Archive for the ‘Multirotors’ Category

How much power is needed to hover ?

by Sergiu Baluta, Starlino Electronics, revised 10/30/2015

This article is a theoretical venture that aims to answer a series of practical questions, such as:

– given a certain electrical setup that can generate a certain power, what is the maximum thrust that we can achieve ?

– can a human-powered aircraft be built ?

– can I tell the expected thrust generated by a copter simply by knowing the power it consumes and vice-versa ?

– are larger propellers really more “efficient” ?

– which multicopter configuration is more efficient:  tricopter ,  quadcopter ,  hexacopter or octacopter  ?

– I heard that for every gram of mass I add to my multicopter, the flight time will decrease by 1 second, can you put any sense in this ?

– and many more…

When selecting motors for an RC model you will often come across the thrust tables that tell you how much thrust (or “pull”) a specific motor can generate. This usually depends on few factors: the propeller used and the voltage applied. Next to these two parameters you will usually see the current and power consumed and the resulting thrust generated, usually expressed in grams. If you want your model to hover, you must ensure that your motors can generate a thrust equal to or greater than the mass of the model.

The power that your motor consumes is calculated based on the simple formula:

P = V * I , where V  is the voltage and I is the current.

Power represents the amount of energy we’re consuming per second, which is expressed as follows:

P = E / t, where E is the energy.

The efficiency of a specific setup consisting of a propeller and a motor is often calculated as:

Eff = Thr / P , where Thr is the thrust force generated expressed in grams and P is the power consumed expressed in Watts.

However this efficiency is not expressed in percentage as you would usually expect so it does not tell us if our motor-propeller setup is consuming  energy exclusively to generate lift or wasting it somewhere else. To compute an efficiency value in percentage we would need to know the minimum or “ideal” power necessary to generate a specific thrust given our setup and environment.

We have to mention from the start that such an “ideal” model, taking into account all the possible factors would probably be too complex to use for practical purposes. So instead our goal is to first deduct and then define a “theoretical” or “reference” power formula. Finally this formula will be applied to a series of practical experiments and the resulting “theoretical” power will be compared to the real-world observed power. To avoid confusion with the other efficiency let’s call this ratio “Theoretical Thrust Ratio” or TTR:

TTR =  P(real) / P(theoretical)

So let’s  dive into our calculations. But before we do that, for the impatient reader,  here are the formulas that we’ll be deducting and using for computing our “theoretical” power (or thrust – if we flip the formula around):

clip_image002[55]            (Formula 1.1)

 

clip_image002[57]            (Formula 1.2)

 

clip_image002[59]      (Formula 1.3)

 

 

Here P is the power expressed in Watts., F is the thrust expressed in Newtons,  r is the radius of the propeller expressed in meters and  K is a air density dependent coefficient, with a nominal value of 0.3636 assuming air pressure of 1atm and air temperature of 20C.

The formulas above are expressed in international physical units, however for those doing RC I am also providing the following convenient formula for computing thrust in grams Tgram, based on a propeller diameter expressed in inches Dinch:

clip_image002[61]              (Formula 2.1)

 

clip_image002[67]      (Formula 2.2)

clip_image002[65]          (Formula 2.3)

Here C is an air density dependent coefficient with a nominal value of 0.0278 assuming air pressure of 1atm and air temperature of 20C.

Below is a lookup table for K and C coefficients at various temperatures and air pressure of 1atm.

Temperature
(degrees C)
Air Density (kg/m^3) @ 1atm K C
35 1.1455 0.372745594 0.02850295
30 1.1644 0.369708101 0.02827068
25 1.1839 0.366650731 0.028036891
20 1.2041 0.363562254 0.027800722
15 1.225 0.360447503 0.027562545
10 1.2466 0.357311097 0.027322712
5 1.269 0.354143483 0.027080492
0 1.2922 0.35094996 0.026836291
−5 1.3163 0.347722365 0.026589484
−10 1.3413 0.344466588 0.026340523
−15 1.3673 0.341175753 0.026088881
−20 1.3943 0.337856246 0.025835046
−25 1.4224 0.334502366 0.025578583

 

The Deduction

Let’s get back to the main question of this article – “how much power is needed to hover an object ?” , or in other words how much energy we need to consume per second to maintain this object “in the air”. Well, as it turns out “it all depends…”. For example we do not need to consume any energy to keep a book on a shelf or a tire suspended on a rope. Clearly we did not formulated our question correctly! So let’s try again and this time be more specific. “How much power  does a craft powered by a spinning propeller needs in order to hover in the air ?” Here you go – much better ! Let’s see if we can answer this question.

