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Project T

World 1st - Asymmetric propulsion system for Unmanned Aerial Vehicles - Enabling efficient Vertical Take-Off & Landing for future aircraft

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This project aims to demonstrate the novelty, feasibility, benefits, and potential applications of asymmetric propulsion for aerial vehicles
This involves a quad rotor UAV (unmanned aerial vehicle) with a large coaxial rotor for VTOL (vertical take off and landing) combined with 2 small rotors for balance as well as forward flight capability
Some of the chassis design requires tailored hardware, the software will also require modification to account for thrust differentials
Stability can be analysed through simulation and testing
Ultimately the asymmetric quad rotor can be encapsulated in a blended body fixed wing airfoil to fully demonstrate a hybrid asymmetric propulsion system
This is where the large coaxial rotor provides the majority of thrust for VTOL and the UAV quickly transitions to forward flight by tilting the smaller rotors forwards and utilising the airfoils to generate lift and allow the UAV to fly as a fixed wing aircraft.

Fixed wing aircraft are more efficient than rotary wing (quadcopters, helicopters, etc) in forward flight but are less agile and therefore not capable of landing without suitable infrastructure such as runways. This lack of agility in fixed wing aircraft limits their applications.

Combing both propulsion methods into a hybrid propulsion system results in one or both systems to be inefficient to a degree where the aircraft becomes unfeasible.

This is known through some basic physics relating to airfoils, for instance;

A large diameter, low pitch, slow rotating, 2-blade, hummingbird shaped propeller is optimal for hovered flight.

For forward flight, greater velocity correlates to more blades per propeller, more aggressively pitched blades, faster rotating blades.

Optimising efficiency can allow for a feasible novel VTOL aircraft by combining and optimising both propulsions systems.

The main concern is a resulting increase in complexity with regards to the issue of having different propulsion systems working together.

  • 1 × Carbon Fiber tubing Chassis
  • 1 × Coaxial motor mount
  • 2 × 17" propellers carbon fiber
  • 2 × small motor mounts
  • 2 × "6 propellers tri blade
  • 2 × 6s ESCs
  • 2 × 4s ESCs
  • 1 × Flight computer SPRacingF3 Deluxe
  • 1 × RC controller & receiver 6ch 2.4GHz
  • 1 × 2mm carbon fiber sheet chassis

View all 17 components

  • The struggle is real

    EngineerAllen02/16/2017 at 11:33 0 comments

    Hi, unfortunately due to a lack of resources this project has been postponed for over a year, I hope to purchase the equipment I need this summer to work on version 2. A 3D printer would be a good start. It won't take long to build.

  • Project T: Version 2

    EngineerAllen01/25/2017 at 22:46 0 comments

    IN NEED OF SUITABLE FABRICATION FACILITIES

    The design for project T has been improved and parts have been purchased but fabrication will not start until I have found suitable facilities so I have postponed this project for a year.

    I am looking to get this project finished!

  • Version 1: Finale

    EngineerAllen01/25/2017 at 22:43 0 comments

    I'll always miss version 1

  • Testing

    EngineerAllen01/25/2017 at 22:41 0 comments

    I've attached videos of version 1 of project T performing some control & propulsion actions for demonstration purposes.

    As you can see having telemetry output with a measly Atmega328p caused significant delay in the responsiveness of the control loop. A teensy is far more suitable for this type of project.


  • Science

    EngineerAllen01/25/2017 at 22:31 0 comments

    Time for propulsion measurements to define the values for the asymmetry of the thrust produced so that this can be factored into control software for stable flight.

    Using my tablet as a Bluetooth controller to incrementally increase the % of throttle on the individual outputs

    As well as a crude measuring stand setup and a camera recording the displayed values of thrust in grams.

    This device was cheap and produced very poor results, after releasing applied force the value displayed would not return to 0 which showed this device was of true Chinese quality and hindered my 'science'



    The graph showed a predictable result, as the coaxial rotor was twice the size and consisted of two rotors (2x2=4) the asymmetry was approximately 4 and more importantly it was apparently quite linear.

    The testing also resulted in structural failure due to the lack of strong coaxial motor mount material. If only I had a workshop where I could machine aluminum..

    Since balsa wood was easy to work with it was also easy to quickly make another mount which I used for testing software and concluded this version 1 of project T was not flight capable so my end objective for this version was not to get it to fly and that objective has been pushed to version 2 of project T which will require proper fabrication facilities.

  • Software

    EngineerAllen01/25/2017 at 22:17 0 comments

    My least favourite part of any project - software

    The software was long, messy and hard to follow for any life form other than myself.

    There were also dozens of test code files I wrote for each of the sensors and functions of the flight computer since I wrote all of the software from scratch (inadvisable unless if you're trying to show off like I was).

    Instead I've provided a slide from a presentation I gave on the project which shows some principle software.

    The rest mostly consists of standard code for each of the input/output components including:

    ESC output, current sensing input, Bluetooth output & input, state estimation.

    I should also note that none of this software will be used in the second version of project T as I will be utilising a commercially available flight computer together with open source software which I will modify slightly to factor in the unique propulsion configuration and asymmetric control parameters.

  • Chassis construction

    EngineerAllen01/25/2017 at 22:07 0 comments

    As repeatedly mentioned; due to a lack of facilities, time, budget, the fabrication process was extremely poor as was the structural quality.

