the robotic palm

8/9/2019 The Robotic Palm

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THE ROBOTIC PALM

Since the dawn of robotics, it has been the goal of scientists and engineers to

build robots similar humans. They have strived to build near human features into

robots.

The earliest robots or robot like mechanisms were the automatons. They were

complex machines, by the standards of the time and age. Time has since passed

and today we can see the likes of Asimo, Honda’s humanoid robot dancing.

The build up to this has not been without innovation and inspiration.

ost robotic applications came up from the need for prosthetics and industrial

applications.

!hile large bulky machines were good enough for industries, human like

features, or anthropomorphism remains the goal for rehabilitation tools involvingany degree of robotic application.

However, current industrial developments are mainly limited to speci"c purpose

grippers and tools that are insu#cient when the robot has to deal with any shape

and si$e ob%ects. &n order to achieve the above applications, adopting the human

hand design seems to be an ade'uate solution, since the human hand is the

most sophisticated and complex outer extremity on human body and an

evolutionary result of millions of years.

&t is not an unknown fact that fre'uently many robotic hands with a very high

degree of resemblance with the human hand but with wide functional limitationsand a poor dexterity level could be found. (therwise, there are hands with a

huge manipulation possibility although with a decrease resemblance with a

human hand. That means that anthropomorphism is not necessary in order to

achieve dexterity in a robotic hand. However, there are others reasons to prefer

an anthropomorphic design in end)e*ectors. They are related to the speci"c

applications of the end)e*ectors like prosthesis and rehabilitation task, or the

environment where the device is going to work, for instance, it can operate in a

man oriented environment and also it can be tele)operated by a man though

interfaces that can reproduce the operator hand behaviour. +esides this, the

relationship between robot and human being is of great importance, for example,service robots should operate in places that are designed for human hand. The

human hand has uni'ue features that enable it to hold a large variety of ob%ect

shapes and coordinate an in"nite movement’s variety. Thus, anthropomorphism

in the design of an arti"cial hand enables the robot to interact correctly with the

environment, between more advantages. Therefore, robotic hands with a high

level of anthropomorphism have become a desirable goal in "nal e*ectors

design.

ooking at recent advances in this "eld, despite the wide research that has been

done and exposed on the literature, as well as the advances made in design,


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control and sensory systems, there are still issues to be solved or need more

improving on robotic hands.

An index to measure the robotic hand capability is termed -dexterity. /exterous

robotic hands have certain characteristics that make them a desirable design.

However, robotic hand dexterity could not only be a*ected but also wasted withan inappropriate sensory and actuator system. This in addition to the lack of

advanced control procedures can present typical problems related to multi)

"ngered hands kinematic, transmission systems etc. among others.

any solutions have been proposed and developed about improving actuator

system0 pneumatic 1exible "ngers are used mostly because they don’t need any

external actuator. Also, some of the most complex devices use articulated "ngers

actuated by electrical motors and tendon transmission. 2on)conventional

actuators have been developed and they have become a good alternative to the

typical actuators used. The improvement in sensory systems and the

accomplishment of new techni'ues in actuator systems in recent years, now

permits the implementation of under)actuated robotic hands, that compared to a

typical robotic hand have better features such as self)adaptive grasping and

allowing applying easy control techni'ues, and also a better dexterity index.

The human hand is connected to the wrist through the palm. &t has 34 ma%or

bones 5eight carpals, "ve metacarpals and the phalanges6, and at least 78 %oint

articulations with 39 degrees of freedom 5/o:6 driven by about forty muscles.

;rasps that involve all hand "ngers can exert up to about ach

"nger consists of a proximal, middle, and distal phalanx, and the thumb has a

proximal and distal phalanges. >ach of the %oints of the "ngers exhibits 1exionand extension, but only the proximal phalanges exhibit abduction and adduction.

The thumb which has the most complex structure exhibits 1exion?extension,

abduction? adduction, and also rotation around the axis of the metacarpal %oint

on the metacarpal phalange. The human hand’s musculoskeletal structure and

its movements are shown in "gure576 below.