You might recall from school physics a rule called “preservation of energy”, it simply states that the energy does not like to go away or disappear, all it does – it transforms from one form to another. We certainly know that our craft consumes energy in the form of electricity or burned fuel, but where does it go ? Didn’t we say that we don’t need energy to hover an object such as a book on a shelf or a tire hanging on a rope ? The reality is that not every object is as lucky as a book on a shelf or a tire suspended on a rope. In both these cases – the book and the tire have the benefit of a “reaction force” of the shelf and rope respectively. The book pushes on the shelf with its weight and the shelf will always push back with an equal force in the opposite direction. If you’re confused it’s probably because of a common misconception that an existence of a “force” implies that energy is consumed. The later is not true – a  “force” can exist simply because of the setup of the nature, for example the gravitational force, the magnetic force and the reactive force they all simply exists without consuming energy. It’s  their action that might or might not lead to the transfer of energy.

Back to our model of a propeller-powered craft, since our craft is suspended in the air, there must clearly exist an opposing force F that is directed in a opposite direction:

F = m * g , where m is the mass of our craft and g is the acceleration of gravity ( approximately 9.8 m / s^2 ).

In fact this force is not much different from the “reaction force” that a shelf exerts on the book, except our medium “the air” is less dense than the shelf and as a result of this force,  as we push “against” it with the propeller, the air starts moving. Here you go! We found were our energy goes. The electrical or fuel energy consumed by an aircraft is transferred to the kinetic energy of the moving air.

Let’s imagine a spinning rotor that generates a thrust F (in case of hover it is equal to mg) and a cylinder of air of infinite height with the rotor placed in the middle. The rotor is sucking air from the top and then pushing it down from the bottom. The rotor will have very little influence on the air on the top (since it’s very-very far away) so we can assume the speed of the air starts at 0, then slowly increases as it passes the rotor to w/2 (due to symmetry of our model from top and bottom) and finally as it reaches the bottom of the cylinder it stabilizes at a speed w, again rotor has very small influence on the air from the bottom of cylinder since it’s far-far away.

 

image

Let’s examine our model for a period of time t that it takes for a particle of air to travel from the top to bottom of cylinder . Let’s note the area of the cross-section of our cylinder as A and since it’s defined by the radius of our rotor we have:

clip_image002[3]

The volume of air Vol that passes through the rotor during the time t, can be calculated by monitoring how much “height” of air passes through the rotor at the speed v, h=v*t and multiplying by the cross section area A.

clip_image002[15]

Given the air density Qair we can calculate the mass of air that passes through the rotor in the time period t:

clip_image002[13]

Let’s note that since the air starts at zero speed so its starting momentum is zero, thus it’s momentum change will be equal to final momentum Mair * w, where w is the final speed. From momentum conservation theory we can recall that the force that we apply on a mass is equal to the rate of change of momentum:

clip_image002[19]

Finally combining the last two formulas we get:

clip_image002[21]

From here we can get the speed v at the rotor:

clip_image002[23]

Next let’s note that the power consumed is equal to the work done by the force F at the rotor (work and power are both defined by the rate of change of energy), which is given by another classical formula W=F*v:

 

clip_image002[31]

Note that we substituted the circle area A = PI*r^2 formula. Finally, by extracting some coefficients we get:

 

clip_image002[35]

and the inverse formula for thrust is:

clip_image002[51]

