Design is the first phase in the digital manufacturing process. In this course, through a series of lectures and hands-on lessons, we’ll examine a designer’s approach to the design and manufacturing process—from concept to 3D model. We’ll start by applying design thinking to understand user needs, and then we’ll explore design criteria as we dive deeper into Autodesk® Fusion 360™ sketching, modeling, rendering, and documentation features.
Design Criteria: Component Selection | Part 2
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3D Model Creation with Autodesk Fusion 360
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Conceptual Design
This week covers the fundamentals of laying out multiple sketches for a complex part. With a design like a quadcopter, it is important to understand the artistic freedom and the mechanical constraints. Through concept sketches, we explore the shape and form in various 2D views. This allows us to understand physical volume constraints for components like a controller, batteries, and camera while playing with the overall shape.
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In this design criteria lesson,
we're going to carry on with part two of our component selection.
After completing this lesson,
you'll be able to understand multirotor component basics,
apply basic calculations to compare components,
and make informed design decisions.
So, we want to carry on with
the big picture of all the components that go into a quad copter.
Now, first, we want to talk about what some of the numbers of these components mean.
You have to understand what these numbers mean in order to help you pick them yourself.
Now, if you just want to follow along using the exact components
that we've picked out for this course, that's completely fine.
But if you're taking this course to help you understand
not only the design aspect on Fusion 360 but also more about quad copters in general.
I want to make sure that we pass along that knowledge so that
you're armed with everything you need to design your own.
The motors that I've picked for this course are made by a company called DYS.
The specific motor is an MR2205-2750KV.
Now the important thing here is we need to figure out what those numbers mean.
Right now, those numbers are meaningless.
If you've never built a flying quad copter multi rotor before,
you've never messed with any RC components before,
this means absolutely nothing to you.
And that's completely fine.
But we want to break it down so that you
understand what these numbers are and how they will
affect the performance of your device. So now, the MR.
The MR is actually just the code that DYS
uses to signify that this is one of their racing motors.
The next four numbers,
the 2205, are going to be very important to us.
The 22 is the diameter,
and the 05 is the height.
Now these aren't the outside dimensions of the motor but
rather the diameter and the height of the stator.
These are going to affect the performance of the motor.
In general, this size motor is great for a 250 series quad.
That means 250 millimetres between opposing motors on the X pattern of the quad.
So, this is a great motor choice or
a great size choice for the size of quad that we're building.
We're going to be in roughly the 250 to 270 millimeter range for our size,
so this is great for what we're doing.
But the 22 and 05 numbers will determine things like how much torque the motor has,
how high of an RPM it can go to, and so on.
Now, the 2750KV is a very important number.
The KV in the case of these precious motors stands for constant velocity,
has nothing to do with kilo volt or anything like that,
which you would assume if you have any experience in electronics.
But the KV generally stands for constant velocity,
and lets us know what the RPM is per one volt.
Now, this is important because the voltage changes based on our battery configurations,
and we'll talk about batteries in just a second.
But in general, we're going to have two main battery voltages that
we're going to be dealing with, 11.1 and 14.8.
This KV number, or this constant velocity number,
is multiplied by those voltages to give us the max RPM unloaded,
with no prop on.
So if we take 11.1 and we multiply it by 2750,
we get roughly 30 and a half thousand RPM.
If instead we take that 14.8,
multiply it out, we get almost 41,000 RPM.
So why is this important to us?
Well, as we look at the specs for this motor without
having to go through any spec sheets or look at anything else,
just looking at the part number,
we're going to know the diameter and the height of the stator,
and we're going to know roughly what the max RPM is going to be.
As you look at motors,
the higher the KV number,
the higher the RPM, generally,
they're set up for smaller props.
If you have a lower KV number,
let's say that it's 800KV,
those are generally setup for
larger props which will spin slower but still give you a lot of thrust.
So as you pick through catalogs and you're looking for
motors that you want to explore and think about more,
you can look at these KV numbers and you can look at the 2205,
and know that you're in the right ballpark.
Now for the MR2205 series,
DYS actually does offer a couple different KV values.
I think they have a 2300,
which is a little bit lower than this,
which means that we're probably spinning 25 to 30,000 RPM in the various voltage ranges.
