NUCLEAR BATTERIES

 Micro electro mechanical systems

(MEMS) comprise a rapidly expanding research field with potential applications varying from sensors in air bags, wrist-warn GPS receivers, and matchbox size digital cameras to more recent optical applications. Depending on the application, these devices often require an on board power source for remote operation, especially in cases requiring for an extended period of time. In the quest to boost micro scale power generation several groups have turn their efforts to well known enable sources, namely hydrogen and hydrocarbon fuels such as propane, methane, gasoline and diesel.

         Some groups are develo ping micro fuel cells than, like their micro scale counter parts, consume hydrogen to produce electricity. Others are developing on-chip combustion engines, which actually burn a fuel like gasoline to drive a minuscule electric generator. But all these approaches have some difficulties regarding low energy densities, elimination of by products, down scaling and recharging. All these difficulties can be overcome up to a large extend by the use of nuclear micro batteries.

           Radioisotope thermo electric generators (RTGs) exploited the extraordinary potential of radioactive materials for generating electricity. RTGs are particularly used for generating electricity in space missions. It uses a process known as See-beck effect. The problem with RTGs is that RTGs don’t scale down well. So the scientists had to find some other ways of converting nuclear energy into electric energy. They have succeeded by developing nuclear batteries.

NUCLEAR BATTERIES

Nuclear batteries use the incredible amount of energy released naturally by tiny bits of radio active material without any fission or fusion taking place inside the battery. These devices use thin radioactive films that pack in energy at densities thousands of times greater than those of lithium-ion batteries. Because of the high energy density nuclear batteries are extremely small in size. Considering the small size and shape of the battery the scientists who developed that battery fancifully call it as “DAINTIEST DYNAMO”. The word ‘dainty’ means pretty.

Types of nuclear batteries 

Scientists have developed two types of micro nuclear batteries. One is junction type battery and the other is self-reciprocating cantilever. The operations of both are explained below one by one.

The kind of nuclear batteries directly converts the high-energy particles emitted by a radioactive source into an electric current. The device consists of a small quantity of Ni-63 placed near an ordinary silicon p-n junction – a diode, basically.

WORKING:

As the Ni-63 decays it emits beta particles, which are high-energy electrons that spontaneously fly out of the radioisotope’s unstable nucleus. The emitted beta particles ionized the diode’s atoms, exciting unpaired electrons and holes that are separated at the vicinity of the p-n interface. These separated electrons and holes streamed away form the junction, producing current.

            It has been found that beta particles with energies below 250KeV do not cause substantial damage in Si [4] [5]. The maximum and average energies (66.9KeV and 17.4KeV respectively) of the beta particles emitted by Ni-63 are well below the threshold energy, where damage is observing silicon. The long half-life period (100 years) makes Ni-63 very attractive for remote long life applications such as power of spacecraft instrumentation. In addition, the emitted beta particles of Ni-63 travel a maximum of 21 micrometer in silicon before disintegrating; if the particles were more energetic they would travel longer distances, thus escaping. These entire things make Ni-63 ideally suitable in nuclear batteries. 

                       INTROUCTION to Wireless Power Transmission via Solar Power Satellite 

                 The major problem facing Planet
Earth is provision of an adequate supply of clean energy . It has been that we
face “…three simultaneous challenges — population growth, resource consumption,
and environmental degradation — all converging particularly in the matter of
sustainable energy supply.” It is widely agreed that our current energy practices
will not provide for all the world’s peoples in an adequate way and still leave
our Earth with a livable environment. Hence, a major task for the new century
will be to develop sustainable and environmentally friendly sources of energy.

                Projections
of future energy needs over this new century show an increase by a factor of at
least two and one Half, perhaps by as much as a factor of five. All of the scenarios
from reference 3 indicate continuing use of fossil sources, nuclear, and large
hydro. However, the greatest increases come from “new renewables” and
all scenarios show extensive use of these sources by 2050. Indeed, the projections
indicate that the amount of energy derived from new renewables by 2050 will exceed
that presently provided by oil and gas combined. This would imply a major change
in the world’s energy infrastructure. It will be a Herculean task to acquire this
projected amount of energy. 

