1

Abstract — A robot-eye system with a similar control system tothe synthesized binocular motor system model based onphysiological and anatomical fact is built. The robot-eye systemshows some special characteristics that exist in human-eyemovements but have not been realized in conventional robot eyes.The main characteristics of the robot-eye system are:(1) The both eyes will not gaze at two different targets at thesame time, i.e. the both eyes move in tandem and have the sametarget in the central pits. This characteristic is considered a basiccondition for structuring stereo-image using the image signalsfrom both eyes.(2) If one eye is shut or obstructed by an obstacle, the eye willfollow up the movement of the other eye so that it can find thetarget swiftly when the eye is opened or the obstacle is removed.(3) The binocular motor system can realize VOR not only forhead rotation, but also for head translations in order tocompensate for the blurs caused by head movements. (250 words)

Index Terms-- binocular motor system model, robot, conjugateeye movement, vergence eye movement, VOR.

I. INTRODUCTION

nlike chameleon eyes, human eyes cannot gaze at twodifferent targets at one time. Instead, a human’s eyes can

easily catch the same point of the subject at both central pitsand use the two symmetrical images from both retinas toproduce a stereovision space in the visual cortex. In this paper,the point viewed is called a target. We call the ability to gaze atthe same target by both eyes simultaneously as “same pointgazing tendency,” and we believe it to be one of the basicconditions for structuring a stereovision in the visual cortex.The proposed robot-eye system, consisting of the same controlsystem as the binocular motor model described in the last paper[17], will demonstrate such a characteristic. Human eyes always show conjugate movement, even whenone eye is shut or blocked by an obstacle. An obvious functionof the characteristic is that when the eye is opened or theobstacle is taken off, the eye will follow up the target pursuedby the other eye quickly. The conjugate eye movements arerealized using the proposed robot-eye system. Because the eyesof the robot-eye system are not fixed to each other likeconventional robot eyes [1]-[3], they also could performvergence eye movement simultaneously. To obtain 3-D information about an object, active visualsensors have been used in conventional researches, with goodresults [5]-[12]. However, the most active visual sensors use

This study was presented in part in proceedings of the 15th symposium onBiological and Physiological Engineering, sponsored by SICE, Japan, in2000.

The authors are with the Faculty of Medicine, Tokyo Medical and DentalUniversity.

independent systems to control each eye. So these visual sensorsystems can not realize the human characteristics outlinedabove. To fix the optical lines on the target on the head movement,the vestibulo-ocular reflex (VOR) plays an important role inthe ocular motor system. Wagner R, Galiana H and others hadproposed binocular motor robots, which realized VOR for headrotations [13], [14]. In the last paper, we proposed a binocularmotor system model that included VOR mechanisms not onlyfor head rotation (VOR-R) but also for head translation(VOR-T, conventionally named as the otolith-ocular reflex [4]).In this paper, we use our robot-eye system to realize all types ofVOR in horizontal eye movement.

II. STRUCTURE OF THE ROBOT-EYES SYSTEM

In this research, we constructed a binocular motor controldevice (robot eyes) with the same system structure as thebinocular motor system model that we had proposed on thebasis of the anatomic structure and physiological function ofthe brainstem [17], as shown in Fig.1. This robot has 2 degrees of freedom for each “eyeball” and 1degree of freedom for the neck. DC motors are used as theactuators (Maxson DC motor, 2322-982-52-235-200 foreyeballs, and M99051-A-1 for neck, Swiss made). The imagesignals from cameras (CCD camera, TOSHIBA IK-CU43) aretaken into the computer via an image processing board(MATROX METEOR II). The target’s position and velocityrelated to the optical line (camera’s central line) can beobtained by image processing using the computer. The resultsof the image processing are transferred in real time through aPIO board to the computer used for robot control. The rotaryangle of each motor can be detected using its own encoder(MTL, MEH-20-2000, Japan). The encoder in the neck motorwill be substituted for the horizontal semicircular canals.Figure 2 is the exterior of the robot-eye system. Figure 3(a) is the layout of the robot eyes. Figure 3(b) is thecoordinate system of the robot eyes. In Figure 3(b), OE-l andOE-r are the origins of coordinate systems for both cameras(xE-l-yE-l-zE-l, and xE-r-yE-r-zE-r, we called them as eyeball fixedcoordinate system). OE-l is defined at the crossing point ofmotor 1 and motor 3, xE-l-axis is defined on the central line ofleft camera, and yE-l-axis is defined on parallel with lateralpixels line of the CCD camera. The right camera fixedcoordinate system xE-r-yE-r-zE-r is similar to the left one. The leftorbit fixed coordinates systems (xO-l-yO-l-zO-l) is defined as inFig. 3(b), where yO-l-axis is defined on the axis of motor 3, andzE-l-axis is defined on the axis of motor 1. The right orbit fixedcoordinates systems (xO-r-yO-r-zO-r) is similar to the left.

