Why Quadrotors are so Popular for Research?

February 27, 2012

Over the past few years a number of videos featuring unusual looking flying machines with four propellers have appeared on YouTube. The videos, from a variety of universities, have shown the machines called quadrotors, performing increasingly complex aerial manoeuvres.

As the moves they produce have got more impressive, the number of viewers and fans has increased. They have now been seen by millions of people, featured on countless tech websites and now are even making the way into major newspapers.

Perhaps the most astounding footage has come from the General Robotics, Automation, Sensing and Perception (GRASP) at The University of Pennsylvania. The videos show these machines performing routines that look so spectacular that you would be forgiven of you thought they were special effects from the latest sci-fi movie.

The footage shows swarms of the miniature machines hovering in mid-air, in formation, before autonomously performing complex flying routines such as flips, darting through hula-hoops and organising themselves to fly through windows as a group. The latest video even shows them playing musical instruments.

So why have these machines become the vehicle of choice for universities? Well, there are a number of reasons. They are highly manoeuvrable, as can be seen in the videos, this means that they could be useful in all kinds of situations and environments.

They are relatively cheap, available in a variety of sizes and their simple mechanical design means that they can be built and maintained by amateurs. But surprisingly, it is one of their major downfalls that make them so attractive to researchers and academics.

Quadrotors are inherently unstable. They rely on fixed and equal value of thrust from each of their four propellers to remain stable. This is very difficult to do manually, and any tiny variation in the amount of thrust generated could cause the quadrotor to veer off wildly or spin out of control.

In order for the machines to change speed, direction and height, the power to each of the four rotors need to be varied in a controlled way and the quadrotor has to return to a stable flying or hovering position once the move has been completed. This requires complex sensors capable of inertial movement and advanced flight control in

This means that flying them properly represents a test. In academic speak ‘they are a challenging example of a safety critical embedded real time system’. In other words, get it wrong and they will crash and burn.

Quadrotors are a great tool for university students and researchers to test and evaluate new ideas in a number of different fields, including:

  • Flight control theory
  • Navigation
  • Real time systems

The cross fertilization of ideas and approaches that these projects generate are also a major benefit. Academics from a number of fields need to work together In order to make significant improvements to the way quadrotors perform. Quadrotor projects are typically collaborations between computer science, electrical engineering and mechanical engineering specialists.

Quadrotors are currently used in the real world for surveillance and reconnaissance by law enforcement agencies and the military as well as search and rescue missions in urban environments.

It is hoped that the research being carried out today will soon have even greater benefits in the real world.  Quadrotors capable of autonomous flight could help remove the need for people to put themselves in any number of dangerous positions.


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