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[Music]
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[Music]
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before we proceed ahead
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let us quickly capture what we have done
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so far
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on vehicle dynamics what we did is that
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at vehicle when it is moving
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we looked at all the forces that are
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applied to the vehicle
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the aerodynamic resistance
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the rolling resistance the gradient
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resistance
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and the force due to acceleration when
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we accelerate it
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that gave us the total force
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that is required for the vehicle to
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accelerate at a certain point
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and run at a certain velocity
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we are able to compute this for all
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kinds of vehicles two wheelers three
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wheelers
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four wheelers and even small trucks we
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were able to compute that
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what we did is that once we knew the
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force
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we said well we also know therefore
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what is the power required because the
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force multiplied by the
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velocity gave us the power
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and when we took the power got the power
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we could also integrate and find out the
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energy required
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that is something that we have done
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at the same time once we knew the force
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at any state we also knew
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what the torque requirement is
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and at different speed what the torque
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requirement will be
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what the power requirement will be and
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we also got the energy required
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this is what was a fundamental that we
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had to do
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to get things going
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after that what we did
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in the last class we introduced the
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concept of a drive cycle
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said this is fine but
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if i want to compare some manufacturers
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to wheeler
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to another manufacturer's two wheeler
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we can compare that that how much energy
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does that two wheeler takes to
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carry out a drive and a similar drive
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how does the
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another two wheeler takes
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so the concept of similar drive came in
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and we sort of said that world over
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there are various
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entities regulators
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which define some standard drives
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and you have to obtain the performance
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of the vehicle
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as per that drive and that drive
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is the drive cycle and we introduced the
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concept of driver cycle
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and we said based on that drive cycle we
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can compute what is the maximum power
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required what is the torque maximum
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torque required
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what is the maximum energy what is the
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energy required
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what is the energy efficiency watt hour
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per kilometer
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will figure out all these things and
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we introduced this concept
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slowly and then we defined
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the first standard drive cycle the two
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wheel air
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drive cycle called india drive cycle now
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different cities may have different
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drive cycles
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why because in different cities the
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roads may be of different kind
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the slopes may be there or not there
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in different cities you may have traffic
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moving at different speeds
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but there is a india drive cycle which
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is widely used
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to compare one two wheeler with another
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pretty much around the country
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and we defined this what
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this cycle was the drive cycle what did
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we do we sort of say every instant of
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time
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what is the velocity at which it travels
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next instead of time what is the
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velocity at which it travels
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so we are able to also figure out what
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is the acceleration required
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and for how long does it travel at that
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velocity or with that acceleration
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we are able to figure out and once that
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table
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is created that every instant
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and i sort of say we can take it every
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second we can take it
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every half a second we know exactly how
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the vehicle is
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moving once we know exactly how the
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vehicle is moving that is what the drive
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cycle tells us
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a standard drive cycles then we
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start using whatever we had
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learned so far to create a spreadsheet
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where you sort of say every second what
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is the distance that it will travel what
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will be the acceleration
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what is the force required due to
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acceleration
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what is the rolling resistance force
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what is a drag force required
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and therefore we added all this what are
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the traction force required
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and we computed also traction torque
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and then we computed what is the power
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required to move at that
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second and then we integrated the power
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and obtain the energy and we said this
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can be very nicely done
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on a spreadsheet
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all right now if you notice in this what
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i have not done
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is the slopes because the india drive
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cycle does not define the slope
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but in one of the assignment problem
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that i gave you i actually included the
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slope
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so the spreadsheet will change a bit
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will include one more force called the
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force due to climb force due to gradient
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and you have to add that and do the need
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for
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and based on that we took defined a two
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wheeler we have to define all the
