So, um I wanted to start off with this, when
you look at knee stability the factors that
influence it are the load line. How the load
line is located with respect to the knee then
of course, you have your hip moment that can
be used to influence the load line. And of
course, the location of the knee center itself
where the knee center is located.
These are three factors that wouldassuming
that the knee by itself does not have some
breaking mechanism. If there is some breaking
mechanism that moment would also play a part.
But assuming there is nobreaking system in
the knee, the three factors which influence
the stability of the knee are the hip moment,
the load line and the location of the knee
center ok at that particular instance .
So, this animation we had trouble making it
play yesterday, but you can see here for a
single access knee . If the load line is behind
the knee then the moment at the knee joint
will tend to make it buckle right.
So, to prevent the buckling what the user
does is they apply a hip extension moment
which causes it to hit the bump stop, which
causes the knee to lock by contacting the
bump stop. And, that moves thee by moving
that load line it now generates an extension
moment about the knee.
Now, in the case of push off the moment at
the knee joint due to the load line is an
extension moment. And now so, the user applies
a flexion moment to shift the load line and
initiate flexion. So, this is theworking together
of thehow the user can use that residual hip
moment or that normal hip moment to shift
the load line in order to create extension
or flexion at the knee in the absence of active
control at the knee directly, because you
are controlling the knee through the hip here
ok. So, I just wanted to show you thisanimation.
Moving on we will see so, this is an example
of a sophisticated knee which has a microcontroller
it is called a C-Leg .It is quite expensive,several
tens of thousands of dollars,I do not know
what the current price is ah, but this is
a very sophisticated knee that has a microprocessor
on board and it has some sensors. So, there
are sensors that detect loading at the foot
and ankle, there are sensors that detect the
knee angle ok . So, depending and there is
an algorithm which looks at the interrelationship
between. So,these quantities to decide you
know whether it 
is a a stumbling situation or whether it is
a normal situation .
And you know how to regulate the movement
of the knee by controlling the hydraulic unit
that is in there ok. So, the hydraulic unit
it makes so,the controller makes adjustments
to the hydraulic unit in order to control
the movement of the shin with respect to the
thigh. So, this is an so, it has a rechargeablebattery
it hasso, the microprocessor reads with a
frequency of 50 hertz 50 times per second
it processes this data. So, and then you have
loading. So, and then if you want to sort
of do other activities ok there is like a
switch and that is by tapping the toe ok.
So, they they so, you will have different
programs for this knee ok, it will be programmed
with different things. So, if they want to
bicycle for instance ok, in order for the
they will tap this toe to activate that program.
So, it is like a switch ok. So, they have
a mechanism to switch programs, say the person
wants to dolet the knees swing freely as when
they are cycling or something like that or
if they want to stand for a long time and
so, they just want to lock it ok.
They do not want to have to worry about it
or think about it, then they can access those
different programs by just tapping the toe
repeatedly. So, there are so, this isthere
are othermicroprocessor controlled kneesas
well and these knees you know can help a user
go down step by step, you know when they are
climbing downstairs or climbing upstairs.
So, they allow the user a more natural gate,
but they are very very expensive very expensive.
So, today I just wanted to talk to you about
different kind of so, we have talked about
assistive devices for walking ok. We have
looked at walking in detail and we have talked
aboutan orthotic or a prosthetic limb for
walking, but for many people with impairments
walking may not be a possibility ok. So, for
those people a wheelchair is themay be a preferred
mode of transport. It gives them independence,
it enables them to move around which they
otherwise would not have and move around in
a fairly energy efficient manner ok.
So, today I just wanted to talk to you about
you know in the development of an assistive
device, what does a design journey look like
ok. And, we will talk about the development
of this standing wheelchairbecause, one aspect
is understanding the user needs and developing
a design, but to actually make that design
reach the market what are some of thesteps
involved . So, I thought you I could give
you a glimpse into this design journey today
.
So, if you look at the statistics over 30
million people in India alone are affected
by some kind of locomotor disability ok; which
means they would need some kind of an orthosis,
prosthesis or a wheelchair ok, three broad
categories ofmobility devices. And, it could
be because of various types of impairments,
it could be spinal cord injury, you know paralysis,
traumatic brain injury,some kinds ofgenetic
disorders,cerebral palsy, muscular dystrophy
etcetera. There are various causes and therefore,
some of the needs are also going to be different.
