The fourth sensor which we will be discussing will be magnetometer. Now as the name suggests
it has to be something with magnetic field something that site magnetometer basically
measures your magnetic field, now suppose I have a conductor this is my conductor and
I pass a current through it, this is current, this is your i there is a transmit flow from
one side to another side if I apply a voltage, this is a simple phenomena when I apply a
current to a conductor that across will flow from one side and it will come then the circuit
will be completed. But as you know if there is no magnetic field
in this conductor and I have given a constant current to this, constant I am giving a constant
current to this particular conductor. And if there is no magnetic field if I measure
potential of this particular surface it will be zero. In presence of magnetic field this
line will get distorted, so it will be something like this. As I am giving this constant current
then voltage will be some Vh this is known as hall voltage.
And this whole phenomena is known as hall affect. Now your major magnetometer sensors
which come in for your web searches you can call it or for your appreciations use this
phenomena or hall affect for calculating your earth magnetic field. When you give application
magnetometers are used to calculate or to find your magnetic north which is different
from your actual note. Now the magnetic north constantly varies according
to your location magnetic north. Now this magnetic north will constantly vary according
to a particular location where you have means, if you have GPS data then there are data’s
and label when you can give a connection factor to align your vehicle to true north. The major
application of using magnetometer is that it has zero basing effect or means zero error
hence if you have give your UAV to head to a particular direction say a particular heading
we gave given. So since your magnetometers have zero error
so it will automatically concocted your heading your automatic at your heading angle so that
is why it is very good for UAV application when your are focusing the focusing on particular
direction in which your UAV as to follow but the defect of this magnetometers are since
a magnetic field is involved. So there are different instruments are different
equipments in UAV or in plan itself which quite which have electrometric field such
as you cannot mount a magnetometer near router because it as magnetic field so it can be
start your readings and also when you have a large landing gyre which is metallic the
problem comes of the magnetic field that is the mounting of magnetometer as to be consider
where it should be mounted so your electromagnetic field does not vary now these where regarding
to accelero gyro and magnetometers the three sensors which we discuss in our accelero.
. Rate gyro and magneto meters usually you will
find circuits where the these all three are available on a single unit we usually name
it as IMU or initial measurement unit for your experimental purpose we will be using
MPU 6050 and 9250 these are the very simple IMUS which are available in the market and
we will in our domain this lecture we will be showing you how to capture data using IMUs
6050 this was regarding to initial measurement unit now we will be seeing what are angle
of act sensors and why angle of act sensors is need so the next sensor will be.
. Angle of attack sensor. As you already know
angle of attack is your angle between this is the section of your wing when I connect
your leading edge to your training edge this is known as cord line this is your free sting
velocity these are all parallel and the angle which this free stem velocity makes with your
chord line that is your angle of attack represented by alpha now why we need to calculate angle
of attack. Because it helps in Stoll warning systems
alpha angle of attacks sensors are basically of two forms first is Vane type sensors, second
is your pressure sensor pressure type sensor now first we will be discussing what are value
type of sensors and what are pressure type of sensor both angle for angle of attack.
. First vane type, vane type of angle of attacks
sensor the properties are first A these are small F1 types small F1 shape which are free
to rotate, second they line up relative to air flow, now since they line up relative
to air flow so they cannot be mounted in down wash areas such as just behind your vane downwash
and D as it is free to rotate the rotation is calibrated to a potential meter.
And we will be getting voltage with respect to rotation of this vane type of
angle of attack sensor, this was for vane type of angle of attack sensor this is a small
angle of attack sensors used for small wave is when small aircraft now the principle is
same as of vane type of angle of attack sensor here instead of vane a small flag is there
as you can see this will align when the aircraft will be more flowing moving in the air this
will align according to particular air flow. Now suppose it aligns in this particular direction,
now you can see this is mounted and it can rotate and based on that rotation a potential
will be generated which we can sense or calibrate according to this particular relation as you
saw for while calibrating your control surfaces the same phenomenon was used while deflecting
the control surface there was a potential meter involved and based on that a particular
voltage we got in valve program same principle is used here also, based on the deflection
your rotation up potential meter the voltage will be generated and that can be calibrated
according to particular angle of attack and as you know these angle of attack sensors
is majorly used for false tall warnings. So this is than efficient in that, now second
type of sensors which will be using a second type of angle of attack sensors are pressure
type sensor. Now what are pressure types of sensors?
