In our current research, we are developing a holonomic mobile system which is capable of running over the step. This system realizes omni-directional motion on flat floor using special wheels and passes over non-flat ground in forward or backward direction using the passive suspension mechanism. In order to realize the high mobile performance during step climbing, it is required to reduce wheel slippage for maximizing wheel traction. This paper proposes a new plural wheel control method based on wheel slip estimation. Our key idea is estimation of wheel slippage comparing with the loads and rotation velocities of all actuated wheels, and using this result for wheel control of the vehicle for reducing wheel slippage. The controller can adjust control tractions of plural wheels when the wheel begins to slip and can improve the mobile performance of the vehicle. The performance of our proposed control scheme is experimented by computer simulations and experiments

We are conducting research and development in technology for unifying the information of a large number of intelligent sensors distributed in a disaster-stricken area. Operating effectively as a system in real time, network household electric appliances, a personal digital assistant (PDA), a robot, etc. provided information and an action plan for a stricken area's situation. In this paper we introduce ubiquitous device "intelligent data carriers for rescue (IDC-R)" and formation of a dynamic network, and development of a means of disaster information communication (a group of people, a robot, an adhoc network, a home network, etc.). Target experiment for actual proof is also introduced

In our current research, we are developing a holonomic mobile system which is capable of running over the step. This system realizes omni-directional motion on flat floor using special wheels and passes over non-flat ground in forward or backward direction using the passive suspension mechanism. The vehicle changes its body shape according to ground condition when it runs over the rough terrain. This paper proposes a new wheel control method according to the change of the vehicle's body shape for passing over the step. Our key idea is the modification of its kinematic model referring to the body configuration dynamically and using this model for wheel control of the vehicle. The controller can adjust the wheel control references when the vehicle passes over the rough terrain changing the body shape and can reduce the slippage and the rotation error of the wheels. The performance of our proposed method is experimented by computer simulations and experiments.

In this study, we propose a new holonomic mobile mechanism which is capable of step-climbing. This mechanism realizes to move in any direction on the flat floor and pass over steps and slopes in one (fore and hind) direction. The vehicle equips with seven omni-directional wheels with cylindrical free rollers and a passive body axis that provides to change the shape of the body on the rough terrain. There is no need for additional actuators or sensors for the passive body axis. In our previous work, we constructed a prototype mobile mechanism and analyzed its kinematic characteristics. In this paper, we design a new control scheme and improve the mechanism for passing over the steps more stably, The performance of the prototype system is verified through experiments and computer simulations.

We propose a decentralized motion control algorithm of multiple mobile robots transporting a single object in cooperation with a human based on a path generated from an environment. Each mobile robot is controlled as if it had caster-like dynamics around a representative point attached to the object and its representative point moves along the path based on the intentional force applied by a human. The proposed decentralized control algorithm is experimentally applied to three omni-directional mobile robots referred to as DR Helper. Experimental results illustrate the validity of the proposed control algorithm.

We propose a decentralized motion control algorithm of multiple mobile robots transporting a single object in cooperation with a human based on a path generated from an environment. Each mobile robot is controlled as if it has a wheel with a free rotational joint and moves along the path based on the intentional force applied by a human. The proposed decentralized control algorithm is experimentally applied to the omni-directional mobile robots referred to as DR Helpers. Experimental results illustrate the validity of the proposed control algorithm.

We propose a decentralized control system of multiple mobile robots transporting a single object in coordination without using force/torque sensors. In this system, each robot is controlled as if it has a specified impedance dynamics without using a force/torque sensor. The robots transport an object in coordination using a leader-follower type control algorithm. The effect of parameter identification errors is discussed and a method to reduce it is proposed. The proposed control algorithm is experimentally applied to two mobile robots, and the experimental results illustrate the validity of the proposed control algorithm.

We propose a decentralized control algorithm of multiple robot helpers, called DR Helpers, which have been developed for manipulating a large object in cooperation with humans. In this algorithm, each robot is controlled as if it has a caster-like dynamics around a representative point attached to the object, and manipulation of a large or long object in cooperation with a human can be realized easily. The proposed control algorithm is experimentally applied to two DR Helpers and experimental results illustrate the validity of the proposed control algorithm.

We propose a decentralized control algorithm of multiple mobile robots transporting a single object in coordination. In this algorithm, each robot is controlled as if it has a caster-like mechanism and transportation of a single object by multiple mobile robots is realized without using the geometric relations among robots. The proposed control algorithm is experimentally applied to two mobile robots. Experimental results illustrate the validity of the proposed control algorithm.