But, a wheelchair is a mode of transport that
is either you know in an assisted manner or
selfoperated manner that can give a person
who can otherwise not walk mobility.
Even aging you know many of us once we get
past a certain age, it may there may come
a point where we may need to use a wheelchair
for mobility ok. So, any any of theseso, an
assistive device is not necessarily something
that only a specific portion of the population
will use. I mean as we as the lifespan is
increasing more numbers ofus are going to
need assistive devices. In fact, all of us
even now use assistive devices. What assistive
devices do you is commonly see, your spectacles
right it is a compensatory device forbetter
eye functioning . So,but it is become very
accepted. So, and its even become a fashion
statement right, people have different glasses
that they use when theywear different clothes
for instance or for different modes I do not
know .
So, I mean people do have multiple you know
it has become a fashion statement ah. So,
when you are developing an assistive device
you have to keep that in mind. So, when you
design an assistive device it is there it
is a lot about the functionality, but it is
also going it should also be something that
a person feels proud to own ok. It should
not just be that ok here is a device and that
is it you know, it should be something that
you feelhappy to own. Not only is it providing
you more functionality, but also something
that is a matter ofright.
So, in the development of assistive devices
a lot of engineering knowledge goes in, but
along with it there is also a biomechanics
knowledge that will go in. Because, most assistive
devices there is the human device interaction
is very close; you know with the prosthesis
or the orthoses you are literally you are
wearing it. With a wheelchair you are probably
spending many many hours sitting on it. And,
you know how you interact with thedifferentoperations
in the wheelchair all those you know how much
force can you apply.
What is the correct posture that you can sit
in so, that it does not hurt you in the long
run or that you do not develop otherpain or
things like. So, there is a lot of biomechanics
knowledge that will go into designing an assistive
device as also a lot of engineering knowledge.
So, in our lab a lot of what we do is mechanical
engineering. So, we do notwe have not used
we have not designed a lot of devices that
require you know microprocessor control or
although we will eventually get there. But,
right now we focus a lot on mechanical devices
for two reasons: one is affordability anytime
you go into motors, controllers, batteries
the cost significantly goes up.
The other reason is in India power is still
still a luxury for mean we still experience
power cut. So, if you are for a device that
is essential for a person's daily life, if
the dependence on external power is high then
that it is that in itself becomes a disabling
factor. So, you want to minimize thatdependence
on external power. So, a lot of the devices
that we develop tend to use muscular effort
to accomplish the task.
So, now we will look at this. So, wheelchair
is for mobility it is you know and there could
be like I said various reasons for using it.
Spinal cord injury is a bigreason for using
a wheelchair, polio polio to some extent yes,
if they are not able to use you know if they
have used a lockni for too long and it starts
hurting they may have tomove to a wheelchair,
aging of course, etcetera cerebral palsy and
all there are also problems. So, while a wheelchair
can be a a huge enabler for independence the
prolonged sitting can also cause various problems
in the long run. We all know you know even
in sedentary lifestyles today right you are
encouraged to get up and walk after every
few minutes. You know people say do not keep
sitting in one place looking at a screen get
up and walk around a little bit right.
So,the reason for that is if you are sitting
for prolonged periods of time and especially
if you already have other problems, because
of which you are in a wheelchair you are using
a wheelchair then you could have issues like
pressure sores. So, for instance many people
with spinal cord injury lose sensation also.
So, they will not know that they are putting
too much pressure on a particular area. So,
if the posture is not correct or you know
if there are some they may not even sense
anything that is wrong with the wheelchair;
say there is some sharp protrusion or they
they may not even realize it.
And if there is a pressure sore and it is
not detected early it could be a life threatening
complication. Just sitting for prolonged periods
of time your weight is being it will cause
pressure sores in those area especially, where
there are bony prominences because the contractors
could develop because you are not exercising
the range of motion at those joints right.
So, they may get frozen atin certain positions,
swelling of legs and feet and because you
are not loading your bones in the lower limb
slowly the bones start regenerating. With
the result that if you happen to fall down,
your risk of fracture goes significantly higher
because your bones become more brittle ok.