So that means, it's probably going to be a little bit more torquey motor and
have less top speed or less higher RPM.
The next thing that we want to talk about with the motor is thrust.
Now, this is going to come from a chart that we're going to talk about in
another lesson when we get into the specifics of picking out what these mean.
But the thrust is based on the battery,
which in our case is going to be the voltage,
and it's also going to be based on the prop.
Now any reputable motor manufacturer is going to give you this information.
They're going to give you a chart, they're going to give you a list,
and they're going to tell you what props this motor was designed for.
In our case, DYS tells us that a five-by-four-and-a-half,
which is five inch diameter by four and a half pitch,
and a six-by-four-and-a-half are going to be the ideal prop choices for this motor.
Now, they give you the thrust outputs at various percentages
for 11.1 volts on both the five and the six-inch prop,
and then they give you the outputs for the 14-and-a-half-volt setup on a five-inch prop.
So this is going to be great information.
It helps us pick out what batteries we're going to use,
how much amperage we need for the flight time we want,
and how much thrust we're going to get out of it.
The next thing to consider when you're looking at motors is the amperage draw.
And again, this is going to come from that list,
that value that we're going to talk about in
terms of the thrust and the input and the output.
But generally, the amperage draw or how
much the motors are going to use increases with throttle.
Just like it does in your car when you press the gas pedal down, you use more gas.
Pretty simple to think about it in that relationship.
But in our case, we're going to have an ideal range,
where we have a certain RPM or a certain percentage of
throttle that's going to give us the most out for the least amount in.
So we're going to look at this and we're going to try to plan
for the maximum amount of thrust that
we need for just a stable hover with the minimum amount of input.
So we're going to look for the 25 to 35 percent input range,
and we're going to try to plan out our output or the thrust that we need for that range.
And lastly, when we talk about motors,
we're going to talk about an ideal prop setup.
Now again, it's going to be based on battery,
it's going to be based on the weight and the amount of thrust we need,
and we'll get into the specifics of those.
So next we want to talk about battery specifications.
The batteries that I picked out for this course,
I have three different battery choices that we're going to look at,
they're all Turnigy, they're all Lipo.
And we want to explore what these numbers mean.
Now, the battery that we're talking about here is a Turnigy Lipo 3s 1500mAh 20-30C.
Now, the first thing that we want to understand is the Lipo part of it.
This is a lithium polymer battery,
and this has a very high discharge rate,
while being fairly light,
and these are standard in the quad copter and flying device,
you know flying airplanes,
and helicopters and all these things,
it's a common type of battery.
Now, it's one that we need to be very careful with,
when you're charging and discharging it and so on.
So, it's important that we understand what these numbers mean.
So first, let's talk about the 3s number.
Now, the 3s, stands for three cells.
Each cell is going to be roughly three point seven volts.
So when we talk about a 3s battery,
that's eleven point one volt battery.
We talk about a 4s battery,
that's going to give us fourteen point eight.
And we were just talking about the motors, remember that,
eleven point one volts,
or fourteen point eight volts,
will change the max RPM of the motor.
Now, at eleven point one,
we were roughly 30 and a half thousand RPM,
but we went up to about 41000 RPM when we went to a 4s,
or a fourteen point eight Volt setup.
The next number, is the 1500mAh or merely amp hour.
So, when we talk about amp hour or merely amp hour,
we're talking about how much current battery can supply for a one hour.
Now, in our case we're going to be using two batteries,
they're going to be wired in parallel,
and that's going to give us the same 11.1 volt or 14.8 volt,
but it's going to give us twice the million power twice the capacity.
The last numbers, the 20 to 30 C, is the discharge.
Now this number again,
it's a very general term and it really helps you when you're comparing batteries,
but you never want to plan out a build,
or that 20 C is exactly what you want,
you always want a little bit of a margin in there.
So, the discharge, is you take the 20 C,
the 20, and you multiply it by the one point five amps.
So what this tells us,
is that our 1500 million,
or one point five at battery,
can supply 30 amps continuously until you run down to the point where you want to stop.
So, this number is telling us that this battery can handle that amount of supply,
without overheating or without damaging itself.