             This author asserts that there are really only a few
good options for meeting the additional energy needs of the new cen Projections
of future energy needs over this new century show an increase by a factor of at
least two and one Half, perhaps by as much as a factor of five. All of the scenarios
from reference 3 indicate continuing use of fossil sources, nuclear, and large
hydro. However, the greatest increases come from “new renewables” and
all scenarios show extensive use of these sources by 2050. Indeed, the projections
indicate that the amount of energy derived from new renewables by 2050 will exceed
that presently provided by oil and gas combined. This would imply a major change
in the world’s energy infrastructure. It will be a Herculean task to acquire this
projected amount of energy. This author asserts that there are really only a few
good options for meeting the additional energy needs of the new century in an
environmentally acceptable way.One
of the so-called new renewables on which major reliance is almost certain to be
placed is solar power. 

       

         Solar power captured on the Earth is familiar to all. However,
an alternative approach to exploiting solar power is to capture it in space and
convey it to the Earth by wireless means. As with terrestrial capture, Space Solar
Power (SSP) provides a source that is virtually carbon-free and sustainable. As
will be described later, the power-collecting platforms would most likely operate
in geosynchronous orbit where they would be illuminated 24 hours a day (except
for short eclipse periods around the equinoxes). Thus, unlike systems for the
terrestrial capture of solar, a space-based system would not be limited by the
vagaries of the day-night cycle. Furthermore, if the transmission frequency is
properly chosen, delivery of power can be carried out essentially independent
of weather conditions. Thus Space Solar Power could provide base load electricity.

A neural network is a powerful data modeling tool
that is able to capture and represent complex input/output relationships . In
the broader sense, a neural network is a collection of mathematical models that
emulate some of the observed properties of biological nervous systems and draw
on the analogies of adaptive biological learning. It is composed of a large
number of highly interconnected processing elements that are analogous to
neurons and are tied together with weighted connections that are analogous to
synapses.

To be more  clear, let us study the model of a neural
network with the help of figure.1. The most common neural network model is the
multilayer perceptron (MLP). It is composed of hierarchical layers of neurons
arranged so that information flows from the input layer to the output layer of
the network. The goal of this type of network is to create a model that correctly
maps the input to the output using historical data so that the model can then
be used to produce the output when the desired output is unknown.

Neural network is a sequence of neuron layers. A
neuron is a building block of a neural net. It is very loosely based on the
brain’s nerve cell. Neurons will receive inputs via weighted links from other
neurons. This inputs will be processed according to the neurons activation
function. Signals are then passed on to other neurons.

In a more practical way, neural networks are made
up of interconnected processing elements called units which are equivalent to
the brains counterpart ,the neurons.

Neural network can be considered as an artificial
system that could perform “intelligent” tasks similar to those
performed by the human brain. 

Neural networks resemble the human brain in the
following ways:

1.    
It requires no physical inetraction on behalf of the
user.

2.    
 It is accurate
and allows for high enrolment and verification rates.

3.    
 It does not
require an expert to interpret the comparison result.

4.    
 It can use your
existing hardware infrastructure, existing camaras and image capture devices
will work with no problems.

5.    
 It is the only
biometric that allow you to perform passive identification in a one to many
environment (eg: identifying a terrorist in a busy Airport terminal.

The face is an important part of who you are and how people identify you.
Except in the case of identical twins, the face is arguably a person’s most
unique physical characteristics. While humans have the innate ability to
recognize and distinguish different faces for millions of years , computers are
just now catching up. For face recognition there are two types of comparisons
.the first is verification. This is where the system compares the given
individual with who that individual says they are and gives a yes or no
decision. The second is identification. This is where the system compares the
given individual to all the other individuals in the database and gives a
ranked list of matches. All identification or authentication technologies
operate using the following four stages:

1. capture: a physical or behavioural sample is captured by the
system during enrollment and also in identification or verification process.