So, these are some of theissues withprolonged
sitting.
So, a standing program is actually prescribed
for many wheelchair users. So, as part of
therapy they are supposed to follow a standing
program. And, a standing posture really benefits
you in multiple ways, one is better functionality
yes .
.
In activity of muscles the muscles are not.
So, the bones are not being loaded yeah, but
it is a living structure I have mentioned
this before. If the bones the mineral composition
changes, if the bones are not loaded then
the composition of the bones changes they
startbecoming more brittle. So, that is why
the risk of fractures goes up .
.
You are not using the bone.
.
It becomes .
.
It becomes more ductile, why would you say
that.
.
Ductile is so, when is fracture immediate.
I mean in the sense a ductile material will
yield.
Yeah.
Before bone is not like that, the composition
is such that it is more likely to crack ok.
So, it is a it fracturesrather than yielding
you do not see boneok. So, if there is a fall
it is going to be a fracture that happens.
So, a standing position can provide you better
functionality you can access so, in most places
if you see switches or shelves will be located
at higher levels. So, if you are able to stand
or you know if you havea job where you have
to work at a table that typically requires
a standing posture for you to be able to work
effectively. So, functionality is improved
if you are able to stand even more than that
the psychological well being.
Because, this were you know in many cases
so, for instance with people with spinal cord
injury they were able to stand, they were
able to walk before the injury happened. So,
if they are nowso, being able to stand or
if you are in a room full of people who are
standing and you are the only one in a chair
in a wheelchair. Then there is there could
be issues with self esteem, you feel that
everybody is talking down to you. So, being
able to stand can also have an effect on your
psychological well being .
And, besides this there is a lot 
of research that shows that there are a lot
of health benefits to standing. It improves
circulation, it improves the bone health because
of the loading.Range of motion at the joints
and vital organ functioning also your respiratory
system, your excretory system everything work
better if you are also able toif you are able
to be in the standing posture forsome time.
And, then it reduces the incidence of pressure
sores, urinary tract infections, spasticity
and contractures. So, these are all benefits
that that are well knownforstanding.
So, a wheelchair user is encouraged to follow
a standingstanding therapy on an everyday
basis. Most wheelchair users should are encouraged
toincorporate some kind of standing in their
everyday routine, but it is a very difficult
task to perform. You know if you you say many
of them will then have to wear like an orthosis
with a lockni or depending on the level of.
So, they may have to wear an orthosis, they
may have to use crutches or somebody will
have to help lift them out of the wheelchair.
And, then they have to stand for say 20 minutes
a day, you know or they may be put in something
called a standing frame which provides support
at the hips and at the knee to make them stand.
But, at least 2 or 3 people will have to lift
them out of the wheelchair and help them get
into the correct positioning in this. So,
it is a very difficult to and other than you
know just accomplishing the standing it does
not really improve the functionality a whole
lot it can be done for therapy. But so, integrating
the standing into the wheelchair can provide
a lot of benefits in terms of better functionality.
And, it is also integrating that action into
their everyday life. You know it is like our
putting aside time to exercise, you know if
you are encouraged to walk for 30 minutes
a day putting aside that time.
And then getting on a treadmill or going for
a walk versus ok, let me just walk to work
or let me keep myyou know path my car far
away and walk a little bit extra. Let me climb
stairs, integrating it integrating that exercise
into your everyday activities is a more effective
way of ensuring that it gets done. Rather
than saying put some time aside and go stand
for 20 minutes.
So, that was the thought behind the standing
wheelchair. There are somemodels available
in western countries extremely expensive,
they costabout 15,000 US dollars ok. So, but
if you look at it, it is essentially a mechanism
design problem. If you look at the functioning
of the standing wheelchair you know it is
you have to make that chair come up to a standing
position. So, so we started looking at it
as ok it is just an interesting mechanism
design problem.
Let us let us see if we can design the mechanism
that can get this chair from a sitting to
a standing position, that is what it started
off with; the kinematic design of the mechanism
to accomplish this task. So, this journey
started about more than 5 years ago ok.
