Vertical Thrusters Research Articles

Steering and Rising Testing of an Innovative Tourist Submarine

An innovative tourist submarine was studied by scale-model tests in a towing tank to determine its steering capabilities and detect motion instabilities during usual manoeuvres and emergency rising. Motion instabilities are caused by the combination of the submarine motions and the fluid flow, leading to excessive roll and pitch that can cause severe endangerment to passenger safety. The submarine model was built on a scale of 1:9. The model had six thrusters to conduct the tested manoeuvres, i.e., two main thrusters at the stern, two side thrusters, and two vertical thrusters. The thrusters were computer-controlled, so each thruster had a speed controller and could run forwards and backwards. Six different steering tests and four rising tests were conducted, with at least two runs per test. During the tests, the roll and pitch were measured. Lifting the submarine by a crane was also a part of the experimental campaign. In general, the steering capabilities of the submarine were satisfactory and rolling instabilities were absent. Just a few deficiencies in the steering capabilities were detected. The rising tests were performed without any major motion instabilities, but in one case, the final position of the model at the surface was unstable.

Underactuated hovering control of the minitype autonomous underwater helicopter

This work presents the development of the MAUH, a new type of minitype autonomous underwater helicopter capable of autonomous hovering using only four vertical thrusters. A nonlinear dynamic model of the MAUH was derived based on this underactuated hovering mode. The outer loop controller adopts integral sliding mode control (ISMC) to compute the intermediate command signal needed for the inner loop controller, while the inner loop controller, based on non-singular terminal sliding mode control (NTSMC), is utilized to track orientation error. Finally, simulations and experimental results demonstrate the effectiveness of the proposed underactuated hovering mode and control methods.

UUV Platform Optimal Design for Overcoming Strong Current

This paper proposes an optimal design method for an unmanned underwater vehicle (UUV) platform to overcome strong current. First, to minimize the hydrodynamic drag components in water, the vehicle is designed to have a streamlined disc shape, which help maintaining horizontal motion (zero roll and pitch angles posture) while overcoming external current. To this end, four vertical thrusters are symmetrically mounted outside of the platform to stabilize the vehicle’s horizontal motion. In the horizontal plane, four horizontal thrusters are symmetrically mounted outside of the disc, and each of them has the same forward and reverse thrust performances. With these four thrusters, a specific thrust vector control (TVC) method is proposed, and for external current in any direction, four horizontal thrusters are controlled to generate a vectored thrust force to encounter the current while minimizing the vehicle’s rotation and maintaining its heading. However, for the numerical simulations, the vehicle’s hydrodynamic coefficients related to the horizontal plane are derived based on both theoretical and empirically derived formulas. In addition to the simulation, experimental studies in both the water tank and circulating water channel are performed to verify the vehicle’s various final performances, including its ability to overcome strong current.

Analysis of landing strategies and influencing factors of an autonomous underwater vehicle

The Autonomous Underwater Vehicle (AUV) studied in this paper can land and rest on the seafloor using a mooring system. In order to analyze its landing strategies and influencing factors, kinematics and dynamics models of three-dimensional motion of the AUV are established. Forces’ mathematic models of variable buoyancy system and vertical thrusters are developed and control algorithm of vertical thrusters is designed. Based on the above-mentioned models, landing simulation system is built using S-function of Matlab. Two kinds of landing strategies of the AUV with mooring system are proposed, i.e., diving freely under the effect of negative buoyancy and landing under the control of vertical thrusters. On these bases, the effects of mass and position of the water entering into the AUV on landing parameters are analyzed. Finally, the influences of vertical thrusters on landing process are discussed through comparing the two landing strategies.

Research on Stable Motion Control Method of Underwater Robot Based on Collaborative Filtering Technology

As countries in the world continue to deepen marine research and development and the need for national defense construction, unmanned underwater robots are playing an increasingly important role in scientific experiments, seabed oil and gas exploration and testing, and military affairs. The motion stability of underwater robots is the key to ensure the safe and reliable operation of underwater robots, and it is the main content of stability control research to make underwater robots return to the initial state of motion after being disturbed. Therefore, it becomes very important to study stability control methods. It’s necessary. This thesis first analyzes the motion characteristics of collaborative filtering technology in water, and establishes a dynamic model of an underwater robot system composed of main thrusters, double vertical thrusters and double-sided thrusters, and performs basic fluid flow for underwater robots.

