Noury Bouraqadi

Distributed Constraint Reasoning Applied to Multi-robot Exploration

Exploration of an unknown environment is one of the major applications of Multi-Robot Systems. Many works have proposed multi-robot coordination algorithms to accomplish exploration missions based on multi-agent techniques. Some of these works focus on multi-robot exploration under communication constraints. In this paper, we propose an original way to formalize and solve this issue. Our proposal relies on distributed constraint satisfaction problems (disCSP) which are an extension of classical constraint satisfaction problems (CSP). Compared to other works, our proposal is fully distributed and guaranties the exploration of an unknown environment with maintenance of connectivity between all the members of a robots’ team.

CLIC: a component model symbiotic with Smalltalk

Evolving object-oriented code such as replacing a part of a system, is not always as easy as it should be. This is because object-oriented languages do not enforce code modularisation. Component-oriented approches target this issue by expliciting software architecture in terms of components and connections between them. However, there is little language support for component-oriented programming. Existing attempts are not really well integrated with the hosting object-oriented language. In this paper, we present the CLIC component model, its integration and its support in the Smalltalk language.

Vector Maps: A Lightweight and Accurate Map Format for Multi-robot Systems

SLAM algorithms produce accurate maps that allow localization with typically centimetric precision. However, such a map is materialized as a large Occupancy Grid. Beside the high memory footprint, Occupancy Grid Maps lead to high CPU consumption for path planning. The situation is even worse in the context of multi-robot exploration. Indeed, to achieve coordination, robots have to share their local maps and merge ones provided by their teammates. These drawbacks of Occupancy Grid Maps can be mitigated by the use of topological maps. However, topological maps do not allow accurate obstacle delimitations needed for autonomous robots exploration. So, robots still have to handle with Occupancy Grid Maps. We argue that Vector-based Maps which materialize obstacles using collections of vectors is a more interesting alternative. Vector Maps both provide accurate metric information likewise Occupancy Grid Maps, and represent data as a graph that can be processed for path planning and maps merging as efficiently as with topological maps. Conclusions are backed by several metrics computed with several terrains that differ in size, form factor, and obstacle density.

Mocks, Proxies, and Transpilation as Development Strategies for Web Development

With the advent of HTML 5, we can now develop rich web apps that rival classical standalone apps. This richness together with the portability of web technologies, turned HTML 5 into a viable (and in the case of mobile - essential) solution to develop cross-platform apps. This possibility is heavily dependent on Javascript having acceptable performance, good testability, and a modern development environment. Despite its extensive use in creating highly interactive environments, most Javascript development environments currently use a compile/run paradigm. Similarly, testing is frequently tacked on, rather than being an integrated part of the development cycle. We propose PharoJS which leverages the Smalltalk IDE with a seamless transition from native Smalltalk tests, through proxied browser tests, to full browser-resident tests. We support the standard event-driven browser model and transpile Smalltalk code into efficient Javascript for execution in the browser. We further support testing - both manually and automatically - in a range of browsers to provide assured consistency upon deployment. In addition to transpiling the Smalltalk code to Javascript to perform tests in the browser, we can also run non-interactive tests within the Smalltalk environment. The unique feature we provide is the ability to run interactive tests largely within the Smalltalk IDE, so as to fully exploit the debugging and development environment, while the actual interaction occurs on the browser. We exhibit this new mode of development via a simple application.

Implementing modular class-based reuse mechanisms on top of a single inheritance VM

Code reuse is a good strategy to avoid code duplication and speed up software development. Existing object-oriented programming languages propose different ways of combining existing and new code such as e.g., single inheritance, multiple inheritance, Traits or Mixins. All these mechanisms present advantages and disadvantages and there are situations that require the use of one over the other. To avoid the complexity of implementing a virtual machine (VM), many of these mechanisms are often implemented on top of an existing high-performance VM, originally meant to run a single inheritance object-oriented language. These implementations require thus a mapping between the programming model they propose and the execution model provided by the VM. Moreover, reuse mechanisms are not usually composable, nor it is easy to implement new ones for a given language. In this paper, we propose a modular meta-level runtime architecture to implement and combine different code reuse mechanisms. This architecture supports dynamic combination of several mechanisms without affecting runtime performance in a single inheritance object-oriented VM. It includes moreover a reflective Meta-Object Protocol to query and modify classes using the programming logical model instead of the underlying low-level runtime model. Thanks to this architecture, we implemented Stateful Traits, Mixins, CLOS multiple inheritance, CLOS Standard Method Combinations and Beta prefixing in a modular and composable way.

Towards Robots-Assisted Ambient Intelligence

An integrated network of mobile robots, personal smart devices, and smart spaces called “Robots-Assisted Ambient Intelligence” (RAmI) can provide for a more effective user assistance than if the former resources are used individually. Additionally, with the application of distributed network optimization, not only can we improve the assistance of an individual user, but we can also minimize conflict or congestion created when multiple users in large installations use the limited resources of RAmI that are spatially and temporally constrained. The emphasis of RAmI is on the efficiency and effectiveness of multiple and simultaneous user assistance and on the influence of an individual’s actions on the desired system’s performance. In this paper, we model RAmI as a multi-agent system with AmI, user, and robot agents. Moreover, we propose a modular three-layer architecture for each robot agent and discuss its application and communication requirements to facilitate efficient usage of limited RAmI resources. Our approach is showcased by means of a case study where we focus on meal and medicine delivery to patients in large hospitals.

Benchmarking des performances de systèmes multirobots. Application à l’exploration

RÉSUMÉ. Le benchmarking de performance est un thème important dans la robotique. C’est un moyen essentiel de comparer des solutions dans des conditions différentes. Nous nous intéressons à l’analyse comparative des performances des systèmes multirobots dans le cadre de l’exploration et la cartographie d’espaces inconnus. Nous proposons une sélection de métriques pour comparer objectivement les algorithmes de coordination de systèmes multirobots pour l’exploration. Ce travail est une démarche concrète pour résoudre le problème général de l’évaluation quantitative de différents algorithmes de coordination multirobot. Nous identifions des paramètres qui influent sur la performance de flottes robotiques. En faisant varier ces paramètres, nous arrivons à identifier les atouts et les limites d’un algorithme. Nous illustrons ces contributions avec des simulations réalistes d’une stratégie d’exploration basée sur les frontières. Ces simulations ont été mises en œuvre à l’aide de l’intergiciel ROS (Robot Operating System).