José Melo

Cyclic Behavior of Substandard Reinforced Concrete Beam-Column Joints with Plain Bars

ACI Structural Journal, V. 110, No. 1, January-February 2013. MS No. S-2011-088.R1 received April 13, 2011, and reviewed under Institute publication policies. Copyright

Guidance and control of an ASV in AUV tracking operations

The following addresses the control of an autonomous surface vehicle (ASV) to follow the trajectory made by an autonomous underwater vehicle (AUV) when the last is performing any given pre-programmed mission. In fact, it has been proved to be of great interest to have an ASV that could follow on the surface and even catch up the trajectory performed by the AUV, when executing a given mission. In order to achieve this desired coordinated motion between AUV and ASV, it would make sense just to program each of the vehicles with the same mission. However, due to the nature of vehicles, missions and also due to the localization system used, with this kind of solution some problems would arise, namely related with timings and synchronization, which are indeed difficult to overcome. The solution proposed here tries to estimate the AUV position, by tapping the signals exchanged between the former and each of the beacons of the acoustic localization network, and control and actuate the ASV in accordance.

Characterization of measurement errors in a LBL positioning system

There are several sources of error affecting the accuracy of underwater ranging using acoustic signals. These errors have a direct impact in the performance of Long Baseline (LBL) navigation system. This paper presents the results of experiments designed to characterize the most significant sources of errors in acoustic ranging. For the experiments, we use a set of acoustic devices and compare distances given by GPS differences with and acoustic ranges. We describe the experimental procedure and we process the results to provide a qualitative and quantitative analysis of the errors.

A PHD filter for tracking multiple AUVs

In this paper we address the problem of tracking multiple AUVs using acoustic signals. Using For this challenging scenario, we propose to use a Probability Hypothesis Density Filter and present a suitable implementation of the Sequential Monte Carlo PHD filter. It will be demonstrated that a particle filter implementation of the aforementioned filter can be used to successfully track multiple AUVs, changing in number over time, using range measurements from the vehicles to a set of acoustic beacons. Simulation results will be presented that allow to evaluate the performance of the filter.

Towards LBL positioning systems for multiple vehicles

In this article we discuss the use of LBL acoustic networks for operations with multiple AUVs. Differently from standard LBL configurations, we propose to use the One-Way-Travel-Time of acoustic signals to compute the ranges between all the devices. Moreover, we derive the suitable algorithms for both the navigation of multiple vehicles, but also their external tracking. Experimental results are provided that support the evidence that our approach is successful in operations for multiple vehicles.

Tracking multiple Autonomous Underwater Vehicles

In this paper we present a novel method for the acoustic tracking of multiple Autonomous Underwater Vehicles. While the problem of tracking a single moving vehicle has been addressed in the literature, tracking multiple vehicles is a problem that has been overlooked, mostly due to the inherent difficulties on data association with traditional acoustic localization networks. The proposed approach is based on a Probability Hypothesis Density Filter, thus overcoming the data association problem. Our tracker is able not only to successfully estimate the positions of the vehicles, but also their velocities. Moreover, the tracker estimates are labelled, thus providing a way to establish track continuity of the targets. Using real word data, our method is experimentally validated and the performance of the tracker is evaluated.

Estimation of currents with acoustic navigation beacons

In this article we introduce a method to estimate the water current in AUV operation scenarios. The method is based on reciprocal sound transmission between pairs of acoustic navigation beacons, with a minimum of three beacons being required to obtain an estimate of both current velocity and direction. We analyse the sensitivity of the current estimation with respect to the geometry of the beacon location. We demonstrate the applicability of the method with a case study.

The architecture of the CMS Level-1 Trigger Control and Monitoring System using UML

The architecture of the Compact Muon Solenoid (CMS) Level-1 Trigger Control and Monitoring software system is presented. This system has been installed and commissioned on the trigger online computers and is currently used for data taking. It has been designed to handle the trigger configuration and monitoring during data taking as well as all communications with the main run control of CMS. Furthermore its design has foreseen the provision of the software infrastructure for detailed testing of the trigger system during beam down time. This is a medium-size distributed system that runs over 40 PCs and 200 processes that control about 4000 electronic boards. The architecture of this system is described using the industry-standard Universal Modeling Language (UML). This way the relationships between the different subcomponents of the system become clear and all software upgrades and modifications are simplified. The described architecture has allowed for frequent upgrades that were necessary during the commissioning phase of CMS when the trigger system evolved constantly. As a secondary objective, the paper provides a UML usage example and tries to encourage the standardization of the software documentation of large projects across the LHC and High Energy Physics community.