Richard T. Vaughan

Most valuable player: a robot device server for distributed control

Successful distributed sensing and control require data to flow effectively between sensors, processors and actuators on single robots, in groups and across the Internet. We propose a mechanism for achieving this flow that we have found to be powerful and easy to use; we call it Player. Player combines an efficient message protocol with a simple device model. It is implemented as a multithreaded TCP socket server that provides transparent network access to a collection of sensors and actuators, often comprising a robot. The socket abstraction enables platform- and language-independent control of these devices, allowing the system designer to use the best tool for the task at hand Player is freely available from http://robotics.usc.edu/player.

Massively multi-robot simulation in stage

Stage is a C++ software library that simulates multiple mobile robots. Stage version 2, as the simulation backend for the Player/Stage system, may be the most commonly used robot simulator in research and university teaching today. Development of Stage version 3 has focused on improving scalability, usability, and portability. This paper examines Stage’s scalability.We propose a simple benchmark for multi-robot simulator performance, and present results for Stage. Run time is shown to scale approximately linearly with population size up to 100,000 robots. For example, Stage simulates 1 simple robot at around 1,000 times faster than real time, and 1,000 simple robots at around real time. These results suggest that Stage may be useful for swarm robotics researchers who would otherwise use custom simulators, with their attendant disadvantages in terms of code reuse and transparency.

On device abstractions for portable, reusable robot code

We seek to make robot programming more efficient by developing a standard abstract interface for robot hardware, based on familiar techniques from operating systems and network engineering. This paper describes the application of three well known abstractions, the character device model, the interface/driver model, and the client/server model to this purpose. These abstractions underlie Player/Stage, our open source project for rapid development of robot control systems. One product of this project is the Player Abstract Device Interface (PADI) specification, which defines a set of interfaces that capture the functionality of logically similar sensors and actuators. This specification is the central abstraction that enables Player-based controllers to run unchanged on a variety of real and simulated devices. We propose that PADI could be a starting point for development of a standard platform for robot interfacing, independent of Player, to enable code portability and re-use, while still providing access to the unique capabilities of individual devices.

Experiments in automatic flock control

Abstract The Robot Sheepdog Project has developed a mobile robot that gathers a flock of ducks and manoeuvres them safely to a specified goal position. This is the first example of a robot system that exploits and controls an animal’s behaviour to achieve a useful task. A potential-field model of flocking behaviour was constructed and used to investigate methods for generalised flock control. One possible algorithm is described and demonstrated to work both in simulation and in the real world.

LOST: localization-space trails for robot teams

Cushioning member that has a thickness greater than that of a card-type electronic device and is formed of an elastic material is detachably attached to the peripheral edge portion of the electronic device, thereby covering at least the four corner portions of the electronic device. The card-type electronic device having the cushioning member thereon is opposed to a seating surface of a seating portion, and a retaining member is located on the electronic device so as to face the seating surface. The cushioning member is clamped between the retaining member and the seating surface, and the card-type electronic device is held on the seating portion by the cushioning member.

Whistling in the dark: cooperative trail following in uncertain localization space

We demonstrate that a simulated group of robots can co- operate to robustly transport resource between two areas in an unknown environment using an algorithm inspired by the trail following of ants and the waggle dance of honey bees. Rather than directly marking their environment, the robots announce their successful paths through a common localization space. It is found that the algorithm is robust to significant localization error, suggesting that the method will be viable for teams of real robots. relation between the representations maintained by two or more individuals. A prime example is the Global Position- ing System (GPS). Two systems equipped with GPS share a metric localization space in planetary coordinates. Simi- laxly two robots that start out with known positions in the same coordinate system and maintain a position estimate via odometry share a localization space. In both examples each robot has only an estimate of its position in the true space, but the true space is common to both. More abstract localization spaces can be considered, such as the location of a data byte in a hierarchical database or a URL on the Internet. In these cases too, there can be some uncertainty in position; for example if position is described by a fuzzy matching rule or an ambiguous data query. In this paper we demonstrate a cooperative transportation task in a group of simulated mobile robots that communi- cate by leaving landmarks in shared localization space. The method is shown to be robust with respect to significant lo- calization error; indicating that it should be suitable for use in real robots.

HRI in the sky: Creating and commanding teams of UAVs with a vision-mediated gestural interface

Extending our previous work in real-time vision-based Human Robot Interaction (HRI) with multi-robot systems, we present the first example of creating, modifying and commanding teams of UAVs by an uninstrumented human. To create a team the user focuses attention on an individual robot by simply looking at it, then adds or removes it from the current team with a motion-based hand gesture. Another gesture commands the entire team to begin task execution. Robots communicate among themselves by wireless network to ensure that no more than one robot is focused, and so that the whole team agrees that it has been commanded. Since robots can be added and removed from the team, the system is robust to incorrect additions. A series of trials with two and three very low-cost UAVs and off-board processing demonstrates the practicality of our approach.

Blazing a trail: Insect-inspired resource transportation by a robot team

We demonstrate a team of real robots that cooperate to robustly transport resource between two locations in an unknown environment. The robots use a trail laying and following algorithm inspired by the trail following of ants and the waggle dance of honey bees. Rather than directly marking their environment, the robots announce landmarks in their odometric localization space. The system tolerates significant odometric drift before it breaks down.

Reusable Robot Software and the Player/Stage Project

The authors of several well-known robot software systems met at the ICRA 2005 workshop on the Principle and Practice of Software Development in Robotics. The meeting was held to examine the role of software engineering concepts and methods in experimental robotics applications. Everyone at the workshop agreed that extensive reuse of robot software should help to make robot development faster, easier and more efficient, and that this was highly desirable. There exist many robot programming tools and frameworks designed to promote this idea, some of which have been actively developed for several years using very fine software engineering techniques. However, very few supposedly reusable systems are extensively used outside their home institution or their immediate collaborators. Many well-engineered systems are never used at all. This suggests that there is more to getting code widely reused than nice code design, however principled.

Evaluating control strategies for wireless-networked robots using an integrated robot and network simulation

Wireless communication is an enabling factor in multiple mobile robot systems. There is significant interaction between robot controllers and communications subsystems. We present a method for evaluating combined robot control/communication strategies for a team of wireless-networked robots performing a resource transportation task. Two alternative controller designs are compared under established communication and radio propagation models. For each we measure the overall performance of the robot team including the cost of communication. The study illustrates how our evaluation tools can be used for designing controllers for robots operating in wireless communication environments.