Jorge Estrela da Silva

Polytechnic Institute of Porto | IPP · Department of Electrical Engineering

This paper addresses the development of an integrated system to support maritime situation awareness based on unmanned aerial vehicles (UAVs), emphasizing the role of the automatic detection subsystem. One of the main topics of research in the SEAGULL project was the automatic detection of sea vessels from sensors onboard the UAV, to help human ope...

We consider the problem of generating optimal planar trajectories for marine vehicles taking into account the effect of time-varying ocean currents. This is motivated by the need for economic trajectory generation in long-duration operations, and it becomes even more important in scenarios where the magnitude of the ocean current speed is comparabl...

Unmanned air systems are becoming ever more important in modern societies but raise a number of unresolved problems. There are legal issues with the operation of these vehicles in nonsegregated airspace, and a pressing requirement to solve these issues is the development and testing of reliable and safe mechanisms to avoid collision in flight. In t...

A dynamic programming based procedure for the synthesis of near-optimal controllers for sampled data systems is proposed. The main features of the proposed procedure are the approximation of nonlinear systems by piecewise affine systems, the synthesis of control strategy in the form of a piecewise constant map, and handling of state constraints and...

Problems of motion coordination for autonomous vehicles are discussed in the framework of dynamic programming (DP). The challenges of the practical deployment of DP-based controllers are illustrated with a formation control problem.

The SEAGULL project aims at the development of intelligent systems to support maritime situation awareness based on unmanned aerial vehicles. It proposes to create an intelligent maritime surveillance system by equipping unmanned aerial vehicles (UAVs) with different types of optical sensors. Optical sensors such as cameras (visible, infrared, mult...

New problems of optimal path coordination for multiple vehicles are introduced, formulated and solved in the framework of dynamic optimization. The novelty of these problems arises in several ways. The cost function and the dynamics include non-trivial dependencies, modeled through existential quantification over groups of vehicles -this leads to n...

This paper extends the algorithm proposed in (our CDC2013 paper) . In that paper, the numerical approximation of the solution of dynamic programming problems is used as a candidate Lyapunov function, in order to prove convergence of the closed loop system to a given target. That is done in the framework of sampled data systems. The described algori...

The design of feedback controllers based on the numerical solution of the dynamic programming equations leads to quasi-optimal system behaviour. The gap to the optimal behaviour depends on the accuracy of the numerical solution. As the numerical solution gets coarser, stability of the closed loop system also becomes a concern. This paper proposes a...

This paper is concerned with the synthesis of optimal feedback controllers for nonlinear continuous-time systems with switching costs. The design approach is based on dynamic programming techniques. Robustness with respect to model uncertainty and bounded disturbances is encompassed by considering an adversarial input. The problem is solved in the...

This paper reports experimental results obtained with a value function based path following controller for Autonomous Underwater Vehicles (AUV). The value functions are computed using numerical methods for the dynamic programming (DP) equations. We consider the case of planar operation of an AUV with actuation surfaces (fins). A reduced nonlinear m...

This work analyses the problem of data collection in sensor networks with disconnected clusters of sensors leveraging autonomous vehicles and intra-cluster sensor cooperation. The later allows for the vehicle's trajectory to be planned in terms of visiting each cluster instead of visiting individual sensors with important repercussions on the compu...

We investigate the performance of feedback control laws obtained via dynamic programming techniques for deterministic continuous-time systems with contin-uous state-space R n . The control law relies on a value function which is calculated numerically with a semi-Lagrangian (SL) scheme. Both the numerical solver and the control law require interpol...

We consider a dynamic programming approach for solving optimal control problems of sampled continuous-time systems. Robustness to bounded noise and model uncertainties is provided by formulating the problem in the framework of differential games. We use a semi-Lagrangian scheme for the computation of the value function and the state feedback contro...

The problem of 2-dimensional vehicle path following under adversarial behavior is considered. The objective is to keep the cross-track error to the reference path inside a given tolerance interval. The adversarial behavior models system uncertainty and unknown or poorly estimated bounded disturbances. The first step to that objective is the computa...

The problem of path following for autonomous vehicles underadversarial behaviour is considered. The objective is to keep the cross-track error to the reference path inside a given tolerance interval. The adversarial behaviour models system uncertainty and unknown or poorly estimated bounded disturbances to ensure that the concept of weakly invarian...

The problem of path following for autonomous vehicles under adversarial behavior is considered. The objective is to keep the cross-track error to the reference path inside a given tolerance interval. The adversarial behavior models system uncertainty and unknown or poorly estimated bounded disturbances. The first step to that objective is the compu...

A collaborative control scenario is modeled in the framework of hybrid systems. The problem of reaching a given point under adversarial behaviour on a given time frame is modeled as a differential game for hybrid systems. System behaviour is discussed with the help of Krasovskii’s u-stable bridge.

A viability algorithm is developed to compute the constrained minimum time function for general dynamical systems. The algorithm is instantiated for a specific dynamics (Dubin's vehicle forced by a flow field) in order to numerically solve the minimum time problem. With the specific dynamics considered, the framework of hybrid systems enables us to...

