Intelligent Machines

Watch This Robotic Quadcopter Fly Aggressively Through Narrow Gaps

Flying through small gaps will be crucial for aerial vehicles performing search and rescue operations.

Micro air vehicles could one day make a significant contribution to search-and-rescue operations after disasters such as earthquakes or tsunamis. It’s easy to imagine quadcopters assessing buildings, entering through cracked walls, and flying through collapsed spaces to find people who are trapped.

But if these vehicles are ever to manage this task, they will need to navigate autonomously through narrow gaps at speed and at a wide variety of angular accelerations, twisting and turning as they fly to squeeze through the space available.

That’s easier said than done. Indeed, no drone has been able to do this without significant external processing power to help (see “Daredevil Drone Files through the Trees Like an Ace”).

Today that changes thanks to the work of Davide Falanga and pals at the University of Zurich in Switzerland. These guys have developed an autonomous drone that can fly quickly through narrow gaps using little more than the data from a forward-facing camera and some clever on board processing.

The team created a rectangle marked with a thick black edge to ensure that the drone can see it. They then suspend this rectangle in the middle of a room and direct the drone to fly through it under its own steam.

The drone is fitted with a forward-facing fisheye camera, which it uses to sense the gap. To simplify the task, the drone knows the size of the rectangle and needs only to calculate the required trajectory.

This is still a challenging task. The on-board processor performs the trajectory calculation in two stages. It first calculates how the drone should fly through the gap and the particular twist, yaw, or roll it has to perform to traverse the gap. It does his by maximizing the drone’s distance from the edges of the rectangle to avoid a collision.

Having decided on this traverse trajectory, the onboard processor then calculates an approach that brings the drone to the point where it can initiate the traverse trajectory.

The approach trajectory has some additional constraints. For example, this trajectory must keep the rectangle within the field of view of the camera at all times. The drone needs to see the gap so that it can determine its location.

And the processor must continually recalculate the trajectory while ensuring that any required adjustments are within the drone’s aerodynamic capabilities. The processor is capable of designing and testing 40,000 trajectories a second.

One reason the trajectory must be treated in two parts is that the drone cannot see the rectangle during the traverse. So it must perform this maneuver blind, something that is possible because this part of the flight is so short. “The trajectory is generated so as to minimize the risk of collision and, due to its short duration, does not require any visual feedback, which is not available during the traverse,” say Falanga and co.

After passing through the gap, the quadcopter must recover its attitude and hover. For this, it is fitted with a distance sensor and a downward-facing camera which it uses only for this task.

The team tested this approach using a quadrotor with dimensions of 55 by 12 centimeters and a weight of 830 grams. The quadcopter is adapted so that the motors are tilted by 15 degrees. This provides three times more yaw control but loses only 3 percent of the collective thrust.

The rectangular gap measured 80 by 28 centimeters, and the team flew 35 missions through it at speeds of up to three meters per second, requiring a roll angle of up to 45 degrees and a pitch angle of up to 30 degrees.

The results make for impressive reading and can be seen here. The team considers a flight a success if the quadcopter passes through the gap without a collision and then brings itself to a hover afterward. “We achieved a remarkable success rate of 80 percent,” they say. “To the best of our knowledge, this is the first work that addresses and successfully reports aggressive flight through narrow gaps.”

Ref: arxiv.org/abs/1612.00291: Aggressive Quadrotor Flight through Narrow Gaps with Onboard Sensing and Computing

 

Become an MIT Technology Review Insider for in-depth analysis and unparalleled perspective.

Subscribe today

Uh oh–you've read all of your free articles for this month.

Insider Premium

$179.95/yr US PRICE

More from Intelligent Machines

Artificial intelligence and robots are transforming how we work and live.

Want more award-winning journalism? Subscribe and become an Insider.

  • Insider Premium {! insider.prices.premium !}*

    {! insider.display.menuOptionsLabel !}

    Our award winning magazine, unlimited access to our story archive, special discounts to MIT Technology Review Events, and exclusive content.

    See details+

    What's Included

    Bimonthly home delivery and unlimited 24/7 access to MIT Technology Review’s website.

    The Download. Our daily newsletter of what's important in technology and innovation.

    Access to the Magazine archive. Over 24,000 articles going back to 1899 at your fingertips.

    Special Discounts to select partner offerings

    Discount to MIT Technology Review events

    Ad-free web experience

    First Look. Exclusive early access to stories.

    Insider Conversations. Join in and ask questions as our editors talk to innovators from around the world.

  • Insider Plus {! insider.prices.plus !}* Best Value

    {! insider.display.menuOptionsLabel !}

    Everything included in Insider Basic, plus ad-free web experience, select discounts to partner offerings and MIT Technology Review events

    See details+

    What's Included

    Bimonthly home delivery and unlimited 24/7 access to MIT Technology Review’s website.

    The Download. Our daily newsletter of what's important in technology and innovation.

    Access to the Magazine archive. Over 24,000 articles going back to 1899 at your fingertips.

    Special Discounts to select partner offerings

    Discount to MIT Technology Review events

    Ad-free web experience

  • Insider Basic {! insider.prices.basic !}*

    {! insider.display.menuOptionsLabel !}

    Six issues of our award winning magazine and daily delivery of The Download, our newsletter of what’s important in technology and innovation.

    See details+

    What's Included

    Bimonthly home delivery and unlimited 24/7 access to MIT Technology Review’s website.

    The Download. Our daily newsletter of what's important in technology and innovation.

/
You've read all of your free articles this month. This is your last free article this month. You've read of free articles this month. or  for unlimited online access.