Background

How to select the best drone for development

Selection of drone for your interest is very tough when it comes to various and vast drone domain.

Drone technology has become very famous last couple of years and domain has expanded with more product variations. This makes selecting a drone for our interest very tedious work.

Senior Tech Lead

Testimonial Author

Gayan Priyanatha

Even though we have the luxury of selecting and purchasing one for our need, at what cost is the question. In that aspect how about engineering and designing drone by yourself. This will be led to have all features or many features of a drone to be in top score.

To do this one must have electronic knowledge and embedded development capabilities, but in this article I am here to ease your pain on background for these aspects.

Features we are looking at to be in our drone
  • Auto level and stable hovering
  • Automated waypoints navigation
  • Auto altitude control and altitudes hold, position hold
  • Return to launch and fails safe landing
  • Automatic takeoff and landing
  • Drive a pan-tilt camera for photography and move making
  • Mobile devices Control
  • Long distance video streaming and control

I’m not going to elaborate on these as this will make the article more longer, But as drone enthuses you can search for those on internet.

Why a quadcopter
  • Fullfill above features
  • Reliable
  • Compact
  • Low Maintenance
  • Responsiveness
  • Low cost
Key aspects to consider
  • Aviation Theories
  • Hardware
  • Cost
  • Flight time
  • Complexity
  • Software
  • Flight controller program
  • Ground control station
  • Mobile application
The Aviation theory 101
  • On a quadcopter 4 motors spin in 2 directions, as per left upper image above, 2 motors
         toward Anit-clock wise and other 2 on clock wise.
  • On hoover hold all motors spin power is identical.
  • Roll is rotation of quadrotor around front-toback axis.
  • Pitch is rotation of quadrotor around left-toright axis.
Hovering

Balance of force, SUM(Fi) must be equal to m x g

Tilting

Net aerodynamic torque is based on direction user requests.

The Control theory

Idea is that two control systems—inner controls and outer controls—work against our tendencies to deviate. Control theory can either be classified as centralized or decentralized or neither. Decentralized control is considered as market control.

For example, think of a situation where you are driving a car and you want to maintain speed in a hill. In this case acceleration increases as we climb the hill. This is called feedback control.

PID: Proportional-Integral-Derivative

(P) Proportional – You are applying proportional control to the car speed.

(D) Derivative - Faster the speed is dropping the more acceleration is applied. (amount of speed drop)

(I) Integral - Control as a constant summation function, constantly adding up the error from the target speed and providing feedback proportional.

Consider above example for our drone, we want to make our drone hover around altitude at 1 meter where it needs to take from ground at higher speed but want to gradually reduce speed at 1-meter height.

Power normalization graph with time

The power given to drone motors to control the spin is elaborated.

Open source hardware

Consists of physical artifacts of technology designed and offered by the open design movement. Both free and open-source software (FOSS) as well as open-source hardware is created by this open-source culture.

Open Hardware-software Selection
Flight controller boards features
Winner is arduocopter pixhawke cube 2
Wiring Layout
Frame selection
  • 650, 550, 450, 350, 250
  • Light weight readymade plastic
  • In-built power distribution
  • Board for direct ESC wiring & motor placing slots
  • Frame weighs approximately 200g
ESC (Electronic Speed Control) Selection
  • Rated at least 150% of the motor current
  • Amperage for 3S use 30A
  • Firmware – BLHeli. (SimonK is outdated now)
Frame selection
  • 2300kv type motors for a first build that you can run on 3S or 4S are good candidates. DJI series is very good for your purpose
Propellers
  • 4 x 8.2 inch propellers
  • One pair consists of an Anticlockwise & a clockwise propellers. A 8.2 inch diameter propeller can lift upto 600g
  • 4 x 8.2 inch can lift 2400g (2.4 Kg)
  • Maneuverability increases and thrust decreases as propellers diameters shorten and vice versa
2.4 GHZ 6-CHANNEL Tx & Rx
  • Range of upto 1km
  • 6 channels
  • RF Power: Less than 20db
  • PPM signal at 50Hz from Rx
GPS & Compass Module
  • High precision with concurrent reception of up to 3 GNSS (GPS, Galileo, GLONASS, BeiDou)
  • 167 dBm navigation sensitivity
  • Security and integrity protection
  • Supports all satellite augmentation systems
  • Advanced jamming and spoofing detection
  • GNSS is good product for this
Li-Po Battery
  • Minimum weight as possible. 125g if possible
  • Maximum capacity as possible. 10500
  • Discharge current rate around 25C
  • Venom is good product for this
Power module
  • Must have this to detect and trigger failsafe modes on low battery level and 6 pin module is enough for our purpose
Wireless Telemetry
  • 150 dBm strength
  • 433Mhz range
  • 5Km distance
  • Dji is good product for this
Camera & Gimbal
  • Go Pro is the best camera I have seen so far
  • It supports 4K
  • Best action camera in the market
  • DJI gimbal for Go Pro is the best I recommend for our purpose
Vibration to flight controller

Make sure to have good vibration controllers so that flight controller IMUs (gyros) are secured from the vibration. Following figure compares before and after adding vibration dampers to secure the flight controller board

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