Shigeru Kokaji

National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan

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Publications (64)25.56 Total impact

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    ABSTRACT: A new prototype of a self-reconfigurable modular robot, M-TRAN III, has been developed, with an improved fast and rigid connection mechanism. Using a distributed controller, various control modes are possible: single-master, globally synchronous control or parallel asynchronous control. Self-reconfiguration experiments using up to 24 modules were undertaken by centralized or decentralized control. Experiments using decentralized control examined a modular structure moved in a given direction as a flow produced by local self-reconfigurations. In all experiments, system homogeneity and scalability were maintained: modules used identical software except for their ID numbers. Identical self-reconfiguration was realized when different modules were used in initial configurations.
    No preview · Article · Mar 2008 · The International Journal of Robotics Research
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    ABSTRACT: Metamorphosis by a self-reconfigurable modular robot is presented in this report. We have developed a new prototype, “M-TRAN III”, which is improved in its high speed and rigid connection mechanism. Using its integrated design of a multi-CPU controller with various programming tools, experiments of self-reconfiguration were successfully carried out through single master synchronous control. Based on the obtained results, decentralized and locally synchronous control was accomplished, which controlled self-reconfiguration of up to 20 modules using the same program.
    No preview · Chapter · Jun 2007
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    ABSTRACT: M-TRAN is a self-reconfigurable modular robot: each module has an independent battery, two-degree-of-freedom motion, six-surface-connection capability, and intelligence with inter-module communication. The M-TRAN system can perform flexible and adaptive locomotion in various configurations using coordination control based on a central pattern generator (CPG). Various structures of several modules can perform metamorphosis, such as that between a four-legged robot and a snake-like one. In addition to these self-reconfigurations with synchronous control, M-TRAN structures having regularity can move using parallel distributed control and message exchange via the network bus. Self-reconfiguration using infrared local communication has been attempted to improve the system's scalability.
    Preview · Conference Paper · Jan 2007
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    ABSTRACT: A behavior planning method is presented for reconfigurable modular robots with coherent structure using a randomized planning. Coherent structure is introduced to cope with difficulty in planning of many degrees of freedom, in terms of control system and robot configuration. This is realized by a phase synchronization mechanism together with symmetric robot configuration, which enables the robot to generate various coherent dynamic motions. The parameters of control systems are explored using a randomized planning method called rapidly exploring random trees (RRTs). The RRT planner has an advantage of simple implementation as well as possibility of integrating differential constraints. The dynamic robot motion is thus planned and preliminary simulation results are shown to demonstrate the proposed planning scheme can generate appropriate behaviors according to environments.
    Full-text · Chapter · Dec 2006
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    ABSTRACT: The M-TRAN is a modular robot capable of both three-dimensional self-reconfiguration and whole body locomotion. Introducing regularity in allowed structures reduced difficulties of its reconfiguration problems. Several locomotion patterns in various structures were designed systematically using a CPG controller model and GA optimization. Then they were verified by experimentation. Results showed a feasible scenario of operation with multiple M-TRAN modules, which is presented herein, including metamorphosis of a regular structure, generation of walkers from the structure, walker locomotion, and reassembling of walkers to the structure.
    Full-text · Article · Feb 2006 · Robotics and Autonomous Systems
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    ABSTRACT: This paper presents a design method and experiments for whole-body locomotion by a modular robot. There are two types of locomotion for modular robots: a repeating self-reconfiguration and whole-body motion such as walking or crawling. For whole-body locomotion, designing a control method is more difficult than for ordinary robots because a modular robotic system can form various configurations, each of which has many degrees of free-dom. This study proposes a unified framework for automatically designing an efficient locomotion controller suitable for any mod-ule configuration. The method utilizes neural oscillators (central pattern generators, CPGs), each of which works as a distributed joint controller of each module, and a genetic algorithm to optimize the CPG network. We verified the method by software simulations and hardware experiments, in which our modular robotic system, named M-TRAN II, performed stable and effective locomotion in various configurations.
    Full-text · Article · Jun 2005 · IEEE/ASME Transactions on Mechatronics