Approach to Reconfiguration of a Motion Control System for an Autonomous Underwater Vehicle

Reconfiguration of a motion control system (MCS) for an autonomous underwater vehicle (AUV) in case of failure of some of the controls or actuators that provide the vehicle propulsion and maneuvering is discussed. The features of actuators operating on different physical principles are analyzed. A nonlinear mathematical model of the vehicle motion is formed taking into account the features of the seawater medium due to higher viscosity. Nonlinearity does not allow traditional approaches to reconfiguration of aircraft motion control system to be used for the purposes described in this paper. The approach proposed for reconfiguration of the AUV MCS consists in the preliminary analysis of the conditions for using different kinds of actuators depending on the vehicle speed and maneuver. The choice of alternative efficient actuators is dictated by the need to compensate for the forces and moments generated by the failed equipment or the actuator to the maximum extent possible. The results of the AUV MCS reconfiguration are obtained for a failure of a bow rudders gear during the diving maneuver on the acceleration section of the path. Vertical thrusters are taken as backups capable of compensating for the forces and moments of the jammed bow rudders gear. The comparative quantitative estimates of the AUV MCS reconfiguration were obtained by mathematical simulation of the AUV diving maneuver. Further research is needed to extend the proposed approach to other AUV systems.

UUV Simulation Modeling and its Control Method: Simulation and Experimental Studies

This paper presents the development of an unmanned underwater vehicle (UUV) platform, especially the derivation of the vehicle’s simulation model and its control method to overcome strong sea current. The platform is designed to have a flattened ellipsoidal exterior so as to minimize the hydrodynamic damping on the horizontal plane. Four horizontal thrusters with the identical specifications are symmetrically mounted on the horizontal plane, and each of them has the same thrust dynamics in both forward and reverse directions. In addition, there are three vertical thrusters used to handle the vehicle’s roll, pitch and heave motions. Control strategy proposed in this paper to overcome strong current is that: maximizing the vectored horizontal thrust force against the sea current without or with the least of the vehicle’s rotation on the horizontal plane. For the vehicle model, due to it being symmetric in all of three axes, the vehicle dynamics can be simplified and all of hydrodynamic coefficients are calculated through both of theoretical and empirically-derived formulas. Numerical simulations and experimental studies in both of the water tank and the circulating water channel are carried out to demonstrate the vehicle’s capability of overcoming strong current.

Project of Fault Tolerant Control using a Takagi-Sugeno Fuzzy logic applied in autonomous underwater vehicles.

The main problem suffered by Autonomous Underwater Vehicles (AUV) used for research and inspection of marine environments is the fault of thrusters during the trajectory, which can compromise the mission. So, in this paper was proposed a Fault Tolerant Control (FTC) using the Levi-Civita connection and a Takagi-Sugeno Fuzzy logic. First, was described the six degreeof-freedom (DOF) nonlinear equations of dynamics and kinematics of the AUV which has four horizontal thrusters and two vertical thrusters, and then we propose a Fault Tolerant Control of the AUV using a Takagi-Sugeno Fuzzy Logic. Using the Fuzzy logic, it was possible to distribute the forces and moments of the faulty thruster in the healthy ones using the same plane of action. The control performance was validated via numerical simulations of the AUV occurring fault of two horizontal thrusters in specific time during the simulation. Even with disturbance caused by variable current and fault of two AUV's thrusters, with this method it was capable of keeping good track of the AUV, enhancing the robustness, assuring asymptotic stability, and the success of the mission.

Experimental test of the acoustic-based navigation and system identification of an unmanned underwater survey vehicle (SAGA)

In this study, a nonlinear mathematical model for an unmanned underwater survey vehicle (SAGA) is obtained. The structure of the mathematical model of the vehicle comes from a Newton–Euler formulation. The three-dimensional motion is realized by a suitable combination of right, left and vertical thrusters. The navigation problem is solved by a combination of the inertial navigation system and acoustic-based measurements, which are integrated to obtain more accurate vehicle navigation data. In addition, a magnetic compass and a depth sensor are used to support vehicle attitude and depth information. A pool experimental set-up is designed for the navigation system. The performance of the resultant navigation system can be analysed by creating suitable system state, measurement and noise models. The vehicle navigational data are improved with a Kalman filter. The mathematical model of the vehicle includes some unknown parameters, such as added mass and damping coefficients. It is not possible to determine all the parameter values as their effect on the state of the system is usually negligible. However, most of the ‘important’ parameters are obtained from a system identification study of the vehicle by means of the estimated navigational data for coupled motion. The entire study is performed in a Matlab/Simulink environment.