The formulas above work with international physics units, thrust F is measured in Newtons, and radius r is measured in meters. For practical purposes in RC we work with propeller diameter in inches and thrust is calculated in grams (which is equivalent to mass this thrust force can hover from  F = mg formula, where g is standard gravity ~ 9.8m/s^2). So let’s define another equivalent set of formulas:

 

clip_image002[1]

clip_image002[45]

 

clip_image002[3]

clip_image002[5]

and the inverse formula is

 

clip_image002[53]

 

 

Experimental Results

To verify these theoretical results I conducted a series of thrust tests using different motors and propellers commonly used in RC. Also I verified thrust tables randomly found on the internet (forums or motor specs):

Motor: DYS 1306 3100KV BX    Source: http://www.banggood.com/DYS-1306-3100KV-BX-Series-Brushless-Motor-For-Multicopter-CW-CCW-p-962149.html

Prop Diam " Prop Ptich V A Thrust(g) W Eff (g/W) Theoretical Thrust (g) TTR=Thrust /Theoretical Thrust
5 3 7.4 1.4 70 10.36 6.8 151 46.2%
5 3 7.4 3.3 140 24.42 5.7 268 52.2%
5 3 7.4 5.7 220 42.18 5.2 386 57.0%
5 3 11.1 2.1 100 23.31 4.3 260 38.5%
5 3 11.1 5.5 210 61.05 3.4 494 42.5%
5 3 11.1 9.4 350 104.34 3.4 706 49.6%
6 2 7.4 1.3 70 9.62 7.3 163 43.0%
6 2 7.4 3.7 150 27.38 5.5 327 45.9%
6 2 7.4 7.9 230 58.46 3.9 542 42.4%

 
Motor: EMAX MT1804 2480KV Source: http://www.rcgroups.com/forums/showthread.php?t=2172324

Prop Diam " Prop Ptich V A Thrust(g) W Eff (g/W) Theoretical Thrust (g) TTR=Thrust /Theoretical Thrust
5 3 12.1 7.3 345 88.33 3.9 632 54.6%
5 3 12.2 6.2 330 75.64 4.4 570 57.9%
5 4 12.1 9 370 108.9 3.4 727 50.9%
6 3 12.2 8.6 410 104.92 3.9 800 51.2%


Motor:
DYS BE1806 2300KV Source: http://www.rcgroups.com/forums/showthread.php?t=2180080That 

Prop Diam " Prop Ptich V A Thrust(g) W Eff (g/W) Theoretical Thrust (g) TTR=Thrust /Theoretical Thrust
5 3 12 9 415 108 3.8 723 57.4%
5 3 12.2 3.6 230 43.92 5.2 397 58.0%
5 3 12.1 7.5 360 90.75 4.0 643 55.9%
5 3 12.2 3.3 205 40.26 5.1 374 54.8%
5 4 12 10.6 440 127.2 3.5 806 54.6%
5 4 12.1 4.2 225 50.82 4.4 437 51.5%
6 3 12 10.2 485 122.4 4.0 887 54.7%
6 3 12.1 4 240 48.4 5.0 478 50.2%
6 4.5 11.8 16.1 580 189.98 3.1 1189 48.8%
6 4.5 12 5.1 235 61.2 3.8 559 42.1%
5 3 16.3 11.5 570 187.45 3.0 1044 54.6%
5 3 16.4 5.1 280 83.64 3.3 609 45.9%

 

A more extensive list of test can be downloaded here, the Excel Spreadsheet contains a _TEMPLATE_ sheet that you can use to fill in and verify your own data:

http://starlino.com/wp-content/uploads/data/power_thrust/Motor_Thrust_Tests.xlsx

 

Example Uses

 

Q: Can I build a human powered helicopter ?

