R. Sklyar, 'Induction Magnetic Field Sensor as an Organ of Robot Vision' (unpublished)

7th International Conference on

Climbing and Walking Robots and the Support Technologies for Mobile Machines

September 22-24, 2004 MADRID - SPAIN

Final Programme Organised by the

Industrial Automation Institute of the Spanish Council for Scientific Research on behalf of the

EC GROWTH Thematic Network CLAWAR

Welcome by the Conference Chairmen

Y Baudoin CLAWAR’98 (Brussels)

G S Virk CLAWAR’99 (Portsmouth)

M A Armada CLAWAR’00 CLAWAR’04 (Madrid)

K Berns CLAWAR’01 (Karlsruhe)

P Bidaud CLAWAR’02 (Paris)

G Muscato CLAWAR’03 (Catania)

After the very successful Conferences of CLAWAR’98 (Brussels), CLAWAR’99 (Portsmouth), CLAWAR’00 (Madrid), CLAWAR’01 (Karlsruhe), CLAWAR’02 (Paris) and CLAWAR’03 (Catania) we are now, on behalf of the EC GROWTH Thematic Network CLAWAR, in charge of organising CLAWAR’04, that will be held in Madrid (Spain) from 22-24 September 2004, hosted by the Industrial Automation Institute of the Spanish Council for Scientific Research (IAI-CSIC).

Our conference is the seventh of a series of conferences sponsored by the European Commission in the framework of a European Network on Climbing and Walking Robots (CLAWAR), where most of research groups and industries in Europe dealing with these subjects are working together.

The interest in climbing and walking robots has remarkably augmented over recent years. Novel solutions for complex and very diverse application fields (exploration/intervention in severe environments, personal services, emergency rescue operations, transportation, entertainment, medical, etc.), has been anticipated by means of a large progress in this area of robotics.

Moreover, the amalgamation of original ideas and related innovations, the search for new potential applications and the use of state of the art supporting technologies permit to foresee an important step forward and a significant socio-economic impact of advanced robot technology in the forthcoming years. In response to the technical challenges in the development of these sophisticated machines, a significant research and development effort has to be undertaken. It concerns embedded technologies (for power sources, actuators, sensors, information systems), new design methods, adapted control techniques for highly redundant systems, as well as operational and decisional autonomy and human/robot co-existence.

The European Commission is funding the CLAWAR Network. However, our aim as scientists and industrialists in this exciting field of robotics, is not only to promote the knowledge and applications of the complex mechatronic devices under development inside the EU and to show how them can contribute to a competitive and sustainable growth in our countries, but to disseminate our technology outside Europe and to be very receptive of what is being done all around the world. Confirming this situation greatest interest has been received for CLAWAR’04, and after a careful reviewing procedure the conference finally accommodates 118 papers of high quality, where the number of authors goes over 250. Papers and Members of International Organising Committee account 26 countries, pointing out the high level of international activity in this field that is continuously growing and where many new research groups are being set up throughout the world.

As a summary of the conference it can be said that includes both state of the art and more practical presentations dealing with implementation problems, support technologies and future applications. A growing interest in passive locomotion is reflected by a very interesting number of contributions, and some outstanding new climbing and walking robots are also included. The conference is going together with a robot exhibition and the traditional climbing robot

competition. Best Paper Award will be offered by Emerald: Industrial Robot: An international Journal, and special issues of some of the foremost scientific journals on robotics will be published after the conference (for more information please refer to the CLAWAR’04 web site (http://www.iai.csic.es/clawar04). Of major relevance is the commitment with our new editors, Springer Verlag, that are in charge of the Conference Proceedings edition. In this occasion the Proceedings will be mailed to the registered participants after the Conference.