In, this paper, we discuss a problem relating to the force/moment transformation for the handling of a large object by multiple mobile robots in coordination. We propose a control algorithm using geometrical constraints among the grasping points and the representative point of the object, which reduce the effect of noise amplified by force/moment transformation. We extend this algorithm to the decentralized control algorithm of multiple robots handling an object in coordination. The proposed control algorithm is experimentally applied to the mobile robots. Experimental results illustrate the validity of the proposed control algorithm.

This paper presents a novel concept of self-organizing collective robots with morphogenesis in a vertical plane. It is potentially applicable to autonomous mobile robots. For physical reconfiguration of a swarm of robots against gravity, new types of mechanisms and control strategies are proposed and demonstrated. Prototype robots have been fabricated in order to confirm the basic feasibility of the mechanisms. Each robot is composed of a body and a pair of arms. The body can be regarded as a cube with edge length of 90 mm, and is equipped with permanent magnets for bonding with another robot. The arms change the bonding configuration by rotating and sliding motions. As for the control strategies, we proposed the algorithms which can locally generate specific global formations of robots, with minimum interactions between neighboring robots. The overall scheme is similar to cellular automata. The control algorithms proposed have been tested by simulations.

In this paper, we discuss autonomous navigation in multirobot environment based on local communication. To carry out cooperative tasks using multiple autonomous robots, navigation systems should be implemented to the robots because mutual alignment of their positions and collision avoidance to each other become important. Therefore, it seems a collision avoidance and a self-localization are indispensable as elemental techniques for the navigation. Although these techniques need to recognize situation of robots surrounding environment, conventional devices to acquire information around them can not work sufficiently in such environment. For this problem, we propose techniques based on the local communication and the navigation system by combining them for multirobot environment. It is shown that robots can arrive their goal precisely without collision among them through proposed navigation systems.

In this paper, we propose a new mobile robot architecture with a body force sensor. The body force sensor is the force/torque sensor which is located between the drive mechanism and the body of the mobile robot. The use of the body force sensor almost realizes the collocation of sensors and actuators, and makes the whole body of the mobile robot sensitive to external force/moment. Decentralized motion control algorithm for handling a single object by multiple robots in coordination is implemented in each mobile robot and stable handling of an object is realized by multiple mobile robots with the body force sensor. Experimental results illustrate the validity of the proposed architecture.

We discuss adaptive behavior acquisition for collision avoidance among multiple autonomous mobile robots which are equipped with the locally communicable infrared sensory system (LOCISS). The LOCISS is a local sensing device for collision avoidance by which robots can detect other robots and obstacles and discriminate them by exchanging relevant information. We (1996) reported previously a collision avoidance method between two robots based on the predetermined rules using LOCISS. It is, however, difficult to realize collision avoidance among three or more robots by the predetermined rules only because situations around the robots become more complicated as the number of robots increases. Thus, it is desirable for the robots to have an adaptive capability for acquisition of the behaviors to avoid collision with other robots and obstacles. To acquire the adaptive behavior, the reinforcement learning is introduced in this paper. It is shown that appropriate behaviors for collision avoidance can be successfully acquired through the proposed learning process.

Collision avoidance is an essential problem for applications of multiple mobile robots. The authors have proposed new sensor system called LOCISS (Locally Communicable Infrared Sensory System) to detect robots and obstacles using infrared local communication. Robots mounting LOCISS can exchange useful information for collision avoidance such as speed and moving direction. In this paper, a set of rules for collision avoidance among multiple autonomous mobile robots using LOCISS is proposed. Each robot mutually carries out collision avoidance using the proposed rule. The validity of this set of rules is shown through a series of experiments using mobile robots.

A concept of mutual transportation by cooperative multiple mobile robots is proposed in this paper, which enables robots to process complicated or heavy-duty tasks, and overcome the large obstruction in an environment. A method of mutual transportation utilizing forklift mechanisms is introduced with discussion on the lifting process and moving process. Cooperative mobile robots including a holonomic omni-directional platform and a forklift mechanism are developed. Finally, as an example of applications of mutual transportation, step-climbing motion is presented, and the motion realized by the developed mobile robots is shown.

