JAIST Repository
https://dspace.jaist.ac.jp/Title

Progress Report in 2007 : Research on Fault
Tolerance of Mobile RobotsAuthor(s)YANG, YanCitation
Issue Date

2008‑03‑04

TypeConference Paper

Text version

publisher

URL

http://hdl.handle.net/10119/8244

RightsDescription

JAIST 21世紀COEシンポジウム2008「検証進化可能電子社会」= JAIST 21st Century COE Symposium 2008
Verifiable and Evolvable e‑Society, 開催：2008年
3月3日〜4日, 開催場所：北陸先端科学技術大学院大学, GRP研究員発表会 セッションC‑2発表資料

Japan Advanced Institute of Science and Technology

Progress Report in 2007---- Research on Fault Tolerance of Mobile Robots
Yan YANG
School of Information Science
Japan Advanced Institute of Science and Technologyy.yang@jaist.ac.jp

1. Introduction of our research
Mobile robots cooperating in groups offer several advantages, e.g., redundancy
and flexibility, and can sometimes perform tasks that would be impossible for one
single robot. Recent advances in robotics have started making it feasible to deploy
large numbers of inexpensive robots for tasks such as military scout vehicles,
satellite exploration and surveillance missions [1]. However, coordination ofmultiple robots to accomplish such tasks remains a challenging problem [2].
One of the important applications of multiple robots is the flocking problem. In
short, flocking is the ability of a group of robots to move in formation and topreserve it while moving. Concretely, simple robots are allowed to move, with basic
rules governing their movement. The moving in formation has many applications,for instance, transporting large objects, exploring hazardous areas and surveillance.
Even though the cheap, simple and relatively weak robots have many advantages in
the applications, those characteristic of robots also may bring its proneness to crash.
Specially in flocking application, all robots coordinately generate a certain
formation. If some robots are crashed, the other robots can not distinguish the alive
robots in waiting state from the crashed ones. Thus, the desired formation with thecurrent robots can not maintain while moving. Therefore, it is necessary to find amethod that can distinguish the correct robots in waiting state from the crashed ones.
Therefore, fault tolerance of robot systems becomes very important in thecoordination of multiple mobile robots. While, the design of fault-tolerant
distributed flocking algorithm for multiple robot systems is very necessary and stilla largely unexplored direction. Specially in flocking application, all robots
coordinately generate a certain formation. If some robots are crashed, the otherrobots can not distinguish alive robots (not faulty robots) in waiting state from thecrashed ones (who will stop working and never recover). Thus, the desired
formation with the current robots can not maintain while moving. Therefore, it isnecessary to find a method that can distinguish the correct robots in waiting statefrom the crashed ones. As we know, it is not applicable in dynamic applications likeflocking, because the probability of robot failure during execution is much high due
to influence of various environments.

2. Progress of this year:- Propose a fault tolerant flocking algorithm for mobile robots in CORDA modelwith K bounded scheduler. The proposed algorithm includes three modules: nonfaulty robot selection module, preprocessing module and flocking module. In thefirst module, the non-faulty robots are selected based on K-bounded scheduler. In
this part, we don't only consider initial crash of robots, but also we take into
account crash of robots during execution. This is different from the existed
schemes. In the preprocessing module, the robots that are initially located at
random places can self-organically generate a desired formation (regular polygon).

Finally, in the third module, for a given desired regular polygon, we provide amethod for robots to maintain such quasi-regular polygon while moving.
- Propose a novel and simple flocking algorithm, which can achieve and keep thedesired distance with its neighbors when there is no obstacle, also can avoid
collision between a robot and its neighbors and between robots and obstacles when
there are obstacles in the environment. By simulation results, this algorithm caneffectively achieve the above two goals simultaneously.
- Compares several parametric and adaptive failure detection schemes in terms of theirrespective QoS. We proposed an improvement over existing methods, called TAM
FD, and evaluate their benefits. First, we propose an optimization to enhance theadaptation of Chen’s FD, which significantly improves QoS, especially in theaggressive range and when the network is unstable. Second, we address the problem
of most adaptive schemes, namely their need for a large window of samples. We
study a scheme that is designed to use a fixed and very limited amount of memory
for each monitored–monitoring link. Our experimental results over several kinds ofnetworks (Cluster, WiFi, wired LAN, WAN) show that the properties of theexisting adaptive FDs, and that the optimization is reasonable and acceptable.
Furthermore, the extensive experimental results show what is the effect of memory
size on the overall QoS of each adaptive FD.

3. Future direction:
The specific concept is as follows- Extend the dependable methods in traditional distributed computing into mobilecomputing, for example, find consensus methods for sensor network, ad hoc
network and robotic network;- Evaluate the proposed failure detectors for mobile network mainly from two
properties, that is, completeness and accuracy;- Multiple goals would be considered simultaneously in designing a failure detector,
for example, in sensor network, the energy saving, packet loss

4. Publications in 2007
[1] N. Xiong, Y. Yang, X. Defago, “Comparative analysis of QoS and memory
usage of adaptive failure detectors”, in Proceeding of the 13th IEEE Pacific RimInternational Symposium on Dependable Computing (PRDC 2007), pp. 27-34,
Melbourne, Victoria, Australia, December 17-19, 2007.
[2] X. Defago, N. Xiong, Y. Yang and N. Hayashibara, “Pragmatic accrual failuredetection with Kappa-FD”, Technical report, JAIST, Japan, November 2007.
[3] Y. Yang et.al, “A Decentralized and Adaptive Flocking Algorithm forAutonomous Mobile Robots”, accepted by the 2008 International Symposium onAdvances in Grid and Pervasive Systems, in Kunming, China.

References[1] M. J. Daigle, X. D. Koutsoukos, and Gautam Biswas, “Distributed diagnosis informations of mobile robots,” IEEE Transactions on Robotics, vol. 23, no. 2, pp.
353-369, April 2007.
[2] H. Ando, Y. Oasa, I. Suzuki, and M. Yamashita, “A distributed memoryless point
convergence algorithm for mobile robots with limited visibility,” IEEE
Transactions on Robotics and Automation, vol.15, no.5, pp. 818-828, October 1999.