Dominic Létourneau

Code reusability tools for programming mobile robots

This paper describes two initiatives aiming at improving code reusability for programming mobile robots: robotflow/flowdesigner, a data-flow programming environment; MARIE (mobile and autonomous robotics integration environment), a programming environment allowing multiple applications, programs and tools, to operate on one or multiple machines/OS and work together on a mobile robot implementation. Robotflow/flowdesigners objective is to provide a modular, graphical programming environment that would help visualize and understand what is really happening in the robots control loops, sensors, actuators, by using graphical probes. MARIE aims at avoiding making an exclusive choice on particular programming tools, making it possible to reuse code and applications.

Robotic Software Integration Using MARIE

This paper presents MARIE, a middleware framework oriented towards developing and integrating new and existing software for robotic systems. By using a generic communication framework, MARIE aims to create a flexible distributed component system that allows robotics developers to share software programs and algorithms, and design prototypes rapidly based on their own integration needs. The use of MARIE is illustrated with the design of a socially interactive autonomous mobile robot platform capable of map building, localization, navigation, tasks scheduling, sound source localization, tracking and separation, speech recognition and generation, visual tracking, message reading and graphical interaction using a touch screen interface.

Multi-Modal Locomotion Robotic Platform Using Leg-Track-Wheel Articulations

Other than from its sensing and processing capabilities, a mobile robotic platform can be limited in its use by its ability to move in the environment. Legs, tracks and wheels are all efficient means of ground locomotion that are most suitable in different situations. Legs allow to climb over obstacles and change the height of the robot, modifying its viewpoint of the world. Tracks are efficient on uneven terrains or on soft surfaces (snow, mud, etc.), while wheels are optimal on flat surfaces. Our objective is to work on a new concept capable of combining different locomotion mechanisms to increase the locomotion capabilities of the robotic platform. The design we came up with, called AZIMUT, is symmetrical and is made of four independent leg-track-wheel articulations. It can move with its articulations up, down or straight, allowing the robot to deal with three-dimensional environments. AZIMUT is also capable of moving sideways without changing its orientation, making it omnidirectional. By putting sensors on these articulations, the robot can also actively perceive its environment by changing the orientation of its articulations. Designing a robot with such capabilities requires addressing difficult design compromises, with measurable impacts seen only after integrating all of the components together. Modularity at the structural, hardware and embedded software levels, all considered concurrently in an iterative design process, reveals to be key in the design of sophisticated mobile robotic platforms.

Autonomous spherical mobile robot for child-development studies

This paper presents the design process of a spherical robot capable of autonomous motion, and demonstrates how it can become a tool in child-development studies. The robot, named Roball, is capable of intentional self-propelled movements and can generate various interplay situations using motion, messages, sounds, illuminated parts and other sensors. Such capabilities allow Roball to interact with young children in simple and interesting ways, and to provide the potential of contributing to the development of their language, affective, motor, intellectual and social skills. Trials done with 12-24-month-old children demonstrate how Roball can be used to study childrens interest in a self-propelled and intentional device. An experimental methodology to conduct such studies is presented: it is based on quantitative and qualitative techniques to evaluate interactions, thus enabling the identification of challenges and opportunities in child-robot interaction studies.

Autonomous initialization of robot formations

Real life deployment of robot formation cannot assume that robots are going to be correctly positioned to move in a particular configuration. To do so, we propose an approach that allows the group to determine autonomously the most appropriate assignment of positions in the formation. Our approach is distributed and uses directional visual perception to localize robots. Inter-robot communication allows them to share information on which robots are nearby, so that each can evaluate it ability to be the conductor of the group and assign formation positions to the other robots by minimizing repositioning. The assignment search is done using a distributed bounded depth-first with pruning search. The robot with the best score is selected as the conductor, and the other robots receive from the conductor their assignment in the formation. Validation of our work is done in simulation and with Pioneer 2 robots.

Coordinated Maneuvering of Automated Vehicles in Platoons

To eventually have automated vehicles operate in platoons, it is necessary to study what information each vehicle must have and to whom it must communicate for safe and efficient maneuvering in all possible conditions. This paper formulates the problem in terms of sensing and communicated information. By emulating platoons using a group of mobile robots, the authors demonstrate the feasibility of maneuvers (such as entering, exiting, and recuperating from an accident) using different distributed coordination strategies. The coordination strategies studied range from no communication to unidirectional or bidirectional exchanges between vehicles and to fully centralized decision by the leading vehicle. One particularity of this paper is that instead of assuming that the platoon leader or all vehicles globally monitor what is going on, only the vehicles involved in a particular maneuver are concerned, distributing decisions locally among the platoon. This paper reports experimental trials using robots having limited and directional perception of other things, using vision and obstacle avoidance sensing. Results confirm the feasibility of the coordination strategies in different conditions and various uses of communicated information to compensate for sensing limitations

Dynamic robot formations using directional visual perception

Recent research projects have demonstrated that it is possible to make robots move in formation. The approaches differ by the various assumptions about what can be perceived and communicated by the robots, the strategies used to make the robots move in formation, the ability to deal with obstacles and to switch formations. After suggesting criteria to characterize problems associated with robot formations, this paper presents a distributed approach based on directional visual perception and inter-robot communication. Using a pan camera head, sonar readings and wireless communication, we demonstrate that robots are not only able to move in formation, avoid obstacles and switch formations, but also initialize and determine by themselves their positions in the formation. Validation of our work is done in simulation and with Pioneer 2 robots.

Ultrasonic relative positioning for multi-robot systems

Coordination of a group of mobile robots is facilitated when they are able to determine their positions relative to each other. Instead of using an absolute positioning approach with fixed beacons in the operating environment, we have developed a ultrasonic relative positioning system that allows each robot to perceive the distance and the angle of other nearby robots in relation to its own position. The system is based on time-of-flight evaluation of ultrasonic pulses and a RF communication link. The system has a precision of 8 mm and of 3deg over a 6.7 m range. This paper describes the system, its performance and its use on four Pioneer 2 robots moving in formation.

Design and Control of a Four Steered Wheeled Mobile Robot

This paper presents the kinematical analysis of AZIMUT-2, a four steered wheeled mobile robot. The utilization of a new wheel concept called the AZIMUT wheel allowed us to create an innovative omnidirectional non-holonomic robot. Novelty of this wheel concept resides in the non-conventional positioning of the steering axis and the wheel axis. We propose a kinematical model based on the geometrical constraints of these wheels. The degree of mobility, steerability and maneuverability are studied. Additionally, we describe a special design implementation of the wheel mechanism to overcome a hyper-motorization issue inherent to the wheels geometrical properties. Finally, we describe AZIMUT-2s two operational and seven locomotion modes, along with a control algorithm based on the kinematical model of the robot

AZIMUT, a leg-track-wheel robot

AZIMUT is a mobile robotic platform that combines wheels, legs and tracks to move in three-dimensional environments. The robot is symmetrical and is made of four independent leg-track-wheel articulations. It can move with its articulations up, down or straight, or to move sideways without changing the robots orientation. To validate the concept, the first prototype developed measures 70.5 cm/spl times/70.5 cm with the articulations up. It has a body clearance of 8.4 cm to 40.6 cm depending on the position of the articulations. The design of the robot is highly modular, with distributed embedded systems to control the different components of the robot.