Home Knowledge Base Phantom 4 v/s Typhoon H: Optical vs Ultrasonic in UAV Collision Avoidance

Phantom 4 v/s Typhoon H: Optical vs Ultrasonic in UAV Collision Avoidance


Guest Post by DJI

A recently posted YouTube video (embedded below) running a new Yuneec Typhoon H through its collision-avoidance paces shows some interesting differences from DJI’s Phantom 4.

The video — most likely shot by a DJI fan or employee — isn’t the prettiest. But it does highlight why Shenzhen-based DJI has won the first round in the obstacle-avoidance battle.

Yuneec Typhoon H collision avoidancePardon the spoiler, but in the video, the Typhoon H eventually crashes into a wall when it approaches from an oblique angle. We’re sure the shooter intended the failure of avoidance to be the video’s high point, but it shouldn’t be to most tech nerds. Instead, we’re interested in how the Typhoon H’s technology behaves differently from a Phantom 4 in a similar situation.

At the start of the said video, the Typhoon H is flown toward a wall. We know that because the video editor helpfully includes a subtitle in pidgin English, “approach to the wall in slow speed.”

The Typhoon H’s avoidance system works, stopping the craft before impact. As the sound waves bounce back from the wall to the sensors on the front of the UAV, the Typhoon H bobs and weaves a bit. In the next cut, a window-in-window shot shows full-throttling of the H head-on toward the wall. The Typhoon H’s avoidance system worked again, but you can see the craft getting wobbling back and forth from returning sound waves.

Next up was a flight directly at some trees, which were also moving from the wind. Even without breathless pseudo-English subtitles, it was clear the pilot almost lost control of the Typhoon H. It swayed a few feet in either direction as he maintained full throttle, bouncing in the air.

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And then, as we mentioned, the Typhoon H’s sensors didn’t work in the 45-degree approach, resulting in chaos and mayhem (OK, we made that up), but we do see it bounce off the wall from two different angles and either lose a bit of something, or maybe it was the wall that lost a bit of something. Watch it here:

Now, to the Phantom 4, which came out two months ago and features an optical avoidance system — front-mounted stereo cameras. In this another video (embedded below), at around 7:50, you can see how the DJI craft behaves when they fly it, first fairly slowly, then at full-tilt, at their house.

With the optical avoidance system engaged, the cameras “see” the obstacle, map it and slam on the brakes. While there’s an initial, “uh-oh” moment where the drone backs up a few inches, it then stops on a dime and just holds, without a wiggle. Watch it here:

Part of that precision is also due to two more cameras and two ultrasonic sensors that are pointing downward, letting the Phantom 4 know where the ground is and maintain its altitude. So, what you’re getting is precision in three dimensions.

Precision is a good word, because it’s one of the two key differences between the Yuneec Typhoon H’s avoidance system and that of the DJI Phantom 4. A sound wave gives the craft a general sense of what’s in front of it, and it works, but not as precisely as an optical system, nor at the same operating distance.

phantom4_resultThe Phantom 4’s optical sensors are good out to about 15 meters and have a 60-degree-wide field of view and almost the same horizontally. The Typhoon H’s sensors only operate at 1/10th that distance.

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The other difference is speed. Obstacle avoidance on the Phantom 4 works at speeds up to 10 meters per second, about five times as fast as “Turtle Mode” on the Typhoon H, which makes sense, because it’s “better safe than sorry” when your craft isn’t 100% sure what’s in front of it.

And there’s one other difference between the avoidance systems: machine learning. In its autonomous “TapFly” mode, the Phantom 4 can actually decide to climb over an obstacle if, from its map and onboard processor, it determines that at its speed and heading, it can safely do so. That feature is not available with the Typhoon H.