We would like to take this opportunity to thank all those involved in organising CLAWAR'04. To the Plenary Speakers, to the International and National Organising Committees, to the Sponsoring Organisations, and to the Authorities our acknowledgement for their invaluable help and kind assistance. CLAWAR Network partners have been very supportive with their extensive work in the backstage, promoting, widening and rationalising the CLAWAR technology, filling existing gaps, defining new concepts and expanding the applications horizon of climbing and walking robots. Their work has been fundamental for the preparation of this 7th Conference.

Special thanks are for the IAI-CSIC colleagues, for its Technical and Administrative Staff and for the members of the Automatic Control Department, because without their invaluable assistance CLAWAR’04 would never been a sound reality.

We would like to welcome you to CLAWAR’04 and wish you a fruitful scientific conference and a nice stay in Madrid.

We are looking forward to meet you next year in London for CLAWAR’05.

Yours sincerely, Yvan Baudoin Gurvinder S Virk Manuel Armada Karsten Berns Philippe Bidaud Giovanni Muscato

CLAWAR’04 ROADMAP 09.00

Opening Session 10.00

Plenary Session I Coffee Break 11.15

W E D N E S D A Y 22

Plenary Session II 12.00

Robot Exhibition and Climbing Robot Competition Lunch Break

14.00

Session 1 CONTROL 1

Session 2 DESIGN 1

Session 3 SENSORS Coffee Break

16.15

Session 4 CONTROL 2

Session 5 DESIGN 2

Session 6 SENSORS, TELEOPERATION AND TELEPRESENCE

18.15

POSTER SESSION, Robot Exhibition and Video, Climbing Robot Competition 19.00 09.00

Plenary Session III 09.45

Plenary Session IV Coffee Break

Robot Exhibition and Climbing Robot Competition

T H U R S D A Y 23

11.00

Session 7 CONTROL 3

Session 8 EFFICIENCY AND ACTUATION

Session 9 HOPPING, BIPED AND HUMANOID ROBOTS 1 Lunch Break

14.00

Session 10 PASSIVE WALKING

Session 11 APPLICATIONS

Session 12 HOPPING, BIPED AND HUMANOID ROBOTS 2 Coffee Break

16.15

Session 13 PASSIVE WALKING AND LOCOMOTION 18.35

Session 14 CLIMBING

Session 15 HOPPING, BIPED AND HUMANOID ROBOTS 3

Robot Exhibition and Video, Climbing Robot Competition

21.00 F R I D A Y

09.00

24

12.15

Conference Dinner

Plenary Session V Coffee Break

10.00

Session 16 INNOVATIVE SYSTEMS

Session 17 LOCOMOTION 2

Session 18 CLIMBING AND NAVIGATION

Close of Conference Lunch

CLAWAR 2004

FINAL PROGRAMME

MADRID 22-24 SEPTEMBER

CLAWAR’04 CONFERENCE TIMETABLE Tuesday 21 September 2004 17.00 19.30

Conference registration desk opening and exhibition set-up

Wednesday 22 September 2004 08.15 08.45

Conference registration

Room A

Salón de Actos del CSIC. CSIC Headquarters Main Building

09.00 10.00

Opening Session

10.00 10.45

Plenary Session I

10.45 11.15

Coffee Break

11.15 12.00

Plenary Session II

12.00 13.00 13.00 14.00 14.00 16.00 16.15 18.15

16.00 16.15 18.15 19.00

Prof. R. DILLMANN BIOLOGICALLY MOTIVATED CONTROL OF WALKING MACHINES

Prof. R. MCNEILL ALEXANDER PROBLEMS OF SCALE FOR WALKING AND CLIMBING ANIMALS Robot Exhibition and Climbing Robot Competition Lunch Break Room A Room B Room C Session 1 Session 2 Session 3 Coffee Break Session 4 Session 5 Session 6 Poster Session, Robot Exhibition and Video, Climbing Robot Competition