A Robot-Eye Control System Based on Binocular Motor Mechanism

Xiaolin Zhang and Hidetoshi Wakamatsu, Member

U

2

Motor 3

Motor 0

Binocular axescontrol device

Motor 1

Motor 2 Target

PIO board

Counter & D/A board

Motor drivers

CCD camera

Motor 4

Image processing board

Fig. 1 Structure of robot eyes according to binocular motorsystem model

Computer for motor control

Computer for image processing

Pictures from eyes TargetRobot-eye

Motor drivers

Board unit

Image processing monitor

Motor control monitor

Fig.2 Entire exterior of robot-eyes system

OH is the origin of the head-fixed coordinates system (xH-yH-zH)which is defined at the point of the axes of motor 0 crossed tothe horizontal plane through OE-l and OE-r. OB is the origin ofthe base coordinates system (xB-yB-zB). Since we consider only horizontal eye movements, thecontrol loops of motor 3 and 4 will not be explained here, i.e.the translation of the head in zH axis direction and θ3, θ4 willnot be considered. So, the horizontal coordinate systems of Fig.3(a) are drawn in Fig. 4. Since the robot-eye system has nodegree for translation, in the real system xh = 0, yh = 0. In theexperiments of the case of head translation, xh(t), yh(t) and“retinal slip” (ϕD-l, ϕD-r), will be given by computer directly.From Fig. 4, the desired values of each eyeball are given as thefollowing equations:

( )( )heheht

hehehtl trtxtx

trtytytt

ϕθϕθ

θϕ+−−+−−

−= −

)(cos)()()(sin)()(

tan)()(0

010

(1)

( )( )heheht

hehehtr trtxtx

trtytytt

ϕθϕθ

θϕ−−−−−−

−= −

)(cos)()()(sin)()(

tan)()(0

010

(2)

Motor 1Motor 2

Motor 0

Motor 3Motor 4

Camera 2 Camera 1

xE-r

yE-r

zB

xH

yHzH

zE-rxE-l

yE-lzE-l

xO-r

yO-r

zO-r

xB

yB

xO-l

yO-lzO-l

θ0 θ2

θ1

θ4

θ3

OB

OHOE-l

OE-r

(a) Robot-eyes layout (b) Coordinate framesFig. 3 Structure of robot eyes

xH

yH

rheϕhe

Base coordinates

xB

yB

Bx′

By′

θ0

yh

xh

OB

Tg

yt

xt

ϕht

xO-l

xE-l

yE-r

θ1

ϕl

yO-l

yO-r

yE-l

θ2

ϕr

rht

The right CCD camera

The left CCD camera

ϕC-l

ϕC-rOH 0θ

Fig. 4 Horizontal coordinate systems for robot-eye systems

Target of labile number 1

Fastest object in the visual field

Background position

Central pit

Edge of the target The moving objectsin the visual field

Left Eye Image Right Eye Image

Fig.5 The results of image processing

3

-sk

sk

k di

p ++

-sk

sk

k di

p ++

)(tlϕ

)(trϕ

-

-

s1

s1

+

+

+-

+

−

ρ

rρ

rρ

+

−

+

-

+

+

+

)(toθ&

srr ησ +sησ +

sησ +

srr ησ +

ρ

Image processing results (camera 1)