So, and then the very first prototype was
built byone of mystudents former students
who did it who did did this as his dual degree
project ok. So, initially in a in a kinematics
course some students had come up with a few
different designs, but they did not make a
fullprototype. Harshal the first student he
took it up as his dual degree project, did
all the analysis and he actually built this
was his his second prototype.
So, the first prototype he had the mechanism
designed he knew it was, but when he tried
to stand up on it ok; beyond a certain point
he could not apply enough torque to lift himself
up. Remember a person has to apply torque
with their arms enough to lift themselves
up to the standing, lift their entire body
weight to the standing position. So, it is
not an easy task .
So, then we looked at spring balancing and
we realized that ok without a spring. So,
you have a gas spring here or actually Harshal
first started off with a regular compression
spring, but that spring sort of balances the
weight and that enables you to apply a torque
that is possible by a human being ok. So,
using a spring he built this version 0 and
it was made out of wood and aluminum and you
know it was really a rickety structure that
only he had the courage to stand on. So, that
was the first prototype that was built ok
and you can see that he is, the second one
then we said ok we have to make the design
more robust ok.
So, we did some more analysis because you
know time constraint Harshal left, then next
bunch of students they took upthey did some
more design calculations,did some more optimization.
And,using stronger materials fabricated a
prototype that could now be used by some able
bodied users, some of us could try the prototype.
It was sturdy enough to tryand it was essentially
to validate the standing mechanism. So,and
this time we used a gas spring because with
the the problem with the compression spring
is there is no damping.
So, if the standing mechanisms if there is
no person in the wheelchair and the standing
mechanisms gets actuated it just jumps up
like that, that is a huge safety issue. You
cannot have a device designed for a human
being that behaves like that. Gas springs
you know it isthere is somedamping inherentlypresent.
So, we were and they are also well used in
many industrial applications. So, they aremore
durable. So, this standing functionality was
the first thing that we validated.
Now, the next thing is the intended user for
this wheelchair is not an able bodied user
ok. So, when we try to test version 1 with
a volunteer,who is actually a wheelchair user
we found some interesting things. For instancethis
person has a spinal cord injury so, as they
tried to come up to the standing position
their feet kept slipping of the footplate,
none of us had experienced that. So, that
shows that you know there are so many adjustments
and compensations that we make that we are
not even aware of, we were all gripping the
footplate with our feet without even realizing
it. When a person does not have that muscle
power to do that that is when you start noticing
some of these things.
It starts it started slipping off, the feet
started slipping off thefoot plates that was
one thing. Then of course, for a person with
this kind of an impairment it is veryyou have
to have a lot of adjustability. Because, if
the standing posture is not correct you know
then it could do more damage to them, you
know could do more damage than good. So, that
is something you have to be very careful about
it, again we make adjustments we do not need
all the restraintsand so, we are able to adjust
toan able bodied user is able to adjust to
that and still may the mechanism work. But,
because the intended user is a person who
has an impairment we had to put in more safety
features, many of them would not have trunk
control suitable trunk controlmay not be.
So, they need to make you need to make sure
they do not fall forward when they arein this
standing position, then the knee support is
critical.
So, when a person if a person cannot stand
it is because, they do not have stability
at the knee. So, you have to ensure that that
knee is stable. So, the knee support is critical
for an actual wheelchair user; so, designing
the knee support then the seat depth adjustment.
So, that when they get into the standing posture
they are not putting undue pressure on the
knee, see because these are some of these
people have not may not have stood for on
a regular basis for a while. So, again you
have to be careful that you are not loading
places in an abnormal fashion ok.
So, you are not causing more damage. The gas
spring so, this this is it is to balance the
weight of the person different people different
weights. So, how do you make the gas spring
adjustable so that it canso that you can try
this with various users because, these prototypes
take a long time to make ok. So, it is not
going to happen,you cannot have multiple prototypes
to start with for different users ok. And,
that is one of theso, when we set out to do
this project and we said we would create an
affordable device these are some of the things.
So, if you look at some of the other standing
wheelchairs many of them you it is like a
one sizetheythe bad ones will be like a one
size fits all which is not a goodstrategy
for a very diverse population.