2. Extraction: unique data is extracted from the sample and a
template is created.

3. Comparison: the
template is then compared with a new sample.

4. Match/non match : the system decides if the features
extracted from the new sample are a match or a non match.

Face recognition starts with a picture,
attempting to find a person in the image. This can be accomplished using
several methods including movement, skin tones, or blurred human shapes. The
face recognition system locates the head and finally the eyes of the
individual. A matrix is then developed based on the characteristics of the
individual’s face. The method of defining the matrix varies according to the
algorithm (the mathematical process used by the computer to perform the
comparison). This matrix is then compared to matrices that are in a database
and a similarity score is generated for each comparison.

Artificial intelligence is used to simulate human
interpretation of faces. In order to increase the accuracy and adaptability,
some kind of machine learning has to be implemented.

There are essentially two methods of capture. One
is video imaging and the other is thermal imaging. Video imaging is more common
as standard video cameras can be used. The precise position and the angle of
the head and the surrounding lighting conditions may affect the system
performance. The complete facial image is usually captured and a number of
points on the face can then be mapped, position of the eyes, mouth and the
nostrils as a example. More advanced technologies make 3-D map of the face
which multiplies the possible measurements that can be made. 

Thermal imaging has better accuracy as it uses
facial temperature variations caused by vein structure as the distinguishing
traits. As the heat pattern is emitted from the face itself without source of
external radiation these systems can capture images despite the lighting
condition, even in the dark. The drawback is high cost. They are more expensive
than standard video cameras. 

Face recognition technologies have been
associated generally with very costly top secure applications. Today the core
technologies have evolved and the cost of equipments is going down dramatically
due to the intergration and the increasing processing power. Certain
application of face recognition technology are now cost effective, reliable and
highly accurate. As a result there are no technological or financial barriers for
stepping from the pilot project to widespread deployment.

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                                                   CELLULAR POSITIONING

Introduction:

          Location
related products are the next major class of value added services that mobile
network operators can offer their customers. Not only will operators be able to
offer entirely new services to customers, but they will also be able to offer
improvements on current services such as location-based prepaid or information
services. The deployment of location based services is being spurred by several
factors:

Competition :
 

            The
need to find new revenue enhancing and differentiating value added services has
been increasing and will continue to increase over time. Regulation The Federal
Communications Commission (FCC) of the USA adopted a ruling in June 1996 (Docket
no. 94-102) that requires all mobile network operators to provide location information
on all calls to “911”, the emergency services. The FCC mandated that
by 1 st October 2001, all wireless 911 calls must be pinpointed within125 meters,
67% of the time. On December 24 1998, the FCC amended its ruling to allow terminal
based solutions as well as network based ones (CC Docket No. 94-102, Waivers for
Handset-Based Approaches). There are a number of regulations that location based
services must comply with, not least of all to protect the privacy of the user.
Mobile Streams believes that it is essential to comply with all such regulations
fully. However, such regulations are only the starting point for such services-
there are possibilities for a high degree of innovation in this new market that
should not be overlooked.

 Technology

        There
have been continuous improvements in handset, network and positioning technologies.
For example, in 1999, Benefon, a Finnish GSM and NMT terminal vendor launched
the ESC! GSM/ GPS mapping phone.

Needs
Of Cellular Positioning:
 

            There are a number of reasons why it is useful
to be able to pinpoint the position of a mobile telephone, some of which are described
below. Location-Sensitive billing Different tariff can be provided depending upon
the position of the cell phone. This allows the operator without a copper cable
based PSTN to offer competitive rates for calls from home or office. Increased
subscriber safety. A significant number of emergency calls like US.911 are coming
from cell phones, and in most of the cases the caller can not provide the accurate
information about their position. As a real life example let us take the following
incident. In February 1997 a person became stranded along a highway during a winter
blizzard (Associated press 1997).She used her cellular phone to call for help
but could not provide her location due to white-out conditions. To identify the
callers approximate position authorities asked her to tell them when she could
hear the search plane flying above. From the time of her first call forty hours
elapsed before a ground rescue team reached her. An automatic positioning system
would have allowed rescuers to reach her far sooner.