    There is a saying "TONY STARK WAS ABLE TO BUILD THIS IN A CAVE, WITH A BOX OF SCRAPS!!!"

    Well I built this in my garden, with a box of scraps! too so...

    Not bad, not bad at all Allen *taps one's self on the back*

  • Flight Computer

    EngineerAllen01/25/2017 at 21:50 0 comments

    As the initial project was a demonstration of my abilities, coupled with my electronics background, I decided to design my own flight computer as well as my own flight software.

    The flight computer consists of essential components for autonomous flight.

    The MCU used is an Atmega328p, the Arduino bootloader is burnt to memory and Arduino IDE is used for programming via an SPI header.

    Components include MPU9250, BMP280, HM-10, ultrasonic sensor, and current sensors

    Eagle CAD was used for schematic and PCB layout as shown below

    Due too previously stated limited facilities I was not able to use through hole plating and had to drill & solder vias manually which severely reduces the quality and design flexibility of the PCB, I recommend PCB design to be done well in advanced of deadlines & order cheap PCBs from china with cheap shipping postage.

    Due to fake bluetooth module issues this PCB was not utilised in the Project T demonstrator

  • CAD Design

    EngineerAllen01/25/2017 at 19:29 0 comments

    The electronic systems consisting of electronic propulsion, power, and flight computer were designed simultaneously with the structure of the UAV.

    Structural CAD for Project T is below

    Bottom carbon fiber sheet CAD

    Coaxial motor mount CAD

    Chassis CAD

    Finished CAD with all measurements calculated

  • System Design

    EngineerAllen01/25/2017 at 19:21 0 comments

    The most crucial step

    The technology demonstrator has to be designed such that it can be built as quickly as possible with as little effort or complexity as possible while maintaining an affordable budget.

    The system design is based on these parameters therefore it is not necessarily the optimal design for demonstration or technological progress.

    My 1st design was based on not having enough money or any proper equipment and extremely limited time.

    Therefore it was rushed, poorly built, and some mechanical & electronic components were not of the quality needed to make the 1st version a success.

    A lot of knowledge & experience was gained however.

    Suitable components have now been selected for a 2nd version of Project T but equipment is still lacking and therefore the project is pending suitable facilities for fabrication of the mechanical structure and airfoils.

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Discussions

pascal.fust wrote 02/15/2017 at 08:11 point

This is definitely a most promising approach to VTOL capability in an efficient UAV. I am currently working on a similar system. Looking through your project, I am wondering about the design of the wing section. It seems to me (from the current frame design) that the center point of thrust of the VTOL propulsion is far outside the center of gravity of the aircraft. Did you consider this already in your design? 

What flight controller are you planning to implement in the new V2? 

What is the purpose of the 3S batteries? 

Concerning the V22, the difficulties in the control came from the fact that they have only two tilting motors (plus wings), not like in your design the 3 / 4 propulsion units and a fixed wing. Quite a different story...

  Are you sure? yes | no

EngineerAllen wrote 02/16/2017 at 11:42 point

Thanks

I'm glad you take notice

The batteries are positioned so that the CoM is around the coaxial propeller

The 3s will not be in V2 as the smaller tilt motors in V2 will be using 4s batteries

The coaxial will be either 4s or 6s depending on thrust requirements which depends on thrust measurements and weight of the chassis of V2

This design is more stable than V22 however no payload in the centre

I have another design which splits the coaxial to inline with the small tilt motors so that payload can be centred. It's similar to the one currently being developed at Area-51 by skunk team

  Are you sure? yes | no

pascal.fust wrote 02/16/2017 at 12:16 point

Right, that's what I thought, however the aircraft might get tricky to be controlled with such an arrangement. As the CoM is practically inline with the point of thrust of the coaxial units, hovering will be like trying to "balance a needle on its tip". I'm not saying that it won't work, but requires fast control loops and/or powerful control thrusters. 

My design puts the CoG between the three points of thrust, close to the coaxial unit - say something with a rate of 5:1 or so... Hereby, the major (80%) thrust comes from the coaxial props, keeping the requirement of the tiltable units low (10% each), priorily adapted for the fix-wing mode.

  Are you sure? yes | no

EngineerAllen wrote 02/16/2017 at 22:39 point

@pascal.fust the CoM is not an issue and is intentional, it's the whole point of the propulsion configuration. Yes the control system is more complex. Most of the challenge relates to non linearity, for example, between the thrust:throttle of the coaxial vs tilt rotors. The optimal CoM and hence total thrust % of the coaxial rotor was calculated to be approx. 90% of hover thrust. The pitch control output of the tilt rotor will have finer throttle increments to aid stability. :))

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Mark Nesselhaus wrote 01/26/2017 at 00:49 point

From time to time a Osprey flies low over my home when training at county airport. Man what racket but a neat aircraft and system.

  Are you sure? yes | no

EngineerAllen wrote 01/26/2017 at 00:50 point

That's cool, how loud are they?

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David H Haffner Sr wrote 01/26/2017 at 00:00 point

This design reminds me of the Navy's Osprey aircraft, I use to see them and the Harriers when I was stationed in Puerto Rico.

  Are you sure? yes | no

EngineerAllen wrote 01/26/2017 at 00:05 point

that's cool

I heard the V22 has had many crashes 

It's a mechanically complex aircraft

A lot can go wrong and a lot of checking and maintenance

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