Image processing results (camera 2)

)(tyh& ryy κκ +

+

+)(txh&

)(20 tθ& ( )ryy

hv

sr

κκ −

rxx κκ −

−+

rxhvxhv rr κκ +

rϕϕ κκ +

−

+

)(1 tθ

)(2 tθMotor 2

Motor 1

−1

+

+

Motor control systems

ϕC-l

ϕC-r

Fig. 6 Block diagram for robot-eye control system [17]

)(tlϕ

)(trϕ

-

-

s1

s1

+

+

+-

-

+

ρ

rρ

rρ

+

−

+

-

+

+

+

)(toθ&

srr ησ +sησ +

sησ +

srr ησ +

ρ

)(tyh& yδ

)(txh& xδ

−ϕδ

−

+

)(1 tθ

)(2 tθ−1

Generated by computer

ϕC-l(t)

ϕC-r(t)Fig.7 Simplified block diagram of robot-eye system

III. IMAGE PROCESSING FOR THE ROBOT EYES

For this paper, we used a white ball as the target of therobot-eye system. Image processing includes: 1) obtaining thegray-level histogram, 2) binalization using the histogram, 3)edge extraction, 4) circles detection using Houghtransformation, 5) checking the color of original image in thecircles, 6) labeling the extracted circles, 7) calculating thevelocity of the circles, 8) detecting the background movement,9) detecting the moving object related with background. Figure5 shows an example of the display of the computer for imageprocessing. The mark + is the position of the target which labilenumber is 1, obtained through the previous methods 1)-7). Themark 〇 represents the object that is moving fastest in thevisual field. The arrows at each side of the visual fieldsrepresent the position of the background. It is not the mainobject to introduce the image processing in detail here. In thefollowing experiments, only the target’s position and itsvelocity are used. The processing cycle time is about 66-166ms.

IV THE CONTROL SYSTEM FOR THE ROBOT EYES

The binocular motor model we had proposed on the basis of theanatomic structure and physiological function of the brainstem

is shown in Figure 6 [17]. The motor control systems (in thedashed-line boxes) are based on the PID control law, and theparameters of PID control are defined by the ultimatesensitivity method. The sampling time is 3ms. As the motorcontrol systems are accurate enough compared with the imagedetecting errors and delays, in this paper, we may to considerthe transfer functions of motor control systems as 1. Set κy=κyr,the influence of centrifugal force will be canceled, and unifythe parameters as,

xrvexver rr κκκκδ ϕϕϕ −−+=

xrxx κκδ −= , yryy κκδ +=

Figure 6 can be simplified as Fig.7.From Fig.7 the following equation is obtained.

−

−+

−+−

−=

)(

)(

1)()(

2

1

sxsx

sss

h

h

rr

r

x

&&

ηηρρ

σσ

δθθ

−−

−+

−+−

−+−+

)()()()(

121

ssss

s

ss

lr

rl

rr

r

rr

ϕϕϕϕ

ηηρρ

σσ

ηησσ

++

+++

−)()(

1

1

0 ssy

s

h

y

y

rr

r

θδδδδ

ηηρρ

σσ ϕ

ϕ

&&

++

++

+++

++++

)()()()(

121

ssss

s

ss

lr

rl

rr

r

rr

ϕϕϕϕ

ηηρρ

σσ

ηησσ (3)

Since the robot-eye system has only one encoder to detectthe rotational angle of head θ0, and no sensor is designed todetect the head translation xh and yh, in this paper the inputsignals hx& and hy& are generated by the computer directly.

