Case Studies of Successful Robot Systems

AI Magazine Volume 19 Number 4 (1998) (© AAAI) Book Review

mental cleanup. However, with a few Review of exceptions (for example, Dorigo and Colombetti 1998), it is rare to find thorough, holistic descriptions of the Artificial Intelligence and techniques and software organization used in these practical robots. Mobile Robotics: Case Studies Enter Artificial Intelligence and Mobile Robots: Case Studies of Successful of Successful Robot Systems Robot Systems, which, as the title says, is about AI algorithms, representations, and software for perception, planning, and robot control. As the subtitle says, the chapters often Chris Brown describe practical, successful, and competition-winning robots. The book concentrates on the organization of high-level functions in mobile robots, not mechanical or electronic n the 1970s, a schism developed have not yet demonstrated the ability design: Most of the robots mentioned between (symbolic) AI and robotics to perform complex real tasks. Practi- are commercial products, and robot I(including computer vision). cal autonomous systems tend to use construction is not usually addressed. Today, mobile robotics is an increas- more complex, multilevel organiza- The book is likewise not concerned ingly important bridge between the tions of robot capabilities. Common with traditional control theory for two areas. It is advancing the theory components are a deliberative, strate- low-level systems such as direction or and practice of cooperative cognition, gic, or cognitive level (in the domain speed control. Its strength is its perception, and action and serving to of symbolic AI); a tactical action- description of software, which is at a reunite planning techniques with sequencing level; and a real-time con- level of detail and breadth that one sensing and real-world performance. trol level (which often can be imple- does not find in conference papers or Further, developments in mobile mented as reactive behaviors). usually in the archival literature. Cou- robotics can have important practical Papers in the robotics literature pled with an existing text on mobile economic and military consequences. often concern specific technical robot construction and programming, For some time now, amateurs, hob- aspects of robot research and develop- this book would be an excellent pri- byists, students, and researchers have mary or supplementary text for the had access to how-to books on the next classroom stage beyond a suc- low-level mechanical and electronic cessful subsumption robot. It is also a aspects of mobile-robot construction Artificial Intelligence source book for professionals who (Everett 1995; McComb 1987). The and Mobile Robotics, must build software architectures for famous Massachusetts Institute of robot perception and control because Technology (MIT) 6.270 robot-build- eds. David Kortenkamp, it contains detailed, current best-prac- ing course has contributed course R. Peter Bonasso, and tice solutions from proven authorities. notes and hardware kits that are now Robin Murphy, AAAI The book begins with an editorial available commercially and in the introduction and intellectual history form of an influential book (Jones Press, Menlo Park, Cali- of robotics, a brief description of robot 1998; Jones and Flynn 1993). The fornia, 1998, 390 pp., competitions, and an overview of the MIT-inspired materials concentrate volume. Three main sections follow: mainly on Rodney Brooks’s subsump- ISBN 0-262-61137-6. (1) four chapters on navigation and tion architecture. This approach to mapping, (2) three on vision, and (3) robot control relies on simple reactive six on architecture. Throughout, the behaviors, notionally running in par- ment. At the same time, several robot main theme is the organization of allel, with only simple inhibitory con- competitions (run by the American robot intelligence: what abstractions, nections between them. Actions are Association for Artificial Intelligence connections, representations, and determined by the sensed state of the [AAAI], the International Joint Con- techniques have proven successful in external world, but internal represen- ferences on Artificial Intelligence robustly carrying out practical tasks tation of the world is held to be [IJCAI], and the Department of Trans- under a wide variety of conditions. unnecessary. With these tenets, it is portation [DOT], for example) have Because the chapters are often descrip- possible to produce robots with reli- emphasized integrated, practical tions of entire working systems, these able, robust, compelling, but arguably approaches to increasingly general topical divisions are suggestive but limited, repertoires of behavior. versions of real-world problems such not mutually exclusive. There is no Indeed, pure subsumption robots as driving, inspection, and environ- real intellectual dependence between

Illah Nourbakhsh formalizes and rec- ognizes progress in a plan as the evolution of a set of state variables. The plan- KDD-98 Now Available! ner interleaves maximum-likelihood assumptions with execution and state

