Quadrotors – An Introduction

February 28, 2012

What is a Quadrotor?

A quadrotor helicopter or quadrotor for short is an aircraft lifted and propelled by four motors and propellers. They are extremely manoeuvrable and are capable of hovering and vertical takeoff and landing.

Example Quadrotor

The X4 Draganfly Quadrotor

The first type of quadrotors were flown in the 1920’s with the aim to be used as manned vehicles, but the first successful manned flight was in the1960’s when the Curtiss-Wright X-19A  was developed.

These early quadrotors lacked systems that provided stability during flight and controlling four motors individually made them difficult for pilots to control and the manned development programmes were scrapped.

However, recent advances in technology mean that onboard computers can correct instabilities and control is much easier. Due to their design they are much simpler than helicopters to fly. They are now becoming much more common and the most recent types of quadrotors are designed to be unmanned aerial vehicles.

How do Quadrotors Work?

Quadrotors work using a symmetrical design with the motors located in each of the four corners. The rotors are fixed in their pitch with two of the rotors move clockwise and two of them move anti-clockwise. This design naturally cancels out torque and prevents quadrotor from rotating in the air. Control over the aircraft is produced by changing the speed of the motors.

Quadrotor Flight Controls Diagram

The simplicity of the design has a number of advantages over traditional helicopters. Quadrotors are free from complex mechanical control linkages which mean that they require less maintenance and are more efficient at smaller sizes (increased flight times or higher payloads).

In addition, by surrounding the rotors within a frame, the rotors can be protected from damage during collisions. This allows flights indoors and in cluttered surroundings, with minimal risk of damaging the aircraft or its environment.

These safety benefits speed-up the design and test flight process as flights can be carried out indoors, by inexperienced pilots, with a quick turnaround time after an incident.

Where are Quadrotors Used?

Simple mechanics, ease of control, high manoeuvrability, and the ability to carry a heavy load make quadrotors the top choice for a variety of uses. Quadrotors are now used by:

  • Amateur model aircraft fans for self-build projects
  • Military and civilian observation roles
  • University research

A team from the University of Pennsylvania, famous for its quadrotor research, have programmed them to carry out a number of tasks autonomously. Videos of their feats are proving to be a hit on the internet, with their examples of swarm behaviour amazing the public.

In the future quadrotors could be used for a wide variety of tasks including the mapping and scanning of terrain and buildings. They can also be used to lift and move things in environments that are unsafe for humans, such as nuclear power reactors.

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