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    ABSTRACT: Geometric self-reconfiguration sequences and a distributed control method are developed for the modular robot M-TRAN. Large scale self-reconfiguration contains several clusters of modules moving in parallel. A decentralized and asynchronous control is suitable for such a task. A multi thread type simulation program was developed to design and verify such self-reconfiguration sequences. A distributed controller system was developed for the new M-TRAN hardware, which can realize decentralized and asynchronous control of modules. Its basic functions were verified by experiments.
    Full-text · Conference Paper · Jan 2005
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    ABSTRACT: A method for behavior planning is presented for a modular robot that applies a randomized planner to coherent structure of the robot. To cope with difficulty in planning of many degrees of freedom (DOFs) of a modular robot, coherent structure is introduced in terms of control system and robot configuration. As the control system, a simple phase synchronization mechanism is introduced that can control the robot with many DOFs with reduced number of parameters. Together with symmetrical configuration, this control system generates various dynamic motions. In order to plan the behaviors of the modular robot determined by the parameters of the control system, we adopt a randomized planner called rapidly exploring random trees (RRTs). This can benefit from a number of advantages of RRT planner, including simple implementation, uniform search, and applicability to a dynamic system with differential constraints. By exploring parameter space of the coherent control system, behaviors including dynamic motions can be planned. We have applied the proposed planner to M-TRAN modular robot to demonstrate the effectiveness of the proposed method through preliminary simulation results.
    Full-text · Conference Paper · Nov 2004
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    ABSTRACT: This paper analyzes hydrogen production from alcohol with a pair of electrodes from an energy-exchange perspective. The electric energy between the electrodes was transformed into the kinetic energy of the emitted electrons and alcohol molecules for inducing their collisions. The collision caused the decomposition of alcohol molecules and the dissociation of hydrogen ions. The hydrogen ions were attracted to the negative electrode and produced hydrogen molecules during the electrode's electrical neutrality. Application of the classical electromagnetic theory was useful for understanding the series of reactions from an energy-exchange perspective.
    No preview · Article · Aug 2004 · The Journal of Physical Chemistry A
  • Hiroshi Matsuura · Tamio Tanikawa · Shigeru Kokaji
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    ABSTRACT: We investigated the transition of liquid geometry as a function of the frequency of the sinusoidal electric potential applied to the surface of a liquid. The application of an electric potential of low frequency generated a hemispherical liquid geometry, and the hemisphere narrowed as the frequency was increased, forming an electromeniscus. This electromeniscus was applied in erecting a carbon nanotube (CNT) on the substrate. In this paper, we analyze the dynamic mechanisms of the electromeniscus phenomenon. The application of canonical theory explains the mass-reduction mechanism of the oscillating liquid.
    No preview · Article · Jul 2004 · Japanese Journal of Applied Physics
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    ABSTRACT: A modular robot has a distributed mechanical composition which can make various configurations and also make locomotion in a wide variety of configurations. Modular robots are thought to be useful in extreme or unknown environments by adaptively changing their shape and locomotion patterns. As for locomotion, two types can be used; one is whole-body fixed-configuration locomotion and the other is locomotion by self-reconfiguration. In this paper we deal with the former type of locomotion which is realized by coordinated joint actuation. So far, proposed control methods for whole-body locomotion by modular robots have been based on predefined locomotion sequences. However, locomotion based on predefined sequences cannot adapt to changing terrain conditions such as uphill, downhill, slippery and sticky grounds. To solve such problems, we propose a distributed control mechanism using a CPG controller which enables adaptive locomotion by modular robots. Besides the real-time CPG control we introduce a decentralized control mechanism for detecting the situation that the robot is stuck and initiating transformation to another shape for recovering the situation. The results of various hardware experiments by 4-legged structure prove the feasibility of the method for adaptive locomotion and transformation by our M-TRAN II modules.
    Full-text · Conference Paper · Jan 2004
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    ABSTRACT: The M-TRAN is a modular robot capable of both three dimensional self-reconfiguration and whole body locomotion. The difficulties of its self-reconfiguration problem were reduced by introducing regularity in allowed structures. Several locomotion patterns in various structures were designed systematically and verified by experiments. Based on those results, a feasible scenario of operation with multiple M-TRAN modules is presented, including metamorphosis of a deformable multi-module structure, generation of walkers from the structure, walker locomotion and reassembling of walkers to the structure.
    Full-text · Article · Jan 2004