(a) (b)


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(c)

FIGURE 1: Human hand (a) Musculoskeletal structure. DIP (distal

interhalan!eal "oints)# PIP (ro$imal interhalan!eal "oints)# M%P

(metacarohalan!eal "oints) (&)# (c) mo'ements that can &e made

The aspects that de"ne the anthropomorphic level in a robotic hand are@

a6 The presence of the main hand morphological elements like opposite

thumb, amount of phalanges and the palm.b6 The way in which contact is made with ob%ects over the entire hand

surface.c6 The robotic hand si$e resemblance with the human hand real si$e and the

correct si$e ratio between all the hand links.

At the same time, those aspects take in consideration more speci"c features that

are very important when a robotic hand is classi"ed, and they permit to evaluate

each robotic hand anthropomorphism level. These are shown in "gure 3.

FIGURE : Ro&otic hand anthroomorhism le'el


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The primary role of the human hand itself is grasping and manipulation. &n a

robotic hand, grasping can be de"ned as the combination of procedures and

operations that must be developed to hold an ob%ect within the hand. (ne of the

dexterous robotics hand’s challenges is to achieve a design capable of carrying

out a powerful hold, as well as having "ne manipulative skills and versatility.

&n :igure below, four fundamental steps of a robotic hand’s manipulation task

is presented.

FIGURE : Grasin! rocess

The pre)grasp is the initial pattern in which the arm?hand system is placed to

start the contact with the ob%ect to be achieved. The grasp per se is the second

phase where the hand makes contact with the ob%ect0 here, it is possible to alter

the initial position of the ob%ect, even break it, when the force and motion control

algorithms are not suitable. The third phase, Bost)grasp transport, is performed

after the ob%ect is grasped and stabled, and it consists on moving the ob%ect from

one position to another, taking into account possible colliding with external

obstacles. The "nal step is achieved when the ob%ect is placed in the desired

position, which re'uests robust and reactive position?force control strategies.

Some of the most advanced robotic palms have managed to approach human

hand like dexterity. +elow, we look at a few such advances. These are some of

the most advanced platforms today.

BRAHMA HAND

A new concept of arti"cial hand, whose prototype was called +CAHA 5+ra$ilian

Anthropomorphic Hand6 was development by Daurin, with 33 degree of freedom

5dof6,


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FIGURE *: +he ,R-HM- PR++/PE

The +CAHA was a new concept for an arti"cial hand, and its mechanical links,

%oints and transmission are an attempt to learn some characteristics of the

human hand. The links are made of a biocompatible polymer, the %oints are

biologically inspired contact %oints and conventional rotary %oints are not used.

The coupling between the actuators and the %oints is done by cables and is

modelled as an e'uivalent to springs and dampers.

High re%ection levels of commercial hand prosthesis revealed that hand

prosthesis re'uire more than proper functionality. +etter aesthetics, greater

functionality and a more human friendly behaviour might hold possible answers

for both "elds. The pro%ect of the +ra$ilian Anthropomorphic Hand was

undertaken to serve as a basis for analysis of future strategies for friendly

interaction between man and machine. The robot hand is intended to be, in "rst

place, thought of as an open and useful environment for executing manipulation

tasks that approximate the abilities of human hands.

KANGUERA HAND

Eanguera is a robot hand developed by the Fniversity of SGo Baulo. &t runs the

x!orks operating system. The goal of this research pro%ect is to model the

kinematic properties of a human hand so that better anthropomorphic robotic

grippers or manipulators can be developed. The name, Eanguera, is an ancient

indigenous word for Ibones outside the bodyI. Some of the ob%ectives of the

Eanguera pro%ect are to develop strategies for dexterous robotic manipulation

and to create new designs for robotic hands which are biologically inspired.

These new designs and strategies will be used for user friendly human machine

interface and for upper limb rehabilitation technologies.


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The hand has an anthropomorphic shape, and is the si$e of a large human hand.

