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Publications

Publications by CRAS

1997

A vector architecture for higher-order moments estimation

Authors
Alves, JC; Puga, A; CorteReal, L; Matos, JS;

Publication
1997 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, VOLS I - V: VOL I: PLENARY, EXPERT SUMMARIES, SPECIAL, AUDIO, UNDERWATER ACOUSTICS, VLSI; VOL II: SPEECH PROCESSING; VOL III: SPEECH PROCESSING, DIGITAL SIGNAL PROCESSING; VOL IV: MULTIDIMENSIONAL SIGNAL PROCESSING, NEURAL NETWORKS - VOL V: STATISTICAL SIGNAL AND ARRAY PROCESSING, APPLICATIONS

Abstract
Higher-order statistics extend the analysis methods of non-linear systems and non-gaussian signals based on the autocorrelation and power spectrum. The main drawback of their use in real time applications is the high complexity of their estimation due to the large number of arithmetic operations. This paper presents an experimental vector architecture for the estimation of the higher-order moments. The processor's core is a pipelined multiply-accumulate unit that receives four data vectors and computes in parallel the moment taps up to the fourth-order. The design of custom cache memory organization and address generation circuits has led to more than 11 operations per clock cycle. The architecture was modeled and simulated in Verilog and is presently being implemented in XILINX field-programmable gate arrays (FPGAs) and one custom integrated circuit for the multiply-accumulate unit.

1997

Implementation and evaluation of mixed current / voltage testing using the IEEE P1149.4 infrastructure

Authors
Da Silva, JM; Alves, JC; Matos, JS;

Publication
IEE Colloquium (Digest)

Abstract
This paper presents experiments carried out with a prototype test chip provided by the IEEE P1149.4 Mixed-Signal Testing Working Group, which explore the architecture of the proposed analogue boundary module to implement simultaneous observation of power supply current and output voltage, towards mixed current/voltage testing of analogue and mixed-signal circuits.

1997

ProHos-1 - A vector processor for the efficient estimation of higher-order moments

Authors
Alves, JC; Puga, A; CorteReal, L; Matos, JS;

Publication
VECTOR AND PARALLEL PROCESSING - VECPAR'96

Abstract
Higher-order statistics (HOS) are a powerful analysis tool in digital signal processing. The most difficult task to use it effectively is the estimation of higher-order moments of sampled data, taken from real systems. For applications that require real-time processing, the performance achieved by common microprocessors or digital signal processors is not good enough to carry out the large number of calculations needed for their estimation. This paper presents ProHos-1, an experimental vector processor for the estimation of the higher-order moments up to the fourth-order. The processor's architecture exploits the structure of the algorithm, to process in parallel four vectors of the input data in a pipe-lined fashion, executing the equivalent to 11 operations in each clock cycle. The design of dedicated control circuits led to high clock rate and small hardware complexity, thus suitable for implementation as an ASIC (Application Specific integrated Circuit).

1997

Multiple AUVS for coastal oceanography

Authors
Sousa, J; Cruz, N; Matos, A; Pereira, FL;

Publication
OCEANS '97 MTS/IEEE CONFERENCE PROCEEDINGS, VOLS 1 AND 2

Abstract
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.

1997

A hybrid feedback control system for a nonholonomic car-like vehicle

Authors
Almeida, J; Pereira, FL; Sousa, JB;

Publication
1997 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION - PROCEEDINGS, VOLS 1-4

Abstract
This paper addresses the design of a hybrid feedback control system enabling a car-like, rectangular vehicle to perform a tight L-shaped turn maneuver, This case constitutes an effort towards the definition of a general purpose methodology for hybrid feedback control synthesis. The design effort encompasses the synthesis of a set of modalities and mechanisms to detect relevant events enabling the overall motion coordination so that a global goal is attempted, Simulations of the implemented controller have shown a strong robustness with respect lo modeling uncertainty and execution errors.

1997

On the design of a hybrid feedback control system for a nonholonomic car-like vehicle

Authors
Almeida, J; Pereira, FL; Sousa, JB;

Publication
ECC 1997 - European Control Conference

Abstract
This paper addresses the design of a hybrid feedback control system enabling a car-like, rectangular vehicle to perform a tight L-shaped turn maneuver. This case constitutes an effort towards the definition of a general purpose methodology for hybrid feedback control synthesis. The design effort encompasses the synthesis of a set of modalities and mechanisms to detect relevant events enabling the overall motion coordination so that a global goal is attempted. Simulations of the implemented controller have shown a strong robustness with respect to modeling uncertainty and execution errors.

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