F. Lobo Pereira

Development and implementation of a low-cost LBL navigation system for an AUV

A reliable navigation system is a key factor for the success of an operational mission with an AUV in a real scenario. We address the main issues involved in the implementation of a long baseline (LBL) navigation system for a REMUS AUV. This system replaces both the original hardware and software of the vehicle with a simpler, faster, less expensive and more precise system, based on a Kalman filter. We also discuss the influence of transponder location in the overall performance of the LBL navigation, and present results obtained with this new system in operational missions.

Coordinated Control of Networked Vehicles: An Autonomous Underwater System

The specification and design of coordinated control strategies for networked vehicle systems are discussed. The discussion is illustrated with an example of the coordinated operation of two teams of autonomous underwater vehicles collecting data to find the local minimum of a given oceanographic scalar field.The specification and design of coordinated control strategies for networked vehicle systems are discussed. The discussion is illustrated with an example of the coordinated operation of two teams of autonomous underwater vehicles collecting data to find the local minimum of a given oceanographic scalar field.

ON THE DESIGN OF A CONTROL ARCHITECTURE FOR AN AUTONOMOUS MOBILE ROBOT

In this chapter we present a model of a hierarchic control architecture for Autonomous Mobile Robots (AMR) as well as its use in the design of an autonomous wheeled mobile platform for transportation in an industrial environment. This model results from successive incremental refinements consolidated over the years with the experience accumulated in a number of R&D projects (e.g., [1], [2]) with special emphasis for the NATO funded PO-Robot project [3].

Multiple AUVS for coastal oceanography

This paper presents the recent developments of the project Multiple Autonomous Underwater Vehicles for Coastal Oceanography, of the University of Porto. The project envisages the development of a highly operational and low-cost system for scientific and environmental data collection in the Portuguese coastal waters. The project activities suggested the development of a generalized vehicle (GV) control architecture for multiple vehicles. Reconfigurability, reliability and operational effectiveness, are at the basis of this control architecture, which encompasses human intervention besides the cooperation among AUVs and other system devices. A simulation environment was developed in SHIFT, to support the design and testing of the GV control architecture. SHIFT is a new specification language for describing dynamic networks of hybrid automata, which constitute the most adequate formalism for this problem domain.

A dynamically configurable architecture for the control of autonomous underwater vehicles

This paper presents a control architecture for autonomous underwater vehicles AUVs. The proposed architecture has its foundations on a hierarchic structure organized linguistically where parallel operations take place in real-time. this hierarchic structure is composed of three levels: organization, coordination and functional layer, structured according to the principle of increasing precision with decreasing intelligence. The main contribution is the concept of dynamically configurable architecture where the notion of architecture coordinator plays a crucial role. This system dynamically configures the connections among modules of the functional and maintains the state of this configuration so that the most adequate translation of planned actions into execution commands takes place. These coordination features are also used to incorporate the emergence of reactive behaviours in this hierarchic architecture. >This paper presents a control architecture for autonomous underwater vehicles AUVs. The proposed architecture has its foundations on a hierarchic structure organized linguistically where parallel operations take place in real-time. this hierarchic structure is composed of three levels: organization, coordination and functional layer, structured according to the principle of increasing precision with decreasing intelligence. The main contribution is the concept of dynamically configurable architecture where the notion of architecture coordinator plays a crucial role. This system dynamically configures the connections among modules of the functional and maintains the state of this configuration so that the most adequate translation of planned actions into execution commands takes place. These coordination features are also used to incorporate the emergence of reactive behaviours in this hierarchic architecture.<<ETX>>

