boat, negligible inertial effects of the towline are introduced in order to study the steady-state phase. Flexible cable modeling and hydrodynamic forces are coupled to rigid body statics to create a model able to determine the angles of the hydrodynamic profiles in order to maintain zero-pitch orientation at a given depth. Finally, a GUI interface, to help designers to predispose different strategies and to analyze equilibrium when some relevant parameters are varied, is developed. Two algorithms have been implemented inside the GUI interface to test steady-state equilibrium. A first direct algorithm computes total forces and pitch torque with assigned depth and angles of the ailerons/stabilizers. The second inverse algorithm finds, if possible, the angles of attack of the hydrodynamic profiles necessary to reach equilibrium.

Nonlinear adaptive control of an underwater towed vehicle

This paper addresses the problem of simultaneous depth tracking and attitude control of an underwater towed vehicle. The system proposed uses a two-stage towing arrangement that includes a long primary cable, a gravitic depressor, and a secondary cable. The towfish motion induced by wave driven disturbances in both the vertical and horizontal planes is described using an empirical model of the depressor motion and a spring-damper model of the secondary cable. A nonlinear, Lyapunov-based, adaptive output feedback control law is designed and shown to regulate pitch, yaw, and depth tracking errors to zero. The controller is designed to operate in the presence of plant parameter uncertainty. When subjected to bounded external disturbances, the tracking errors converge to a neighbourhood of the origin that can be made arbitrarily small. In the implementation proposed, a nonlinear observer is used to estimate the linear velocities used by the controller thus dispensing with the need for costly sensor suites. The results obtained with computer simulations show that the controlled system exhibits good performance about different operating conditions when subjected to sea-wave driven disturbances and in the presence of sensor noise. The system holds promise for application in oceanographic missions that require depth tracking or bottom-following combined with precise vehicle attitude control.

Associations of lobsters (Homarus americanus) off southwestern Nova Scotia with bottom type from images and geophysical maps

Abstract Tremblay, M. J., Smith, S. J., Todd, B. J., Clement, P. M., and McKeown, D. L. 2009. Associations of lobsters (Homarus americanus) off southwestern Nova Scotia with bottom type from images and geophysical maps. – ICES Journal of Marine Science, 66: 2060–2067. Images from an underwater towed vehicle (Towcam) were used to estimate densities and to evaluate bottom-type associations of lobsters (Homarus americanus), crabs (Cancer spp.), and scallops (Placopecten magellanicus). Images were obtained in October 2006 along 14 line-transects off southwestern Nova Scotia in an area with productive lobster and scallop fisheries. Lobsters were observed in 4% of the 2044 images, crabs in 7%, and scallops in 40%. On sand, gravel, and cobble seabed, lobsters were readily observable. On rougher substrata with boulders, some lobsters were still evident either in the open or partially hidden in shelters. Estimated densities of lobsters from the images on some transects were 0.04 m−2, approximately half of the estimates of lobster density for adjacent inshore areas from scuba, but 34 times higher than estimates from scallop drags in the same area. Models of animal presence by bottom type were evaluated with categories that were (i) geophysically based (map of bottom type from geophysical characteristics) and (ii) image-based (sediment size from images). Significant relationships were evident with both types of seabed categorization, suggesting that it would be beneficial to stratify surveys using geophysical categories. Depth was also significant in determining presence/absence of lobsters and crabs. There is potential to develop indicators of lobster abundance using underwater imaging, and stratification by bottom type should be incorporated into surveys.

Nonlinear adaptive depth tracking and attitude control of an underwater towed vehicle

This paper addresses the problem of simultaneous depth tracking and precise attitude control of an underwater towed vehicle integrated in a two-stage towing arrangement. A nonlinear Lyapunov-based output feedback controller is designed to operate in the presence of plant parameter uncertainty and proven to regulate pitch, yaw, and depth tracking errors to zero. When subjected to bounded external disturbances, the tracking errors converge to a neighborhood of the origin that can be made arbitrarily small. In the implementation proposed, a nonlinear observer is used to estimate the linear velocities used by the controller. The results obtained with computer simulations including sea wave driven disturbances and sensor noise, show that the controlled system exhibits good performance about different operating conditions and holds considerable potential for oceanographic missions that require simultaneous depth and attitude control.

Underwater Towed Vehicle Manoeuvrable in Both Vertical and Horizontal Axis

This paper proposes a new concept of guidance and control of underwater towed vehicle to perform operation in both vertical and horizontal axis with stable attitude.The control architecture of the vehicle has hierarchical structure consisting of attitude control, guidance, navigation, path planning and communication. CCV (Control Configured Vehicle) technology was adopted to perform the attitude control for the decoupling of motion.Two types of the attitude control in the vertical axis and in the horizontal axis are executed independently. Guidance is performed asynchronously with attitude control to give target values of the attitude control.Fuzzy algorithm was applied to determine the target values of the attitude control in the guidance process as well as to perform the decoupling of motion in the attitude control process.For four types of guidance, i. e. (i) horizontal movement survey, (ii) vertical movement survey, (iii) vertical and horizontal movement survey and (iv) seabed survey in vertical plane with constant altitude, control strategies were made. Target values for the attitude control and the effects of motion of towing mother ship in waves and tidal current were investigated through numerical simulations.

Underwater Towed Vehicle Manoeuvrable in Both Vertical and Horizontal Axis

This paper proposes new concepts of configuration and attitude control of underwater towed vehicle to perform operation in both vertical and horizontal axis with stable attitude.The principal configuration composed of fuselage, main wing, horizontal tail, vertical canard, upper and lower vertical tails designed taking into account stability and manoeuvrability in vertical and horizontal planes. The manoeuvrability was estimated by use of lamped mass method for equilibrium equations of motion of towed cable and vehicle. The dynamic stability was analysed by use of eigenvalue analysis based on linear equations of motion.CCV (Control Configured Vehicle) technology was adopted to perform the attitude control. Three types of decoupled mode were considered, i) pitch angle and vertical velocity, ii) pitch angular velocity and vertical velocity, iii) roll angle, yaw angle and side slip velocity. Fuzzy algorithm was applied to CCV attitude control.The effect of motion of towing mother ship in waves was simulated numerically based on non-linear equations of motion of cable and vehicle to examine the effectiveness of attitude control in vertical axis. Not only drifts of velocity components and pitch angle, but also oscillation of pitch angle are remarkably suppressed.The effect of tidal current was simulated numerically to examine the attitude control in horizontal axis. Oscillations of side slip velocity, roll angle and yaw angle are almost eliminated.