From (3), a sufficient condition can be obtained as thefollowing equation [17]:

0,0,,, >>>>> yxrrr δδηησσρρ (4)

Here set

rρρδϕ +

=1 　 (5)

4

Since when (5) is stand the VOR-R will show the bestperformance [17]. According to equation (4) and (5), here defined that δϕ=0.5，ρ = 1.5, ρr = 0.5, δx=0.1 rad./m, σ = 1, σr =0.5, η = 0.5, ηr=0.2,δy＝1.2 rad./m. All those parameters were selected by theexperiments repetitively. In the initial state, the xH and yH axis of the head fixedcoordinate system of the robot-eye system are set to accord thebase coordinate system, and the xE and yE axis of the eyeballfixed coordinate systems are set to accord the orbit fixedcoordinate systems, i.e.

rad0)(,rad0)(,rad0)(,m0)(,m0)(

210 =====

ttttytx hh

θθθ.

The target position is set at xt(0) =1 m, yt (0) = 0 m.

V EXPERIMENTS TO CONFIRM CHARACTERISTICS OFCONJUGATE AND VERGENCE EYE MOVEMENT

A. The characteristics of same point gazing tendency The faculty of conjugate eye movement means that two eyescannot look at different targets at the same time. The skillfulrelation of conjugate and vergence movement of human eyescause the abilities, such as that both eyes can easily catch thesame target on the central pits of the retinas. In this experiment,we will confirm the occurrence of the same point gazingtendency in the robot eyes. The circumstances of the experiments are shown in Fig. 8,and the movies can be downloaded from our homepage [18].First, fix the head, set a fixed target in front of the head, thenshow a pendulum swinging from right to left. The weight on thetop of the pendulum with the same shape as the first targetbecomes the second target. The experiment was repeatedcountless times. Each time, both eyes simultaneously looked atonly one target, either the first or the second. One of theexperiment results is shown in Fig. 9, which shows the momentthat both eyes moved their gaze from the first to the secondtarget. For easy explanation, in Fig. 9 draw the desired values ϕl andϕr calculated geometrically. Where 1ϕl and 1ϕr in Fig.9 are thelocus of the first target related to each eyeball, 2ϕl and 2ϕr arethe locus of the second target, and ϕC-l(t) and ϕ C-r(t) are the“retinal slips” (errors detected by image processing). The t1

shown in Fig. 9 is the instant that shows the second target to therobot eyes. The t2 is the instant that the left eye recognizes thesecond target, and from t3 to t5, the left eye loses its target. t4 andt5 are the instants that the right eye and the left eye recognizethe second target. Fig. 9 shows when the left eye recognizes thesecond target at t2, the left eyeball (θ1) begins to leave the firsttarget and pulls the right eyeball (θ2) to leave the first target too.This causes the right eye to recognize the second target (theobject near the central pit will be processed in priority). Thereare cases when the right eye does not recognize the secondtarget and pulls the left eyeball to recognize the first targetagain. Nevertheless, the optical lines of the eyeballs separateslowly and for only an instant when the two eyes recognizedifferent targets, and they will tend to move together soon.

(a) Showing a first target (b) Showing the second target

Fig. 8 Circumstances of the experiments of same pointgazing tendency [18].

-10

0

10

20

0 1.5 6.0 9.0-20

-10

0

10

4.5 7.5 10.5t1

t2

t3

t4

t5

Lef

t eye

pos

ition

(deg

)

Time (Sec)

Rig

ht e

ye p

ositi

on (d

eg)

-50

5

05

1ϕl(t)

θ1(t)

2ϕl(t)

-5

1ϕr(t)

θ2(t)

2ϕr(t)

Lef

t ret

inal

slip

(deg

)R

ight

retin

al s

lip (d

eg)

ϕC-l

ϕC-r

Fig. 9 The characteristic of eye movement by which twoeyes gaze at only one target at the same time.