KDD-98—New York, New York monitoring to achieve high-level control. This robot won a difficult office- Proceedings of the Fourth International Conference on delivery AAAI robot competition. Sven Koenig and Reid Simmons Knowledge Discovery and Data Mining provide a comprehensive application Edited by Rakesh Agrawal and Paul Stolorz of partially observable Markov deci- As an interdisciplinary field, KDD has made important strides by generating sion-process (POMDP) models to nav- cross-fertilization of ideas between individual disciplines. In keeping with this igation, including the learning of the theme, KDD-98 was collocated with the Conference on Very Large Databases models and the compiling of them (VLDB-98) with the goal of catalyzing discussions and interactions between from prior but uncertain maps and researchers in the two fields. Paper topics in this proceedings include theory sensor models, the application of the and foundational issues in KDD, data-mining methods and algorithms, models to state and state-sequence database-centric data mining, and KDD process and human-interaction appli- estimation, sensor interpretation, cations.. obstacle avoidance, and environment modeling. A POMDP is a probabilistic ISBN 1-57735-070-7 392 pp., index, $60.00 softcover mechanism that estimates and uses KDD-97—Newport Beach, California probability distributions instead of point probabilities. This chapter, as Proceedings of the Third International Conference on well as several others, illustrates the Knowledge Discovery and Data Mining power of simulation in developing and quantifying control algorithms. Edited by David Heckerman, Heikki Mannila, Daryl Pregibon, and Ramasamy Uthurusamy Vision ISBN 1-57735-027-8 320 pp., index, $60.00 softcover Ian Horswill describes how a low-cost vision system and an organization of To order, call 650-328-3123 or visit the parallel strategies work together to AAAI Press web site at www.aaai.org/Press/ take advantage of prior constraints of a particular environment (office build- ing) to produce complex and robust behavior (giving a laboratory tour). The vision system’s reliable produc- chapters, so they can be read in any are illustrated. Maps are used for jobs tion of percepts (such as person-ahead? order. Each of the chapters has its own such as route planning, exploration, and blocked?), as well as sequencing charm: Some explore general ques- and obstacle avoidance. Details of the logic and navigational algorithms, is tions, some present enough detail to computer vision and obstacle avoid- of particular interest. let the reader understand a system in ance during fast driving are provided. Robin Murphy compares two gener- depth. The pages are rich with block David Kortenkamp and several col- ations of entries to a DOT obstacle- diagrams, code fragments, graphics, leagues describe, in useful technical course competition and shows the photographs, graphs, and maps show- detail, their entrant to a three-stage evolution of their high-level behav- ing experimental results. AAAI robot competition (static and ioral control scheme. This chapter The following brief paragraphs do dynamic obstacle avoidance, object gives a clear description of reactive, not do full justice to the chapters, location, and a race to visit previously hierarchical, and hybrid control styles which often tell complete integrated located objects). A vector field his- and relates them to current theories stories of complete integrated systems. togram representation of space (a dis- from cognitive psychology. The per- crete two-dimensional [2-D] grid with formance of the basically reactive Navigation and Mapping probabilistic contents) stores robot robots is examined in terms of these and goal locations and the locations of theories, and recommendations for Sebastian Thrun and several col- obstacles sensed by ultrasound. This 2- successful sensing strategies are given. leagues produce geometric and topo- D world representation is used for glo- Bill Schiller and several colleagues logical (adjacency) maps using several bal path planning and obstacle avoid- participate in the SAFETRUCK program, sensors and a well-founded probabilis- ance. Good descriptions of obstacle which is to use vision to help vehicles tic framework. The beneficial effects of avoidance, vision, and self-localiza- stay in their lane. This chapter gives position estimation on map making tion algorithms are given. technical detail about multitasking

142 AI MAGAZINE Book Review implementations of robot control, pipelined real-time vision hardware and algorithms, and a comparison of edge and region vision techniques. There is a detailed description of lane keeping and obstacle-avoidance control using range sensors, local maps, computed potentials, and the transfor- Insert Mitre Ad mation of potentials into control algorithms to steer around obstacles.

Architecture Erann Gat gives a readable history, philosophy, and anatomy of the canonical three-layer system—(1) low- level controller, (2) intermediate-level sequencer, (3) high-level delibera- tor—with a case study. This chapter could well be read first of the volume as well as first in this section. Kurt Konolige and Karen Myers describe SAPHIRA, a flexible architecture capable of controlling any robot server by means of a standard interface. SAPHIRA is designed to coordinate activ- ity, maintain a coherent model of local perceptual space and prior infor- mation, and communicate with other agents. Low-level control is reactive, initiated by fuzzy-control ideas ap- plied to the local perceptual space. Computed potentials are used in an interesting way. A high-level procedu- ral reasoning system includes goal-ori- ented analysis of activities and goal sequencing. An overview of communication modalities for use with mobile robots is given. This detailed chapter is motivated by a challenging real-life scenario specification, but (rather frustratingly) we never find out about performance. James Firby, Peter Prokopowicz, and Michael Swain use a two-layer architecture to control their entrant in the IJCAI-95 competition (locate, classify, two domains: (1) the Defense Ad- The UGV demonstration illustrated and put away trash). Low-level skills vanced Research Project Agency’s multirobot formation keeping along are controlled by a special robot lan- unmanned ground vehicle (UGV) with communication of a comman- guage, and task sequencing of high- DEMO II and (2) the AAAI-94 office- der’s intentions. The three-robot level skills is controlled by the reactive cleaning competition (which their cleaning team is described in consider- action plan (RAP) system. The details of three-robot team won). These exam- able technical detail, including several skills, plans, and their connection are ples illustrate schema-based systems, pseudocode illustrations of control- described along with several good which control behavior through vari- ling schemas. examples of RAP programming and ous biologically motivated methods Huosheng Hu and Michael Brady details of world map representations such as vector summation for action use the domain of manufacturing to and the vision system. fusion, context-dependent behavior motivate a description of the plan- Ron Arkin and Tucker Balch’s work instantiation and deletion, and event- ning, sensing, and representational is in controlling cooperating robots in triggered sequencing (Arkin 1998). components of a typical robot. Their

