Inexpensive time-of-flight sensor for sense and avoid

We've been evaluating this on Pixhawk-based platforms, and it's a performing well. Best used with other sensors, such as cameras, but a lot better than just sonar. 

From IEEE Spectrum:

The World Wide Web is the most famous technology to emerge from the needs of the international particle physics research center CERN, but it’s not the only one. In the latest example, a lightweight, inexpensive (and maker-friendly) range sensor has come about because scientists want to use drones to survey tunnels and vaults without smashing into expensive and difficult to replace equipment.

They approached a drone services company, but it was soon discovered that there was no way to create a drone that was small enough to operate in the cluttered spaces and yet had sensors that would let it locate itself with enough precision to avoid collisions. The result was the founding of Terabee in 2012, explains Massimiliano Ruffo, the company’s CEO, who I met at CeBIT’s airy press center yesterday. 

In 2015 Terabee was recognized formally as a CERN spin-off and selected to join the research center’s business incubation partner Innogex. Terabee began selling its first sensor, the TeraRanger One, the same year.

The matchbox-sized TeraRanger One sells for 125 euro (US $140) and weighs just 8 grams. Measuring the time-of-flight for infrared pulses generated by an LED allows the TeraRanger One to determine the distance to a single point-like region ahead 1000 times per second. The maximum distance that can be measured indoors (or, of course, underground) is about 14 meters, with a range accuracy of four centimeters. Ruffo says that with some sensor-by-sensor calibration and a slower rate of measurement, the accuracy can be increased to about two centimeters. Maximum distances closer to five to six meters are possible in sunlight.

The TeraRanger One’s onboard electronics takes care of all the post processing required from the sensor’s raw time-of-flight data and spits out the distance as a number that represents the number of millimeters measured. A5-volt UART serial interface is used by default, and a 5 V I2C bus can be used with a firmware change, making the sensor trivial to hook up to an Arduino, and only slightly more complicated to connect to a Raspberry Pi. (That’s due to the latter’s aversion to voltages higher than 3.3 volts).

Inexpensive ultrasonic range finding sensors of TeraRanger One’s size and weight have been available for some time, but they lack its speed and angular precision. LIDAR systems, which often employ a rotating mirror to scan a sensing laser beam around, are also fast and provide high resolution at good distances but are bulkier and more expensive than the TeraRanger One. (Although that may change if DARPA’s phased-array LIDAR-on-a-chip ever comes to the mass market.) Stereo vision systems are another alternative for rangefinding, and can provide depth information over a wide field of pixels, but Ruffo believes that TeraBee again has the edge because the time-of-flight data produces more reliable distance measurements over a longer range.

For systems that require more complex measurements, such as those the doing the kind of SLAM (simultaneous location and mapping) required for the original CERN surveying, TeraBee currently offers a hub which allows measurements from up to eight separate sensors to be integrated. A pre-built eight sensor “tower” is in the works, says Ruffo, and the company also offers an evaluation version of a small LIDAR-type scanning platform

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Comment by Gary McCray on March 18, 2016 at 4:07pm

Really cool Chris thank you for bringing us this.
The size, weight and price point make this very attractive.
I am working more with terrestrial rover type robots at the moment (New Traxxas XMAXX) and this is a perfect device for that, 1000hz data rate is excellent for the price and even though about 20 feet max distance operation in sunlight, that should work great for navigation and SLAM.
I am currently evaluating Lightware's new fast rangefinder and will get one of these too.
Instead of the current common horizontal 360 degree circular scan I am working on a conical scan moved from side to side.
So a bit of a departure that does not use slip rings and produces a forward image of determinate width and height only.
Using 200 step step motors with micro stepping so resolution and speed of scan easy to change also.
The math for making images from it sucks though.

Comment by Gary McCray on March 19, 2016 at 10:06am

The $450.00 high speed Lightware SF30B I am using for my scanner has a refresh rate many times higher than the scanner presented here and its performance does not degrade nearly as quickly at increased distances.

The PDF linked to above is very skewed because it uses an older and much, much slower Lightware rangefinder for comparison.

Comment by John Campen on March 26, 2016 at 6:54pm

what is ROACH?

Comment by Phil Klemm on March 31, 2016 at 2:56am

Has anyone used radar for sense and avoid? it's one of the most reliable sensors but I can't see anything for drones on the market

Comment by Laser Developer on March 31, 2016 at 3:37am

@Phil - up to now radars have been quite big and expensive making them a rare commodity on small drones. We have an experimental model in development specifically for wide-angle sense and avoid to compliment our laser products. Radar has some technical difficulties that make it unreliable to use close to the ground but it has a place as a long range early warning system during higher altitude flying. It will be later in the year before we start providing public information ;).

Comment by Phil Klemm on March 31, 2016 at 5:28am

@ Laser Developer - sounds interesting. What do you mean exactly by wide-angle? Wide-angle beam steering, or single beam wide-angle? Our start-up is considering moving into this space, and I'm aware of general radar limitations which you've mentioned. But still it's surprising how little has been done for the drone market.   

Comment by Laser Developer on March 31, 2016 at 5:41am

@Phil - most of the low cost radar modules that you can buy are based on very small antenna arrays so they have a horrible beam pattern and they can't beam steer. I agree that very little has been done to make better radar technology accessible to the drone market - even basic fixed beam devices with a suitable beam pattern.

Comment by Phil Klemm on March 31, 2016 at 6:07am

@ Laser Developer - beams from antenna arrays are what they are, I'm not sure why would you call it "horrible" ? What is the beam pattern you're after? Or what is not "horrible" for you? 

Comment by Al B on April 15, 2016 at 12:55pm

Unfortunately, I don't think ROACH will be available to the market for another 2-3 years.

Comment by Phil Klemm on April 15, 2016 at 1:29pm

@ Al B - why do you think it will take so long? technology is already there. I'm sure radar sensors will make it into drone market much sooner. It's the most reliable sensor and will be a must in high end/commercial drone market 

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