&t has < "ngers, and a simpli"ed thumb, each one with four degrees of freedom

5/(:6. >ach "nger is treated as an individual robot, giving the overall system,

from the wrist on, 3= /(: in total. The "ngers are constructed from a special

resin, and the %oints are designed to mimic human %oints they are not physically

%oined, but in close contact, using the resinJs friction and cables to work together. The motion of each /o: is driven though a servo, and a cable transmission

system. This transmission system is more accurate than the ones uses by

previous robotic hands, and is thus more suitable for the implementation of

complex tra%ectory algorithms, such as adduction and abduction capacity for

both the "ngers and the thumb. The computational hardware is based on a ;>

:A2FD microcontroller with a ;< processor, mounted on a standard compact BD&

bus. The operating system used to run the simulations is x!orks 9.4, and the

simulation environment is handled with ;rasp&tK software, where a model of the

hand was developed in order to visuali$e it.

An incremental self)organi$ing map, called State Tra%ectory ;enerator 5STCA;>26

is employed to plan state tra%ectory of this robot. STCA;>2 can deal with

di*erent criteria to construct topological maps of the problem space, choosing

neighbours that match these criteria and optimi$e di*erent measures of the

learned map. STCA;>2 can also learn heterogeneous information, such as

angles, tor'ues and positions of a manipulator, preserving their characteristics. &t

was "rst tested on the Eanguera.

The Eanguera Hand deals with the nonlinear behaviour using a new transmission

concept, where mechanical cams replace the traditional pulley mechanism.

These cams provide a linear displacement for the cables between the motor and

the %oints, avoiding undesired dead $ones and hysteresis.


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FIGURE 0: Detailed Hand Hardare.

a) +he hand s2stem emhasi3in!

the ca&le transmission s2stem

and the actuators outside the

hand structure.&) Detail o4 the hand.

c) %a&le !uided inside thestructure

d) Formulation to desi!n the cam

s2stem.e) Unmounted hand arts.

f6 4) +he atented DF "oint


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Fi!ure 5: 6imulation 1: +ra"ector2

4rom a closed 7st to an oen hand#

!enerated &2 6+R-GE8

Fi!ure 9: 6imulation : +ra"ector2 4rom

an oen hand to a closed 7st#

!enerated &2 6+R-GE8

SHADOW HAND

The Shadow /exterous Hand is a humani)form robot hand system developed by

The Shadow Cobot Dompany in ondon. The hand is comparable to a humanhand in si$e and shape, and reproduces all of its degrees of freedom. The Hand is

commercially available in pneumatic and electric actuated models and currently

used in a wide range of institutions including 2ASA, +ielefeld Fniversity and

Darnegie ellon Fniversity, and >F research pro%ects such as HA2/>. The

Shadow /exterous Cobot Hand is the "rst commercially available robot hand

from the company, and follows a series of prototype humanoid hand and arm

systems.

The Shadow /exterous Hand has been designed to be as similar as possible to

the average hand of the human male. The forearm structure is slightly wider

than the human forearm as it contains all of the system actuation.

The Shadow /exterous Hand has 3< %oints. &t has 3= degrees of freedom, a

greater number than that of a human hand.L3M &t has been designed to have a

range of movement e'uivalent to that of a typical human being. The four "ngers

of the hand contain two one)axis %oints connecting the distal phalanx, middle

phalanx and proximal phalanx and one universal %oint connecting the "nger to

the metacarpal. The little "nger has an extra one)axis %oint on the metacarpal to

provide the Hand with a palm curl movement. The thumb contains one one)axis

%oint connecting the distal phalanx to the proximal phalanx, one universal %oint

connecting the thumb to the metacarpal and one one)axis %oint on the bottom of the metacarpal to provide a palm curl movement. The wrist contains two %oints,

providing 1ex?extend and adduct?abduct.

The hand is available in both electric motor driven and pneumatic muscle driven

models. The motor hand is driven by 3= /D motors in the forearm, whereas the

muscle hand is powered by 3= antagonistic pairs of Air uscles in the forearm.

All hands have Hall >*ect sensors integrated into every %oint to provide precise

positional feedback. The motor hand includes force sensors for each degree of

freedom and the muscle hand includes pressure sensors for each muscle. There

are also several options for tactile sensing on the hand from basic pressuresensors to the +ioTac multimodal tactile sensor from Syntouch D.


