After several years of developing multiple RoboCup small-size robot soccer teams, our CMDragons robot team achieved a highly successful level of performance, winning both the 2006 and 2007 competitions without losing a single game. Our small-size team consists of five executing wheeled robots with centralized, off-board perception and decision making. The decision making framework consists of a set of layered components, consisting of perception, evaluation and strategy, robot tactics and skills, and real-time navigation. In this paper, we present the strategy, action selection, and execution aspects of our architecture, with a focus on passing as an example of effective coordinated teamwork. The design enabled our robot team to score using multiple methods, from direct shooting up to 3D passes deflected in midair, resulting in a rich set of actions that were difficult for adversaries to counter. We provide several performance quantified claims supported by testing in our laboratory and in competition settings.

This paper introduces a refinement of the classical sense-plan-act objective maximization method for setting agent goals, a real-time randomized path planner, a bounded acceleration motion control system, and a randomized velocity-space search for collision avoidance of multiple moving robotic agents. We have found this approach to work well for dynamic and unpredictable domains requiring real-time response and flexible coordination of multiple agents. First, the approach employs randomized search for objective maximization and motion planning, allowing real-time or any-time performance. Next, a novel cooperative safety algorithm is employed which respects agent dynamics limitations while also preventing collisions with static obstacles or other participating agents. An implementation of our multilayer approach has been tested and validated on real robots, forming the basis for an autonomous robotic soccer team

Adversarial multi-robot problems, where teams of robots compete with one another, require the development of approaches that span all levels of control and integrate algorithms ranging from low-level robot motion control, through to planning, opponent modeling, and multiagent learning. Small-size robot soccer, a league within the RoboCup initiative, is a prime example of this multi-robot team adversarial environment. In this paper, we describe some of the algorithms and approaches of our robot soccer team, CMDragons'02, developed for RoboCup 2002. Our team represents an integration of many components, several of which that are in themselves state-of-the-art, into a framework designed for fast adaptation and response to the changing environment.

Fast pattern detection and identification is fundamental problem for many applications of real-time vision systems. The desirable characteristics for a solution are that it requires little computation, localizes a pattern robustly and with high accuracy, and can identify a large number of unique pattern identifiers so that many of these markers can be tracked within a field a view. We will present a system that can accurately track a broad class of patterns both accurately and quickly, when used with a suitable low level vision system that can return calibrated coordinates of regions in an image. Both pattern design and the detection algorithm are considered together to find a solution meeting the above criteria. Along the way, assumptions are verified to make informed choices without relying on guesswork, and allowing similar system to be designed on a solid experimental and statistical basis.

Mobile robots often must find a trajectory to another position in their environment, subject to constraints. This is the problem of planning a path through a continuous domain Rapidly-exploring random trees (RRTs) are a recently developed representation on which fast continuous domain path planners can be based. In this work, we build a path planning system based on RRTs that interleaves planning and execution, first evaluating it in simulation and then applying it to physical robots. Our planning algorithm, ERRT (execution extended RRT), introduces two novel extensions of previous RRT work, the waypoint cache and adaptive cost penalty search, which improve replanning efficiency and the quality of generated paths. ERRT is successfully applied to a real-time multi-robot system. Results demonstrate that ERRT is significantly more efficient for replanning than a basic RRT planner, performing competitively with or better than existing heuristic and reactive real-time path planning approaches. ERRT is a significant step forward with the potential for making path planning common on real robots, even in challenging continuous, highly dynamic domains.

Vision systems employing region segmentation by color are crucial in real-time mobile robot applications. With careful attention to algorithm efficiency, fast color image segmentation can be accomplished using commodity image capture and CPU hardware. This paper describes a system capable of tracking several hundred regions of up to 32 colors at 30 Hz on general purpose commodity hardware. The software system consists of: a novel implementation of a threshold classifier, a merging system to form regions through connected components, a separation and sorting system that gathers various region features, and a top down merging heuristic to approximate perceptual grouping. A key to the efficiency of our approach is a new method for accomplishing color space thresholding that enables a pixel to be classified into one or more, up to 32 colors, using only two logical AND operations. The algorithms and representations are described, as well as descriptions of three applications in which it has been used.