Positioning
Techniques :
 

            There are a variety of ways in
which position can be derived from the measurement of signals and these can be
applied to any cellular system including GSM. The important measurements are the
Time of Arrival (TOA), the Time Difference of Arrival (TDOA), the Angle of Arrival
(AOA) and Carrier phase. All these measurement put the object to be positioned
on a particular locus. Multiple measurements give multiple loci and the point
of their intersection gives the position. If the density of the base stations
is such that more measurements can be done than required then a least square approach
can be used. If the measurements are too few in number the loci will intersect
at more than one point result in ambiguous position estimate. In the following
discussion we assume that the mobile station and base station are lying in the
same plane. This is approximately true for most networks unless the geography
include hilly topology or high rise buildings.

Time
of Arrival (TOA):
 

           In a remote positioning system this involves the measurement
of the propagation time of a signal from the mobile phone to a base station. Each
measurement fixes the position of the mobile on a circle. With two stations there
will be two circle and they can intersect in a maximum of two points. This gives
rise to an ambiguity and it is resolved by including a priory information of the
trajectory of the mobile phone or making a propagation time measurement to a third
base station.

           The TOA measurement requires exact time synchronization between
the base stations and the receiver should have an accurate clock, so that the
receiver knows the exact time of transmission and an exact TOA measurement have
made by the receiver.

             Near infrared light consists of light just beyond visible red
light (wavelengths greater than 780nm). Contrary to popular thought,
near infrared photography does not allow the recording of thermal
radiation (heat). Far-infrared thermal imaging requires more specialized
equipment. Infrared images exhibit a few distinct effects that
give them an exotic, antique look. Plant life looks completely
white because it reflects almost all infrared light (because of
this effect, infrared photography is commonly used in aerial photography
to analyze crop yields, pest control, etc.) The sky is a stark
black because no infrared light is scattered. Human skin looks
pale and ghostly. Dark sunglasses all but disappear in infrared
because they don’t block any infrared light, and it’s said that
you can capture the near infrared emissions of a common iron.

            

             Infrared photography
has been around for at least 70 years, but until recently has
not been easily accessible to those not versed in traditional
photographic processes. Since the charge-coupled devices (CCDs)
used in digital cameras and camcorders are sensitive to near-infrared
light, they can be used to capture infrared photos. With a filter
that blocks out all visible light (also frequently called a “cold
mirror” filter), most modern digital cameras and camcorders
can capture photographs in infrared. In addition, they have LCD
screens, which can be used to preview the resulting image in real-time,
a tool unavailable in traditional photography without using filters
that allow some visible (red) light through.

INTRODUCTION:

             Near infrared
light consists of light just beyond visible red light (wavelengths
greater than 780nm). Contrary to popular thought, near infrared
photography does not allow the recording of thermal radiation
(heat). Far-infrared thermal imaging requires more specialized
equipment. Infrared images exhibit a few distinct effects that
give them an exotic, antique look. Plant life looks completely
white because it reflects almost all infrared light (because of
this effect, infrared photography is commonly used in aerial photography
to analyze crop yields, pest control, etc.) The sky is a stark
black because no infrared light is scattered. 

            Human skin looks
pale and ghostly. Dark sunglasses all but disappear in infrared
because they don’t block any infrared light, and it’s said that
you can capture the near infrared emissions of a common iron

             Near-infrared
(1000 – 3000 nm) spectrometry, which employs an external light
source for determination of chemical composition, has been previously
utilized for industrial determination of the fat content of commercial
meat products, for in vivo determination of body fat, and in our
laboratories for determination of lipoprotein composition in carotid
artery atherosclerotic plaques. Near-infrared (IR) spectrometry
has been used industrially for several years to determine saturation
of unsaturated fatty acid esters (1). Near-IR spectrometry uses
an tunable light source external to the experimental subject to
determine its chemical composition.

           Industrial utilization of
near-IR will allow for the in vivo measurement of the tissue-specific
rate of oxygen utilization as an indirect estimate of energy expenditure.
However, assessment of regional oxygen consumption by these methods
is complex, requiring a high level of surgical skill for implantation
of indwelling catheters to isolate the organ under study.

