Nagoya University, Graduate
School of Information ScienceOhka Lab.

April, 2007
Reproduction forbidden
without our permission.

Three major projects

Sensing

Virtual Reality

Psychophysics

Address：Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
Nagoya University, Graduate School of Information
Science, Faculty of Complex Systems Science
Masahiro Ohka
In our laboratory, we are focusing our study Email: ohka@is.nagoya-u.ac.jp
in sensing, psychophysics and virtual reality,http://ns1.ohka.cs.is.nagoya-u.ac.jp/

which are cooperatively progressed.

Themes for master and doctoral theses
zPsychophysics on human tactilesensation
Human capability of sensing pressure and shearingforce
Human perceptive ability of the tactile coordinate

zTactile sensors

A brief history of three axis tactile sensor
Almost two decades are spent before we
successfully developed a three axis tactile
sensor using semiconductor processing, which
was the first succession in the world. In thepresent, we are expecting that the three-axis
tactile sensor is able to apply to a dexterous
hand.

A tactile sensor using CT algorithm
An optical three-axis tactile sensor
A tactile sensor using stochastic resonancezTactile displays
Two-axial micro actuators
Combined presentation of tactile and force
Combined presentation of pressure and shearingforce

zMobile robots
Cooperative behavior of collecting robots
Environment recognition of humanoid robots usingtactile sensing

1986-1993
Semiconductor
processing
In Fuji Electronic
Research andDevelopment, Ltd.

1993-2003
Opticalwaveguide
typed I

2004-the present
Opticalwaveguide
typed IIIn Shizuoka
Institute ofScience andTechnologyIn Nagoya
UniversitySelf-introduction

Two-axial micro actuator
Objectives
We are attempting to develop a high-end tactile display capable of presenting pressure
and slippage force caused on human finger surface. The two-axial micro actuator isused as a key part of the tactile display.
Principle of the actuator

Measurement
Bimorphpiezoelectric
actuator
Movable end

Displacement of the movable end ismeasured by image data processing
obtained by a micro scope.
Experimental results
Vertical and horizontal movement aregenerated by in-phase and out-of-phaseapplied voltages, respectively.
Neural control
The present
neuralnetwork isfeatured withintegral
elements anda feedback
connection.

Since characteristics of the left and rightactuators are different, two neuralnetworks are incorporated into thecontrol system to drive independently theleft and right actuators.

Left actuator

Right actuator

The difference between the left and rightactuators is well presented with the twoneural networks.
Applications

A tactile displace is composed of large
number of the present actuators. A micro
hand is composed
まとめ of a pair of the present
actuators

Psychophysics on human tactile sensation
TypeDensity

TemperaturedependenceHigh in finger tip

Weak

Low and constantMarkedHigh in finger tip

Weak

Low and constantMarkedAs shown in the above table, human mechanoreceptive units, FA I, FA II, SA I, SA II, havedifferent temperature dependence. Difference of density between finger tip and thenar
depends on the type of mechanoreceptive unit. Using these characteristics, we examine
psychological response of mechanoreceptive unit caused by several stimuli and differenceof environment condition. Remarks obtained by this study is utilized for evaluation of tactile
display and modeling of human tactile sensation.

Tactile display

We have developed several tactile display composed of bimorph piezoelectric actuators
combined with a master manipulator (the left figure) and a tactile mouse produced by FujiXerox (the right figure). These tactile displays are utilized for experiments of virtual reality
such as virtual peg-in-hole and virtual texture recognition.

Tactile sensor
load
SpecimenIR-light

Rubber sheet
Acrylic board

Photo transistor
Support plate
Hemispherical projection

In the left sensor, IR-light absorption caused between an IR-diode and a photo-transistor ismeasured to identify the applied force. One dimensional distribution of the absorption isreconstructed according to computer tomography algorithm to obtain pressure distribution.
The right panel shows an optical three-axis tactile sensor, which is attempted to be attached
on a fingertip of a robotic finger. 41 red rubber feelers arranged on the hemispherical finger
tip measure distribution of three-axial force.

Multi-fingered hand

Since the three-axis tactile sensor can measure not only normal force and but also shearing
force, the robot can grasp an object without dropping the object. However, if the robotgrasps any object with same grasping force, the robot crushes a soft object as shown in theleft panel. To overcome this problem, the robot measures hardness of the object at firsttouch, and grasps the object with adjusted grasping force according to the hardness asshown in the right panel

Collective robotics
Sensor input

Motor output

S1

S2

S3

S4

S5

L1

L0

R1

R0

0

0

0

00

101

10000

1

1000000

100000Goal area
Agent 4・・・1

111

1000Object

1

Agent 1Agent 2
L1L0R1R0L1L0R1R0L1L0R1R0101110000000・・・

L1L0R1R00001

Agent 3

Length of gene locus : 32 × 4 ＝ 128 [bit]In this project, we are developing an artificial mechanism to make a robot acquireautonomously its behavior pattern. We define a gene comprised of sequence of 1 and 0(128-bits), which represents multi-sensor status and multi-actuator status as shown in the leftpanel. We evolve the gene using GA（Genetic Algorithm) to make collective robots convey
efficiently an object to a specified place. The right panel shows that 4 robots equipped withthe optimum gene covey cooperatively an object to a goal.

Humanoid robotics

YaｗZRolXPitch
YWe are using tactile sensation in a dark place, when we search a switch on the wall. In thisproject, we are examining a method to make the robot acquire environmental information
using tactile sensing. The left panel shows a humanoid robot BontenMARU II produced byNasu Lab. in Yamagata University, which is used in this project. The right panel shows anarm unit, which is used for a testing and equipped with robotic fingers.