  • No preview · Article · Jan 2004
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    ABSTRACT: We have been developing a self-reconfigurable modular robotic system (M-TRAN) which can make various 3-D configurations and motions. In the second prototype (M-TRAN II), various improvements are integrated in order to realize complicated reconfigurations and versatile whole body motions. Those are a reliable connection/detachment mechanism, on-board multi-computers, high speed inter-module communication system, low power consumption, precise motor control, etc. Programing environments are also integrated to design self-reconfiguration processes, to verify motions in dynamics simulation, and to realize distributed control on the hardware. Hardware design, developed software and experiments are presented in this paper.
    Full-text · Conference Paper · Nov 2003
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    ABSTRACT: In this paper we present the development of hardware and software of self-reconfigurable modular robots in National Institute of Advanced Industrial Science and Technology (AIST), Japan. Thanks to their flexibility, versatility and fault-tolerance, self-reconfigurable modular robots are expected to be used in various application fields, such as space, rescue or micro-sized world. Our research group has been pioneering this new field and developed several hardware prototypes and corresponding software that exploit the robots' potential. We have been successfully demonstrated the feasibility of the self-reconfigurable modular robots based on experiments from different aspects. Starting from two-dimensional (2D) self-assembling and self-repairing machine fractum, we review hardware development in diverse directions, like to micro-world, three-dimensional (3D) structures and motions; as well as the progress of control software, including distributed control and recent evolutionary motion inquisition.
    Full-text · Conference Paper · Nov 2003
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    ABSTRACT: Locomotion, one of the most basic robotic functions, has been widely studied for several types of robots. As for self-reconfigurable modular robots, there are two types of locomotion; one type is realized as a series of self-reconfiguration and the other is realized as a whole body motion such as walking and crawling. Even for the latter type of locomotion, designing control method is more difficult than ordinary robots. This is because the module configuration includes many degrees of freedom and there are a wide variety of possible configurations. We propose an offline method to generate a locomotion pattern automatically for a modular robot in an arbitrary module configuration, which utilizes a neural oscillator as a controller of the joint motor and evolutionary computation method for optimization of the neural oscillator network, which determines the performance of locomotion. We confirm the validity of the method by software simulation and hardware experiments.
    Preview · Conference Paper · Oct 2003
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    ABSTRACT: In this paper we present a couple of evolutionary motion generation methods using genetic algorithms (GA) for self-reconfigurable modular robot M-TRAN and demonstrate their effectiveness through hardware experiments. Using these methods, feasible solutions with sufficient performance can be derived for a motion generation problem with high complexity coming from huge configuration and motion possibilities of the robot. The first method called ERSS (Evolutionary Reconfiguration Sequence Synthesis) applies GA (Genetic Algorithm) to evolution of motion sequence including configuration changes though natural genetic representation. The effectiveness of the generated full-body dynamic motions are verified through hardware experiments. The second method called ALPG (Automatic Locomotion Pattern Generation) Method seeks locomotion pattern using a neural oscillator as a CPG (Central Pattern Generator) model and GA to optimize the parameters for locomotion. A number of efficient locomotion patterns has been derived, which are also experimentally verified.
    Full-text · Conference Paper · Aug 2003
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    ABSTRACT: We have developed a modular robotic system (M-TRAN), which can change its configuration by itself. By using many DOFs of mechanism and self-reconfiguration capability, it can realize several types of motion, and can make various configurations. We have made two models of the system (M-TRAN I & II). In M-TRAN II, various improvements are integrated such as onboard multi-computers, reliable inter-module communication system, low power consumption, precise motor control, etc. Its hardware design, basic experiments and examples of motion are presented in this paper.
    Full-text · Conference Paper · Jan 2003
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    ABSTRACT: In this paper, a novel robotic system called modular transformer (M-TRAN) is proposed. M-TRAN is a distributed, self-reconfigurable system composed of homogeneous robotic modules. The system can change its configuration by changing each module's position and connection. Each module is equipped with an onboard microprocessor, actuators, intermodule communication/power transmission devices and intermodule connection mechanisms. The special design of M-TRAN module realizes both reliable and quick self-reconfiguration and versatile robotic motion. For instance, M-TRAN is able to metamorphose into robotic configurations such as a legged machine and hereby generate coordinated walking motion without any human intervention. An actual system with ten modules was built and basic operations of self-reconfiguration and motion generation were examined through experiments. A series of software programs has also been developed to drive M-TRAN hardware, including a simulator of M-TRAN kinematics, a user interface to design appropriate configurations and motion sequences for given tasks, and an automatic motion planner for a regular cluster of M-TRAN modules. These software programs are integrated into the M-TRAN system supervised by a host computer. Several demonstrations have proven its capability as a self-reconfigurable robot.
    Full-text · Article · Jan 2003 · IEEE/ASME Transactions on Mechatronics
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    ABSTRACT: Growing complexity of artificial systems arises reliability and flexibility issues of large system design. Robots are not exception of this, and many attempts have been made to realize reliable and flexible robot systems. Distributed modular composition of robot is one of the most effective approaches to attain such abilities and has a potential to adapt to its surroundings by changing its configuration autonomously according to information of surroundings. In this paper, we propose a novel three-dimensional self-reconfigurable robotic module. Each module has a very simple structure that consists of two semi-cylindrical parts connected by a link. The modular system is capable of not only building static structure but also generating dynamic robotic motion. We present details of the mechanical/electrical design of the developed module and its control system architecture. Experiments using ten modules with centralized control demonstrate robotic configuration change, crawling locomotion and three types of quadruped locomotion.
    No preview · Article · Jan 2003 · JSME International Journal Series C

Publication Stats

2k Citations
25.56 Total Impact Points

Institutions

  • 2002-2008
    • National Institute of Advanced Industrial Science and Technology
      • Intelligent Systems Research Institute
      Tsukuba, Ibaraki, Japan
  • 2003-2004
    • Japan Advanced Institute of Science and Technology
      KMQ, Ishikawa, Japan
  • 2002-2003
    • Tokyo Institute of Technology
      • Department of Computational Intelligence and Systems Science
      Edo, Tokyo, Japan
  • 1997-1998
    • Advance Institute of Science and Technology
      Dehra, Uttarakhand, India