                                      NUCLEAR BATTERIES -DAINTIEST DYNAMICS 

           Micro electro mechanical systems (MEMS) comprise a rapidly expanding
research field with potential applications varying from sensors
in air bags, wrist-warn GPS receivers, and matchbox size digital
cameras to more recent optical applications. Depending on the
application, these devices often require an on board power source
for remote operation, especially in cases requiring for an extended
period of time. In the quest to boost micro scale power generation
several groups have turn their efforts to well known enable sources,
namely hydrogen and hydrocarbon fuels such as propane, methane,
gasoline and diesel. Some groups are developing micro fuel cells
than, like their micro scale counter parts, consume hydrogen to
produce electricity. Others are developing on-chip combustion
engines, which actually burn a fuel like gasoline to drive a minuscule
electric generator. But all these approaches have some difficulties
regarding low energy densities, elimination of by products, down
scaling and recharging. All these difficulties can be overcome
up to a large extend by the use of nuclear micro batteries.

           

           Radioisotope
thermo electric generators (RTGs) exploited the extraordinary
potential of radioactive materials for generating electricity.
RTGs are particularly used for generating electricity in space
missions. It uses a process known as See-beck effect. The problem
with RTGs is that RTGs don’t scale down well. So the scientists
had to find some other ways of converting nuclear energy into
electric energy. They have succeeded by developing nuclear batteries.

NUCLEAR BATTERIES

            Nuclear batteries
use the incredible amount of energy released naturally by tiny
bits of radio active material without any fission or fusion taking
place inside the battery. These devices use thin radioactive films
that pack in energy at densities thousands of times greater than
those of lithium-ion batteries. Because of the high energy density
nuclear batteries are extremely small in size. Considering the
small size and shape of the battery the scientists who developed
that battery fancifully call it as “DAINTIEST DYNAMO”.
The word ‘dainty’ means pretty.

            Scientists
have developed two types of micro nuclear batteries. One is junction
type battery and the other is self-reciprocating cantilever. The
operations of both are explained below one by one.

 JUNCTION TYPE
BATTERY

           The kind
of nuclear batteries directly converts the high-energy particles
emitted by a radioactive source into an electric current. The
device consists of a small quantity of Ni-63 placed near an ordinary
silicon p-n junction – a diode, basically.

WORKING:

            As the Ni-63 decays it emits beta particles, which are high-energy
electrons that spontaneously fly out of the radioisotope’s unstable
nucleus. The emitted beta particles ionized the diode’s atoms,
exciting unpaired electrons and holes that are separated at the
vicinity of the p-n interface. These separated electrons and holes
streamed away form the junction, producing current.

                                                CARBON NANOTUBE FLOW SENSORS

Introduction:

           Direct
generation of measurable voltages and currents is possible when a fluids flows
over a variety of solids even at the modest speed of a few meters per second.
In case of gases underlying mechanism is an interesting interplay of Bernoulli’s
principle and the See beck effect: Pressure differences along streamlines give
rise to temperature differences across the sample; these in turn produce the measured
voltage. The electrical signal is quadratically dependent on the Mach number M
and proportional to the Seebeck coefficient of the solids. 

            This
discovery was made by professor Ajay sood and his student Shankar Gosh of IISC
Bangalore, they had previously discovered that the flow of liquids, even at low
speeds ranging from 10 -1 meter/second to 10 -7 m/s (that is, over six orders
of magnitude), through bundles of atomic-scale straw-like tubes of carbon known
as nanotubes, generated tens of micro volts across the tubes in the direction
of the flow of the liquid. Results of experiment done by Professor Sood and Ghosh
show that gas flaw sensors and energy conversion devices can be constructed based
on direct generation of electrical signals. The experiment was done on single
wall carbon nanotubes (SWNT).These effect is not confined to nanotubes alone these
are also observed in doped semiconductors and metals.

          The
observed effect immediately suggests the following technology application, namely
gas flow sensors to measure gas velocities from the electrical signal generated.
Unlike the existing gas flow sensors, which are based on heat transfer mechanisms
from an electrically heated sensor to the fluid, a device based on this newly
discovered effect would be an active gas flow sensor that gives a direct electrical
response to the gas flow. One of the possible applications can be in the field
of aerodynamics; several local sensors could be mounted on the aircraft body or
aerofoil to measure streamline velocities and the effect of drag forces. Energy
conversion devices can be constructed based on direct generation of electrical
signals i.e. if one is able to cascade millions these tubes electric energy can
be produced.