This paper proposes a new strategy for knowledge sharing among multiple autonomous mobile robots using newly developed intelligent data carriers (IDCs) to make the multi-robot system more flexible and robust against complex environmental conditions and, to reduce the amount of global communication for mutual exchange of information which is useful locally in a limited area. The IDC is an immobile but portable device (data carrier) for information storage and management with a unique mushroom-like structure to be easily handled by a forklift mechanism which can be mounted on actual mobile robots. A robot can place a unit at a specific location in its working environment and write locally relevant knowledge into the unit. Other robots can share the knowledge which should indicate the existence of specific instruments, objects or topographies, e.g., dead ends, drop-offs, steps, etc., by reading from the placed IDC units. The handling method of the IDC unit is examined through the experiment using an omni-directional mobile robot. It is shown that the robot succeeded in placing the unit at an appropriate location to share the information indicating that a dead end exists.

A new driving mechanism for holonomic omnidirectional mobile robots is designed, which enables 3 DOF motion control by three correspondent actuators in a decoupled manner with no redundancy. A prototype of the omnidirectional mobile robot with the driving mechanism is developed including a parallel link suspension mechanism. The kinematics of the omnidirectional mobile robot is also analyzed, and simulation for velocity control of the robot is performed by a method for velocity modulation with interpolation to achieve the given target position and velocity.

Distributed autonomous robotic systems which are composed of multiple robotic agents have been attracted the attention of many researchers as a new strategy for flexible and robust robotic systems. For cooperative multiple mobile robots in distributed autonomous robotic systems, recognition of the dynamic environment is required. In this paper, a new sensory system with local communication functionality is developed utilizing infra-red devices. Based on the discussion on sensing and communication for cooperative multiple mobile robots, requirements for the sensory system are derived. Then, the infra-red sensory system is designed and developed taking account of the required function. This system enables not only detection of collisions against obstacles or other robots but also local communication between robots. This system can also detect interference of plural infra-red signals. Finally the developed system as introduced, and its performance obtained as a results of experiments is shown.

This paper first discusses the relation between the human operator and the decentralized autonomous robotic system. The operator relates himself to the system loosely in the decentralized autonomous system. The authors position the operator as a problem solver and a monitor of the system. The human operator is regarded as an agent in the decentralized autonomous robotic system. Then strategies of communication between the human operator and agents are discussed. The authors propose explicit and implicit communication strategies to monitor the system, and several monitoring methods to implement them: time-based and event-based monitoring for explicit communication and eavesdropping messages for implicit communication. The authors compare the monitoring methods in order to ascertain how much information the human operator can gather in each method using simulation. Finally, the characteristics of each monitoring method are analyzed.

As a flexible and robust intelligent robot system, we have been developing an autonomous and decentralized robot system called ACTRESS, which is composed of multiple robotic agents. In this paper, introducing an idea of cooperative action with group organization and a strategy for cooperative task processing using communication, a method for team organization by efficient negotiation is presented. The efficient negotiation is realized by a newly developed communication functionality called groupcast and a learning mechanism utilizing historical records on past negotiation. The negotiation procedures for team organization are implemented, and as a result of simulation experiments, the efficiency of the learning mechanism is verified.>

The authors describe the basic design of Fun-ARM, and discuss the strategy of the fault tolerance on distributed manipulator. The fault model is described, and assumptions in the system are discussed. The methods to realize fault tolerance are proposed, including methods for fault-detection, fault-localization and fault-containment.

This paper addresses a method for synchronizing motion by multiple autonomous mobile robots using radio communication. The autonomous and decentralized robot system, ACTRESS, is a multi-agent robotic system including multiple autonomous mobile robots. The autonomous mobile robots are developed so as not only to act individually, but also to cooperate with the other robots if they cannot accomplish the task alone. The synchronized motion is sometimes required to execute such cooperative tasks. Every agent of ACTRESS is equipped with the communication system, which enables a message passing between any robotic agents. The prototype ACTRESS system is introduced, and cooperation among multiple robotic agents is discussed. A method for synchronization using the communication system is proposed. The method is applied to the prototype system, and side-by-side motion on the actual mobile robots is implemented as a example of synchronized motion.

Deals with a kind of cellular robotic system (CEBOT), called self organizing manipulator system. In this system the configuration of the manipulator can be changed according to the given task. The authors use two manipulators to assemble, disassemble, and reassemble cellular universal manipulator by cooperation work. When a simple task is given, the system can analyze the task and generate the structure of the cellular manipulator. The assembling work was divided into modular subtasks, and then the system generate the macro command based on the database. The order of subtask and the collision avoidance are considered for planning the cooperation work by using the collision database which was calculated before hand. They show the algorithm for calculation the collision database and for planning the cooperation work. The results of the simulation and the experiment are shown.>