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The Shadow Hand software system is based on Cobot (perating System, through

which con"guration, calibration, simulation and control of the hand is

implemented. A simulation of the Shadow hand can be downloaded and installed

in C(S.

FIGURE : ;inematic la2out o4 the

6hado Hand

FIGURE


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A remote system using the Shadow Hand technology will allow an operator to

work in an inaccessible area. This could be a harmful environment where

radiation, toxic chemicals or biological ha$ards are present. The Shadow

/exterous Hand can also allow specialists to be present, whenever needed,

anywhere across the world, even in places where humans cannot reach. This way

machine repair could be done for example on drilling platforms, inside windturbines etc. Also medical examination, education and training by experts could

be done on long distance. >ven bomb disposal could be done this way.

ROBONAUT

2ASA, working with its partner ;eneral otors, developed the Cobonaut 3 5C36

hand as a device that could work with a wide range of human interfaces, going

beyond the original mandate of using tools designed for Space !alking

Astronauts.

FIGURE 1=:

R,8-U+ hand

FIGURE 11: +he Ro&onaut hand and

4orearm ith all a'ionics

!hile several grippers have been designed for space use and some even testedin space, no dexterous robotic hand has been 1own in >A conditions. The

Cobonaut Hand is one of the "rst under development for space >A use and the

closest in si$e and capability to a suited astronaut’s hand.

Noint travel for the wrist pitch and yaw is designed to meet or exceed the human

hand in a pressuri$ed glove. The hand and wrist parts are si$ed to reproduce the

necessary strength to meet maximum >A crew re'uirements.

The Cobonaut Hand has a total of fourteen degrees of freedom. &t consists of a

forearm which houses the motors and drive electronics, a two degree of freedom

wrist, and a "ve "nger, twelve degree of freedom hand. The forearm, whichmeasures four inches in diameter at its base and is approximately eight inches


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long, houses all fourteen motors, 73 separate circuit boards, and all of the wiring

for the hand.

The hand itself is broken down into two sections @ a dexterous work set which is

used for manipulation, and a grasping set which allows the hand to maintain a

stable grasp while manipulating or actuating a given ob%ect. This is an essentialfeature for tool use. The dexterous set consists of two three degree of freedom

"ngers 5middle and index6 and a three degree of freedom opposable thumb. The

grasping set consists of two, one degree of freedom "ngers 5ring and small6 and

a palm degree of freedom. All of the "ngers are shock mounted into the palm.

FIGURE 1: R,8-U+ hand assem&l2

Cobonaut uses several novel techni'ues for establishing remote control of its

subsystems and enabling the human operator to maintain situation awareness.

Telepresence re'uires that a human operator control the actions of a remotely

operated robot. &n the case of the Cobonaut pro%ect, the human operator must

control forty)three individual degrees of freedom. The use of three axis hand

controllers would present a formidable task for the operator. +ecause Cobonaut

is anthropomorphic, the logical method of control is one of a master)slave

relationship whereby the operatorJs motions are essentially mimicked by the

robot. The operator performs the arm, head and hand motions for the re'uiredtasks and a master)slave control mechanism duplicates the same motions in the

Cobot. The goal of telepresence control is to provide an intuitive, unobtrusive,

accurate and low)cost method for tracking operator motions and communicating

them to the robotic system. Some of the component technologies used in

CobonautJs telepresence system includes Helmet ounted /isplays 5H/6, force

and tactile feedback gloves and posture trackers.


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As can be seen, huge advances have been made over the "rst robotic hands that

were made in the 7O4=’s. This is a "eld where technology is still in its infancy.

There is still a lot to achieve and a lot of new challenges to overcome.

C>:>C>2D>S

7. elo , >rika 2athalia ;ama , SPnche$, (scar :ernando AvilQs, Hurtado,

/arRo Amaya@ - Anthropomorphic Robotic Hands: a Review”, Fniversidad

ilitar 2ueva ;ranada 5Dolombia6, &ngenieria desarollo, olume 3, no. 3,

Nuly)/ecember 3=7< 5&SS2@ =733)

the robotic palm

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