The really good ones are custom made. So,
they will come if you are a wheelchair user
so, we wanted to get one of those devices
for benchmarking. They said tell us where,
the user is we will come where where the user
is in the US, we will come take measurements
and then build the wheelchair for you. So,
it is a custom built device. So, there is
huge expense involved if you are making a
device of this complexity, if your are making
a custom device each time ok. So, our objective
so, in making it affordable one is make it
mechanical, design it from scratch ok. So,you
you know you own the IP to the design, but
also how do you make it customizable and yet
mass manufacturable. For it to be economical,
for it to be affordable it has to be mass
manufacturable ok.
You cannot be making one part at a time, it
has to be mass manufacturable at the same
time how do you incorporate all the adjustability
that you need to fit a wide range of users.
So, these were some of the challenges that
werethat we dealt with. So, here we found
that so, it had safety features it had the
heel support you know to prevent the foot
slipping. It had knee supports and the chest
support, adjustments for the user height and
weight . And,we tested this single prototype
with over 50 wheelchair users different age
groups, different height, weight etcetera.
And, to see you know what is standing functionality
worked well, each time you have to make adjustments
you can adjust the location of the gas springs.
So, thatthe same gas spring can be used for
all these people. And,we found that everybody
was happy with how this time; the effort required
to use the standing functionality was about
the same. So, if they could propel the wheelchair
then they were able to use the standing functionality,
they were able to lift themselves to the standing
position . Then we decided at that point because,
for this particular project the goal is to
get these out especially to theeconomically
disadvantaged users.
Because, they are the ones who lack access
to therapy ok, but and many of them we found
that when we went on a lot of field visits
we found that they are not using even when
they are given meals as they are not using
it. Because, many of their wheelchairs are
unsuitable for use and, use outdoors because
of the rough terrain; so, we said ok we are
providing the standing functionality. But,
if they are not you know if their houses are
too small to use this inside and if what they
really need is outdoor mobility, then outdoor
mobility is also something that we need to
provide in this wheelchair.
So, here you can see the gas spring you can
customize, footrest, height and the seat depth
are also ah. So, here is a video of an actual
user. So, it functions like a regular self
propelled wheelchair . And then so, this is
a user with spinal cord injury at the T9 level
thoracic 9, remember your spinal cord ok,
T9 level. And, then you can see they come
up to the standing position, it locks in that
position there is a um and then they can use
their own arm power to again come back down
ok. So, this was in this version we also hand
this linkage to kind of bring the foot rest
to the ground. So, that you know it increases
the base of support.
When we realize that we are going to go for
an outdoor mobility we looked at existing
outdoor wheelchairs none of these have standing
functionality, but you know most of them will
have. So, if you look at these regular 4 wheel
wheelchairs most of them have a small base
of support. For them these are mainly for
indoor use, it is for maneuverability, it
is for good maneuverability.If you look at
an outdoor wheelchairs that will have a longer
base of support ok. So, that in outdoors you
have betterstability .
The really good ones that we found have a
3 wheel configuration. So, they have only
1 caster in the front and 2 wheels and that
gives you the tripod support. So, no matter
what terrain you are on because, here with
the 4 wheels right; if one of the driving
wheels gets stuck right it is very difficult
to with the 3 wheel support you can navigate
uneven terrain better ok.
So, we said ok let us make the standing wheelchair
with a 3 wheel base support and that also
helped us to eliminate all those linkages
to make the footrest move down and contact
the ground ok. So, now everything when they
are in the standing position they stay within
the base of support. Because, if they move
outside the base of support your are going
to lose stability you do not want the person
to topple in the standing position. So, for
that so, we went with adevice of this nature
with a 3 wheel base and with an increased
base length ok.
And, a lot of industrial design inputs go
into start going into the design because,
you know how does the user interact, you know
what kind of a handle, how do they hold it,
what is a better way. So, a lot of ergonomics
goes intoseeing how the user interacts, you
know there should not be pinch points. You
know where are the likely places where a users
finger could get stuck and how do you eliminatethings
like that. And so, you know theobjective was
to make the propulsion comfortable on rough
terrain.
So, you can see as the design evolved thethe
looks started getting better aesthetics started
getting better, we also made it portable.