A: A trained cyclist can generate 500W peak power (or even 1500W according to some reports), let’s a assume the cyclist weights 70Kg and the weight of the copter is 30Kg, thus the thrust needed for lift off is 100Kg. From this formula:

clip_image002[55]    

we can compute the radius of the propeller that this human-powered helicopter will need to have :

r = K * (mg) ^ (3/2) / P = 0.3636 * (100*9.8) ^ (3/2) / 500 = 22.3 (meters)

In fact human powered machines have been built. Let’s analyze for example the Gamera II built by University of Maryland:

Weight:  ~ 37kg + Pilot ~ 90kg
Rotors Radius:  ~ 7.2m  ( x 4)

Since this craft has 4 rotors , each rotor would need to produce at least 1/4 of the thrust or  90Kg / 4 = 22.5Kg . Using our formula we can calculate power needed for each rotor:

 

P =  K * (mg) ^ (3/2)  / r = 0.3636 * (22.5*9.8) ^ (3/2) / 7.2 = 165.35

 

Thus the total power required is estimated at 165.35W*4 = 661.4 W , which is quite manageable for a trained cyclist. In reality no motor is 100% efficient. Still,  an advantageous effect for take-off is the “ground effect”. As air is pushed into the ground its density increases, as a result our K coefficient will decrease, meaning there’s less power required to generate same thrust compared to less dense air.

 

Q: I am buying a motor that is rated at  200W, assuming I will use a battery  that has a voltage high enough to result in all 200W being drawn from the motor and  a 10” prop,  how much thrust can I expect from this motor and what will be  the gram/Watt efficiency ?

A:  Simply apply this formula to get the thrust in grams:

 

 clip_image002[53]

Tgrams =  ( P * Dinch / C) ^ (2/3) = ( 200 * 10 / 0.0278) ^ (2/3) =~ 1730 gram,  gram/Watt efficiency immediately follows: Eff = 1730 / 200 = 8.65. From practice, knowing that most brushless motors setup used in RC will deliver  50-60% of theoretical thrust and efficiency you can divide the above theoretical values by 2 to get a real-life estimate , so  P ~ 865g,  Eff ~ 4.3 g/ W.

 

 

revised 10/30/2015

by Sergiu Baluta,  Starlino Electronics

My plateless Anti-vibration mounts

image

image

image

image

These 3d printed ball adapters work great! I thought that the adapter plates that come with these are too heavy so I designed and printed these white adapters, now I use them on all my models – much better than sticky foam plus they are removable!

Finally here is the test flight, note how relatively stable the tricopter is. This is without any prop or motor balancing and with stock PID setting, absolutely no tuning.

Cheers,

//starlino//

Introducing the QuadHybrid – a stable, maneuverable and cheap flying robotic platform

Introduction & Demo of the QuadHybrid Design

I’ve been experimenting for quite a while with different configurations of Multi-Copters and RC Helicopters, basically looking for a stable robotic platform that can be used for my machine vision or other sensor-enabled flying robotic projects. RC helicopters have been around for quite a while, however (with the exception of some 3-Channel helicopters) they are not easy to fly, not very stable and not too precise in maneuverability – in other words not exactly good match for a flying robot. Then came the quadcopters and everyone loved them, talked about them , and eventually wanted to or actually built one.  I built a few – and what I learned is that  they have a great lifting power, great maneuverability (basically equivalent to a 4ch or 6ch heli), however   they rely entirely and heavily on relatively expensive IMU sensors  to achieve this stability.  I a QuadCopter you basically have four “monster” motors on each beam than must be synchronized precisely. Because you’re controlling so much power with your IMU sensors – any small deviation or lack of callibration and your platform is no longer stable. That’s why the sensors are crucial in a quadcopter  – without them the quadcopter will not fly at all ! 

After many trial designs – my conclusion was that a suitable flying robotic platform must not rely too much (or at all) on its sensors to be stable while hovering. It must be mechanically symmetric, preferably with it’s center of mass in the center.  At the same time it must have the maneuverability  capabilities of a quadcopter –  and namely I wanted it to fly sideways, forward & back  and rotate around its axis. Although the solution I came up with might seem to some (including myself) a little strange  and out of the ordinary –  as turned out it flew surprisingly well , was very stable and maneuverable, and best of all – had a very low price tag due to the fact that it was easy to built from the off-the-shelf toy helicopter replacement parts.

Without further adieu – below is the picture of the machine that I called “QuadHybrid”:

image

My very first QuadHybrid prototype.

