Norihiko Kato

Design and control of a microrobotic system using magnetic levitation

Presents a prototype microrobot based on magnetic principles. Miniature items are to be transported and assembled in hazardous environments. A microrobot can be remotely operated with 3 DOF in an enclosed environment by transferring magnetic energy and optical signals from outside. The magnetic drive unit consists of 8 electromagnets (4 pairs), 2 permanent magnets, a return yoke and a pole piece. The microrobot is manipulated under the pole piece by regulating magnetic field. It consists of a magnetic head, a body (electronic circuit and batteries), and copper alloy ribbon ringers. A shape memory alloy actuator activates the fingers by illuminating/extinguishing several LED. PID controls were applied. To cope with uncertainties and variations in payload masses, an adaptive control law was also employed for positioning along the z axis to enable the controller parameters to be adjusted in real-time. Effectiveness of the control was verified by the results of several experiments. The microrobot has a net mass of 8.1 g and it can elevate and manipulate objects with masses up to 1.5 g within a volume of 29/spl times/29/spl times/26 mm/sup 3/ with a precision of 0.05 mm.

Development of underwater microrobot using ICPF actuator

It is our purpose to develop an underwater microrobot that has the characteristics of flexibility, driven by a low voltage, good response and safety in body. In this paper, we propose a new prototype model of an underwater microrobot utilizing ionic conducting polymer film (ICPF) actuator as the servo actuator. The fish-like propulsion using ICPF actuator as a propulsion tail fin for a microrobot swimming structure in water or aqueous medium is developed. The overall size of the underwater microrobot prototype shaped as a boat with a pair of fins is 40 mm in length, 10 mm in width and 2 mm in thickness. The characteristic of the underwater microrobot is measured by changing the frequency of input voltage from 0.1 Hz to 5 Hz. The experimental results indicate that the swimming speed of the proposed underwater microrobot can be controlled by changing the frequency of input voltage.

Mechanism configuration evaluation of a linear-actuated parallel mechanism using manipulability

The linear-actuated parallel mechanism that changes the motion characteristic according to the actuator configuration is known. The authors previously (2000) reported on the kinematics and the motion characteristic on the basis of the motion transmissibility. In this report, we analyze the changed in motion characteristics using the measures of manipulability. Indices of manipulability are given with components of the value determined by the singular value decomposition. The typical index is a volume of the manipulability ellipsoid. We clarify the features of the motion characteristics according to a change in the actuator configuration using these indices. Finally, we show the recommended application examples that are designed for mechanisms using the obtained result.

Performance improvement of a magnetically levitated microrobot using an adaptive control

This paper deals with an application of an adaptive control to a magnetically levitated microrbot. Using an electromagnetic device, a microrobot is levitated and manipulated within a 3-D space inside a magnetic field. The microrobot has two fingers that can grasp and elevate objects. PID controls are applied for positioning of the microrobot in the three axes. However, as the microrobot deals with various payloads, a PID control may not be sufficient to maintain the microrobot on high performance in the vertical axis. To improve the performance, an adaptive control law is also examined for the positioning in the vertical axis so that the controller parameters become adjustable in real-time to cope with uncertainties and variations in payloads. A model-reference adaptive system (MRAS) based on the augmented error is designed, and simulations and experiments are conducted to verify the effectiveness of the control. The simulation and experimental results for PID and adaptive control are shown for comparison.

A fish microrobot using ICPF actuator

It is our purpose to develop an underwater microrobot that has the characteristics of flexibility, driven by a low voltage, good response and safety in the body. We propose a prototype model of an underwater microrobot utilizing an ICPF (ionic conducting polymer film) actuator as the servo actuator. Biomimetic fish-like propulsion using an ICPF actuator as a propulsion tail fin for a microrobot swimming structure in water or aqueous medium is developed. The overall size of the underwater microrobot prototype shaped as a boat is 40 mm in length, 10 mm in width and 2 mm in thickness. There is a pair of fins. The characteristic of the underwater microrobot is measured by changing the frequency of input voltage from 0.1 Hz to 5 Hz. The experimental results indicate that the swimming speed of the proposed underwater microrobot can be controlled by changing the frequency of input voltage.