Thursday 23 September 2004 Room A 09.00 09.45

09.45 10.30 10.30 11.00 11.00 13.00 13.00 14.00 14.00 16.00 16.15 18.35

16.00 16.15 18.35 19.15 21.00

Salón de Actos del CSIC. CSIC Headquarters Main Building Prof. D A WINTER WHAT BIPEDAL HUMAN LOCOMOTION CAN TEACH Plenary Session III US ABOUT MOTOR CONTROL SYNERGIES FOR SAFE ROBOTIC LOCOMOTION Prof. A L RUINA Plenary Session IV SOME MECHANICS PERSPECTIVES ON ROBOT LOCOMOTION Coffee Break + Robot Exhibition and Climbing Robot Competition Room A Room B Room C Session 7 Session 8 Session 9 Lunch Break Room A Room B Room C Session 10 Session 11 Session 12 Coffee Break Session 13 Session 14 Session 15 Robot Exhibition and Video, Climbing Robot Competition Conference Dinner

Friday 24 September 2004 Room A

Salón de Actos del CSIC. CSIC Headquarters Main Building

09.00 09.45

Plenary Session 5

09.45 10.00 10.00 12.00

Coffee Break Room A Session 16

Room A

Salón de Actos del CSIC. CSIC Headquarters Main Building

12.15 13.00 13.00 14.00

Close of Conference Lunch

Prof. M XIE ROBOT VISION: A HOLISTIC VIEW Room B Session 17

http://www.iai.csic.es/clawar04

Room C Session 18

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CLAWAR 2004

FINAL PROGRAMME

MADRID 22-24 SEPTEMBER

Scientific Programme Tuesday 21 September 2004 17.00 19.30

Conference registration desk opening and exhibition set-up

08.15 08.45

Conference registration

Wednesday 22 September 2004

Chairman 09.00 10.00

Opening Session

J M F LABASTIDA VICE-PRESIDENT CSIC Room A

Plenary Session I

Chairman G S VIRK Room A

10.00 10.45

Prof. R. DILLMANN BIOLOGICALLY MOTIVATED CONTROL OF WALKING MACHINES 10.45 11.15

Coffee Break

Plenary Session II

Chairman P GONZALEZ Room A

11.15 12.00

Prof. R. MCNEILL ALEXANDER PROBLEMS OF SCALE FOR WALKING AND CLIMBING ANIMALS 12.00 13.00

Robot Exhibition and Climbing Robot Competition

13.00 14.00

Lunch Break

Session 1

CONTROL 1

14.00 14.20

INTEGER VS. FRACTIONAL ORDER CONTROL OF A HEXAPOD ROBOT M F SILVA, J A TENREIRO MACHADO, A M LOPES

14.20 14.40

SYNCHRONOUS LANDING CONTROL OF A ROTATING 4-LEGGED ROBOT, PEOPLER, FOR STABLE DIRECTION CHANGE T OKADA, Y HIROKAWA, T SAKAI, K SHIBUYA