That's the low value,
that's the 20 C number.
The 30 C is essentially a burst.
This is telling us that 30 times one and a half amps,
will allow us to draw forty five amps,
for roughly five to ten seconds.
Now this is important if you're planning out a fast drone,
a racing drone, where you're going to be
trying to get as much out of it for a very short period.
Now, we're not going to be pushing these batteries to any extent like that,
but that's what these numbers mean 20 to 30
C. So let's talk a bit more about multi Router basics.
We know what components we need,
we know that sort of general idea of what is going to have
to be on our quad copter,but now let's talk more specifics.
When you're standing on the ground,
when you're flying a quad copter,
when you're controlling the throttle, or the pitch,
or the role, you're going to be sending a signal to an RX or a receiver module.
Now again, this is paired directly with our controller, in most cases,
you can buy the controller and the receiver as a prepared set,
in some cases you'll have a controller already,
and you'll simply pair it to a new receiver.
So the first picture shows the receiver.
The gray wire is the antenna wire essentially where the signals coming in from,
and then each of the wires going out, the yellow,
the green, the white, the blue,
is an individual signal.
One of them will be throttle,
one of them will be for roll,
one of them will be for pitch,
and those will go directly to the flight controller,
this is the brains of the quad copter.
And the flight controller,
has several sensors on it a gyroscope, an accelerometer,
and additional inputs that you can plug into it for various things like GPS,
and it knows exactly which directions forward,
it knows if it's pitching,
or rolling or yawing,
and it also knows what the current speed of all the motors are.
Now the flight controllers,
configured by you and we'll go over that and our course as well,
and it'll do things like,
it'll know how quickly you want your quad copter to react to your inputs.
It'll know what type of flight you want to do if you're doing acrobatics,
or if you're just trying to achieve slower more stable flight,
that can all be programmed into these flight controllers.
So, the signal sent from your controller, to the receiver,
to the flight controller board,
and then that converts whatever we do to a motor output.
It sends that signal to the ESC of the speed controller,
and then the speed controller relays that onto the motor.
And those are the very basics of what we need to control the quad copter.
Now, we can get into various add-ons,
additional things that we can put on our designed to increase its functionality,
maybe make it easier to fly, or safer to fly,
and the first of those,
is a PDB or Power Distribution Board.
Now, the one that we have on the screen here is fairly unique,
because it also includes some additional functionality,
by using an OSD or an on screen display,
but this will allow us to take in the battery,
It'll take the battery voltage,
it'll send directly out to the ESC,
it's powering the ESC,
and they're waiting for a signal from
the flight controller to then relay that onto the motors.
So it takes that voltage and sends it out,
but it also converts the voltage down to five volts so that we can power a camera,
and we can control our servo,
and we can have a 12 old or direct battery voltage,
send that out to the transmitter for the video signal.
So the OSD, is on screen display,
and in this specific board allows us to take the video signal in,
and then when it sends it down to us on our monitor at the ground,
it will display the battery voltage for us.
Next we have the camera,
in this specific camera that we're going to be using,
comes with a tilt servo and a pan servo on it.
Now modifying this one for are designed to only have tilt,
but this is a great option because it has a self-contained unit with the camera,
as well as the two servos,
so it's very easy to incorporate into a generic build.
Next we have the transmitter,
that sends the video signal back down to us on the ground.
Various different options when you're picking out these,
you have different antenna options,
you have different input voltage options,
different signal options, various things that we can play with and configure,
between the camera and the transmitter module.
And again, we'll get into all that when we pick out our components,
but right now just understand what each of these is.
Then we also have some additional things we can add into our build,
to do various tasks.
So Servos or Brushless Gimbal motors,
these are things that we can add on to do various tasks for us.
For instance, a Servo could be used to open or close a claw,
to allow us to pick things up,
or drop things off.
Now in our case we're planning for a fairly small quad copter.
We're not going to have a lot of lifting capacity,
but these are things that we can use these types of devices for.
We can also add additional sensors,
or cameras things like GPS, or ultrasonic sensors,
that will allow us to control the quad copter,
and if it senses things like walls,
or any obstructions, it can intervene and stop us from flying into them.
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