B. The characteristic when one eye is prevented from viewingthe target When an eye is shut or the target is blocked with an obstacle,the eye will move with the other eyeball. This characteristic letsthe eye follow up to the target quickly when the obstacle isremoved. The following experiment confirms the occurrenceof conjugate eye movement: Fix the head and set a target on the top of a pendulum, thenswing it from right to left in front of the head. Thecircumstances of the experiments are shown in Fig. 10. One ofthe experiment results is shown in Fig. 11. In the term of t1 to t2,

the left eye is intercepted using a mask as shown in Fig. 10 (a).Figure 11 shows that even though the left eye cannot follow thetarget accurately while it is blocked, it follows up the targetvery smoothly when the mask is taken off.

5

(a) Shutting the left eye (b) Taking off the obstacle

Fig. 10 The circumstances of the experiments ofobstructing one eye’s view for a moment [18].

Time (Sec)

Lef

t eye

pos

ition

(deg

)R

ight

eye

pos

ition

(deg

)

0

10

0 3 6 9 12 15

0

10

0

0

2.5

-2.52.5

-2.5

t1 t2

-5

5

15

Lef

t ret

inal

slip

(deg

)R

ight

retin

al s

lip (d

eg)

ϕl(t)

θ1(t)

ϕr(t)

θ2(t)

ϕC-l

ϕC-r

Fig. 11 Tracking of optic axes for smooth pursuit when theleft “eye” was shut out in a term (t1 to t2).

C. Characteristics of vergence eye movement If a binocular motor control system had only conjugate eyemovements, the system would not have any significancebecause it would mean the two eyeballs were fixed to eachother. Vergence eye movement is needed for catching a targetat the central pits of both eyes when the target is approaching orreceding from the eyes as shown in Fig. 12. To observe thecharacteristics of vergence eye movement of the robot eyes, thestep response is obtained in the following experiment: Fix the head and set the initial positions of each eyeball toparallel with the midline, namely,

xh(t)=0 m, yh(t)=0 m,θ0(t)=0 rad, θ1(0)=0 rad, θ2(0)=0 rad,

Setting a target at the position ofrht=0.2 m, ϕht = −5 deg = −0.087 rad.

From (1) and (2), the desired values of each eyeball are givenas the equations (7) and (8).

hehehtht

hehehthtlotl rr

rrtt

ϕϕϕϕ

ϕϕcoscossinsin

tan)()(−−

−== −−

1 (7)

hehehtht

hehehthtrotr rr

rrtt

ϕϕϕϕ

ϕϕcoscossinsin

tan)()(−+

−=−= −−

1 (8)

Fig. 12 The circumstances of the experiment of vergence[18].

0 2 4 6 8 10-30

-20

-10

0

10

Posi

tion

(deg

)

Time (Sec)

ϕC-r(t)

ϕC-l(t)

θ2(t)

θ1(t) −ϕot-l(t)

ϕot-r(t)

Fig. 13 Tracking of optic axes for vergence eye movement

0 1 2 3 4 5 6-30-20-10

0102030

Posi

tion

(deg

)

Time (Sec)

ϕC-r(t)

ϕC-l(t)

θ1(t)

θ2(t)ϕl(t)

ϕr(t)

Fig. 14 Tracking of optic axes for optokinetic responsewhen ρ1 = ρ2 .

Since the robot eyes were designed asrhe=0.09 m, ϕhe=22.88 deg =0.400 rad.

From equation (7), (8),ϕl = −24.3 deg = -0.424 rad, ϕr=8.6 deg = 0.150 rad

are obtain. The experiment situation is shown in Fig. 13. Figure13 shows the controlled errors (ϕC-l(t) and ϕC-r(t)) became 0,and the eyeballs’ positions (θ1(t), θ2(t)) closed to the desiredvalues (ϕl, ϕr). Figure 13 also shows that the settling times ofvergence eye movement are much slower compared to those ofconjugate eye movement. From (3) if set ρ = ρr or σ = σr, η = ηr, the vergence eyemovement will disappear. The experiment of ρ = ρr is shown inFig. 14. Figure 14 shows θ1(t) and θ2(t) are moving togethercompletely, i.e. there is no vergence movement.