          As the state of art moves towards the atomic scales, sensing
presents a major hurdle. The discovery of carbon nanotubes by Sujio Iijima at
NEC, Japan in 1991 has provided new channels towards this end. A carbon nanotube
(CNT) is a sheet of graphene which has been rolled up and capped with fullerenes
at the end. The nanotubes are exceptionally strong, have excellent thermal conductivity,
are chemically inert and have interesting electronic properties which depend on
its chirality. The main reason for the popularity of the CNTs is their unique
properties. Nanotubes are very strong, mechanically robust, and have a high Young’s
modulus and aspect ratio. These properties have been studied experimentally as
well as using numerical tools. Bandgap of CNTs is in the range of 0~100 meV, and
hence they can behave as both metals and semiconductors.

          

             A lot of factors like the presence of a chemical species, mechanical deformation
and magnetic field can cause significant changes in the band gap, which consequently
affect the conductance of the CNTs. Its unique electronic properties coupled with
its strong mechanical strength are exploited as various sensors. And now with
the discovery of a new property of flow induced voltage exhibited by nanotubes
discovered by two Indian scientists recently, has added another dimension to micro
sensing devices.

CNT Electronic
Properties

 
           Electrically CNTs are both semiconductor and metallic in nature
which is determined by the type of nanotube, its chiral angle, diameter, relation
between the tube indices etc. The electronic properties structure and properties
is based on the two dimensional structure of Graphene. For instance if the tube
indices, n and m, satisfies the condition n-m=3q where q is and integer it behaves
as a metal. Metal, in the sense that it has zero band gap energy. But in case
of armchair (where n=m) the Fermi level crosses i.e. the band gap energy merges.
Otherwise it is expected the properties of tube will be that of semiconductor. 

Fluid
Flow Through Carbon Nanotube

 
            Recently
there has been extensive study on the effect of fluid flow through nanotubes,
which is a part of an ongoing effort worldwide to have a representative in the
microscopic nano-world of all the sensing elements in our present macroscopic
world. Indian Institute of Science has a major contribution in this regard. It
was theoretically predicted that flow of liquid medium would lead to generation
of flow-induced voltage. This was experimentally established by two Indian scientist
at IISc. Only effect of liquid was theoretically investigated and established
experimentally, but effect of gas flow over nanotubes were not investigated, until
A.K Sood and Shankar Ghosh of IISc investigated it experimentally and provided
theoretical explanation for it.

           The same effect as in case of liquid was observed,
but for entirely different reason. These results have interesting application
in biotechnology and can be used in sensing application. Micro devices can be
powered by exploiting these properties.

Here we are providing Seminar Topic on Mesh Radio. This topic will useful to most of the students who are eagerly searching about Mesh Radio.

         Governments are keen to encourage the roll-out of broadband interactive multimedia services to business and residential customers because they recognise the economic benefits of e-commerce, information and entertainment. Digital cable networks can provide a compelling combination of simultaneous services including broadcast TV, VOD, fast Internet
and telephony. Residential customers are likely to be increasingly
attracted to these bundles as the cost can be lower than for separate provision. Cable networks have therefore been implemented or upgraded to digital in many urban areas in the developed countries.

ADSL has been developed by telcos to allow on-demand delivery via copper pairs. A bundle comparable to cable can be provided if ADSL is combined with PSTN telephony and satellite or terrestrial broadcast TV services but incumbant telcos have been slow to roll it out and ‘unbundling’ has not proved successful so far. Some telcos have been accused of restricting ADSL performance and keeping prices high to protect their existing business revenues. Prices have recently fallen but even now the ADSL (and SDSL) offerings are primarily targeted at provision of fast (but contended) Internet services for SME and SOHO customers. This slow progress (which is partly due to the unfavourable economic climate) has also allowed cable companies to move slowly.

