In ACTRESS, an agent cooperates with other agents using wired and wireless communication systems. Likewise, the human operator communicates with the ...
A Human Interface for Interacting with and
Monitoring the Multi-Agent Robotic System TSUYOSHI SUZUKII, KAZUTAKA YOKOTA2, HAJIME ASAMA3, YOSHIKI ISHIDA4, AKIHIRO MATSUMOT05, HAY ATO KAETSU3, and ISAO ENOO3 IGraduate School of Science and Eng., Saitama Univ., Saitama, 338 Japan 2Dept. of Mechanical Systems Eng., Utsunomiya Univ., Tochigi, 321 Japan 3The Inst. of Physical and Chemical Reseach (RIKEN), Wako, 351-01 Japan 4Computer Center, Kyushu Univ., Fukuoka, 820 Japan 5Dept. of Mechanical Eng., Toyo Univ., Saitama, 350 Japan Abstract We are developing an autonomous and decentralized robot system ACTRESS. There are two classes of humans who deal with ACTRESS. One is the developer who develops robotic agents of the system, and the other is the operator who runs the system for specific tasks. We have developed a human interface system for the multi-agent robotic system to be used in both development and run-time environments. The paper discusses communication between operators and agents which is essential to realize the human interface system which lets the op.erator monitor the system and give or get some information. In ACTRESS, an agent cooperates with other agents using wired and wireless communication systems. Likewise, the human operator communicates with the agents using the same communication systems. He also uses communication to monitor the system. However, in ACTRESS, communication bandwidth is limited. Therefore, the communication of monitoring must not degrade the performance of the communication in the system. We discuss efficient communication to monitor the behavior of agents. And we modeled and evaluated the amount of communication and information for various communication types. It is found that eavesdropping message exchange among agents will reduce necessary communication for the human operator and ease communication traffic. The human operator can make efficient monitoring with the agents using both explicit communication and eavesdropped messages. Keywords: Decentralized Robotic System, Human Interface, Communication, Monitoring, Mobile Robot Simulation
1.
Introduction
In recent years, human-machine interaction has been studied in various research areas. Among these studies, there are few studies on the human interface system for the multi-agent environment [I] [2]. To handle many agents, there are some issues like communication between a human operator and many agents or handling of information in a system to be addressed. We have been discussing the human interface system which enables communication between the human operator and many agents in the distributed autonomous robotic system. In distributed autonomous system, an operator usually does not have to intervene in the system because he relies on the system's autonomy. However the operator must intervene in the system in some cases as follows: - when he gives start or stop command of tasks to the system, - when he assigns tasks to the agents, - when he is required for some cooperation from agents, - when he is asked to solve problems which the agents cannot do so themselves. To realize these communication between the operator and agents, we are developing a human interface system. In this paper, monitoring methods to gather information of the system using communication is discussed. The human interface system of ACTRESS is introduced. The System Monitor of the
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H. Asama et al. (eds.), Distributed Autonomous Robotic Systems © Springer-Verlag Tokyo 1994
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human interface system for the ACTRESS is designed. Communication types for the monitoring system are proposed. Monitoring methods in each communication type are discussed. Communication frequency and reliability of information in each method are analyzed. Finally, characteristics of monitoring methods are discussed.
2.
Human Interface System of ACTRESS
2.1. Concept of ACTRESS To execute high level tasks such as maintenance in nuclear power plants or flexible automation in manufacturing plants, ACTRESS has been developed. ACTRESS stands for ACTor-based Robots and Equipments Synthetic System [3]. ACTRESS is the multi-agent robotic system based on the concepts of function distribution and cooperation [4]. In ACTRESS, robots and equipments which have various functions are all regarded as agents. All agents have a wired or wireless communication system. Each agent works autonomously, or cooperates with other agents using the communication system. Figure 1 shows the prototype system of ACTRESS. The system comprises mobile robots and workstations providing various services.
E'~
1) 2L V' I where N, v, and L denote the number of the agents in the environment, the fixed velocity of the agents, and the length of the segment in the environment. V·/i
The indices of Type A are obtained as follows : The System Monitor must monitor N agents within the time Ii. Then, the number of communication in an unit time is calculated as FA = N/li. If the agent has moved the distance 1in a segment when the System Monitor communicates with the agent, the System Monitor can correctly assume the location of the agent thereafter until it reaches the end ofthe segment, as it is moving at the fixed velocity (Fig.4).
.....
L
I
.,
I :
v ~ agent egment Fig.4 Definition of segment In other words, for the next period of (L-l)/v, the location of the agent is known. The reliability of the information RA is, thus, defined as (L-l)/(v*II) . Figure 5 shows the relation between RA and I . Because the velocity of the agent is constant, the probability where the agent exists in one segment is uniform. Therefore, the reliability lU. is average of the shaded portion of Fig.5 (a). 1 L 1 L L lU.=_.L - - - = - ( - -