Below you can see some flying test video:

 

So What Exactly is a QuadHybrid ?

Let’s have a closer look at QuadHybrid’s pictures. A simple way to look at it is:  a co-axial helicopter on top of a quadcopter – it’s actually as simple as that.

In total QuadHybrid has 6 motors and 6 propellers (2 large one center from the helicopter + 4 small on each arm from the quadcopter).

The two large center propellers in the center consist of 2 heli-type blades – they provide all the lifting power needed. They spin in opposite directions to compensate for the yaw rotation introduced by any rotating propeller and are stabilized by an optional vertically mounted MEMS gyroscope  (the only sensor used in this design). The slight difference in speed of the top and bottom blades is used to control the desired yaw rotation.  Thus the center motors provide the throttle and yaw control of the QuadHybrid – in other words ability to fly up/down or rotate about its center vertical axis.

The four small rotors on the four arms are actually small tail motors from a 3ch helicopter, they provide the remaining maneuverability  functions – pitch/roll or – or in other words the ability to fly  forward & backwards or shift sideways  (right / left) . 

The resemblance to a quadcopter and a helicopter can be seen in the picture below where they are put side by side.

QuadHybrid_Origins

 

How Does a QuadHybrid Work and How to Build One

QuadHybrid has all the maneuverability of a 4 channel helicopter or a quadcopter (throttle, yaw, pitch and roll). A 3 channel helicopter as we know it – only has 3 controls (throttle, yaw and pitch). The problem with a co-axial 4CH helicopter for instance is that it relies on a swash plate and servos to achieve the pitch/roll control. Basically it is a servo mechanism for tilting the axis of rotation of the bottom rotor – it is not easy to fine tune and it needs frequent maintenance. A 3CH toy helicopters on the other hand relies on a tail rotor to achieve the pitch control – and this is one of the ideas I used for QuadHybrid – basically I multiplied the tail boom and rotor on a 3CH helicopter by four.

eh-ek-e303ra-7_3

This is how a typical 4CH helicopter is build. Please note that the bottom blade can be tilted by using 2 servos that tilt the swashplate. In the QuadHybrid design we are going to eliminate the servos and the swashplate and replace them with 4 small motors mounted on 4 arms (beams), just like on a quadcopter.

I built my QuadHybrid, from spare RC or “toy” heli  parts. They are widely available and thanks to the fact that manufactures copy each other in some cases bluntly, these parts are compatible in many cases  so I was able to mix-and-match. I took the electronics from a E-Sky Lama V3 helicopter  – that is a 4 channel heli so it has a swashplate and 2 servos to control the pitch and roll. Because I didn’t wanted the swashplate (the roll/pitch on QuadHybrid is controlled by the 4 small quadcopter style rotors), I used the frame and blades from another toy helicompter  – Syma S001 and I was able to fit the Esky motors into that frame which are bigger and more powerful than the S001 stock motors. 

To clarify the design let’s look at the guts of the E-Sky Lama V3 helicopter . I actually used all electronics in this 4CH helicopter, except the servos (as will become clearer in the next diagram):

lama_v3_electronics

 

The main idea of the QuadHybrid design is: to achieve a better Pitch/Roll  control I replaced the servos with a custom control board called “QuadHybrid Controller V1”. This board basically takes the servo RC signals (Pitch and Yaw) as inputs and controls the 4 arm motors using a set of 4 transistors. This allows QuadHybrid to fly just like a quadcopter in “+”  or “X”  configurations (for explanation of “+” or “X”  flying configurations  see for example http://technicaladventure.blogspot.com/2012/09/quadcopter-stabilization-control-system.html).

 

QuadHybrid_electronics

 

On the mechanical part – the swashplate on the bottom blade was replaced with a fixed blade mount from a 3CH helicopter. This made the bottom blade of the 4CH fixed. Normally on a 4CH heli it is being tilted by servos that are connected to the swashplate using 2 links.