On the receding horizon hierarchical optimal control of manufacturing systems

This paper concerns the development of a hierarchical framework for the integrated planning and scheduling of a class of manufacturing systems. In this framework, dynamic optimization plays an important role in order to define control strategies that, by taking into account the dynamic nature of these systems, minimize customized cost functionals subject to state and control constraints. The proposed architecture is composed of a set of hierarchical levels where a two-way information flow, assuming the form of a state feedback control, is obtained through a receding horizon control scheme. The averaging effect of the receding horizon control scheme enables this deterministic approach to handle random and unexpected events at all levels of the hierarchy. At a given level, production targets to the subsystems immediately below are defined by solving appropriate optimal control problems. Efficient iterative algorithms based on optimality conditions are used to yield control strategies in the form of production rates for the various subsystems. At the lower level, this control strategy is further refined in such a way that all sequences of operations are fully specified. The minimum cost sensitivity information provided in the optimal control formulation supports a mechanism, based on the notion of a critical machine, which plays an important role in the exploitation of the available flexibility. Finally, an important point to note is that our approach is particularly suited to further integration of the production system into a larger supply chain management framework, which is well supported by recent developments in hybrid systems theory.

A general control architecture for multiple vehicles

This paper presents a general architecture for the control of multiple vehicles based on the concept of generalized vehicle. This embodies an extension of the dynamically reconfigurable control architecture previously proposed by the authors (1994, 1995). Besides the capabilities of each vehicle inherent to the individual autonomy, the set of vehicles may be seen providing a pool of functionalists whose reconfiguration enables the emergence of a global features overcoming the single vehicle limitations. Unlike some other approaches, cooperation does not take place only at a deliberative level, but it results from a global coordination level implemented via an adequate protocol specified in the the global mission plan. The design of this architecture was driven by requirements extracted from the analysis of operational scenarios involving multiple vehicles.This paper presents a general architecture for the control of multiple vehicles based on the concept of generalized vehicle. This embodies an extension of the dynamically reconfigurable control architecture previously proposed by the authors (1994, 1995). Besides the capabilities of each vehicle inherent to the individual autonomy, the set of vehicles may be seen providing a pool of functionalists whose reconfiguration enables the emergence of a global features overcoming the single vehicle limitations. Unlike some other approaches, cooperation does not take place only at a deliberative level, but it results from a global coordination level implemented via an adequate protocol specified in the the global mission plan. The design of this architecture was driven by requirements extracted from the analysis of operational scenarios involving multiple vehicles.

AUV system requirements for coastal oceanography

Classes of oceanographic missions addressing relevant distinct scientific and applied objectives in the Portuguese coastal waters are examined in the context of an R&D project aiming at providing a methodological framework adapted to the specific requirements of AUV-based systems design. Preliminary results consisting on the mapping of requirements onto a modular system are presented.Classes of oceanographic missions addressing relevant distinct scientific and applied objectives in the Portuguese coastal waters are examined in the context of an R&D project aiming at providing a methodological framework adapted to the specific requirements of AUV-based systems design. Preliminary results consisting on the mapping of requirements onto a modular system are presented.

A dynamically configurable control architecture for autonomous mobile robots

This paper presents a dynamically configurable architecture for the control of autonomous mobile robots based on hierarchic structure whose three levels, organization, coordination and functional layer, are organized linguistically. The main contribution is the concept of dynamic reconfigurability where the notion of architecture coordinator plays a crucial role. The design of the functional layer establishes the primitives for dynamic configuration.This paper presents a dynamically configurable architecture for the control of autonomous mobile robots based on hierarchic structure whose three levels, organization, coordination and functional layer, are organized linguistically. The main contribution is the concept of dynamic reconfigurability where the notion of architecture coordinator plays a crucial role. The design of the functional layer establishes the primitives for dynamic configuration.

On the design of the PO-ROBOT system

This paper describes the main design options of the PO-ROBOT project. The PO-ROBOT project consists in the design and the implementation of the vehicle and mission management systems of a mobile platform for autonomous transportation, surveillance and inspection in structured and semi-structured industrial environments. This project is funded by the NATO programme science for stability and the institute for systems and robotics. The vehicle and mission management systems are based in a hierarchical control structure organized linguistically permitting the parallel execution of tasks in real-time. This architecture is composed by the following three levels structured according to the increasing precision with decreasing intelligence principle: organization, coordination and functional layer.