Testing laser rangefinders with ArduPlane

Andrew Tridgell has been testing laser rangefinder with ArduPlane, for more precise autolanding. Here's his report:

Testing the SF/02 laser rangefinder on a Pixhawk on my Meridian. Worked very nicely! Some results:

The baro showed a bit higher than the laser, but the laser was definitely much more accurate - the baro was affected quite a bit by the speed of the plane causing low pressure in the fuselage.
I connected it to the Pixhawk using the analog connection, on one of the two 3.3V ADC connectors. That gives very good resolution, and low noise.

Once PulsedLight's LIDAR-Lite changes to using a laser (as they plan to do) and fix the short range and long range issues (bad values at ranges below 1.5m and bad values at long ranges) I hope the two will have similar performance, and the I2C connection on the PulsedLight module will be a better fit. The LIDAR-Lite prototype I have now has a range of about 12m compared to 40m for the SF/02, and gives bad data at short and long ranges, so right now the SF/02 is better for the work I'm doing on landing, but longer term I'm hoping the LIDAR-Lite will be a great option

There is more discussion of this on the DIY Drones Dev list here.

Using the SF02 alarm output to insure that hexacopter does not come too near dangerous HV poles while filming.

SF02 is mounted on the front arm of one our X flying hexacopters.

Pixhawk has apparently an interface possible: http://copter.ardupilot.com/wiki/common-rangefinder-sf02/

But it would have been so much better to use the great serial link of the SF02! Using long wire between the SF02 analog output and the Pixhawk isn't a nice solution. Capacitive coupling of high electrical noise won't add any precision! So if we need to add analog buffer (voltage follower) driving shielded cable on top that's a bit silly. Practically we set through the SF02 USB interface the alarm at the distance we feel safe and then use the SF02 alarm output to light up the hexacopter like a Christmas tree! We love the precision of the SF02 . It is a beautiful piece of hardware.

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Comments

Developer

Andrew Tridgell August 12, 2014 at 3:01pm

Hi Henri,

The reason I used the analog output is we are very low on UARTs. If you have dual telemetry (for an onboard computer) and two GPS modules then the only UART left is the debug console. I am considering a way to allow the debug console to be used for the SF/02, but right now we can't.

I was delighted to see that LightWare have added I2C on their latest products.

Cheers, Tridge
Henri August 12, 2014 at 2:20pm

Using the SF02 alarm output to insure that hexacopter does not come too near dangerous HV poles while filming.

SF02 is mounted on the front arm of one our X flying hexacopters.

Pixhawk has apparently an interface possible: http://copter.ardupilot.com/wiki/common-rangefinder-sf02/

But it would have been so much better to use the great serial link of the SF02! Using long wire between the SF02 analog output and the Pixhawk isn't a nice solution. Capacitive coupling of high electrical noise won't add any precision! So if we need to add analog buffer (voltage follower) driving shielded cable on top that's a bit silly. Practically we set through the SF02 USB interface the alarm at the distance we feel safe and then use the SF02 alarm output to light up the hexacopter like a Christmas tree! We love the precision of the SF02 . It is a beautiful piece of hardware.
John Dennings June 27, 2014 at 9:29am

Wow ... Add Piksi GPS, maybe a little extra sensor fusion with PX4flow, and we're going to get close to the Vicon flyers ... Thanks Chris, Andrew and Dennis for the update ...
Robert M June 27, 2014 at 6:19am

Looks teriffic! I can't wait to test the 2 I ordered through the campaign. Any news on how to integrate these with the APM and/or Pixhawk platforms?
Jolyon Saunders June 26, 2014 at 9:20pm

I'll be getting one of these babies FOR SURE :)
Jack Crossfire June 26, 2014 at 7:59pm

So this means the NDA on the Lidar lite prototypes has expired.
Developer

Andrew Tridgell June 26, 2014 at 3:29pm

Thanks for the update Dennis, looks good!
Admin

Thomas J Coyle III June 26, 2014 at 2:52pm

Looking good Dennis. I have one on order. I always "buy American" when I can.

Regards,

TCIII ArduRover2 Developer
Developer

Andrew Tridgell June 25, 2014 at 9:13pm

thanks Chris

Note that the link to the LightWare product site is here: http://www.lightware.co.za/shop/en/

They also have some much longer range products which would be excellent for surveying. The longest range goes up to 200m. We plan to support the full range in ardupilot.

Cheers, Tridge

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