This special issue in Robotica contains papers from Japanese authors on microrobots and distributed microactuators. Advances in technology made possible progress in the realm of small but complicated microsystems that include different elements, such as sensors, circuits and actuators. Microsystems are also called micromachines or microelectromechanical systems (MEMS); microsystems which move like insects are termed microrobots.

This paper discusses suitable mechanisms and functions of a mobile microrobot from the point of view ofscale effects. Several assumptions are made using animalscaling. A large scale model is shown to demonstrate these mechanisms. Moreover, microsized models have been built on silicon wafers by using polysilicon as rigidplates and polyimide as elastic joints. The results showthat suitable mechanisms and functions may be different from those of a conventional robot.

Recent topics in the development of micromagneticactuators in Japan are reviewed. Electromagneticmicroactuators less than 1 mm in diameter, e.g.micromotor, and microvalves have been fabricated andtheir high performance has been demonstrated. A newtype microactuator based upon magnetostriction has alsobeen developed and has shown a large cantileverdeflection. In addition, some models of the microrobotsusing micromagnetic actuators were able to move using awireless remote power supply.

A bending and expanding motion actuator which iscomposed of multi-layered PZT unimorph cells has beendeveloped. These cells are piled one against another.Each cell's electrode is divided into three sectors and thefacing sectors are connected to one another. Multidirectionalbending is realized by controlling the drivingvoltage of each sector. The actuator is 12 mm indiameter, 20 mm in length and 6.4 g in weight with 40cells. The bending angle was 2.2 degrees, and the expansion displacement was 700 μm with 150 V. The resonant frequency was 95 Hz at 25 V.

This paper proposes and demonstrates a method toobtain macroscopic work out of distributed microactuatorsfabricated by IC-compatible micromachiningprocesses. We have coordinated the simple and smallmotion of microactuators in order to perform a task. Theconcept and a control scheme are discussed first. In orderto show the feasibility, the fabrication and operation ofarrayed microactuators for conveyors are described. One uses thermally driven cantilevers and the other uses controlled air flow from micronozzles to carry flat objects.

The flexible microactuator (FMA) is a novel pneumaticrubber actuator developed for use in microrobots. Thispaper reports on integrated FMA systems to achievedistributed motion as occurs in intestinal villi, and withmulti-legged arthropods such as centipedes.

For the purpose of miniaturization and integration of FMAs, the authors focussed on two technical issues: A new fabrication process based on stereo lithography and a new FMA design called a restraint beam FMA. Stereo lithography enables fabrication of micro-structures with rubber-like materials suitable for integrated FMAs. The restraint beam FMA makes it possible to fabricate FMAs from a single material, allowing stereo lithography to be used.

As examples of integrated FMA systems, four prototypes are shown: a 5 × 5 FMA array, a 3 × 3 FMA array which has pneumatic circuits at its base, a pipe interior mobile robot, and an amusement system consisting of 30 FMAs, which demonstrates ball handling ability.

A prototype of a catheter which can move like a snake, incorporating distributed shape memory alloy actuators, is described. Since this active catheter has an instrumental navigation ability, minimally invasive diagnosis and interventional therapy will be possible. The outer diameter of the active catheter is 2.8 mm and it has many links fabricated by 3-dimensional silicon micromachining. The silicon batch process was used for the fabrication of the link to minimize assembly work. A new heating method (indirect heating) is suggested which is necessary when the JC chip is mounted on the link.

To perform dextrous manipulation efficiently, it is necessary to coordinate the interactions of many component processes. This paper investigates one approach to coordination: discrete-event systems. The applicability of discrete-event systems to the modeling of dextrous manipulation tasks is studied. Discrete-event control theory offers formal methods for determining whether a coordinator of the components can be generated. A representative dextrous manipulation task, the planar Grasp-Lift-Replace task of Howe and Cutkosky, is presented as a discrete-event process. The task is extended to include two-fingered exploratory procedures. The effectiveness of the discrete-event system approach is illustrated through simulations of several test cases.

A new model for the construction of a sonar map in a specular environment has been developed and implemented. In a real world, where most of the object surfaces are specular ones, a sonar sensor surfers from a multipath effect which results in a wrong interpretation of an object's location. To reduce this effect and hence to construct a reliable map of a robot's surroundings, a probabilistic approach based on Bayesian reasoning is adopted to both evaluation of object orientations and estimation of an occupancy probability of a cell by an object. The usefulness of this approach is illustrated with the results produced by our mobile robot equipped with ultrasonic sensors.

A novel off-line technique for automatic calibration of kinematic parameters for hydraulic manipulators is presented. Hydraulically actuated manipulators have joints which are always powered and, unlike conventional robots, may not have conventional joint sensors to exploit in the calibration procedure. Instead, our approach employs an external three-dimensional linkage, termed “the calibrator”, which has sufficient number of joints with corresponding sensors. One end of the calibrator is grasped by the manipulator's end effector while the other end is attached to a passive spherical joint fixed to the world coordinate system. The mobile closed kinematic chain thus formed has the added advantage of eliminating the explicit measurement of the manipulator's endpoint location. A sequential identification technique that uses a least squares numerical search algorithm has been developed based on link-by-link movement of the manipulator. Simulation and experimental calibration results on a typical mobile hydraulic manipulator are reported in this paper, which show that the proposed technique is globally stable, and potentially fast, inexpensive, and easy to apply on site.

A grid-based method for detecting moving objects is presented. This method involves the extension and combination of two methods: (1) the Hough Transform and (2) the Occupancy Grid method. The Occupancy Grid method forms the basis for a probabilistic estimation of the location and velocity of objects in the scene from the sensor data. The Hough Transform enables the new method to handle non-integer velocity values. A model for simulating a sonar ring is also presented. Experimental results show that this method can handle objects moving at non-integer velocities.

The main objective of this paper is a presentation of an experimental identification of a non-direct drive robot and load dynamic parameters, which appear in the integral model. The last one is based on the energy theorem formulation. In the robotics literature there are not many experimental results known to the authors, concerning the identification of the dynamic parameters of different models. In order to satisfy this, the experimental system has been built around an industrial ASEA IRp-6 robot. In this paper we propose to precompute the friction characteristics which are separated in the integral model. Various aspects of the exciting trajectories are considered. It is shown how to identify the friction coefficients using a short integral model. The experimental results are presented, including comparison of the results for both integral and differential identification. The identified models are verified by computing the predicted torques and trajectories

Learning in the age of information superhighway necessitates a properly-developed efficient vehicle that is not only powerful in directing users to the needed information or to situate in a reality through virtual settings, but also controllable at the various comfortable paces. The goal of this project is to explore a new on-line medium for users to navigate at their own pace in the structured cyberspace—knowledge space composed of concepts, systems design, application-oriented case studies, up-to-date industrial news (trends and product review), and on-line robotic systems, and to use it as a robotics work-bench for conducting controllable experiments/simulations. Through such an electronic learning medium, users will be able to acquire a global outlook as well as an integrated understanding of modern robotics in a manner that is low-cost, time-and-place-free, and student-centered.