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parameters for the two wheelers
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something that we have been doing for
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the last so much time
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and said we will do every second this
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compute
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and we actually computed and started
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putting the spreadsheet
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in fact an assignment i have asked you
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to build a spreadsheet here we have only
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used the spreadsheet
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we then are able to figure out the
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velocity at which
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every second how much it will travel uh
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the incremental velocity
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incremental velocity ah for incremental
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distance travel and similarly the
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distance
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incremental distance that is traveled
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once we are able to figure this out
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we then are able to also figure out the
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power the
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power the torque the total
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force torque power and we are able to
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integrate and get the energy
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and we also introduce the concept of
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regeneration
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if there is 100 percentage regeneration
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what is the energy consumed
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it is a 30 percent regeneration what is
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the energy consumed all this we have
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done it
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and we are able to then plot
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what is the energy consumed and this is
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with hundred percent
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regeneration you can see that while
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energy consumed is high
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up to around 83 seconds and then
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you are able to recover the energy why
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are you able to recover the energy
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because
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right now after that it is at the peak
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speed and slowing down
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this is assuming all the deceleration
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energy is converted
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back to the energy electrical energy
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and put into the battery within saucer
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well that is not always so
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so we introduce the concept of
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regeneration and say
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if i take only 50 regeneration
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then the energy consumed would be little
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more
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and we actually introduced that in the
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spreadsheet we cannot change the
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regeneration to be 30 percent
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or 10 percent or even nothing and we are
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able to compute
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what is the energy per kilometer in
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every single case
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all right this is something that we did
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for two wheeler
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so we essentially have got the hang of
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it
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why did we do individual forces why did
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we look at the total traction force
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why did we look at the total torque the
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total power
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and energy now combined with the drive
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cycle we are able to figure out
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what does it take what is the energy
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that it takes
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now remember that we have not taken into
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account
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the inefficiencies inefficiency due to
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motor
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and motor controller that will be one of
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the major inefficiency
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you lose a certain amount of energy as a
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result of that that will
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so your water per kilometer will change
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we didn't take into account
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the energy required for all kinds of
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other things like
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lights or air conditioning
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you may have to include that in which
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case you will consume more energy per
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kilometer
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so all these things we will be looking
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at it
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but what will now do is pretty much
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repeat the exercise
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almost repeat so will go fairly rapidly
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drive cycles and energy used per
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kilometer for first an
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auto then an ericsson
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and then a compact sedan remember
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that for a two wheeler that was a little
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low end two wheeler
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how we didn't go about 45 kilometer also
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that drive cycle does not go above 45
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kilometer
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it was it could consume between 13 to 17
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water per kilometer
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not taking in efficiencies into account
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so total energy consumed depending on
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the regeneration and if you
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take the inefficiencies it will still be
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under 20
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watt hour per kilometer
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so a two wheeler essentially is like a
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20 watt bulb
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remember its actually consumes very
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little electricity
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once you are able to build that we can
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do things quite well
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let us now look at an auto if i look at
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auto one of the major thing is the mass
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changes the cross vehicle weight
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because number of passengers will be
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about three passengers plus the driver
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that itself will consume quite a bit
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then the vehicle the
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gravity is going to be same rolling
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resistance
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drag all these parameters we have seen
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air density same 1.2 kilogram per meter
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cube
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projected area is 1.6 meter square
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we will use the drive cycle idc auto
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and idc auto is same as the drive cycle
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for idc two wheeler
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so we will use that wheel radius is
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point two meters
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smaller radius and we take regeneration
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efficiency 0.5 will actually
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vary that and as i pointed out we will
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use the same drive cycle
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now one can change the drive cycle and
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redo the computation all that it means
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is that in the spreadsheet
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the velocity at different seconds will
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become different
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so if you do that you do the same thing
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no different