VI THE EXPERIMENTS OF VOR FOR HEAD ROTATIONS

a) Fix the target and rotate the head according to the followingequation:

)3

sin(6

)(0 ttππ

θ = 　 (9)

In this case,m0=== )()()( tytytx thh , xt(t) =1 m (10)

6

Figure 15(a) shows the result of the experiment. Since theleft eye has the same characteristics as the right one, we showonly the right eye’s rotation θ2(t) in Fig. 15. The desired valueϕr in the figure is obtained from equation (8)b) Cut the VOR control loop by setting

δϕ=δx=δy=0,and do the same experiment as (a). The rotation of the righteyeball is shown in Fig. 15(b). Since there are not vestibularreflex control loops in the control systems, this experiment issimilar to fixing the head and rotating the target around thehead according to

)3

sin(6

)( tthtππ

ϕ −= 　 (11)

c) Rotate the head according to equation (9) in darkness. In thiscase the image feedback signals are regarded as 0. Theexperimental result is shown in Fig. 15(c). Experiments a), b) and c) showed VOR have the ability tocancel the blur of the image on the retinas caused by headmovement. However, when the VOR is assumed to be workingalone, it would not catch the target accurately, namely, theimage feedback control loops are necessary for gazing.

-30

30

0 5 10 15Time (Sec)

0

Posi

tion

(deg

) ϕr(t)

(b)θ2(t)

(c)θ2(t)

(a)θ2(t)

Fig. 15 Response of the binocular axis control system(a) Fixing target and rotating head,(b) Fixing head and rotating target,(c) Rotating head in a dark environment.

VII THE EXPERIMENTS OF HEAD TRANSLATIONS

Since the robot eyes have no degree for translate motion, inthe following experiments, the translate signals of head )(txh& ,

)(tyh& , and image signals from CCD cameras ϕC-l(t), ϕC-r(t)will be produced by the computers directly.

A. Characteristics of conjugate for head translations

a) Fix the target and translate the head in yH-axis directionaccording to the following equation.

)3/sin(5.0)( ttyh π= 　　 (12)So, the input signal of VOR is

)3/cos(6/)( ttyh ππ=& 　　 (13)

In this case .rad0)(m,1)(m,0)(m,0)( 0 ==== ttxtytx tth θFrom equations (1) and (2),

hehe

hehel r

rtt

ϕϕπ

ϕcos1

sin)3/sin(5.0tan)( 1

−−−

−= − (14)

hehe

heher r

rtt

ϕϕπ

ϕcos1

sin)3/sin(5.0tan)( 1

−−−

−= − (15)

The “retinal slip” signals are calculated as)()()( 1 ttt llC θϕϕ −=− (16)

)()()( 2 ttt rrC θϕϕ −−=− (17)Figure 16(a) is the result of the experiment. Here, only the righteye’s rotation θ2(t) is shown.

b) Fix the head and move the target in yB-axis directionaccording to the following equation.

)3/sin(5.0)( tty t π−= 　　 (18)In this case .rad0)(m,1)(m,0)(m,0)( 0 ==== ttxtytx thh θFrom equations (1) and (2),

hehe

hehel r

rtt

ϕϕπ

ϕcos1

sin)3/sin(5.0tan)( 1

−−−

−= − (19)

hehe

heher r

rtt

ϕϕπ

ϕcos1

sin)3/sin(5.0tan)( 1

−−−

−= − (20)

The “retinal slip” signals can be obtained. Figure 16(b) is theresult of the experiment.

c) Doing the same experiment as a) but in darkness, namely, the“retinal slips” signals ϕC-l (t), ϕC-r(t) are set as 0. Theexperiment result is shown in Fig. 16(c).

Posi

tion

(deg

)

0 5 10 15Time (Sec)

-30

30

0ϕr(t)

(a)θ2(t)

(c)θ2(t) (b)θ2(t)

Fig. 16 Response of the binocular axis control system (a) Fixed target and moving head in yH-direction, (b) Fixed head and moving target in yB-direction, 　　(c) Moving head in yH direction in darkness.

