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Cuadricopter, Hexacopter, small budget. Aerial photography.

Intro:

          UAV (Unmanned Aerial Vehicle) is a vehicle which is unmanned, it could be completely autonomous, or remote controled, RPA (remote Piloted Aircraft) or mix systems. Traditionally UAV has been employed for military goals, but actually many civil aplications are being developing. Specially I am interested in  aerial phography.

Design and development considerations: (UAV) (wikipedia)

             The United States and Israel were initial pioneers in this technology, and U.S. manufacturers have a market share of over 60% in 2006, with U.S. market share due to increase by 5–10% through 2016. Israeli and European manufacturers form a second tier due to lower indigenous investments, and the governments of those nations have initiatives to acquire U.S. systems due to higher levels of capability. European market share represented just 4% of global revenue in 2006.

Multicoters:

            A multicopter mainly is a helicopter with several axis and independent motors. The are Tripcopter, quadcopter, hexacopter octocopter... They have good stability and large payload capacity. The propellers spin in diferent directions. This avoid that the aircraft rotate itself over a vertical axis. The control is implemented by an electronic board which cahnges the speed of each motor. In this way you can get all the movements.




Civil purpose:

• Aerial security fo large surfaces.
• Transport of goods.
• Science research: remote sensing.
• Search and rescue in natural catastrophe. 
• Other comercial golas like aerial video and photography.  Jeff Scholl is an american guy who work up in this theme. In his facebook profile he has lots of nice vids and photos.Usos no militares: 

www.gravityshots.com

Some of Jeff Scholl's multicopter are:

Some of him videos:

        A Nick and Roll compensation needed if we don't want a dizzy film:

          With two servos and some damperners we can reduce the vibrations. This vibrations come from the motors and props. rubber dampeners, dampeners2.

          From Pennsylcania university, GRASP Lab is developing aggressive maneuvers for autonomous cuadricopter. Here you can see some of their works.

:

           In the following video you can see a group of cuadricopters working together to build a small structure. You can see the potential of these small aircrafts with this example.

Approximate budget:

             Knowing how cost build a cuadricopter or hexacopter is so important. Here you can find a list with the basic components:

• Motors

• Propellers

• Electronic Speed Controller (ESC)

• Electronic control board.

• Radio receiver and emisor

• Frame

Motores: 

Electronic speed controller (ESC):

Emisor-receiver:

Receiver

Propellers

Part	Quantity	Unit price	Total price
Motors	4	20$	80$
ESC	4	12$	48$
Propellers	4+4 replacement	3$	24$
Reciever & emisor	1	53$	53$
Battery	2	25$	50$
TOTAL		TOTAL	250$

Hexacopter: Download here the excel file.

Elemento	Cantidad	Precio unitario	Precio Total
Motores	6 +1	20$	140$
ESC	6	12$	72$
Hélices	6+6 Repuesto	3$	36$
Reciver y emisor	1	53$	53$
Baterias	2	25$	50$
Electrónica	1	250$	250$
chasis	1	¿? $	¿? $
TOTAL		TOTAL	601$

               The frame and the electronic board haven't been added. The electronics board that I have choosen is ArduPilot, based on a Open Source project DIYdrones. it is a board similar  Arduino board. This electronics board can manage any  UAV (Unmanned Aerial Vehicle) aircraft like multicopter, airplane or glider. Almost all necessary sensors are already built-in.

 

       
       
            This board is very modular and it has free pins, so you can add other king of sensors or elements like camera stabilizer... Also you can connect a radio receiver, telemetry and an USB connection for programing. It has too one small relay to activate some load.

         Es muy modulable y posee bastantes pines libres, de forma que puedes ir añadiéndole sensores u otros elementos como estabilizadores para cámaras... Tiene conexión para el receptor de radio, es posible añadir telemetría, conexión USB para programar el micro 1280 y dispone de un relé para accionar periféricos.

The features are:

• 3-axis gyros

• 3-axis accelerometers

• Barometric pressure sensor for altitude

• 10Hz GPS module

• Voltage sensors for battery status

• 16Mb of onboard datalogging memory. Missions are automatically datalogged and can be exported to KML

• Built-in hardware failsafe processor, can return-to-launch on radio loss.

• Include relay can trigger any device, can be controlled by mission scripts.

• (Optional) 3-axis magnetometer

• (Optional) Airspeed sensor

• (Optional) Current sensor

       The kit costs around $250, and the soldered board for $299. Also is necessary a 3 axis  magnetometer if you want point to a specific direction.

        Many designs are valid  for the frame (images). Also many kind of materials can be used  and some constuction process. The best wat is a CNC machine.

      

Cameras:

            The main goal is take pictures or videos, but we use cameras also to send live video for First Person View (FPV) flight. For our multicopter, at first, it won't have cameras.         


            With the FPV camera you can pilot without direct vision. Also is useful to take better videos and photos. This cameras are very light, only about 16 grams.  OSCS420.

          To take pictures, is important use a good photo/video camera. These cameras have remote control of the photo shooter, focus ... and many of them have video output that you can send to your  groundstation. Also is important a good shock absorber system with dampers and a smooth camera stabilizer. 