A significant proportion of customers in suburban and semi-rural
areas will only be able to have ADSL at lower rates because of the attenuation caused by the longer copper drops. One solution is to take fibre out to street cabinets equipped for VDSL but this is expensive, even where ducts are already available. Network operators and service providers are increasingly beset by a wave of technologies that could potentially close the gap between their fibre trunk networks and a client base that is all too anxious for the industry to accelerate the rollout of broadband. While the established vendors of copper-based DSL and fibre-based cable are finding new business, many start-up operators, discouraged by the high cost of entry into wired markets, have been looking to evolving wireless radio and laser options.

One relatively late entrant into this competitive mire is mesh radio, a technology that has quietly emerged to become a potential holder of the title ‘next big thing’. Mesh Radio is a new approach to Broadband Fixed Wireless Access (BFWA) that avoids the limitations of point to multi-point delivery. It could provide a cheaper ‘3rd Way’ to implement residential broadband that is also independent of any existing network operator or service provider.

Instead of connecting each subscriber individually to a central provider, each is linked to several other subscribers nearby by low-power radio transmitters; these in turn are connected to others, forming a network, or mesh, of radio interconnections that at some point links back to the central transmitter.

                                       ANTHROPOMORPHIC ROBOT HAND   

                 

            This
paper presents an anthropomorphic robot hand called the Gifu hand
II, which has a thumb and four fingers, all the
joints of which are driven by servomotors built into the fingers
and the palm. The thumb has four joints with four-degrees-of-freedom
(DOF); the other fingers have four joints with 3-DOF; and two axes
of the joints near the palm cross orthogonally at one point, as
is the case in the human hand. The Gifu hand II can be equipped
with six-axes force sensor at each fingertip and a developed distributed
tactile sensor with 624 detecting points on its surface. The design
concepts and the specifications of the Gifu hand II, the basic characteristics
of the tactile sensor, and the pressure distributions at the time
of object grasping are described and discussed herein. Our results
demonstrate that the Gifu hand II has a high potential to perform
dexterous object manipulations like the human hand.

INTRODUCTION

            IT IS HIGHLY
expected that forthcoming humanoid robots will execute various complicated
tasks via communication with a human user. The humanoid robots will
be equipped with anthropomorphic multifingered hands very much like
the human hand. We call this a humanoid hand robot. Humanoid hand
robots will eventually supplant human labor in the execution of
intricate and dangerous tasks in areas such as manufacturing, space,
the seabed, and so on. Further, the anthropomorphic hand will be
provided as a prosthetic application for handicapped individuals.

           Many multifingered
robot hands (e.g., the Stanford-JPL hand by Salisbury et al.(1),
the Utah/MIT hand by Jacobsen et al. [2], the JPL four-fingered
hand by Jau [3], and the Anthrobot hand by Kyriakopoulos et al.
[4]) have been developed. These robot hands are driven by actuators
that are located in a place remote from the robot hand frame and
connected by tendon cables. The elasticity of the tendon cable causes
inaccurate joint angle control, and the long wiring of tendon cables
may obstruct the robot motion when the hand is attached to the tip
of the robot arm. Moreover, these hands have been problematic commercial
products, particularly in terms of maintenance, due to their mechanical
complexity.

          To solve these
problems, robot hands in which the actuators are built into the
hand (e.g., the Belgrade/USC hand by Venkataraman et al. [5], the
Omni hand by Rosheim [6], the NTU hand by Lin et al. [7], and the
DLR’s hand by Liu et al. [8]) have been developed. However, these
hands present a problem in that their movement is unlike that of
the human hand because the number of fingers and the number of joints
in the fingers are insufficient. Recently, many reports on the use
of the tactile sensor [9]-[13] have been presented, all of which
attempted to realize adequate object manipulation involving contact
with the finger and palm. The development of the hand, which combines
a 6-axial force sensor attached at the fingertip and a distributed
tactile sensor mounted on the hand surface, has been slight.

          Our group developed
the Gifu hand I [14], [15], a five-fingered hand driven by built-in
servomotors. We investigated the hand’s potential, basing the platform
of the study on dexterous grasping and manipulation of objects.
Because it had a nonnegligible backlash in the gear transmission,
we redesigned the anthropomorphic robot hand based on the finite
element analysis to reduce the backlash and enhance the output torque.
We call this version the Gifu hand II.