14.40 15.00

NEURO-CONTROLLERS FOR WALKING MACHINES - AN EVOLUTIONARY APPROACH TO ROBUST BEHAVIOR J FISCHER, F PASEMANN, P MANOONPONG

15.00 15.20

DECENTRALIZED DYNAMIC FORCE DISTRIBUTION FOR MULTI-LEGGED LOCOMOTION T ODASHIMA, Z W LUO

15.20 15.40

AN OUTDOOR VEHICLE CONTROL METHOD BASED BODY CONFIGURATION INFORMATION D CHUGO, K KAWABATA, H KAETSU, H ASAMA, T MISHIMA

15.40 16.00

IMPLEMENTATION OF A DRIVER LEVEL WITH ODOMETRY FOR THE LAURON III HEXAPOD ROBOT J L ALBARRAL, E CELAYA

Chairman J ESTREMERA Room A

http://www.iai.csic.es/clawar04

3 of 13

CLAWAR 2004

FINAL PROGRAMME

MADRID 22-24 SEPTEMBER

Chairman G S VIRK Room B

Session 2

DESIGN 1

14.00 14.20

OPEN MODULAR DESIGN FOR ROBOTIC SYSTEMS I CHOCHLIDAKIS, Y GATSOULIS, G S VIRK

14.20 14.40

MECHANICAL DESIGN OPTIMIZATION OF A WALKING ROBOT LEG USING GENETIC ALGORITHM C REYES, F GONZALEZ

14.40 15.00

KINEMATICS OF A NEW STAIRCASE CLIMBING WHEELCHAIR R MORALES, A GONZÁLEZ, V FELIU, P PINTADO

15.00 15.20

DESIGN TOOLSET FOR REALISING ROBOTIC SYSTEMS Y GATSOULIS, I CHOCHLIDAKIS, G S VIRK

15.20 15.40

DESIGN, DYNAMIC SIMULATION AND EXPERIMENTAL TESTS OF LEG MECHANISM AND DRIVING SYSTEM FOR A HEXAPOD WALKING ROBOT J ROCA, M NOGUES, S CARDONA

15.40 16.00

LIMB-MECHANISM ROBOT WITH WINCH MECHANISM N FUJIKI, Y MAE, T UMETANI, T ARAI, T TAKUBO, K INOUE

Session 3

SENSORS

14.00 14.20

INDUCTION MAGNETIC FIELD SENSOR AS AN ORGAN OF ROBOT VISION R SKLYAR

14.20 14.40

14.40 15.00

Chairman P BIDAUD Room C

RESULTS OF APPLYING SENSOR FUSION TO A CONTROL SYSTEM USING OPTIC FLOW G MARTINEZ, V BECERRA LEARNING ABOUT THE ENVIRONMENT BY ANALYZING ACOUSTIC INFORMATION - HOW TO ACHIEVE PREDICTABILITY IN UNKNOWN ENVIRONMENTS? M DEUTSCHER, M KATZ, S KRÜGER

15.00 15.20

ULTRASOUND SENSOR SYSTEM WITH FUZZY DATA PROCESSING J A MORGADO DE GOIS, M HILLER

15.20 15.40

FINDING ODOURS ACROSS LARGE SEARCH SPACES: A PARTICLE SWARMBASED APPROACH L MARQUES, A T DE ALMEIDA

15.40 16.00

VISION FEEDBACK IN CONTROL OF A GROUP OF MOBILE ROBOTS P DUTKIEWICZ, M KIELCZEWSKI

16.00 16.15

Coffee Break

Session 4

CONTROL 2

16.15 16.35

LOCAL POSITIVE VELOCITY FEEDBACK (LPVF): GENERATING COMPLIANT MOTIONS IN A MULTI-JOINT LIMB A SCHNEIDER, H CRUSE, J SCHMITZ

16.35 16.55

16.55 17.15

Chairman J L CORONADO Room A

MOTION CALCULATION FOR HUMAN LOWER EXTREMITIES BASED ON EMGSIGNAL-PROCESSING AND SIMPLE BIOMECHANICAL MODEL C FLEISCHER, K KONDAK, C REINICKE, G HOMMEL BIFURCATING RECURSIVE PROCESSING ELEMENTS IN NEURAL ARCHITECTURES FOR APPLICATIONS IN MULTIDIMENSIONAL MOTOR CONTROL AND SENSORY FUSION IN NOISY / UNCERTAIN ENVIRONMENTS E DEL MORAL

http://www.iai.csic.es/clawar04

4 of 13

Consejo Superior de Investigaciones Cientificas INSTITUTO DE AUTOMATICA INDUSTRIAL Ctra. de Campo Real, Km. 0,200.