WINTER 1998 143 Book Review

NEW! ISMB-98—Montréal, Quebec, Canada Proceedings of the Sixth International Conference on Intelligent Systems for Molecular Biology

Edited by Janice Glasgow, Tim Littlejohn, François Major, Richard Lathrop, David Sankoff, and Christoph Sensen ISBN 1-57735-053-7 234 pp., index, $45.00 softcover This volume comprises the formal proceedings for the Sixth International Conference on Intelligent Systems for Molecular Biology (ISMB- 98) held in Montréal, Canada from June 28 – July 1, 1998. As with the previous ISMB conferences, this meeting provides a general forum for disseminating the latest developments in bioinformatics. ISMB is a multidisciplinary conference that brings together scientists from computer science, molecular biology, mathematics and statistics. Its scope includes the development and application of advanced computational methods for biological problems. Relevant computational techniques include, but are not limited to: machine learning, pattern recognition, knowledge representation, databases, combinatorics, stochastic modeling, string and graph algorithms, linguistic methods, robotics, constraint satisfaction, and parallel computation. Biological areas of interest include molecular structure, genomics, molecular sequence analysis, evolution and phylogenetics, metabolic pathways, regulatory networks, developmental control, and molecular biology generally. Emphasis is placed on the validation of methods using real data sets, on practical applications in the biological sciences, and on development of novel computational techniques.

To order, call AAAI Press at 650-328-3123 or visit the AAAI Press web site at www.aaai.org/Press/ Prices subject to change without notice

locally intelligent control agent (LICA) take the form of a deterministic finite Everett, H. R. 1995. Sensors for Mobile architecture, like SAPHIRA, transcends automaton or can be as general as a Robots: Theory and Application. Wellesley, any particular implementation, but it Prolog program; it can also be generat- Mass.: A. K. Peters. is particularly well suited to embedded ed by nonprogrammers using a graph- Jones, J. L. 1998. RUG WARRIOR PRO: Hardware microprocessor control. Its modularity ic interface combined with an expert and Assembly Guide. Wellesley, Mass.: A. K. Peters. and scalability are demonstrated, and system. details of a vision system built of The fairly detailed index and the Jones, J. L., and Flynn, A. M. 1993. Mobile unified bibliography add to the book’s Robots: Inspiration to Implementation. LICAs are given. A probabilistic cost- Wellesley, Mass.: A. K. Peters. function approach to navigation and a usefulness. It is priced to be accessible: Although the graphics and pho- McComb, G. 1987. The Robot Builder’s Kalman filter formalization of dynam- Bonanza: 99 Inexpensive Robotics Projects. tographs are clear and the book is ic localization are thoroughly de- New York: McGraw-Hill. scribed. The multilayered perception quite usable, I feel it deserved a better- and multilayered action components looking typeface, more attractive (per- haps hard) cover, and a more modern Chris Brown (B.A., Oberlin College, 1967; are implemented as a multiprocessor, Ph.D., University of Chicago, 1972) is pro- distributed real-time system. layout. Also, a chapter on some of the fessor of computer science at the University Don Brutzman and colleagues high- commercially practical (though possi- of Rochester, where he has been since fin- light the difficulties of underwater bly less AI-intensive) robots emerging ishing a postdoctoral fellowship at the robotics and the potentially crucial from places such as Carnegie Mellon School of Artificial Intelligence at the Uni- contributions of sophisticated sensor University would have been useful. versity of Edinburgh in 1974. He is coau- Still, this very welcome collection is thor of the influential text Computer Vision and control simulation. Their under- well placed in a large, empty niche. It with his Rochester colleague Dana Ballard water robot uses the three-level ratio- is a fine resource for anyone teaching and is coeditor of Real-Time Computer nal behavior model (RBM) for control: about, thinking about, designing, or Vision (Cambridge University Press, 1994), The lowest level is commanded by a among other volumes. His current research producing sophisticated mobile robot mission-script language that is read- interests are computer vision and robotics; perception, reasoning, and control able by robots and humans and is sim- integrated parallel systems performing ani- software. ilar to orders given down the com- mate vision (the interaction of visual capabilities and motor behavior); and the inte- mand chain by officers. The middle References gration of planning, learning, sensing, and tactical layer features multiprocessing Arkin, R. C. 1998. Behavior-Based Robotics. control. His e-mail address is brown@cs. and interprocess communication to Cambridge, Mass.: MIT Press. rochester.edu. implement cooperative navigation, Dorigo, M., and Colombetti, M. 1998. sonar sensing, and replanning. The Robot Shaping: An Experiment in Behavior RBM for the highest strategic level can Engineering. Cambridge, Mass.: MIT Press.

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