Fault-Tolerant Control for ROVs Using Control Reallocation and Power Isolation

This paper describes a novel thruster fault-tolerant control system (FTC) for open-frame remotely operated vehicles (ROVs). The proposed FTC consists of two subsystems: a model-free thruster fault detection and isolation subsystem (FDI) and a fault accommodation subsystem (FA). The FDI subsystem employs fault detection units (FDUs), associated with each thruster, to monitor their state. The robust, reliable and adaptive FDUs use a model-free pattern recognition neural network (PRNN) to detect internal and external faulty states of the thrusters in real time. The FA subsystem combines information provided by the FDI subsystem with predefined, user-configurable actions to accommodate partial and total faults and to perform an appropriate control reallocation. Software-level actions include penalisation of faulty thrusters in solution of control allocation problem and reallocation of control energy among the operable thrusters. Hardware-level actions include power isolation of faulty thrusters (total faults only) such that the entire ROV power system is not compromised. The proposed FTC system is implemented as a LabVIEW virtual instrument (VI) and evaluated in virtual (simulated) and real-world environments. The proposed FTC module can be used for open frame ROVs with up to 12 thrusters: eight horizontal thrusters configured in two horizontal layers of four thrusters each, and four vertical thrusters configured in one vertical layer. Results from both environments show that the ROV control system, enhanced with the FDI and FA subsystems, is capable of maintaining full 6 DOF control of the ROV in the presence of up to 6 simultaneous total faults in the thrusters. With the FDI and FA subsystems in place the control energy distribution of the healthy thrusters is optimised so that the ROV can still operate in difficult conditions under fault scenarios.

Implementation of Heading Angle and Depth Keeping Control of ROV with Multiple Thrusters by Thrust Allocation

This study deals with the heading angle and depth keeping control technique for an ROV with multiple horizontal and vertical thrusters by thrust allocation. The light work class ROV URI-L, which is under development at KRISO, is a redundant actuating system with multiple thrusters that are larger than the ROV's degree of freedom. In the redundant actuating system, there are several solutions for a specific ROV motion to be performed. Therefore, a thrust allocation algorithm that considers the entire propulsion system should be regarded as important. First, this paper describes the propulsion system of the ROV and introduces the thrust allocation method of each motion controller. In addition, the performance of the controller is examined using a heading angle and depth keeping control test in a stationary state.

A Design of Intelligent Routing Inspection Underwater Robot Facing Marine Oil and Gas Pipelines

Submarine pipelines always work in the condition of complex marine environments. They are easily to be damaged, fractured and broken during a long time. We designed and intelligent equipment, which is a Remote operated vehicle(ROV). It is equipped with special underwater bow propellers and vertical thrusters. This robot is combined with optical, acoustic, electric and magnetic sensors, and also equipped with multi-angle automatic rotary High density(HD) camera, so as to ensure the reliable real-time data acquisition. Underwater communication is accomplished by long distance cable cord to achieve local Local area networks(LAN),and this underwater robot completes the tasks of data interaction, real-time data transmission through the Personal computer(PC) monitoring collection under the water. Images can be sent back to the remote client storage for graphical display. It is supposed to make real-time detection of the damages and leakages outside the pipelines, and help to take effective measures to prolong the service life of pipeline, reduce the production cost of oil and gas.

Development of UUV Platform and its Control Method to Overcome Strong Currents: Simulation and Experimental Studies

This paper presents the development of a sort of UUV platform and its motion control method to overcome strong sea current. To minimize the hydrodynamic damping, the vehicle has a flattened ellipsoidal exterior. And four horizontal thrusters, each of them has the same thrust dynamics in both forward and reverse directions, are mounted symmetrically so as to distribute the vectored thrust forces almost uniformly in all of horizontal directions. Three vertical thrusters are also mounted to handle the vehicle’s roll, pitch and heave motions. Control laws for these three vertical thrusters are designed separately from the ones applied to the four horizontal thrusters. Numerical simulations, where hydrodynamic coefficients are calculated through both of theoretical and empirically-derived formulas, and experiments in the circulating water channel are carried out to demonstrate the vehicle’s capability of overcoming strong currents.

Hybrid actuation with complementary allocation for depth control of a Lagrangian sea‐floor imaging platform

AbstractA hybrid depth control approach, which utilizes both active buoyancy control and a bi‐directional vertical thruster, is presented for the Shallow Water Lagrangian Imaging Float. The approach is shown to reduce propulsion power and increase tracking accuracy compared to a single actuator system. Results are presented from field trials at Cordell Bank Marine Sanctuary and Scott Reef Nature Reserve at depths up to 60 m. Using heuristically tuned controllers, the hybrid actuation approach reduces average propulsion power by 65% with respect to a thruster‐only system, and by 73% with respect to a piston‐only system. A further 58% reduction in power consumption, and a 26% reduction in mean tracking error, is realized by combining state feedback control with a pair of complementary filters. The complementary filters are used to allocate vertical force command between the two actuation modes. Simulations are used to demonstrate that the power savings compared to a thruster‐only system result from elimination of steady state trim errors that are otherwise inevitable in field deployments. The control architecture described allows the user to directly tune (a) the time constant of the desired first‐order system dynamics and (b) the frequency cutoff between control using the “slow” active buoyancy system and control using the “fast” bi‐directional thruster. The results indicate that hybrid actuation and complementary filtering for control allocation are enabling technologies for energy‐constrained deep water platforms.