La Poveda 28500 Arganda del Rey Madrid - Spain Phone: + 34 91 871 19 00 Fax: + 34 91 871 70 50

Dr. Manuel Armada

7th International Conference on Climbing and Walking Robots Organised by the EC GROWTH Thematic Network CLAWAR MADRID 22-24 September 2004

Arganda del Rey, 30 May 2004 Dear Author(s), I am very pleased in notifying you that your abstract submitted to CLAWAR04 has been reviewed (at least by two independent experts), and it has been accepted for publication. Please find below the comments of the reviewers, which must be taken into account for the preparation of the final paper. The recommended number of pages for the final paper is 6 to 8, and the papers must be written according to the Guidelines for Authors (http://www.iai.csic.es/clawar04/). The deadline for receiving the final version is 10th July 2004. However this is the final deadline, so it is very much recommended to submit your final paper by 5th July 2004, because in this case there will be still some time for the Organisers to check out for formatting mistakes and to feedback you accordingly if the matter arises.

Abstract Ref.: A017_CLAWAR04 (Please use this for naming your final paper) Title/author(s): Induction Magnetic Field Sensor as an Organ of Robot Vision Rostyslav Sklyar Reviewers comments:

Many thanks for your interest in CLA WAR Conferences. I am looking forward to receive you next September in Madrid.

Yours sincerely,

Dr. Manuel Armada Chairman of the International Organising Committee e-mail: clawar04@iai.csic.es CLAWAR’04 web site: http://www.iai.csic.es/clawar04/

Induction Magnetic Field Sensor as an Organ of Robot Vision Rostyslav SKLYAR Space Sensing Instruments, Verchratskogo st. 15-1, Lviv 79010 Ukraine Tel/Fax: +380-322-762432/769613; r_sklyar@hotmail.com

Abstract. The robotic vision method of the autonomous system based on the orientation of the plane and according to the magnitude and gradient of the natural and industrial magnetic fields (MFs) has been developed. The head sensor(s) of an ambient temperature or superconducting further electronic circuit placed on the robot limb(s) without modifying them. Sensitivity of the robotic vision makes it possible to recognize the linear translation of 10-2 m and disposal in space of 10-3 m3.

I. Introduction. Magnetometers and their robotic applications The measurement of MFs is an important task for the majority of autonomous missions. The distribution of permanent and the value of periodical MFs gives the data about placement of ferromagnetic objects and sources of EM radiation respectively. On the other hand, these signals will z

b

x

y

a

Fig.1 The w alking robotin M F environm ent. a) x-y plane defines the varying D C natural M F; b) around z axis spreads AC industrial M F interference.

2

Rostyslav SKLYAR

be a reference point and guiding line for a walking robot (Fig. 1).

Detection of some magnetic anomalies of the Earth MF and their variations is provided by fluxgate sensors [1]. When the spectrum of EM signals in the environment lies in a wide frequency range (10Hz-500kHz), the application of highly-sensitive induction sensors is necessary. The application of a low-Tc SQUID device is able to embrace both of the said frequency ranges with maximum sensitivity. It is made of non-magnetic material and the principle of operation is to detect two magnetic signals at different distances from the source and arrange for these to be in opposition around a local supercooled circuit. This ‘gradiometer’ approach eliminates most of the noise—caused by spurious MFs originating from, for example, electrical devices or natural (geomagnetic (GM) sources. A typical unshielded laboratory has a noise level in the 0—10 Hz frequency region of about 10-7 T and GM noise in the same frequency range is of the order of 10-10 T. Any small field changes the direction of the MF vector in the space and this produces a distortion in the waveform of the signal in the detection coils. The very expensive use of the SQUID magnetometer up until now has produced many advances in the understanding of MFs from weak sources. The advance of much cheaper room—temperature sensor technologies offers the prospect of much greater use of MF monitoring [2].

As a general rule, scientific instrumentation should impact mass constraints as little as possible; however, robot-mounted instruments in particular must be lightweight to survive deployment under high- stress conditions when used in connection with spacecraft or underwater. This weight constraint can limit both the size of the sensor and its placement on the moving part. Also, autonomous systems require the minimal consumption power. Both factors translate into severe constraints on the capability of the instrument to measure weak EMFs encountered in the environment.

In addition, the outer space and underwater conditions require endurance against variations in the wide range of temperature, humidity, and atmospheric pressure.