Main Rotor Head

This is a swashplate assembly on a 4Ch helicopter it is the black disk under the blades mount. It is connected to the blade mount with two links. Two servos that are controlled by the RC receiver are able to tilt the swashplate and thus alter the axis of rotation of the bottom blade. This is how the roll and pitch is controlled in a 4 channel helicopter. It is far from perfect and requires frequent tune-ups.

 

A gyro-stabilized co-axial 3 channel toy helicopter is fairly stable, as opposed to a 4CH helicopter- it uses the tail rotor to control the pitch (flying forward or backward). Note the bottom blade is fixed , just like on the QuadHybrid.

QuadHybrid Controller Board and Software

Below is the schematic of the QuadHybrid V1 controller (the blue board on the diagram above that controls the 4 motors). This is the only custom component that is not available from RC toys parts.

image

At the heart of the QuadHybrid V1 controller board is a PIC16F1825 microcontroller – it’s main task is to capture the servo signals received on ports RA5(ROLL) and RA4(PITCH) and convert them  to 4 PWM signals that control the 4 rotors mounted on arms. The motors are driven using 4 NPN transistors – these can be any NPN transistors as long as they have a current rating of at least 1A (or the maximum current of your arm-mounted motors) and a low Collector-Emitter resistance (< 0.3Ohm or so).  MOSFET could be used instead of NPN transistors, with slight schematic change – however I found hard to source them in an easy to solder and light-weight TO-92 package so I used NPNs instead.

QuadHybrid V1 controller board operates by default in “+” configuration. If you want to operate it in “X” configuration then connect the X_CONF jumper – this will give you better control with smaller motors , since for example flying forward will activate two motors at once (3 & 2). The only thing to keep in mind when flying in “X” configuration is that the “Front” is a imaginary line between arm #0 and #1 .

QuadHybrid V1 PCB was created as a all through-hole design so that anyone can assemble it and covert a toy RC helicopter into a QuadHybrid:

http://uploads.oshpark.com/uploads/project/top_image/BaiOVPXQ/thumb_i.png

For anyone wishing to spend time on creating their own QuadHybrid V1 controller board – source code and Eagle files are available on the SVN repository, otherwise easy to solder kits will be available in my Store.

If you would like just to peak over the source code here is a direct link:

https://code.google.com/p/quadhybrid-v1/source/browse/trunk/%20quadhybrid-v1/src/main.c

As you can see it is a fairly simple project a(for anyone familiar with C  and microcontrollers) and a good placeholder for further improvements and add-ons.

 

Mechanical Construction

On top of QuadHybrid prototype is basically a stripped down frame of a 3ch helicopter and namely it comes from Syma S001:

image

 

Under the frame are 2 aluminum tubing pieces that form the 4 arms. At the end of each arm I attached a tail rotor from the same Syma S001 helicopter model:

image

 

Then, to house all the electronics and battery I just sandwiched two perforated  boards with nylon spacers (Tip: most bolts,nuts and spacers used in this design are nylon-made to lower the weight) :

image

For landing gear I just used a RC helicopter training kit that consist of a round bracket attached to the bottom deck, four carbon fiber rods and four (orange) ping-pong balls:

image

Please note that: although all the mechanical parts are from a 3Channel helicopter (Syma S001), you will need electronics from a 4Ch helicopter! The main reason for using a 3CH helicopter for mechanical part is because the bottom blade bracket was already fixed (3Ch helicopters have no swashplate):

image

 

It might be more economical to get a 4Ch helicopter (mainly for its electronics that support pitch & roll not just pitch as a 3Ch helicopter) and then just remove the servos and the swashplate and then fix the bottom blade bracket using screws and/or glue.  As I did in the photo below (E-Sky Big Lama parts shown):

image

 

As an alternative to fixing the bottom blade bracket, you can also get a fixed blade bracket from a 3CH helicopter – it must be same inner diameter as the one from your 4CH helicopter. The diameter of the outer drive shafts are typically 4mm ( and 5mm , 6mm and even 8mm for larger helicopters).

