A Brief History of Quad-rotors and an Introduction to Flight Controllers

        Welcome to my blog! In this blog I am going to share interesting research on the development of Micro Air Vehicles (MAVs). I myself am also doing some design and research on MAVs therefore in the future I will also post about my own design and research results.
In my first post I will be briefly talking about the history of quad-copters (from the family of MAVs). I will end with talking about the flight controller that I use.

De Bothezat Helicopter, Edison National Historic Site Archives

      Although most quad-rotors we see today are unmanned, there was a time when these copters were designed specifically for human use. After the first airplane design was successful, the government allocated some money on vehicles that could take off and land vertically. George de Bothezat received funding for his design in the early 1920s. A picture of the built design is show on the right. Quad copters are 6 degree of freedom systems. Although the De Bothezat helicopter flew in 1922, the government shut down the program because it was really difficult to control a quad copter. In the beginning of the video below you can see a De Bothezat Helicopter flying.

As you can see, the De bothezat helicopter is not very stable and it keeps on turning counter clockwise around it's z axis. Today, two of the propellers, in every quad copter, turn in the opposite direction to keep the craft stable. If all four turn the same way, then the forces would add up turning the whole copter. Below is a picture that shows the direction of the propellers on a quad copter.

Ardpilot.com

Since the size of electronics have become smaller we can now mount flight controllers on top of small quad copters. These flight controllers solve the difficult stabilization equations and make it easier for us to control the quads. This article gives a very good introduction on flight controllers. It shows the different flight controllers that are available and their advantages.

Ardupilot.com

    For my design I chose to use the arducopter flight controller. The ardupilot flight controller is an open source board that has a very active developer community. This developer community fixes bugs with the current firmware, adds new features and releases the new firmware. The ground station Graphical User Interface (GUI) also gets updates and looks very modern and runs fairly fast. A picture of the ardupilot board is shown on the right. Some of the features of the flight controller is listed below.

1. Arduino compatible with an integrated Atmega chip.
2. 3 axis gyro and accelerometer
3. Barometer to sense the altitude 
4. 4 Mb datachip on board to log flight details
5. GPS and telemetry inputs. 

On one of my next posts I plan to explain the GUI and its features.