There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Since its beginning, around the 50s decade, until present days, the area of unmanned underwater vehicles (UUV) has considerably grown through time; those have been used for many tasks and applications, from bomb searching and recovery to sea exploration. Initially, these robots were used mainly for military and scientific purposes. However, nowadays, they are very much extended into civils, and it is not hard to find them being used for recreation. In this context, the present research is an effort to make a walkthrough of evolution in this area, showing a diversity of structure designs, used materials, sensor and instrumentation technologies, kinds and the number of actuators employed, navigation control techniques, and what is new in development trends. The paper gives a clear starting point for those who are initializing into this research area; also, it brings some helpful knowledge for those who already have experience.

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Review on Unmanned Underwater Robotics, Structure Designs, Materials, Sensors, Actuators, and Navigation Control

Design of robust control based on linear matrix inequality and a novel hybrid PSO search technique for autonomous underwater vehicle

A predictive guidance obstacle avoidance algorithm (PGOA) in unknown environments is proposed for autonomous underwater vehicle (AUV) that must adapt to multiple complex obstacle environments. Using the environmental information collected by the Forward-looking Sonar (FLS), the obstacle boundary is simplified by the convex algorithm and Bessel interpolation. Combining the predictive control secondary optimization function and the obstacle avoidance weight function, the predicting obstacle avoidance trajectory parameters are obtained. According to different types of obstacle environments, the corresponding obstacle avoidance rules are formulated. Lastly, combining with the obstacle avoidance parameters and rules, the AUV’s predicting obstacle avoidance trajectory point is obtained. Then AUV can successfully achieve obstacle avoidance using the guidance algorithm. The simulation results show that the PGOA algorithm can better predict the trajectory point of the obstacle avoidance path of AUV, and the secondary optimization function can successfully achieve collision avoidance for different complex obstacle environments. Lastly, comparing the execution efficiency and cost of different algorithms, which deal with various complex obstacle environments, simulation experiment results indicate the high efficiency and great adaptability of the proposed algorithm.

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A Predictive Guidance Obstacle Avoidance Algorithm for AUV in Unknown Environments.

ZFAUV is a novel portable modular AUV. There are four fixed thrusters at tail, and two tunnel thrusters are set at front. The maneuverability of ZFAUV is relatively high. It can turn around in situ, move lateral or move up/down vertical. The yaw and pitch can be controlled by tunnel thrusters or differential control of tail thrusters, but differential control will reduce the forward force. Different from propeller-rudder AUVs, the turning radius is related to speed forward: the smaller the speed forward, the smaller the turning radius. The minimum turning radius tends to be zero. The mathematical model is built first; then CFD is used to predict the thrust and torque of tail thrusters and tunnel thrusters. Through numerical simulation, zigzag maneuver analysis in horizontal plane, and trapezoidal steering maneuver analysis in vertical plane, the maneuverability of ZFAUV is obtained. The maneuverability of ZFAUV becomes worse with the increase of speed. The maneuverability of differential control is better than that of tunnel control. In the case of specific thrust distribution of tail thrusters and tunnel thrusters, ZFAUV can turn around in situ (the maximum angular velocity is about 24.1°/s), move lateral or move up/down vertical (the maximum velocity is about 0.4m/s). Finally, an example, PID parameters tuning, is given to illustrate the application of maneuverability analysis. The dynamic performance of ZFAUV can be quickly and accurately analyzed by mathematical method, which has important guiding significance for the choice of control strategy and experiments and also has reference value for the later development of AUVs.

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Maneuverability Analysis of a Novel Portable Modular AUV

Remotely operated vehicle (ROV) is an unmanned underwater vehicle (UUV) used for conducting underwater task to replace a human diver in the risky job. X4-ROV is a micro observation class ROV to be used mainly for visual observation of underwater structure or environment by utilizing a high definition web camera. The designed vehicle structure was aims towards portability and maneuverability in attitude motions of roll, pitch, and yaw, and the translational motion forward/reverse/lateral. This work explains the use and modification of an open-source platform (OpenROV) into X4-ROV system.

Design and development of an X4-ROV

An X4-AUV is nonlinear, coupled and unstable system. In this paper, we present the results of two control schemes applied to an X4-AUV. A direct use of Lyapunov control theory and PD controller technique and backstepping technique have been applied to stabilize the system. We performed the simulations to see the comparative performance result of an X4-AUV under two control schemes.

Comparison of an X4-AUV performance using a direct Lyapunov — PD controller and backstepping approach

This paper presents a particle swarming optimization (PSO) approach in optimizing the performance of the back-stepping control strategies application in stabilizing an underactuated X-4 autonomous underwater vehicle (AUV). The PSO was used to optimize the PID back-stepping controller parameter gain. Twelve controller parameter gains were generated using PSO. The simulation results have shown that the PSO has demonstrated a better performance as compared the manual tuning. The proposed control shows improvements in settling time, and it has rapid responses compare than a controller with manual tuning parameters. The effectiveness of the controllers is verified in a computer simulation using MATLAB software.

PSO approach for a PID back-stepping control method in stabilizing an underactuated X4-AUV

The autonomous underwater vehicle (AUV) mostly has fewer control inputs than the degree of freedoms (DOFs) in motion and be classified into underactuated system. It is difficult tasks to stabilize that system because of the highly nonlinear dynamic and model uncertainties. Hence, it usually required nonlinear control method and this paper presents the stabilization of an underactuated X4-AUV using integral backstepping control method. The X4-AUV system is executed by separating system into two parts subsystem which is translational and rotational subsystems. Integral backstepping control is applied for translational and rotational subsystem. The effectiveness of the proposed control technique for an underactuated X4-AUV demonstrates through simulation.

Integral Backstepping Controller for an Underactuated X4-AUV

In this paper, we are interested principally in dynamic modelling of an autonomous underwater vehicle (X4-AUV) while taking into account the high order nonholonomic constraints in order to develop a new control scheme as well as the various physical phenomena, which can influence the dynamic of a swimming structure. We deal with the design of two controllers, based on backstepping and sliding-mode control techniques to stabilize altitude and attitude of an underactuated X4-AUV. The designed controllers are: full backstepping control for attitude and altitude control, and partially slidingmode control for attitude combine with altitude backstepping control. Some numerical simulations are conducted to demonstrate the effectiveness of the proposed controllers.

NurFadzillah Harun

Papers

Design and development of an X4-ROV

Comparison of an X4-AUV performance using a direct Lyapunov — PD controller and backstepping approach

PSO approach for a PID back-stepping control method in stabilizing an underactuated X4-AUV

Integral Backstepping Controller for an Underactuated X4-AUV

Backstepping and Sliding-Mode Methods for Stabilizing an Underactuated X4-AUV