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you start with at different time one two
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three four five six seven eight
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now why have i not shown z after zero
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straight away sixteen seconds because
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zero to fifteen second is supposed to be
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idling
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so everything will be zero zero zero i
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just not shown it out here
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from 16 second onwards you see the
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velocity is going on increasing
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i put the kilometer per hour we can
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convert it into meters per second
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we actually compute the distance that it
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travel
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and the acceleration we actually compute
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all of this
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and if you plot this the same plot that
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you saw
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because the same drive cycle this is the
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actual velocity at every second
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it starts goes to top velocity 42
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kilometer per hour
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and goes to zero and this gives you the
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incremental distance
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and if you integrate the total distance
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you find that you travel 658 meters
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now the 658 meter is a single drive
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cycle in about
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108 seconds two minutes now you keep
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repeating it six or eight times i had
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done that
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that's how you actually do the
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performance measurement
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this is for an auto now let us look at
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what is the energy consumed
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and this time i am not getting into the
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details the same
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the spreadsheet will give you it will
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give you
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from the velocity and acceleration
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you will be able to then figure out what
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is the
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force due to rolling resistance force
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due to aerodynamic resistance
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no slope i have not taken so that is
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ignored
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force due to acceleration because
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acceleration value that i have
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i calculate the traction force and after
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traction force i will actually compute
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the torque on one side and power on one
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side
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and then i will integrate the power
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that will give me a energy consumed and
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remember
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that when i am decelerating or climbing
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down
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in this case there was no climbing down
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then i get negative
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energy consumed now here i have to put
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in the factor
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what is the regeneration efficiency as i
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do that
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i actually get this and this this
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is the energy required if you take
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0.5 if you take hundred percent
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energy efficiency you get this
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and this is the energy required
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if you take into account the
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regeneration efficiency of 0.5
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so you actually find out that the total
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energy required if i take
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regeneration of approximately ah 50
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percent
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which is by the way high i told you that
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25 to 30 percent is what we'll actually
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get
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it is about 26.64 watt hour that's the
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total energy consumed
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you have traveled 658 meters we had just
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seen
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so you actually consume in auto
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approximately 41 watt
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per kilometer assuming 50 percent uh
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regeneration
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if you took 100 gen regeneration then
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you will only consume 30
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wattage per kilometer what does it mean
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i'll challenge the people who design
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motor
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get me a motor which comes closer to 100
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percent regeneration
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it's a big gain if you can get
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remember from 40 to 30 what does it mean
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we actually consume only three fourth of
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the energy
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my battery size can therefore goes down
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by three fourth
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well but this is the theoretical
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efficiency this
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required simply to move we have just
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taken the rolling resistance
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and the aerodynamic resistance
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inefficiency will be in top of it
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so we'll actually consume about fifteen
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percent to twenty percent more
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there also depends on the motor and
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controller depends on the battery
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we look at some of those things
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the good autos today do consume
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45 watt per kilometer
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so they have a decent regeneration
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efficiency
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and then the motors etc are
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decent so motor controller
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and any other loss of course this does
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not take into account if you put the
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lights on
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that time you will consume more energy
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that is fine
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this is what you can get and this
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this pure from theory now how do you
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reduce
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this further from if somebody says well
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i want it to reduce from 40
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watt per kilometer well of course if i
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makes a regeneration better i will
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i will improve that i can also do by
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reducing weight
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remember that that is the first thing
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that helps m comes in everywhere m comes
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in rolling resistance in acceleration
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it comes when you travel up the slope
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if i reduce the rolling resistance put
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better tire that will improve
00:17:14
will see that in the end if i put better
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aerodynamics
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it will reduce the energy required to
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overcome
00:17:24
the drag that will also improve
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ok and as i pointed out regeneration um
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um so this is something that we have to
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actually do
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so without regeneration you consume as
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much as 50.