B. The characteristics of vergence for translate motions

a) Fix the head and move the target in the xB-axis directionaccording to the next equation.

)/sin(.)( 3501 ttxt π+= (21)In this case .rad0)(m,0)(m,0)(m,0)( 0 ==== ttytxty hht θFrom equations (1) and (2), the desired values of the robot eyesare obtained:

hehe

hehel rt

rt

ϕπϕ

ϕcos)/sin(.

sintan)(

−+= −

35011 (22)

hehe

heher rt

rt

ϕπϕ

ϕcos)/sin(.

sintan)(

−+−= −

35011 (23)

Using (22) and (23), the retinal slips can be obtained by (16)and (17). Figure 17(a) is the result of the experiment.

7

b) Fix the target and move the head in the xh-axis directionaccording to the following equation.

)3/sin(5.0)( ttxh π−= (24)So, the input signal of VOR is

)3/cos(6/)( ttxh ππ−=& 　　 (25)

In this case .rad0)(m,0)(m,0)(m,1)( 0 ==== ttytytx htt θFrom equations (1) and (2), the desired values of the robot-eyesare the same as (22) and (23). Figure 17(b) is the experimentalresult.c) Doing the same experiment as b) but in darkness, i.e. theretinal slips signals ϕC-l (t)=0, ϕC-r(t)=0. The experimentalresult is shown in Fig. 17(c). Experiments a)~c) showed, similar to conjugate movement,vergence movement also work most effectively when the imagefeedback and VOR work together.

(b)θ2(t)-5

0

5

0 5 10 15Time (Sec)

Posi

tion

(deg

)

ϕr(t)

ϕl(t)

(a)θ2(t)

(c)θ2(t)

(c)θ1(t)

(a)θ1(t)(b)θ1(t)

Fig.17 Response of the binocular axis control system(a) Fixing head and moving target in x-direction.(b) Fixing target and moving head in x direction.(c) Moving head in x direction in darkness.

VIII RESULTS AND DISCUSSIONS

Many conventional robot eyes are controlled by eacheyeball’s own control system. Even though the control methodsapparently can perform the conjugate and vergence eyemovement, some peculiar characteristics of human eyes havenever been realized. The solution of fixing the two eyes witheach other is out of the question. The skillful relationship ofconjugate and vergence eye movements is obtained by theproposed binocular motor control system outlined in thispaper.

The characteristic of “same point gazing tendency” wasrealized using the proposed robot-eye system. Thecharacteristic allows the two eyes to take in a pair ofsymmetrical images with the same target in the central pits, andwe believe this characteristic is one of the necessary conditionsfor creating a stereovision in the visual cortex using imagesfrom both retinas.

When one eye is shut or intercepted by an obstacle,conjugate eye movement causes this eye to follow up the targetviewed by the another eye. That means that when the obstacleis removed, the blind eye will find the target viewed by theother eye in an instant.

VOR for both head rotation and head translations is realizedusing a unified control system, which was shown to work inexperiments on the robot-eye system.

Both VOR for head rotation and head translations arerealized using a unified control system and the VOR

mechanism of the robot-eye system were validated by theexperiments.

IV CONCLUSION

The robot-eyes system with a control system similar to thesynthesized binocular motor model based on the physiologicalcharacteristics and the anatomical structure of ocular motorsystem was confirmed to perform several peculiar phenomenaof human eyes that conventional robot eyes do not possess. Theperformances gave us many hints that had never been takeninto account before this robot-eyes system was completed, suchas “same point gazing tendency,” and influences of thecentrifugal accelerations of the maculae. In the near future, more complete oculomotor system modelsshould be built upon the proposed model, and the probableapplications in the field of engineering would be of benefit tothe development of artificial eyes, which is one of the mostimportant “organs” in robot. Furthermore, the applications inthe field of medicine would pioneer some new areas, such asthe location diacritics of neuro-ophthalmology using eyemovement patterns that correspond to the head or targetmovement patterns, based on the oculomotor models [16].

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