II. Induction (superconducting) sensor as the organ of vision Taking into account the said restrictions, it is undesirable to use in robot a fluxgate sensor due to its active type of action. Also is impossible exploiting SQUID device since it needs the liquid helium container.

SQUID systems being almost ideal for the detection of very small amounts of flux from small samples, but less well-suited to the detection of low flux densities (i.e. where very low MFs are encountered). The high coil induc-

!"#$%&! '(%)* +%&,&--./. )*#01 2 3.%+4(-*( .*)+*)*2+(*.

c

c

"limb

a

b

" limb

a

3

Fig. 2 Placement of PC on the limb. a)a winding of PC; b) a ferromagnetic core of PC as a part of the limb(s); c) a wire which connects PC with an electronic circuit in the body.

tance of the induction system, on the other hand, can couple to a large quantity of flux [3]. It appears that these difficulties frequently reduce, in principle, the performance of SQUID magnetometers to a level below that demonstrated in this article using an ambient-temperature induction system. This induction sensor is also compact, robust, operates at room temperature, exhibits a wide dynamic range, and may be easily integrated into differential or multiple sensor gradiometric configurations which are feasible in a multi-limb walking robot.

1. Placing of the PCs on the limbs A PC of walking robot is connected in parallel with the drain of a SuFET cryogenic device or an ordinary OA which are placed in the body (Fig. 2). A PC realizing the oscillatory-forward movement along both AC industrial interferences and quasi-DC natural (Earth) environmental MFs. These fields are distributed on a surface and in space roughly according to Fig. 1. The movement in quasi-DC MF HDC with the defined speed ! and oscillating frequency " with a magnitude #$ gives e.m.f. from PC: (1) EPC=SN"µeffµ0HDCsin$%#$ , where S=µeff&d2N/4 with µ0 -the permeability of free space, µ0=4&%10-7 henry/meter; µeff -the effective relative permeability of a high-µ metal core; d-the average diameter of a PC; N-total turn number of solenoid; $- an angle between PC's magnetic axis and the vector of HDC. Further amplifying/processing circuit depends on the measuring conditions and can vary from the simplest of the ordinary induction sensor modifications to the superconducting one [4].

4

Rostyslav SKLYAR

2. The design of the MF transducer Some combined device, that includes all the best features of the said MF sensors/transducers seems to be the preferable trend for further development as a vision organ [4]. The SuFET is implemented into a wideband induction sensor device in order to acquire the sensitivity threshold below 1fT/'Hz in the frequency range from small values of Hertz to tens of MHz (0.1Hz-107 Hz). The proposed magnetometer (SIM) circuit consists of both room-temperature or cooled (up to superconductive) pickup coil (PC) and a SuFET. Moreover, it gives the possibility of repudiating both windings and electronics of feedback loops that are used in the known magnetometers.

Magnetic induction BPC of AC MF with the frequency "limb of limbs' oscillations produce an e.m.f. in PC: (2) EPC=BPC"limbSN, where S- a cross-section of PC, N- its number of turns. All AC MFs with the frequencies ", high than "limb can be rejected by the passive HF filter [5].On the other hand, the value of EPC can be determined from the output voltage Uout of the specific kind of the induction transducer [4] with known its transfer function G according to the formula: (3) Uout=GEPC. As a result, an output signal receiving spontaneously, during twodimensional travel of a walking robot in a quasi-DC MF. Moreover, by picking up the signals from both horizontal and vertical parts of the limbs, the robot derives its' directional information from the axial course of the field lines and their inclination (defined as the angle between the direction of the field lines and the horizontal) in space. Executing the oscillations of PC with parameters (number of turns N=2%104 and a cross-section area S=&%10-4 m2) [4] in the earth MF B0=50 mkT [6] with the frequency 2 Hz and $=30(, #$=30( arouse e.m.f. with a magnitude 50 mV according to Eq. 1. This e.m.f. will be on average equal to 5 mkV for the possible variations of the said MF with magnitude 1)10 nT [6]. Hence these data it is possible to calculate the value of Uout for all five known of the induction transducer [4] with given parameters of their electrical circuit. Thus so then: a) for the basic transducer's variant with PC's resistance R=2.4 kOhm, inductance L=30 H and capacitance C=50 pF the values of Uout shown in the second column of the table; b) the voltage feedback resistance Rfb=27 kOhm is introduced into the circuit; c) the magnetic flux feedback turns Nfb=1000 is introduced into the device; d) for SuFET the constant partial of gate voltage equal to 0.1 V and "T, which closely relates to the small signal transconductance, are defined [4].