Esky helicopters are best to use in terms of electronics because they have standard signal RC protocols in their transmitter / receiver boards that you can tap-into to get the Pitch/Roll signals needed for the QuadHybrid controller board. Syma helicopters integrated boards are harder to hack into – however some people have managed to hack into them and reverse engineer the signals.

 

Conclusion: What are The Advantages and Disadvantages of the QuadHybrid Design over a traditional QuadCopter or a RC Helicopter

While building the QuadHybrid  I selected the best features of a quadcopter and a helicopter and put them together, this resulted in a machine that took the best of the two worlds:

– QuadHybrid is mechanically symmetrical and stable. As opposed to a QuadCopter it does not rely on sensor to achieve this, the main hovering stability comes from the co-axial design and the centrifugal momentum of the fly-bar (the black bar on top of the blades with two weights on each side) – this is basically the same principle at work as in a mechanical gyroscope.

– QuadHybrid only requires two lifting “powerful” motors, the other 4 small motors are used for steering and are not crucial for device stability. There’s no need for motors to be brushless, and no need for brushless ESC controllers, they can be cheap RC-type brushed motors that can be driven by MOSFETs or transistors, there’s no need to reverse rotation of any motors, however it will be a feature in V2 of the controller board. Also there’s no need for CW and CCW propellers for the motors mounted on arms. All this vastly reduces the complexity and cost of the design.

– Partial or complete failure of any motor will still keep device in the air and give the operator/program a good chance to land it safely. In the worst case scenario – if a driving motor fails , the device will loose lifting power and will spin in the air, but will still at least stay on it’s vertical axis. In case of a quadcopter – failure of any motor is fatal – it will basically flip the quadcopter, or make it fly sideways with great chance to hit something. This is of course debatable, but in any case statistics tells us that the probability of one of the 4 motors to fail is twice of that of one of the two motors to fail (and economics tells us it’s also cheaper to get two motors than four).  Failure of any arm-mounted motor on a QuadHybrid is not critical, the device will still hover in the air and can be landed safely.

– Safety (we all know it should be first). A QuadCopter without  shielded high-powered rotors is a pretty dangerous device,  its propellers are spinning with an incredible force and are ready to cut into anything that falls in their way – they can do a lot of damage to humans, pets or property. QuadHybrid only has four low-powered motors on its arms since they are only used for steering, not lifting. The center driving propellers on a QuadHybrid are shielded away by its arms, also they have a folding design, so if they hit something it will somewhat make the impact less destructive.  Overall QuadHybrid is more suitable for indoor applications such as schools , universities or research facilities. Make no mistake though – QuadHybrid  can  still do damage and safety procedures must he observed at all times !

Few advantages of Quadcopters over QuadHybrid worth mentioning may be:

– because they have four powerful motors, Quadcopters  have greater lifting power. However this is more of a “brute-force” advantage – one could always get more powerful motors and battery for a QuadHybrid to achieve the desired lift power.

– Quadcopters can do some serious aerobatics (if you’re a good pilot)  including fly upside down or do 3D stunts. This is not really an advantage for some people, specifically when you are actually trying to build a nice and stable robotic platform – on the contrary it’s more something you try to avoid. 

In conclusion: although this first version of QuadHybrid was not designed to do 3D stunts or fly with high speeds –  it has a great hovering and maneuvering stability. I think it will find most of its use as a highly stable and controllable indoor flying robotic platform. However similar spin-offs could be expected to be developed for flying outdoors and/or with higher speeds.

 

//starlino//

This article is dedicated to all my math and science teachers !

Quadcopter Prototype using Acc_Gyro and a PIC

For anyone following this site, here is what I've been up to lately – building a quadcopter based on the Acc_Gyro 5DOF IMU sensor and a 16bit PIC. Although it's still a work in progress I decided to start putting together an article placeholder and build it up as project evolves. It's going to be a long one !

The source code will be Open-Source and will be hosted on Google Code, you can get code for quad copter here:

http://code.google.com/p/picquadcontroller/source/browse/#svn/trunk

As usual I like to start with a video demo, it's basically me controlling the tilt of the quad using a RC controller:

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