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so regeneration is very important now
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remember regeneration is
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combination of battery and motors and
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controller first of all motor
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it will as it turns reverse it has to
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act as a generator and give you the
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[Music]
00:17:54
electricity but then you have to convert
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that electricity
00:18:00
back into the voltage which can go into
00:18:02
the battery if you are not able to put
00:18:04
it into the battery that is wasted
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so it requires some careful design of
00:18:10
battery and motor
00:18:12
combine combined kinetic energy
00:18:18
so what is regeneration deceleration
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kinetic energy is getting converted to
00:18:23
electricity
00:18:26
what about climbing up and down um
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when you climb down you have a
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gravitational energy the potential
00:18:33
energy
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you are converting back to electricity
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so that is what you will do i think
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getting 40 is quite easy
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and that's what people are getting so e
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auto summary
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will consume between 40 watt hour to 40
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50 wattage per kilometer as i told you
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most of them today actually consume 45
00:18:54
ah
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remember that 45 consumption is without
00:18:59
lights on if there is any such thing
00:19:02
as lights etcetera on its always extra
00:19:05
its not
00:19:06
counted ah as a standard thing
00:19:10
as i told you inefficiency in motor
00:19:11
control will add up the energy required
00:19:14
driving at higher speed you do not drive
00:19:17
as per the drive cycle
00:19:19
if you drive at higher speed you will
00:19:21
consume more energy
00:19:23
if you overload a vehicle you will
00:19:26
consume more energy
00:19:29
and that is quite common in india
00:19:33
if you climb slopes you will
00:19:37
conver use more energy well range will
00:19:39
go down
00:19:42
the key thing is that you are not
00:19:44
climbing slopes all the time
00:19:47
of course if the regeneration is good it
00:19:50
will only marginally impact
00:19:55
the other thing that is very important
00:19:56
which will go through
00:19:58
as we look at the batteries in more
00:20:00
detail
00:20:01
the battery starts with certain capacity
00:20:03
and as you start using its capacity
00:20:06
keeps coming down coming down coming
00:20:08
down
00:20:09
finally it reaches a certain level where
00:20:11
the energy
00:20:13
in a battery becomes too small even when
00:20:15
it is fully charged
00:20:17
that time you replace the battery so you
00:20:20
must remember that range that you
00:20:22
calculate using this
00:20:23
will come down as the battery becomes
00:20:25
older
00:20:27
all this has to be taken into account in
00:20:29
a vehicle design
00:20:31
let me re do the same exercise
00:20:35
for eric shop now eriksha is a new thing
00:20:39
in india
00:20:40
though we know that the upper limit is
00:20:42
25 kilometer per hour
00:20:44
this is a requirement you do not get a
00:20:46
license if it is above 25 kilometer per
00:20:48
hour
00:20:49
in fact you do not need a driving
00:20:51
license to
00:20:52
drive a reaction and that's a good
00:20:55
regulation
00:20:56
saying that well it has to be under 25
00:20:58
kilometer per hour
00:21:00
just slow moving but a very important
00:21:03
ah part of uh life in india
00:21:06
it has actually replaced all rickshaws
00:21:09
and therefore all slow
00:21:11
moving vehicles traffic
00:21:14
is so slow moving traffic so in fact
00:21:17
ericssons are not allowed on the
00:21:19
highways ericssons are not allowed in
00:21:21
the bridges
00:21:22
it does not have the sufficient torque
00:21:25
for it to climb
00:21:27
[Music]
00:21:29
but with this restriction it works very
00:21:31
well remember that old
00:21:33
hand pulled rickshaw and cycle rickshaw
00:21:36
that used to be used
00:21:38
old person trying to cycle where
00:21:41