!"#$%&! '(%)* +%&,&--./. )*#01 2 3.%+4(-*( .*)+*)*2+(*.

5

Table. The dependence of signal's value Uout from the varying MF BPC. a b c d BPC!Uout 50 mkT 10 V 70 mV 1.4 V 3 mkV+0.1 V 5 nT 1 mV 7 mkV 0.14 mV 0.3 pV+0.1 V (0.1 mkT) III. Using an ambient DC and AC MFs for robot's walking An output signal of the sensor will be involved into differencial (gradiometric) operation between the robot’s limbs. After envelope detection of the quantity Uout, can be presented by changing the corresponding quasiDC MF by the robot’s movement as defined in Fig. 3. In the similar manner, way an AC MF partial can be shown.

HDC, HAC, Vout

1-

1 2

oscillations of a PC modulated by variations of external natural MF;

2-

an envelope of sensor's output voltage UDC as the appropriate quasiDC MF along the walking way;

3-

changing of an AC industrial MF interference into the travel space;

4-

the integral output voltage UAC which determines changing of the interference's power by a distance.

Fig. 3 The variations of measured MF strength HDC, HAC.

4 3

t

The linear travel of the robot can be derived from the known distance between any two limbs and measured during the movement gradient of MF #H, which is presumed constant. Otherwise, the robot can be walking in the direction of minimal or maximal MF strength H according to the said gradient (Fig. 4). In both cases the precision of movement will be defined by the sensors’ sensitivity, which lies in a range of the orders from pT/'Hz to fT/'Hz .

1. Determination of the earth's MF gradient A portable single axis magnetic gradiometer, which is a relative instrument because it measures the spatial variation of the MF, has been described [7]. The finite distance between the magnetic sensors d for detecting the field difference is used to get an expression for the estimate of the exact magnetic gradient, adjusted by a function of the field distance, #Bz=Bz(z+(1/2)d)-Bz(z-(1/2)d), as follows:

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Rostyslav SKLYAR

-B z z

#Bz *0 md 2 , +5 d 4&z 6

,

(4)

where *0=4&10-7 H/m, z is the distance from the dipole to the center of the gradiometer probe and m the magnetic moment of the dipole.

In the case to be treated in the following, the oscillations of the limbs are taking place according to the law closer to harmonical. Then the magnitude value of magnetic induction, which produced by oscillations of PC in the ambient DC MF Bz is: (5) BPC=Bz·sin$·#$ , where $ is an angle between PC's direction of detection and vector of B, #$ is a range (of a value) of this angle variation.

Having substituted Eqs. 1, 3, 5 into Eq. 4, we have the dependence between signals from PCs of any two limbs and the relevant magnetic gradient occurs:

-B z z ,

U out .(z + (1/2)) - (z - (1/2))/ * md 2 +5 0 6 G" limbSNsin$#$ 4&z

(6)

A first order radial gradiometer consists of two axially displaced magnetometer loops, wound in opposing sense from a common wire that is connected to the induction sensor. Two radial magnetometers with opposite polarity can be connected together to form planar gradiometers [8].

Such devices detect tangential gradient of the radial field, and two gradiometers are usually used at each site to detect two orthogonal planar gradients. The planar gradiometer behaviour is qualitatively different from that of the radial gradiometer.