So, somebody wants to take this with them
on the train or in an auto you know this can
these wheels can be removed, the back rest
can be folded etcetera. I think right now
I think in the current when the backrest can
actually be removed.
So, this is the evolution you can see from
you know a design on paper to version 0 to
something that actually looks like a product
and it is a long journey, it is a long journey
tocome there. So, if you look at it we have
tested it with both genders, same prototype
tested with a wide age group, wide weight
range, height 5 feet to 6 feet. So, we are
now in the if you count from the timeHarshal
started working on it, we are in our sixth
year. But, the major development has happened
in the last this is the fourth year of major
development. So, there was a lull for about
2 years because, one student leaves you nobody
everybody wants a new project. The fun is
in for most people, the fun is in seeing the
first prototype work, because this is a lot
of grunt work that goes into making a prototype
into a viable product.
You know you have to look at manufacturability,
you have to look at a lot of details, it is
a lot ofit is a lot of grunt work. It is a
lot of grunt workwhereas, the first part is
the most exciting thing. You even that animation
you just see that and you are like wow, you
know it looks I am done yeah that is that
is. So, it really takes a lot of dedication
for people to make this journey to be even
willing to make this journey from prototype
to product.And, especially in an academic
setting it is even harder because you know
you want people who will stick around and
do things like that. I have been fortunate
because a lot of my former students have stayed
back, they have turned down jobs to stay back
and work to make things into products ah.
So, that is the and this particular version
will probably be more used in the rural areas
because of the because this outdoor version
is a little difficult to maneuver indoor.
But, our next step will be to also create
an indoor version for urban uses, for the
mandate for this project was to reach as many
people as possible withthis kind of a design.
So, this project is funded by a UK foundation
called the Welcome Trust .
So, these are all some of the customizability
that spread. So, seat width so, now, most
wheelchairs come in multiple widths to accommodate
people of different sizes. So, you know we
had to then look at ok, what are the parts
that will remain the same through all the
wheelchairs. What are the parts that need
to be changed depending on the size of the
wheelchair. So, a lot of the manufacturing
aspects also come intothis ok. Then you know
other adjustments; height, seed depth, the
footrest height, knee block all these have
to be made. It has to be properly fitted to
the person the first time they come,to balance
the weight of the person because the effort
you have to optimize it.
So, that it is fairly easy to get up and to
get down, if it is too easy to get that get
up if it is too easy to come to thevertical
position or near vertical position you do
not go give them a fully vertical position
because of stability. One they may not have
the trunk control and two you want to keep
it within the base . So, if it is too easy
tocome up then you have to work against that
same spring to go down. So, they effort to
go down becomes so, there is a lot of analysis
also that has gone intothis design. So, you
look at the forces in the mechanism you look
at you know with the usersitting there what
kind of torques are required to go up, to
go down and then how do you fine tune ok.
So, for each person there' will be a sweet
spot, where the effort to go up and to go
down are about the same ok, then they feel
comfortable with that; if the effort to go
down is if they go down easily then coming
up becomes difficult for them. So, you have
to find that sweet spot optimize it for each
user. Then propulsion, for propulsion the
wheel position should be adjustable because
different people like to have that in different
places to be able to propel easily; again
that has to do with ergonomics loading you
can do. So, there is a lot of biomechanical
analysis thatand there are you know for those
of you who have gone through this course.
And, who may be interested we want to look
at for instance we have instruments that can
measure the metabolic cost by measuring the
volume of oxygen consumed.
So, we want to do some tests propulsion tests
with this field sir and some other comparable
wheelchairs to measure that data. There is
a lot of biomechanical data collection we
want to look at the kinematics, when a person
how is that when the person is interacting
with the wheelchair. You know you have all
doneprojects related tothe motion analysis
now, we want to do the same thing for this
wheelchair look at the action as the person
is going up coming down. So, you can now do
an inverse dynamic analysis compute the loads
at the elbow and shoulderetcetera. So, there
is a lot of biomechanical analysis we want
to look at the interface pressures. The pressure
at the knee block we want to make sure its,
the values are tolerable at tolerable levels.
They will not cause skindegeneration, the
pressure should not be such that they will
do damage to the skin.
