This paper presents a simple and systematic approach to steer an Underwater vehicle model by considering two different cases: (i) when all actuators are functional, and (ii) when one actuator is not working. In first case, the model of an Underwater vehicle is steered by employing a Lie bracket extension of the original system and the resulting feedback law is as a composition of a standard stabilizing feedback control for the extended system and a periodic continuation of a parameterized solution to an open loop, finite horizon control problem stated in the logarithmic coordinates of flows. In second case (which represents a physical example where second level Lie bracket is necessary for controllability), the original system is decomposed into two subsystems; one subsystem, which is fifth dimensional, steered by a similar approach used in case (i) and the second subsystem, which is one dimensional, steered by using sinusoidal inputs. The mixture of both type of control is utilized to steer the actual system. The synthesis method is general, in that it applies to a large class of drift free, completely controllable systems, for which the associated controllability Lie algebra is locally nilpotent.

With regard to the pronounced pressure pulsation and cyclic thrust oscillation observed in the tail flow field of an Underwater vehicle operating under over-expanded conditions, and drawing inspiration from flow control techniques involving porous media structures like submarine coral reefs and breakwaters, this paper presents an innovative proposition to incorporate a porous media layer on the tail wall of the nozzle in order to regulate the structure of the tail gaseous jets. To optimize the flow control of Underwater vehicles, the utilization of porous media layers with varying degrees of porosity is employed to establish a model for Underwater supersonic gaseous jets. This model scrutinizes the intricate structure of the tail gaseous jets, as well as the consequential wall pressure and thrust engendered by the nozzle. The findings eloquently demonstrate that the porous media model, boasting a porosity of 0.34, exerts a diminished influence on the morphological characteristics of the tail gaseous jets, while concurrently yielding a superior flow control effect on the pulsation of tail wall pressure and attenuating the differential thrust generated by the Underwater vehicle. Consequently, this innovative approach effectively mitigates overall thrust oscillation, thereby enhancing the stability of the Underwater vehicle throughout its submerged operations.

In this study, the roll, yaw and depth fuzzy control of an Autonomous Underwater vehicle (AUV) are addressed. Yaw and roll angles are regulated only using their errors and rates, but due to the complexity of depth dynamic channel, additional pitch rate quantity is used to improve the depth loop performance. The discussed AUV has four aps at the rear of the vehicle as actuators. Two rule bases and membership functions based on Mamdani type and Sugeno type fuzzy rule have been chosen in each loop. By invoking the normalized steepest descent optimization method, the optimum values for the membership function parameters are found. Though the AUV is a highly nonlinear system, the simulation of the designed fuzzy logic control system based on the equations of motion shows desirable behavior of the AUV specially when the parameters of the fuzzy membership functions are optimized.

Improving the subsea endurance and the power system efficiency of unmanned Underwater vehicles (UUVs) has become more important in recent years as their growing demands in different applications. Integrated electric power systems are commonly applied in UUVs with different types of batteries as power sources. Utilizing fuel cells hybridized with batteries is one of the most efficient ways to increase the UUV's range and overall system efficiency. In this paper, a conceptual design is presented for fuel cell/battery hybrid UUV. To elaborate on the design process, the UUV fuel cell stacks, the commercial fuel cell UUVs, the technologies of the fuel and oxidant storage, and the electrical energy storage subsystems are reviewed. Also, analytical investigations have been presented on the degree of hybridization (DOH) between fuel cells and batteries. The fuel cell/battery hybrid system for UUV is designed and the technologies of its main components are proposed as the final step of the conceptual design process.

This paper develops an improved robust multi-surface sliding mode controller for a complicated five degrees of freedom Underwater vehicle-Manipulator System with floating base. The proposed method combines the robust controller with some corrective terms to decrease the tracking error in transient and steady state. This approach improves the performance of the nonlinear dynamic control scheme and makes the states stable even in presence of unknown effects of hydrodynamic disturbances and unmodelled dynamics. In this regard, the dynamic model of an UVMS is extracted using the Newton– Euler formulation which has been validated by using an ADAMS 3-D model. The control algorithm is based on Lyapunov technique and is able to provide the stability of the whole system during tracking of the desired trajectory with an acceptable precision. The controller parameters are also optimized utilizing the concept of Genetic Algorithm with the aim of increasing the speed of system while decreasing the tracking error which leads to bounded control inputs. Finally, the efficacy of the control scheme, is compared with other conventional methods and the simulation results show the short settling time, low and smooth control effort and asymptotic stability of the states as well as the sliding surfaces of the proposed controller.

Since the Unmanned Underwater vehicles (UUVs) don’t receive the Global Navigation Satellite System (GNSS) signals under the water, other aided measurements are needed to provide the required accuracy in tilt estimation including roll and pitch angle estimation. Conventional approaches for pressure-based tilt estimation, only consider the relation between the static pressure and the tilt as the measurement model. However, the performance of this approach depends on the dynamic pressure which is caused by the sea waves. This paper improves the accuracy of pressure-based tilt estimation using the more accurate of the measurement model. Also, the proposed approach considers the coupling between the axes of UUV. Due to the cost of the approach and the hardware limitations of installation pressure sensors, the proposed approach is implemented using two pressure sensors. An Extended Kalman Filter (EKF) is used for simultaneous tilt and gyroscopes measurement errors estimation. A Monte-Carlo simulation is developed to evaluate the performance of the proposed approach in comparison with INS only and the conventional static pressure-based tilt estimation. The simulation results show that tilt estimation performance of conventional approach is better than the INS only performance and the performance of proposed approach is better than the both of them.