2. Measuring of the MF signal (noise) in a triaxial arrangement A flux transformer detects more environmental noise if its baseline is long (or if it is a magnetometer). Thus long baseline gradiometers detect not only stronger signal from deep sources, but also larger environmental noise. The noise parameters for different baselines were measured and are shown graphically [8].

Gradiometers can also be configured to detect radial gradient of the tangential MF. Two orthogonal ‘tangential radial gradiometers’ and one ‘radial gradiometer’ can be combined to form a first-order gradiometer equivalent of the vector magnetometer. The vector of the industrial or household man-made AC MF (noise) " can be measured during the complete pass of the robot's walking. Placing of the PC's triplets (the three orthogonal components at each location) on the respective limbs dive the necessary data for the triaxial MF determination according to the geomet

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7

rical summation. In such case, frequency of the limb's oscillations much lower than ambient MF noise. That is why, they do not influence the measured components and, moreover, these oscillations can be additionally suppressed by a passive LF filter [9]. The value of MF induction along a single component will be calculated similarly to Eq. 1 and Eq. 2 by the formula: (7) BPC="SNUout/G Some example of the result of the calculations according Eq. 7 shown in Fig. 4. The dependence of volumetric error on the baseline for environmental noise is shown [8].

z

#HAC(n)

#HAC(m) x

#HDC(m)

#HDC(n)

y

grad(#HDC)

Fig. 4 Orientation of the walking robot in an environmental MF. a) distribution of the detected gradients of DC natural MF over the x-y plane; b) distribution of DC MF interference in the space around z axis as a difference between the limbs.

IV. Conclusions The attempt to solve this problem of simplifying the robotic vision structure and reducing of such performance data as mass, volume and power consumption by the employing of the induction (also superconducting)

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Rostyslav SKLYAR

sensor was done. This method allows us to use the oscillations of limbs during robot's walking for receiving the measured signal and make the vision more natural for this machine. The advanced sensor has an unlimited frequency range from DC to HF, and sensitivity to the ambient MF is closer to the theoretical possibility.

V. References [1] Cerman A., Ripka P., Ka!par P., “Precise Magnetic Sensors and Magnetometers for Military and Space Applications”, Sensors & Transducers Magazine, vol. 38, iss. 12, 2003, pp. 54-58; [2] Mapps D. J., “Remote Magnetic Sensing of People”, Sensors and Actuators A, vol. 106, 2003, pp. 321-325; [3] Prance R. J., Clark T. D. and Prance H., “Compact RoomTemperature Induction Magnetometer With Superconducting Quantum Interference Device Level Field Sensitivity”, Rev. Sci. Instrum., vol.74, No. 8, 2003, pp. 3735-3739; [4] Sklyar R., “SIM- A SuFET Based Induction Magnetometer”, Proceedings of 'Recent Advances of Space Technology: RAST-2003', Nov. 20-22, 2003, Istanbul, Turkey, pp.193-199; [5] Zambresky L. F., Watanabe T., “Equivalent Circuit of a Magnetic Sensor Coil and a Simple Filter for Rejection of 60 Hz Man- Made Noise”, J.Geomag. Geoelectr., vol. 32, 1980, pp. 325-331; [6] Ripka P., “Review of Fluxgate Sensors”, Sensors and Actuators A, vol. 33, 1992, pp. 129-141; [7] Merayo J. M. G., Petersen J. R., Nielsen et al., “A Portable Single Axis Magnetic Gradiometer”, Sens. Act. A, vol. 93, 2001, pp. 185-196; [8] Vrba J. and Robinson S E, “SQUID sensor array configurations for magnetoencephalography applications (Topical review)”, Supercond. Sci. Technol., vol. 15, 2002, pp. R51–R89; [9] Sklyar R., “Suppression of Low-Frequency Interferences in the Induction Sensor of Magnetic Field”, has been considering for publication in Measurement (M03/73).