PID 제어기를 이용한 호버링 AUV의 구현과 자세 제어

An attitude controller for a 6-DOF hovering autonomous underwater vehicle (HAUV) is implemented. We add a vertical thruster, an underwater camera, a wireless communication device, and a DVL to the HAUV that was developed a year ago. The HAUV is composed of 5 thrusters, 2 servo-motors, and 4 apparatus parts. Two rotating thrusters control the surge, heave, and roll of the vehicle. The vertical thruster controls the pitch, and two horizontal thrusters control the sway and yaw of the vehicle. The HAUV’s movement in each direction is controlled by 6 PID controllers. Each PID controller controls the propulsive force and angle of a thruster. In a horizontal and vertical movement experiment, we showed the feasibility of the proposed controller by maintaining a given depth and heading angle of the HAUV.

Bank of controllers and virtual thrusters for fault-tolerant control of autonomous underwater vehicles

This paper proposes a fault-tolerant control based on a virtual thruster approach for autonomous underwater vehicles (AUVs) with four horizontal and two vertical thrusters. This methodology defines that, in case of partial fault or complete fault (failure) in horizontal thrusters located in different action planes (which defines the axis or plane where component(s) of forces are actuating in this plane), horizontal propelling forces are calculated through the allocation matrix, used in the pseudo-inverse method, without any change, and a modified weighted matrix. Then, the resultant forces of the remaining working thrusters are calculated by using virtual forces. These forces correspond to the failing thruster forces projection into the forces of the remaining thrusters located in the same action plane. Additionally, we use a bank of controllers to reconfigure the controller against the fault, which improves the performance. Simulation results of a real vehicle show that this is an effective method to cope with the problem of fault tolerant control of AUVs.

Optimal Autopilot and Guidance of the ROV: SAGA

Abstract: In this study, an optimal autopilot algorithm is developed for 3D motion of SAGA which is an unmanned underwater survey vehicle. Firstly, a nonlinear mathematical model for SAGA is obtained. The structure of the mathematical model of the vehicle comes from a Newton-Euler formulation. The resultant nonlinear system is then controlled by PID controllers. These PID controllers are designed for 3D motion which is realized by a suitable combination of right, left and vertical thrusters. The optimal control problem is that the vehicle is supposed to reach the desired position and rotation with desired velocity by consuming minimum energy. This problem is solved with a genetic algorithm. All of this study is performed in a Matlab/Simulink environment.

Modeling and control of an unmanned underwater vehicle using a mass moving system

This paper describes the mathematical modeling and control algorithms of an unmanned underwater vehicle (UUV) named Minekiller. This UUV has two longitudinal thrusters, one vertical thruster, and an internal mass moving system, which can control the pitch rate. The UUV is equipped with a movable mass for pitch control. It is different from other common UUVs, in that it can maintain a static pitch angle. The UUV's 6-DOF (Degrees of Freedom) dynamics model is derived from the hydrodynamic forces and moments acting on it. We applied these hydrodynamic coefficients to dynamic modeling for numerical simulations by MATLAB/SIMULINK©. To compare the performance in various cases, we used a PID controller for depth and heading control. Also, the navigation controller can analyze the way-point tracking performance. These simulation results show the performance of the control algorithms and maneuvering performance of the underwater vehicle.

회전팔 추진기를 가진 시험용 HAUV의 설계 및 구현

In this paper, we propose the hardware and software of a test-bed of a hovering AUV (autonomous underwater vehicle). Test-bed to develop as the underwater robot for the hovering -type is planning to apply for marine resource development and exploration for deep sea. The RTU that controls a azimuth thruster and a vertical thruster of test-bed is a intergrated-type thruster. The main control unit that collects sensor's data and performs high-speed processing and controls a movement of test-bed is a underwater hybrid navigation system. Also it transfers position, posture, state information of test-bed to the host PC of user using a wireless communication. The host PC checks a test-bed in real time by using a realtime monitoring system that is implemented by LabVIEW.

1P1-G05 受動型スラスタ姿勢維持機構を用いた水中ロボットの海中基礎実験(水中ロボット・メカトロニクス(2))

Authors have been developing an underwater robot that able to execute the object lifting operation. The robot has two vertical thruster that used for vertical movement control. At the object lifting operation, the thrust of these thrusters is used for lifting. We previously proposed the new mechanism "Passivity Posture Maintenance Mechanism for a Thruster", in order to use the thrust effectively and lift up an object easily. We also have already confirmed the effectiveness of this mechanism. Therefore, this paper presents to confirm about object lifting operation by the basic experiments in the sea.