So, there is a lot of biomechanical analysis
thatstill needs to bedone a lot of what we
have done is it is been tested with over 150
users. So, all the user testing has kind of
helped to refine the design as we went alongto
bring it to the stage it is in now and we
expect that this will come to the market maybe
later this year that is the goal. So, if you
look at then for the comfort for the user
the backrest height you know where they get
their lumbar support those things can be adjusted,
the angle of the backrest can be adjusted
etcetera. So, this all this customized ability
is built in to the wheelchair so, that its
fit you know there will be a fitting done
for a person when they get this wheelchair.
And, after that they really do not have to
you knowworry about it too much unless something
you know their weight changes drastically
or something like that .
To test the durability of the wheelchairsso,
quality is another thing right. We want to
make sure that we build a device that meets
international standards for quality. So, there
are some ISO tests and these test rigs were
also designed to execute those ISO tests.There
is a test called a double drum test, where
you have two rollers which make these wheelchairs
move and they also have like slacks in them.
So, that there is a periodic impulse that
is given to the wheelchair. Just as like you
are you are on uneven terrain you know you
hit a bump right, small bumpthat is sort of
to simulate that.
And so, the wheelchair is run on thistest
it has to pass 2,00,000 cycles of this test.
Then after it completes the test that same
wheelchair also has to be loaded on what is
called a curb drop test, that is from the
curb for the footpath. If the wheelchair you
know drops down that 5 centimeter ok, how
manyof those can it withstand ok and the minimum
requirement is about 6666 cycles. So, this
is forthe life of the wheelchair and all these
tests are done with like a 100 kg test dummy
placed on the wheelchair. It is not just the
wheelchair alone, it is like with the 100
kg user sitting on the wheelchair. So, you
have an actual dummy test dummy those of you
who are interested can see inthe lab, then
can see these tests running. I think we have
something going on right now ok.
So, these have to be done, these have to be
done for all the different sizes all that;
then only then we can go for the long term
field testing, where the user will use it
in their everyday life for about a month or
two. And, then we will feel confident that
this product is ready to go out in the market
ok. So, it is a long tedious, detail oriented
process. There are a lot of steps involved.
I have omitted them I have omitted many of
them, because there is a lot of detail you
know there is a lot. So, before we did this
when we actually did the design we did a lot
of FEA: Finite Element Analysis because this
is an expensive and also time consuming way
of testing ok.
Putting something saying if it breaks then
going back and fixing it, now this is the
last step when you are fairly sure this is
to ensure that it will pass. Because, you
have to get these products certified, quality
certifications require that you have to actually
perform these tests. And, because the materials
that you get or say in FEA when you put in
values for things you are putting in estimates
right and you do that to design that. But,
in actuality a weld for instance in solid
works I can make a perfect weld, in real life
a weld may not be that perfect . So, those
are things that you can detect when you actually
test the parts.
So, if something is not right you know; that
means, ok there is some in the process can
we improve the process so, that we get a we
get weld quality. For instance these fixtures
were also designed by students from our lab
two B.Tech students did it as their honours
project .
So, I like to close with you know we have
done testing of this device at so, many different
places, so many rehabilitation centers so,
many NGOs that work with people with disability.
So, many volunteers all across the country
have helped us with testing thiswheelchair
so far. And of course, fundingat very criticalpart
of product development. The majority ofthe
funding has come from the Welcome Trust and
we hope to finish this project this year and
commercialize this design.
The Spinal Foundation is again a user group
of people with the spinal cord injury and
they have they have been really helpful and
giving us you know contacts all over the country
to test these devices . So, that I just wanted
tosort of close out this course by showing
you what a design journey looks like for an
assistive device ok. So, as I said it is a
marriage of biomechanics and design and a
lot of grunt work ok ah. So, thank you.
So, these are some of the other devices those
of you who are interested can look at our
web page, now this is the device. So, you
can see that most wheelchairs are indoor devices,
outdoors you need the longer base and the
tricycle kind of a device is better to maneuver
outdoors. So, this basically converts it into
an outdoor device ok. This is a mechanical
version, we also have a motorized version
of this device . So, this is just to give
you a flavor for the different types of assistive
devices that are there and what it takes to
design a single device .
Thank you .