some two three heavy people have sat
00:21:42
down all this
00:21:45
to some extent has gone because now
00:21:48
with the motor driving it becomes easier
00:21:52
in some cases iriksa is a big boon of
00:21:55
course a slow moving so it can block the
00:21:57
traffic so that those are concerns
00:21:59
but there is a drive cycle defined this
00:22:02
is not a
00:22:03
strictly a standard it is some of us had
00:22:06
got together all with all the ericsson
00:22:08
manufacturers
00:22:09
and figured out what kind of drive do
00:22:11
they actually do
00:22:12
and you find that either they drive they
00:22:15
first
00:22:15
they will go to a certain speed and keep
00:22:18
on going down
00:22:19
then they will go to another speed and
00:22:20
keep on drawing down on the average we
00:22:22
found that with when measuring
00:22:24
that this what they are doing and we
00:22:26
actually define this
00:22:28
and there is a frequent stopping and
00:22:31
increasing the speed
00:22:32
and therefore there is a increase in
00:22:34
speed and going down
00:22:35
now remember if there is regeneration of
00:22:37
hundred percent this will not consume
00:22:39
much energy but otherwise it will
00:22:40
consume energy
00:22:41
and will define that again every second
00:22:43
what happens
00:22:45
every second or for five seconds or nine
00:22:48
seconds
00:22:48
five to nine second speed will be this
00:22:51
we define that
00:22:53
and then from 9 to 18 second speed will
00:22:55
be this
00:22:58
so you can you can compute the
00:22:59
acceleration
00:23:02
okay you can compute the acceleration
00:23:04
put the
00:23:05
input to the spreadsheet every second
00:23:08
what the velocity will be
00:23:10
every half a second what the velocity
00:23:12
will be compute the acceleration
00:23:14
and you take the specification of
00:23:16
ericsson that is very important
00:23:18
this is the input to the spreadsheet the
00:23:20
mass 680 kg
00:23:22
g the rolling resistance drag density of
00:23:26
air projected area the drive cycle
00:23:30
wheel radius and regeneration the
00:23:31
efficiency so you take all of that
00:23:34
and you find that this is
00:23:37
what the drive cycle gives you it is a
00:23:39
727 meter
00:23:41
this plots the incremental distance that
00:23:43
you travel this in
00:23:44
plots the velocity and 727 meter drive
00:23:48
cycle
00:23:49
now you compute the
00:23:52
force traction force power
00:23:56
torque remember so far we have not been
00:23:59
using torque because we went into energy
00:24:01
and energy efficiency torque will play a
00:24:03
very important role
00:24:04
later on when we design the motor as
00:24:07
well as the battery
00:24:11
it will play a very important role and
00:24:13
but we know what the torque will be
00:24:15
and we find again that if i
00:24:19
take the thing with 100
00:24:23
with approximately
00:24:26
[Music]
00:24:28
it takes 24 point
00:24:31
uh 24.53 watt hour
00:24:38
this actually shows me a little higher
00:24:41
ah
00:24:43
at 727 meter this shows me more like 28
00:24:46
29
00:24:47
watt hour this actually shows me 20 so
00:24:50
this is probably a different
00:24:51
regeneration efficiency with 100 percent
00:24:54
regeneration efficiency
00:24:56
it should be 27 watt hour ah
00:25:00
27 watts per kilometer and again the
00:25:03
number here shows different
00:25:05
i'll check this out why it is so but i
00:25:08
am able to i know that travel 727 meters
00:25:11
so i am able to find out the energy
00:25:12
efficiency energy efficiency
00:25:14
is 27 with hundred percent regeneration
00:25:18
efficiency
00:25:19
33 with 50 percent regeneration
00:25:22
efficiency
00:25:23
and without regeneration it is 40. this
00:25:26
is what a e rickshaw consumes
00:25:29
remember its a slow moving vehicle
00:25:33
so in some sense it is different its a
00:25:35
slow moving vehicle
00:25:36
and thats what happens
00:25:39
any questions so i have done it for two
00:25:41
wheelers i have done it for e-rickshaw
00:25:44
i have done it for auto let's do it for
00:25:47
the vehicle that i drive
00:25:51
a small sedan so iriksha summary even
00:25:54
with higher weight
00:25:55
the energy efficiency is below 35 watt
00:25:57
hour per
00:25:58
kilometer with 50 regeneration in
00:26:01
efficiency now what does it mean if i
00:26:03
take a 2.5 kilo
00:26:05
watt hour battery and i am consuming
00:26:08
only 35 watt
00:26:10
per kilometer it can easily give me 50
00:26:13
ah 50 kilometer range even taking into
00:26:16
account that only 85 percent of the
00:26:17
battery is usable
00:26:19
at any time of course you remember that
00:26:22
there is reduction in battery capacity
00:26:25
over time so your 50 kilometer range
00:26:27
will start slowly coming down
00:26:30
overloading and over speeding will
00:26:33
hurt always
00:26:39
you
