Francesco Zanichelli

Rate modulation of soft real-time tasks in autonomous robot control systems

Due to the high number of sensors managed and need to perform complex reasoning activities, real-time control systems of autonomous robots exhibit a high potential for overload, i.e., real-time tasks missing their deadlines. In these systems overload should be regarded as a likely occurrence and hence managed accordingly. In this paper we illustrate a novel scheduling technique for adaptation of soft real-time load to available computational capacity in the context of autonomous robot control architectures. The technique is based on rate modulation of a set of periodic tasks in a range of admissible rates. The technique is shown to be easily computable and several variations in implementation are reviewed within the paper.

DEUS: a discrete event universal simulator

Currently available discrete event simulation tools exhibit important limitations, either being too specific, or providing only a partial API and possibly not enough scalability. In this paper we introduce our novel general purpose simulator, called DEUS, which aims at becoming one of the reference tools in the field of complex system simulation. Its essential Java API provides basic interfaces and classes for modelling nodes, events and processes characterizing the structure and dynamics of any complex system. High usability, configurability and memory efficiency are among the strengths of DEUS, as exemplified in this paper by means of the simulator of Chord peer-to-peer systems we implemented with minor coding effort.

SP2A: a service-oriented framework for P2P-based Grids

Service-Oriented Architectures (SOAs) are rapidly becoming the key approach for achieving new levels of interoperability and scalability in the development of Grid applications. Within SOA solutions, current approaches for advertising service providers and for allowing prospective clients to discover them are mostly based on centralized registries. Envisioning Virtual Organizations in which all participants are both resource providers and consumers, in a peer-to-peer fashion, seems to be an appealing approach.In this paper we propose the Service-oriented Peer-to-Peer Architecture (SP2A), a framework enabling peer-to-peer resource sharing in Grid environments. Resources are not directly exposed but can be accessed through Resource Provision Services, whose semantically enriched interfaces are published in the network. The framework has been implemented as a Java API, which currently supports a number of important technologies such as JXTA (peer-to-peer routing), Web Services (service deployment), and OWL-S (semantic description of services).

Efficient exploration and recognition of convex objects based on haptic perception

The paper describes an efficient technique for recognition of convex objects from tactile sensing. The technique is based on the development of internal and external volumetric approximations of the unknown object, and exploits an effective feature selection strategy along with early pruning of incompatible objects to improve recognition performance. Exploration strategies conceived for a single-finger probing device rely on the developed volumetric approximations to guide sensing along directions where uncertainty about the explored object is larger, and can take into account exploration costs.

A Technique for Adaptive Scheduling of Soft Real-Time Tasks

A number of multimedia and process control applications can take advantage from the ability to adapt soft real-time load to available computational capacity. This capability is required, for example, to react to changed operating conditions as well as to ensure graceful degradation of an application under transient overloads. In this paper, we illustrate a novel adaptive scheduling technique based on rate modulation of a set of periodic tasks in a range of admissible rates. By casting constraints on rate ranges in a linear programming formulation, several adaptation policies can be considered, along with additional constraints reflecting various application requirements. The paper investigates the effectiveness of rate modulation strategies both on simulated task sets and on real experiments.

Simulating mobile and distributed systems with DEUS and ns-3

Mobile and distributed systems are characterized by decentralized goals and control, with high levels of concurrency and asynchronous interaction. Their qualitative and quantitative analysis is usually based on discrete event modeling and simulation. As most simulation tools target a specific class of problems, only a few of them may be considered truly general-purpose, yet they can hardly support the analysis of distributed systems with thousands of nodes, characterized by a high level of churn (node joins and departures) and reconfiguration of connections among nodes. To fill this gap, a few years ago we started developing an open-source, general-purpose and discrete event simulation tool, called DEUS, which is application-level oriented, Java-based, and characterized by ease of use and flexibility. However, it does not provide any package for simulating networking layers and their implementation is not foreseen, since a number of specialized tools are already available. In this paper, we present a general methodology for achieving a more realistic DEUS-based simulation of mobile and distributed systems, by leveraging on ns-3, which is generally known as a highly reliable and complete open-source tool for the discrete event simulation of Internet systems. In particular, we describe our positive experience in using ns-3s LTE-EPC package to support the simulation of a peer-to-peer overlay scheme called Distributed Geographic Table (DGT), which allows mobile nodes to efficiently share information without centralized control.

Vision-based line tracking and navigation in structured environments

This paper describes a vision-based, low-cost line-tracking system suitable for robot or AGV navigation in structured environments. Vehicle navigation takes advantage of the visual information provided by artificial or pre-existing landmarks, specifically lines and signs. This information is efficiently processed using specialized perceptual behaviors, including neural networks and focus of attention techniques, with the help of a multi-threaded real-time control architecture. Attained system performance is compatible with present requirements and practices for typical AGV applications.

Collaborative Mobile Application and Advanced Services for Smart Parking

The main reason of wasting time in search of free parking spaces is the lack of information, in particular for open/roadside parking availability. Various ICT-based solutions have been proposed to solve this issue, but still suffering from limited integration among each other and with external online services, such as touristic information services. In this paper we illustrate a modular, service-oriented smart parking system, which includes web applications for parking operators and end users, as well as mobile applications for end users and parking controllers. The proposed system allows (1) operators to draw parking areas and define their details, (2) end users to be guided to the most suitable parking area, with also the indication of points of interest, and (3) controllers to monitor all vehicles that have been parked in their area. Another important feature is the possibility for end users to share their knowledge about parking occupancy, which is very useful when a parking area is not provided with precise availability counters. The smart parking system has been successfully evaluated in our Campus.

GeoKad: A P2P distributed localization protocol

The widespread use of tracking and localization systems may be hindered by centralized server platforms whose performance can hardly scale up to the needs of very large numbers of concurrent mobile users. In this paper we introduce GeoKad, a peer-to-peer localization protocol based on the new concept of Distributed Geographic Table, that allows to retrieve nodes and resources that are close to any given global position. The preliminary simulation-based evaluation focuses on performance (covered area search, lookup results) and costs in terms of load balancing, protocol overhead and scalability.

Qualitative spatial representations from task-oriented perception and exploratory behaviors

We describe motor and perceptual behaviors that have proven useful for indoor navigation of an autonomous mobile robot. These behaviors take advantage of the large amount of structure that characterizes many indoor, office-like environments. Based on pre-existing structural landmarks, a mobile robot has the ability to explore, map, and navigate one among several office buildings sharing similar structural features, while coping with slow environment variations and local dynamics. The mobile robot develops and maintains an internal spatial representation of the environment in terms of a topological and qualitative map. The types of structural features suitable as navigation landmarks largely depend upon the available sensors. Adequate navigation performance is achieved by subdividing perception and navigation into a number of behaviors layered upon a multi-threaded real-time control architecture.