Drones using sonar for sight

One of the most interesting innovations in robotics in the last year was the development of a sonar system for robots that utilized a simple system of a single speaker and two microphones to mimic the sonar of bats. These “Robats” were developed at Tel Aviv University in Israel early last year.

You might ask what the advantage is of using sonar for robotics when we already have excellent computer vision techniques and LiDaR. There are two main factors to take into consideration. The first is that LiDaR units are both heavy and expensive, though we can achieve a more detailed model of the environment with LiDaR at around a resolution of one centimeter. Measurements are accurate to one centimeter versus the five-centimeter resolution of sonar. These are both problems for developing flight worthy drones.

A typical LiDaR unit bounces a laser beam off of materials in the environment several times a seconds resulting in a lot of data to process in order to map the environment. The sonar unit developed in Tel Aviv sends three pulses every 30 seconds and processes the data to result in an accurate map for navigation with much less data.  

A typical LiDaR unit costs around $150 dollars for a low-end unit that has a resolution similar to the Sonar used in the Robat. The students at Tel Aviv replaced this unit with $15 in parts, showing an overall cost reduction of 90 percent. They also reduced the weight of the mapping unit substantially, from around five pounds to around five ounces.  

Just last month they modified the system from using a single speaker and two microphones to using two speakers and four microphones to allow for 3-D mapping from a flying drone, versus the walking Robat introduced in January 2019.  

I took great interest in this project as I have a lot of junk electronic components lying around and wondered if it would be possible to reproduce their results with simple electronics found around the house. I discovered that not only is it possible, but it is basically how they started the project.  

If you would like to learn how to do something like this, you can follow a project on instructibles.com to build a spinning SODAR (blend between Sonar and LiDaR) to keep from being confused with a real Radar or Sonar system. I plan on building one as soon as I can gather all the components. You can find the project at https://www.instructables.com/id/DIY-360-Degree-SODAR-Device/.

I foresee a lot of people tinkering around with robotics as we are ordered to stay at home. I recommend picking up an ardunio kit that comes with a fairly large number of electronic components and taking some time to learn how to build your own robot. Who knows? You might make the next big robotics discovery in your own home. 

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