Optimal path coordination problems for multi-vehicle systems are formulated in the framework of hybrid systems and solved using dynamic programming techniques. In these problems, the path cost for one vehicle is a discontinuous function of the distances to other vehicles. This leads to a non-standard optimal control problem.

A viability algorithm is developed to compute the constrained minimum time function for general dynamical systems. The algorithm is instantiated for a specific dynamics(Dubin’s vehicle forced by a flow field) in order to numerically solve the minimum time problem. With the specific dynamics considered, the framework of hybrid systems enables us to solv...

This paper presents an overview of the state-of-the-art for underwater vehicle autopilots. We start by reviewing reference frames, vehicle states, typical control surfaces, equations of motion, the different coefficients and how they are obtained, and disturbance models as well. We then consider different possible configurations for the autopilot,...

We present an overview of the state-of-the-art for underwater vehicle autopilots. We start by reviewing reference frames, vehicle states, typical control surfaces, equations of motion, and disturbance models. We then consider different possible configurations for the autopilot, including decoupled lateral and longitudinal loops, maneuver and waypoi...

A layered control architecture for executing multi-vehicle team co-ordination algorithms is presented along with the specifications for team behaviour. The control architecture consists of three layers: team control, vehicle supervision and maneuver control. It is shown that the controller implementation is consistent with the system specification...

On this paper we derive the numerical coefficients for a nonlinear model of new AUV model designed at Oporto University. This is made using theoretical and empirical meth-ods as also by adapting the known results from similar AUVs. We use the derived model on MVS, a simulator which can be embedded in the loop of the control software, by replacing t...

This paper presents a strategy for the coordination of teams of nonholonomic vehicles on phased operations. On each phase, the vehicles should arrive simultaneously to their goal locations. The vehicles establish communication only during brief instants, coinciding with the arrival at the desired locations. The arrival time is minimized by the cont...

A control architecture for executing multi-vehicle search algorithms is pre-sented. The proposed hierarchical structure consists of three control layers, which consist of maneuver controllers, vehicle supervisors, and team controllers. The system model is described as a dynamic network of hybrid automata in the programming language Shift and allows...

A multi-vehicle search strategy based on the simplex algorithm is proposed. The strategy is mapped into a hierarchical scheme with three layers. The upper layer is described by a discrete-event system. The output of this layer is a set of way-points for the vehicles and it is used by the middle layer in order to coordinate the motion of the vehicle...

This paper describes a framework which was used in the implementation of software for the control of autonomous vehicles and whose principles could make it suitable for other kind of applications. The framework acts as a layer over the operating system, hiding its relative complexity from the developer. The framework is based on a location transpar...

A multi-vehicle search strategy for finding an optimum of a scalar based on the simplex search algorithm is proposed. The strategy is described as hierarchical scheme with two layers. A team controller (upper layer) is described by a discrete-event system. The output of this layer is a set of waypoints for the vehicles and it is used by the vehicle...

Electrical impedance spectroscopy is a minimally invasive technique that has clear advantages for living tissue characterisation owing to its low cost and ease of use. The present paper describes how this technique can be applied to breast tissue classification and breast cancer detection. Statistical analysis is used to derive a set of rules based...

The authors address the current developments of the “PISCIS” project. They focus on the experimental results from recent operational missions with an AUV in a estuarine environment. Besides describing mission planning and logistic details, they also present tools for oceanographic data processing and visualization. This is demonstrated with some ex...

This paper describes the mission control software used in the LSTS/FEUP underwater vehicles. This software follows the guidelines of the generalized vehicle architecture, adapts the original idea to encompass the current application requirements and constitutes a first implementation. The work is focused on the design and implementation of an appli...

This paper describes the acoustic based navigation system used by the IES ROV. The paper presents the integration of a LBL system and an acoustic ranging sensor. We report the results obtained at ROV station keeping using this sensors. The impact of the integration of the Sontek Argonaut DVL in the position estimation is also evaluated.

The problems of modelling and control design for systems with evolving structure are discussed. This is done in the context of cooperative multi-vehicle missions where synergistic interactions are mapped onto system capabilities. A pattern of interactions is termed a configuration. Configurations change with time. The problem of configuration contr...

Abstract— The goals, technical challenges, and activities of the project PISCIS ‐ Multiple Autonomous Underwater Vehicles for Coastal and,Environmental Field Studies ‐ are reviewed in the context of the activities of the Underwater Systems and Technologies Laboratory from Porto University. I. I NTRODUCTION The future of humanity is deeply related t...

The practical coordination and control of Un- manned Air Vehicles (UAV) is addressed in a distributed control framework. The key specification concepts are ele- mental maneuvers and team maneuvers. Elemental maneuvers abstract the key modes of operation of each UAV. Team maneuvers prescribe team operations in terms of elemental maneuvers and coordi...

Dissertação apresentada para obtenção do grau de Mestre em Engenharia Electrotécnica e de Computadores (Área de especialização de Informática Industrial), na Faculdade de Engenharia da Universidade do Porto, sob a orientação do Professor Fernando Manuel Ferreira Lobo Pereira