Mario Alberto Jordan

The present work focuses on the exploration of underwater environments by means of autonomous submarines like AUVs using vision-based navigation. An approach called Corridor SLAM (C-SLAM) was developed for this purpose. It implements a global exploration strategy that consists of first creating a trunk corridor on the seabed and then branching as far as possible in different directions to increase the explored region. The system guarantees the safe return of the vehicle to the starting point by taking into account a metric of the corridor lengths that are related to their energy autonomy. Experimental trials in a basin with underwater scenarios demonstrated the feasibility of the approach.

This work deals with the development of a node-based monocular visual methodology for autonomous vehicle navigation which has the goal of exploring unknown regions of the sea bottom with a posterior safe revisiting of them. The work accentuates characteristics of the seabed like self-similarity and backscattering. In a stepwise fashion, a visual guidance system constructs a shape similar to a narrow corridor by optimally creating a heading function on the basis of keypoints threads, which ensures future revisits. The corridor is composed of nodes and paths in between. Each path is composed of a visual-odometry-based trail which is generated in feature-poor environments, in combination with a feature-based trail which emerges in feature-rich regions. A probabilistic analysis of the uncertainties and their impact in the success rate on loop closings is carried out. We work out two case studies, the first employing an ad-hoc benchmark and the second a series of experiments in the real world. From here qualitative conclusions can be drawn out that enable us to anticipate potential applications of the approach in the field of autonomous navigation underwater.

In this work, a trajectory tracking control design is proposed for the planar vertical takeoff and landing (PVTOL) aircraft using linear algebra theory. The resulting control law is implemented easily since the equation to be solved is not complex. The tracking is achieved providing convergence of the tracking errors to zero, and simulation results show the good performance of the proposed controller.

The contribution of this paper is the study of nonlinear oscillations of remotely operated vehicles (ROVs) subject to strong currents and harmonic waves when the vehicle is servocontrolled around a fixed position. A complete model for quasi-stationary dynamics of a ship-cable-ROV system was developed. A high-performance control system was designed, in which the cable force is calculated on the basis of measured end positions. Our analysis reveals that the ROV behavior can transit from period one to chaos without the thrusts enter saturation zones. This feature appears more marked as long as the cable stiffness increases. In view of recent results, one can broadly say that the cable elasticity acts as a suppressor of the complete subspectrum of subharmonics in the vehicle dynamics, and simultaneously, as an effective attenuator of its superharmonics.

In this paper an approach to improve the overall performance of indirect adaptive control systems tailored for non-linear stable plants is presented. The approach involves a commutation of a linear time-varying robustness filter in the feedback path of the control loop in synchronization with an adaptive controller. The algorithm is framed in the celebrated IMC structure for predictive control systems. It can automatically suit to structural changes in the system as order and dead-time, and can deal with plants with zero dynamics. The convergence and stability of the system is analysed in details. It is shown through numeric simulations and experimentation on a heat exchanger with cooling system, that undesired transients due to abrupt and significative changes in the dynamics can be efficiently damped down by the developed control algorithm, achieving a high-quality performance in steady state.

In this paper, a new fault-tolerant control (FTC) strategy is proposed to compensate for the effects of faults and to improve the overall performance for nonlinear stable plants. The FTC approach involves a commutation of a linear time-varying robust filter in the feedback path of the control loop in synchronization with an adaptive predictive controller. The decision of which mode has to work is based on specific conditions accounted in the control algorithm. In addition, the fault-tolerance ability of the controller has been further improved by a fault-diagnosis system (FDS) designed for detecting two fault types: specific bias at the sensor and time delay at the actuator. The FDS is developed by using wavelet decomposition and identification techniques respectively. An implementation on a continuous stirred tank reactor (CSTR) with jacket is presented as a simulation example for analyzing the effectiveness of the FTC linked with FDS methodology proposed here

In this paper a mechanism for reproducing the phenomenon known as "taut-slack" in a cable-body system is presented. The operation of the mechanism consists in forcing an oscillation of a point from which a body immersed in liquid is suspended by means of a cord. For particular values of ad-hoc design parameters of the mechanism, the body can oscillate nonlinearly mainly because the cable transits from a taut to a slack condition cyclically. Both body and suspension point positions are sensed in order to detect the periodicity of the resulting body motion. The modeling of the system dynamics yields a set of two Mathieu differential equations that are combined piecewise according to the cable taut-slack condition. The periodicity detection implemented in this work is based on the analysis of Cauchy series obtained from the Poincare maps. From the experimental results it could be obtained period doubling with the presence of the taut-slack phenomenon. Through comparison with simulated bifurcation diagrams and Poincare maps it could be noticed a good concordance between the signal profiles and also a comparable evidence of the behavior diversity