             A good choice is  GoPro. Special designed for extreme sports like motocross, montainbike, surf, snowboarding, skateboarding... It has only basic features to a first person view video with smart video quality. it weight 94 grams and have a endurable waterproof housing. It cost arround 200$.

The GoPro 2 version is now avaliable.   Here you can fin a GoPro lens protection by fpvmanuals.

Commercial Aerial photography: 

                   Taking photos and videos from the sky is not nothing new, but lately has raised exponentially.
Advances in radio contolled models have made it possible to conduct low-altitude aerial photography. Also  full-size manned aricraft are prohibited from low flights above populated locations. RC (Radio Control)  plane and multicopters are more accessible for DIY fans.
Lots of applications for aerial photography, some of them are:      

• Cartography: A process taht is used in photogrammetric surveys, the basis for topographic maps.
• Environmental studies: Charting the environmental changes that have occurred in a given area.
• Comercial advertising: Obtaining photographs that can be used to create commercial ads.
• Construction progress shots.
• Film production.
• Panoramic views and 360 degree virtual tours.

           Some examples of aerial phothography can be seen here.

           There are lots of methods like planes, helicopter, ballons, kites, rokects, zeppelin, parachutes... The most commercially ussed maeby are Zeppelin. This kind of aircraft are very safety and stable. The principal issues of tradicional helicopters and multicopters are stability from vibrations and fast moves and safety. One accident could produce lots of money loss and humans damages.

        

Zeppelin

hexacopter

       As advantage, the multicopter can create more movement for videos, views like a bird. Here is an example:
   

           This kind of result is not posiblle to obtain with a Zeppelin. Also is needed a good stabilizator to get this videos.

   

Project goals:

          Design and build a multicopter with payload capacity to carry a photo-video cammera. The design part includes:    

• Design the frame based on carbon fiber or aluminum parts mades by a CNC machine.
• Design a 2 axis stabilizator (Nick&Roll) wich can hold any kind of standar cammera.
• Remote control of the cammera and video transmiter from ground.
• Estimate wich motors and ESC can carry the photograph kit.
• Control and programming for a good and stable flight.
• Autonomous control and safety mode.

             The final goal could be able to design and build a commercial photography multicopter for profesional use.        

Multicopter choice:

         Depending the use of the multicopter we are going to choose more or less number of motors. For this project, the objetive is get quiality photography/video works. The main features will be:

     
Simplicidad y bajo peso en la estructur

• Simply and low weight.
• Payload capacity for a good camera.
• Transportable and folding.
• 10 minutes of autonomy.       

         

           All posible configurations are:     (see also mikrokopter)

Tricópter: Barato y fácil de construir, menos estable, partes móviles en la estructura (cola móvil por un servo), bajo empuje y menos tiempo de vuelo (porque los motores tienen que girar más rápido para mantenerlo en el aire).

Cuadricópter: Más simple mecánicamente que el tricópter. Posee 1/3 más de empuje pesando casi lo mismo y suelen ser más estables ya que no  tienen partes móviles en la cola movidas por un servo. Tienen más tiempo en vuelo debido a que pueden llevar baterías más grandes y a que los motores trabajan a menos revoluciones. Todavía no contamos con redundancia: Si un motor falla... cae.

Hexacópter: Todo lo bueno que tienen los cuadricópter pero con más potencia y más capacidad de carga. Posee algo de redundancia: Si pierde un motor todavía puede aterrizar, (perdemos el control del ángulo 'yaw'). Como desventaja son más caros y más grandes.

Octocopter: Todo lo bueno que tienen los hexacópter más redundancia: Si pierde un motor todavía vuela bien. Se usa para asegurar cuando se ponen equipos fotográficos de alto precio. Son más caros que los hexacopter. Requieren mucha energía para volar.

        Descartamos la opción de cuadricópter (quadricopter, quad... ) pora conseguir más capacidad de carga. Sobre la opción de elegir un hexacópter (hexacopter, hexa...) o octocóptero (octocopter, octo... ):

    Ventajas de un mayor número de Motores:

• Mayor capacidad de carga
• No es necesario unos motores tan potentes o unas hélices tan grandes para la misma capacidad de carga.
• Redundancia. Muy importante, en caso de rotura de una hélice, choque...

        6 motores es poco fiable, aunque, probablemente,  sobreviviría a una parada de un motor, hay que irse a 8 motores para tener ambas cualidades: Capacidad de carga y Redundancia.

      A mayor número de motores necesitaremos unas hélices más pequeñas, que dan una respuesta más rápida, resultando más estable. Por eso para conseguir estabilidad los motores/hélices han de poder cambiar de velocidad lo más rápidamente posible.

      Quizá con 6 motores sea más eficiente (Usa menos Watios pare levantar un un Kg.,≈ 5 o 10%) que 8, entre capacidad de carga y peso. Elegiremos 8 sólo si queremos más carga o por la redundancia ya que es mucho más caro (1/3 más caro, motores, ESCs y hélices).

       Las configuraciones coaxiales tienen como principal ventaja la redundancia. Podemos usar Y6 o X8, aunque son menos eficientes debido a que el aire que llega a la segunda hélice está turbulento.

       La configuración en X o en +.

       Conclusión: si el objetivo es la fotografía tienes que irte a Hexa/octo, si el uso va a ser el pilotar una aeronave o las acrobacias  lo más indicado es un cuadricóptero ligero.