. Pressure type, attack of sensors now pressure
type of angle of attack sensors it involves air falls section blade and a holes are mounted
at the leading H symmetrically below and above that particular surface now as air will flow
this particular air as your angle of attack willing these will create a pressure difference,
this is your chord line or this is your chord line here suppose angle of attack is 0 here
angle some positive value. This special difference can be transform in
to a voltage signal using some trans cursers and that can be calibrated voltage signal
through transistors and this voltage signal can be calibrated for angle of high back,
so these are two types of angle of a tax sensor now most of this small UAB is do not use angle
of a tax sensor because this not much need usually they are fly at much lower angle of
attack so they do not reached at high of a stall value.
So this is not required in small UAB applications but for commercially we have cove this is
important sensor so we cannot just neglect this sensor.
. Now so far this were the sensor which you
saw ion flight data recorder rather than your magneto meter now one more type of sensor
which I want to discuss is your GPS because now a days it has quite a lot of applications
starting from your UAB operations to your smart phones you have GPS everywhere, and
it is helping lot of people now what is GPS as commonly known as or all of you know that
if it is global positioning system. Yes this is the full form but what does this
represent it is actually a consultation of many satellites which revolved along the earth
in a fixed or width such that every each and every location on this earth has access to
a t least of four of this satellites at least four are available for every position on this
earth now question arises why four because if you have access to one satellite you can
determine appoint in one dimension with two satellite two dimension three dimension that
is all we need. So why this four satellite is required will
be coming to that let us understand how GPS access a particular point and how avoid this
four satellite are required, we will be coming to that, let us understand how GPS access
a particular point and how, why this four satellites are required. Now the phenomena
which is used to access the particular point is tri alteration, what do you mean by tri
alteration, now all this satellites which are revolving around the world in particular
orbits, have their clock synchronized every day, that is the accuracy these are atomic
clocks, so accuracy is very high, these are as high accurate as one million thousand second,
these are synchronized everyday from earth. Now each and every satellite sense two data
to receive a GPS receiver that is its location, second time, at what it was sent, time okay,
it was sent. Now this satellite sends its location to particular receiver, so this is
receiver, this is a satellite A, this is your satellite B, this is satellite C, when this
satellite sends this signal to particular satellite, so it will calculate the distance
of the satellite using this simple formula, distance = speed * time, here time will be
time at which receiver got its signal – time at which the satellite send this signal, and
speed is the speed of light, meters per second. .
Now as you can see with one particular satellite it will be, now as you can see using this
formula, it can calculate distance at which, from which it got its signal, the receiver
got the signal, so for satellite A suppose a distance for D1, this is D1, so it can anywhere
along this particular circle, this is the circle of radius D1, this is the circle of
radius D1, so your pound can be anywhere in this particular circle. But since this is
in space, so this will be a whole sphere. .
This a sphere so your point can be anywhere on this particular sphere. Now the distance
between distances for satellite B that will be also calculated for the same formula suppose
this will be distance T so another circle with distance d2. Now intersection of this
sphere and sorry this sphere will give you. This particular circle intersection of these
two is will be a circle and you present if with a small circle that is say suppose this
was a circle intersection of these two points. So we are both object can lie anywhere on
this whole circle now suppose this C this is your third satellite and it will also the
distance will be calculated using that formula and therefore it will be circle somewhere
like that so you got two point. This and this now since your are on earth this will act
as a forth point since you cannot travel in space so this is your location.
. So form here it seems you only require three
satellite to get your particular location so what is the need of forth satellite place
are role of accuracy now you know that this is a time at which receiver got your signal.
And this was the time at which your satellite send signal. Now even a small difference of
say 10 to the power -6 delay of -6 second will result in three into 10 for 2 that is
300 meter error. So that is why you require at least four to.
At least four satellite so that this error is significantly reduced and the more number
of satellites are connected to your receiver the more accurate will be your data and other
parameters such as high and down speed can also be calculated using your GPS data. But
that is not for this course so I will be concluding after this portion so as far for sensor part
these are the major sensors which I want to discuss and let you have one idea how this
sensors work. What are general principle and how data position
are data are acquired using sensors so that will be demonstrating you with a small example
first we will also be sharing with a coat for extometer your red diaos as well as angle
of attack I wish I already showed you a small angle of attack we will be sharing the code
and showing how it is done you acquire data using an atrobots and m6 and 5 0 sensors and
end of the attack sensor thank you.