Bats are remarkable creatures, able to fly at night or inside the confines of caves without light to guide their way. A team of researchers at Worcester Polytechnic Institute (WPI) has determined how to use low power ultrasonic sensors to guide drones in obscured environments.

While radar, lidar, and GPS are all great for navigation and sensing, they can run into issues when light is obscured or can take too much power to be practical for the limited battery life of a drone. The researchers found that a dual sonar array could be used to implement a much lower power sensing system for a drone that performs well in environments that would stymie a computer vision system.

A shield placed behind the array cuts down on the sound of the propellers that would otherwise drown out the signal, and further signal analysis via a neural net separates the echoes of objects in front of the drone from the background. The prototype could navigate in various simulated environments like forests, smoke, and snow. It looks like it even got a chance to go for a flight in the actual woods. All the code and hardware designs are Open Source, so have at it!

We’ve covered mosquito-inspired drone sensors before, and if you want to get into echolocation yourself, apparently humans can learn to do it too.

via Entertainment Engineering.

Researchers demonstrate that something interesting happens when a small drone with a spindly airframe spins at a high speed: it very nearly turns invisible. The spidery device is shown mounted in its launcher in the image above. The dark blur at the rightmost side is an outlet on the wall behind the drone, not motion blur from a moving part.

It’s called the Phantom Twist, and while we’ve seen single-motor drones that spin around a central axis before, they have always incorporated a wing-like structure or cleverly leverage the magnus effect to generate lift.

There’s not a lot of detail about the Phantom Twist’s hardware design but it appears to use a downward-angled motor for lift, relying on a high-speed control system to maneuver and maintain altitude.

This does away with the need for a wing, at the cost of only being stable while rotating at a high speed. We imagine it is also a touchy design that depends greatly on being balanced just so.

A hand launcher spins the device up before releasing it for flight. The visual effect once it is up and running is pretty striking; see for yourself in the short video, embedded just below.

Northwestern engineers built a spinning drone that exploits motion blur, making it about ten times less visible than conventional drones.

Last September, Denmark was gripped by a spate of drone sightings near airports. It’s familiar territory for Hackaday, as we reported on a similar drone panic saga at British airports back in the last decade. Back then the British police dragged their feet and hid behind secrecy laws for years to avoid admitting they overreacted, but it seems in Denmark they do things differently (Danish language, Google Translate link.).

The Danish police in Jutland have rolled back their report, and noted that a reported observation alone is not enough to confirm a drone was present. It’s not confirmed why they’ve taken this step, but we’ve been told that there’s been an effort within the drone community to identify possible aircraft flight paths which could have resulted in a false drone sighting at the times in question.

We welcome this correction, and hope that its important message travels widely. Of course it is the right thing to do for a police force to take drone reports seriously, but overreacting as the British police did is of little help. We commend the Danish police for taking this step, and we’re likely to trust any drone reports from them a little bit more in the future. If you’d like to read our plea for a sensible response at the time, it’s here.

Thanks [UAVHive] for the tip.