Path planning based on geographical features information for an autonomous mobile robot

We propose a path-planning algorithm for an autonomous mobile robot using geographical information, under the condition that the robot moves in an unknown environment. Images input by a camera at every sampling time are analyzed and geographical elements are recognized, and the geographical information is embedded in an environmental map. Then the path is updated by integrating the known information and the prediction on the unknown environment. We used a sensor fusion method to improve the mobile robots dead-reckoning accuracy. The experimental results confirm the effectiveness of the proposed algorithm as the robot reached the goal successfully using the geographical information.

Extension Force Control Considering Contact with an Object Using a Wearable Robot for an Upper Limb

Thousands of individuals of all ages are living with a spinal cord injury as a consequence of a traffic, or sports accident or other calamity, and many of these individuals incurred a C5-level spinal cord injury, with a loss of the ability to use their legs and exert extension force from the elbow joints. Many of the motions that are necessary in daily life are difficult or impossible to perform with this level of spinal cord injury, and it is expected that wearable motion-assist robots will someday be available for use by individuals with C5 injuries. In order to be wearable, an assist robot must not limit the users range of motion while being used, and it must be suitable for a wide range of situations. In the present study, we developed an extension force support system that acts in accord with the operators intentions under the effect of external force as the operator use a wearable motion-assist robot for an upper limb. The effectiveness of the developed system was demonstrated experimentally.

Instruction of arm motion for calligraphy using vibrotactile stimulations

Traditional craftsmanship should be handed on to the next generation. Introduction of mechatronics technologies has potential abilities for recording and replaying such craftsmanship. Up to now, there have been some trials to conserve the traditional craftsmanship. However, most of these trials have been aimed for only conservation. In this paper, the way of using brush in calligraphy is focused on as an example of traditional craftsmanship that requires proper motor skills. The authors proposed a method to instruct a masters calligraphic skill to an apprentice using vibrotactile stimulations. Four vibratory motors are attached on the surface of the apprentices hand, and these motors give vibrotactile feedback to the apprentice for correcting his/her inadequate motions. Here, it is expected that the vibratory motors work as an effective device for arm motion guidance. The apprentice moves the arm in the direction of an activated vibratory motor. In a pilot experiment with several subjects, the applicability of using vibrotactile stimulation was confirmed. In the following experiment, instructions of writing three kind of character were achieved by controlling the vibratory motors properly.

An Indicating, Leading Manipulator as a Good Hand at Teaching Strokes: A Mental-Image-Creation Support System.

A mental image creation support system was developed. The mechanical device of the system is a 3-DOF manipulator that is composed of a 2-DOF quadrilateral parallel-link manipulator and an arm-end actuator. A couple of servomotors drive a couple of upper links of the 2-DOF manipulator, and they control the arm-end position. The arm-end actuator is attached to the 2-DOF manipulator’s arm-end: a servomotor controls the orientation of a knob attached to the servomotor axis. The person is assumed to pinch the knob by his/her fingertips. The position of the knob axis traces the strokes of the presented figures sequentially, and the orientation of the knob is controlled to indicate the orientation of the currently tracing point on the stroke. A couple of preeminent functions are embedded to the process: one is the indicating function, and the other is the leading function. That is, the knob indicates to the person with its orientation to which direction the arm end moves: the direction reflects the orientation of the ongoing stroke. And the translation of the knob leads the person along the strokes. The indicating/leading functions play complementary role. Thus, the person is able to perceive the position and the orientation of the strokes of presented images via somatic sensations of his/her fingertip. It is expected to be a good hand at teaching strokes and to be a visual alternative of the blind persons and a visual aid of lazy eye persons at creating mental images.

An artificial fish robot using ICPF actuator

It is our purpose to develop an artificial fish robot that has characteristics of flexibility, driven by a low voltage, good response and safety in body. In this paper, we propose a new prototype model of an artificial fish robot utilizing ICPF (Ionic Conducting Polymer Film) actuator as the servo actuator. Biomimetic fish-like propulsion using ICPF actuator as a propulsion tail fin for an artificial fish robot swimming structure in water or aqueous medium is developed. The overall size of the artificial fish robot prototype shaped as a boat is 40 mm in length, 10 mm in width and 2 mm in thickness. There is a pair of platinum electrodes. Characteristics of the artificial fish robot are measured by changing the frequency of the input voltage from 0.1 Hz to 5 Hz. The experimental results indicate that the swimming speed of the proposed artificial fish robot can be controlled by changing the frequency of input voltage.