Microfluidic and pneumatic logic systems are valuable for applications such as lab-on-a-chip devices, soft robotics, and factory automation. These systems are particularly advantageous when metal or electronic components are impractical or when there are constraints on the control system volume or weight. This paper introduces a novel individual membrane valve that functions as a set-reset latch and can reduce the number of valves required for some pneumatic or microfluidic logic systems. An application of pneumatic logic systems in soft robotics is the access to multiple tethered pneumatic elements through a reduced number of pneumatic lines. To this end, this paper proposes two pneumatic logic systems capable of selecting among multiple distributed sets of pneumatic elements and operating the elements of the set simultaneously and independently through the different pneumatic lines. The selection is achieved via a sequence of pressure pulses applied on the same lines used afterwards for operation. Two prototypes of these pneumatic logic systems were built and successfully demonstrated, consisting primarily of set-reset membrane valves and powered by binary high/low pressure sources. The first prototype features a hierarchical network with four lines and five sets of three pneumatic elements each; the second prototype features a non-hierarchical network with five lines and twelve sets of four pneumatic elements each.

Time division multiple access (TDMA) based on a pulse-coupled oscillator (PCO) model is promising for avoiding collisions in wireless communication networks. In this scheme, to keep the convergent states of node phases in the network, nodes must mutually communicate continuously. Convergent states are broken when the continuous communication is inhibited by, e.g., sleeping. Then a converging process must be conducted again. As described in this paper, we introduce a conservative sleep and wake-up control method that preserves the convergent states of node phases for energy savings. Its effectiveness is evaluated based on an order parameter of desynchronization through simulation. We also assess effects of network configuration change and clock variation.

Mobile robots of various types have been proposed for infrastructure inspection and disaster investigation. For such mobile robot applications, accessing the areas is of primary importance for missions. Therefore, various locomotive mechanisms have been studied. We introduce a novel mobile robot system, named DIR-3, combining a crawler robot and a microdrone. By rotating its arm back and forth, DIR-3, a very simple, lightweight crawler robot with a single 360-degree rotatable U-shaped arm, can climb up/down an 18 cm high step, 1.5 times its height.Furthermore, to inspect high places, which is considered difficult for conventional mobile robots, a drone mooring system for mobile robots is presented. The tethered microdrone of DIR-3 can be controlled freely as a flying camera by switching operating modes on the graphic user interface. The drone mooring system has a unique tension-controlled winding mechanism that enables stable landing on DIR-3 from any location in the air, in addition to measurement and estimation of relative positions of the drone. We evaluated the landing capability, position estimation accuracy, and following control of the drone using the winding mechanism. Results show the feasibility of the proposed system for inspection of cracks in a 5 m high concrete wall.

This paper discusses the refinement of sparse and noisy depth-maps to improve stereo measurements. Our method functions as a post-filter for stereo measurements, to remove outliers and interpolate the depths of invalid pixels. Per-pixel plane fitting is employed to estimate the normals of an object's surface in a depth-map. These normals provide information regarding the interpolation of depth and the removal of outliers by evaluating the directions of surfaces. In our experiments, our method successfully reconstructed a dense and accurate geometry from a sparse and noisy depth-map, even where several dozen percent of pixels were outliers and only a few percent were from the original correct geometry. This result indicates a novel method of fast stereo measurement, because dense reconstruction can be performed without stereo matching for all pixels.

This paper describes a P2P wireless network framework with numerous nodes that can communicate with their neighbors in a stable condition with no collisions of transmissions. Under the network convergence state, every node transmits periodically in order with a cycle shared in the network. To realize that situation, we apply a pulse-coupled oscillator technique to shift the timing of transmission of each node to avoid overlapping with neighboring nodes' transmissions. Additionally, we propose an algorithm to find the suboptimal transmission cycle, preferred small for faster communication, depending on the number of nodes and the network topology based on a class of chromatic number problem in graph theory. We developed a multi-thread simulation platform for multiple node communications to verify the algorithm. Results demonstrate its feasibility both with simulations and with real devices by implementing the method onto an omnidirectional infrared communication device and an RF long-distance communication device.

This article shows how self-description can be realized for construction and computation in a single framework of a variant of graph-rewriting systems called graph-rewriting automata. Graph-rewriting automata define symbol dynamics on graphs, in contrast to cellular automata on lattice space. Structural change is possible along with state transition. Self-replication based on a self-description is shown as an example of self-description for construction. This process is performed using a construction arm, which is realized as a subgraph, that executes a program described in the graph structure. In addition, a metanode structure is introduced to embed rule sets in the graph structure as self-description for computation. These are regarded as universal graph-rewriting automata that can serve as a model of systems that maintain themselves through replication and modification.

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.

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.

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.

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.

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.

Previous work on self-reconfiguring modular robots has concentrated primarily on hardware and reconfiguration algorithms for particular systems. We introduce a type of generic locomotion algorithm for self-reconfigurable robots. The algorithms presented are inspired by cellular automata, using geometric rules to control module actions. The actuation model used is a general one, presuming that modules can generally move over the surface of a group of modules. These algorithms can then be instantiated on to a variety of particular systems. Correctness proofs of the rule sets are also given for the generic geometry, with the intent that this analysis can carry over to the instantiated algorithms to provide different systems with correct locomotion algorithms.

We have proposed a self-reconfigurable robotic module, which has a very simple structure. The system is capable of not only building a static structure, but also generating a dynamic robotic motion. We have also developed a simulator for the motion planning. In this paper, we present details of the mechanical and electrical designs of the developed module and its control system architecture. Experiments using ten modules demonstrate the robotic configuration change, crawling locomotion and three types of quadruped locomotion.

This paper addresses motion planning of a homogeneous modular robotic system. The modules have self-reconfiguration capability so that a group of the modules can construct a robotic structure. Motion planning for self-reconfiguration is a kind of computationally difficult problem because of many combinatorial possibilities of modular configuration and the restricted degrees of freedom of the module; only two rotation axes per module. We will show a motion planning method for a class of multimodule structures. It is based on global planning and local motion scheme selection that is effective to solve the complicated planning problem.

This paper concerns the elimination of higher type quantifiers and gives two theorems. The first theorem shows that quantifiers in formulae of a specific form can be eliminated. The second theorem shows that quantifiers in formulae of a similar form cannot be eliminated, that is, such formulae do not have an equivalent first-order formula. The proof is based on the Ehrenfeucht game. These theorems are important for design of an interpreter of a ν act, which is a representation of mathematical action. Moreover, even if the universe is assumed to be finite, these theorems hold.

In this paper we describe the hardware design of a novel self-reconfigurable robotic system. We have classified previous studies on self-reconfigurable robotic systems into "lattice type" composed of spatially symmetric modules and "string type" like snake robots. The proposed system has both the advantages of simple operation of self-reconfiguration of the former and motion generation ability of the latter. Its simple structure and reliable operation allows us to construct large 3D self-reconfigurable structure which functions as a robotic system such as a legged walking machine. We have examined its basic mechanical functions and verified its reliable operation of self-reconfiguration.

Presents a miniaturized self-reconfigurable modular robotics system using shape memory alloy (SMA). The system is designed so that various shapes can be actively formed by a group of identical mechanical units. The unit realizes rotational motion by using an actuator mechanism composed of two SMA torsion coil springs which generate sufficient motion range and torque for reconfiguration. The fundamental functions of the system are tested by experiments. Applicability of the developed unit model to a 3-D self-reconfigurable system is also discussed.

We propose a self-assembly and self-repair method for a homogeneous distributed mechanical system. We focus on a category of distributed systems composed of numbers of identical units which can dynamically change connections among themselves. Each unit has an onboard microprocessor, and local communication between neighboring units is possible. We discuss a distributed method for a group of such units to metamorphose from an arbitrary configuration into a desired configuration through cooperation by the units. This process, called self-assembly, is realized by identical software on each unit with local inter-unit communication. An extension of self-assembly, self-repair, is also examined. In this process, an occasional cut-off of an arbitrary part of the system is assumed. When some part of the system detects damage, the whole system degenerates and reconstructs itself. Computer simulations show the feasibility of self-assembly and self-repair.

A three-dimensional, self-reconfigurable structure is proposed. The structure is a fully distributed system composed of many identical 3-D units. Each unit has functions of changing local connection, information processing, and communication among neighborhood units. Groups of units cooperate to change their connection so that the shape of the whole solid structure transforms into an arbitrary shape. Also, the structure can repair itself by rejecting faulty units, replacing them with spare units. This kind of self-maintainability is essential to structure's longevity in hazardous or remote environments such as space or deep sea where human operators cannot approach. We have designed and built a prototype unit to examine the feasibility of the 3-D self-reconfigurable concept. The design of the unit, method of reconfiguration, hardware implementation, and results of preliminary experiments are shown. In the last part of the paper, distributed software for self-reconfiguration is discussed.

A three-dimensional self-reconfigurable structure made of identical units is proposed. Each unit has six arms on the surface of its base cube which can connect to neighboring units mechanically. By the connection, cubic lattice structure is formed. A unit can carry its neighbor unit from one node of the lattice to another by rotating its arm by 90 degrees. Repeating this movement, the structure can reconfigure itself to realize various 3D structures. General process of reconfiguration were proposed for this system. Four units were made and basic motions of self-reconfiguration were verified.

A distributed reconfiguration method is proposed for a 3D reconfigurable machine, composed of many identical mechanical units. The method aims to enable the machine to transform itself into desired structure from an arbitrary initial configuration. The proposed method is implemented in such a way that each unit has identical software, so that any unit can play any role in the system. It is also featured by a stochastic relaxation process, which allows the system to converge to a given target structure by searching for a proper unit motion over many degrees of freedom. Furthermore, the method is extended for the structure to reconfigure itself dynamically according to the environment. The effectiveness of the method is confirmed by computer simulations.

A distributed formation control method is proposed for a modular mechanical system. We have developed a totally decentralized system composed of many homogeneous mechanical units which are designed to change their connective configuration using only local information. The control method proposed in this paper enables the systems to re-organize themselves so that various configurations can be formed in a robust way. Computer simulations and experiments are carried out to show its effectiveness.