Using LIDAR-Lite to sweep an arc for sense-and-avoid

I was curious how well LIDAR-Lite, which is just a laser range finder out of the box, would work as a full sweeping LIDAR unit, so I set up this demo unit. The unit updates at 100Hz, so to detect a 10cm object (like a telephone pole) within a 5m arc at 10m distance (with 2x oversampling), I calculate that you need to sweep 30 degrees back and forth each second. (5m = 10m*sin (30)).

That's totally within the speed of a regular servo, so I threw together this test. It just uses APM as an Arduino, sends the LIDAR-Lite and servo position data over serial and reads and graphs the data with a Processing sketch on the laptop. The Arduino code and Processing sketch are here: LIDAR%20sweep.zip.

BTW, the LIDAR-Lite sensor is already fully supported by the APM code as a range finder (for altitude hold with copters and/or autolanding assist with planes). You can read more about using it here.

The code for object avoidance using LIDAR-Lite is already written (thanks to Robert Lefebvre), and this would just add a sweeping component. Here's a video of it working in static mode, on a 2-axis stabilized gimbal:

Some observations:

It works! I can spot telephone poles with no problem
That said, the effective range of the LIDAR-Lite unit in this application is just 10m. I'm not using a low-pass filter on the cable, which is normally recommended, and I'm just taking one data point at each position, so I think that can be improved with a smarter sampling strategy.
In practice, this would be better implemented by moving a mirror, not the entire LIDAR unit, to avoid shaking and other off-axis movement that can get in the way of sampling
Laser range finders are SO MUCH BETTER than sonar.

Hey Dan, Ha Ha, agreed, lots of demo products out there, we often get the "2015, Quarter 3 " answer when asking to purchase, hence we continue struggling along with our own.

Thanks for all those tips, we seem to be in parallel universes on different continents, and I'm about 2 technology leaps behind you!

I must say , a windows board would be great, which one are you using? (if you dont mind saying)

debugging the arduino is so time consuming putting in serial.prints everywhere. Visual micro has been a help as you mentioned in another post. Wouldnt mind something easier to debug.

I am moving to a teensy, even designed a connector PCB board for it (to try and reduce the millions of wires )

My code is working with rudimentary (jerky) front obstacle detection, can keep the quad within about 2m of the ground. All the PC comms and database backend is working , with visual representation of the warehouse and voice commands, all i need is a stable quad!

For Altitude hold i cheated and just activate the "Baro hold" aux. on the APM and then send it wild throttle input if the APM starts drifting off its baro, this wakes up the APM to re-adjust its alt hold.

I must say i couldnt get a straight PID loop to work on alt. hold or front detection. maybe I'm too dumb or not patient enough.

In your opinion, is a small (25cm) frame or large (45cm) frame better?

DroneScan has developed an airborne data collection system to provide large, uniform warehouses with a robotic solution for stock take (inventory), p…

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Comments

Sam Worthington January 27, 2015 at 2:32am

It seems to me that a laser range finder isn't the best starting point for collision avoidance.

I was speaking to the manufacturer of a small LIDAR unit last autumn and they weren't very encouraging. It could be very good if you want to fly up to something an measure the profile of the surface. However, for collision avoidance, what we really need to know is what is in front of us and what is either side of the immediate flight path.

DARPA use this example of a goshawk flying though a forest as inspiration behind their Fast Lightweight Autonomy programme and I think that a laser range finder isn't in trying to keep up.

Laser Developer covered the points pretty well: Laser range finders are good for narrow focus accurate readings. What we need for collision avoidance is speed, range and coverage.

Perhaps a radar or vision based system is a better approach?

Sam
Jethro Hazelhurst January 26, 2015 at 1:57am

Hey guys, check out my website on 3d metal printing: http://www.metalbot.org/forum/index.php

Search the forums for information on 'Galvos', we have many people who are experts on these laser scanners and they could be of great help to developers here.

It is amazing how these two technologies can 'cross-pollinate' like this.

There really are so many interesting options when it comes to laser scanning and mirror arrays and I would truly recommend scanning the forums on Metalbot, we have amassed a wealth of info!
Jasper Pons January 25, 2015 at 1:29am

Aaaargh Dan you have it all. wish i knew this 3 years ago! Looks like you are ready to go on the warehouse scanning, all you need to do is hook into our drone-database protocol. Can you ask your client if they would be interested in being agents for the DroneScan system?

If you are doing airborne barcode scanning, we might need to talk anyway because barcode , rfid and other airborne data collection will be covered under patent application AIRBORNE SCANNING SYSTEM AND METHOD PCT/ZA2014/000029
Dan Neault January 24, 2015 at 2:39am

One of my clients is a major manufacture of servo drives, they gave us the board they use in there drives. I will ask Monday if it is public info. As too frame, I suggest you watch Robert Lefebvre's video, on airframes. Pretty much tells you all you need to know, and we came to same conclusions as well.

No idea why you need to get so close, or hold alt so tight, we scan bar codes at 3m, using our TOF camera's (have normal vision as well) and code from OpenCV,
Jasper Pons January 23, 2015 at 7:58am

Hey Dan, Ha Ha, agreed, lots of demo products out there, we often get the "2015, Quarter 3 " answer when asking to purchase, hence we continue struggling along with our own.

Thanks for all those tips, we seem to be in parallel universes on different continents, and I'm about 2 technology leaps behind you!

I must say , a windows board would be great, which one are you using? (if you dont mind saying)

debugging the arduino is so time consuming putting in serial.prints everywhere. Visual micro has been a help as you mentioned in another post. Wouldnt mind something easier to debug.

I am moving to a teensy, even designed a connector PCB board for it (to try and reduce the millions of wires )

My code is working with rudimentary (jerky) front obstacle detection, can keep the quad within about 2m of the ground. All the PC comms and database backend is working , with visual representation of the warehouse and voice commands, all i need is a stable quad!

For Altitude hold i cheated and just activate the "Baro hold" aux. on the APM and then send it wild throttle input if the APM starts drifting off its baro, this wakes up the APM to re-adjust its alt hold.

I must say i couldnt get a straight PID loop to work on alt. hold or front detection. maybe I'm too dumb or not patient enough.

In your opinion, is a small (25cm) frame or large (45cm) frame better?
Dan Neault January 23, 2015 at 3:51am

Jasper, I have posted pic's of early prototypes, and have given out as much as I can. I have my own automation engineering company, with my primary client a manufacture of mining equipment /services. The unit we now produce, uses an airframe like nothing that has been posted here, which is designed, just to fly in tunnels.

It's all IP, and the client that commissioned, my client, too develop the system. does not wish for it to be made public, yet.

Note I have also added the co-axle fight code to APM base (hint) :)
Jasper Pons January 22, 2015 at 10:57pm

Hey Dan, thats one SICK sensor if it can do what it says it can!

We are finding the flight control is our limiting factor, we have been unable to find any system available that can do what chris is showing in his video down to cm accuracy. Trying to develop our own but its not too successful.

We need to keep our barcode scanner anywhere from: 1m to just before prop strike from the racking in front of us, and at a height accuracy of a few cm. Do you have any quad that can do this? Looking for a partner in North America to carry our patented inventory scanning platform.

(I sent you a DiyDrones PM from my www.dronescan.co email )

DroneScan

DroneScan has developed an airborne data collection system to provide large, uniform warehouses with a robotic solution for stock take (inventory), p…
Dan Neault January 22, 2015 at 6:32am

If it's any help Jasper, we fly in a 8' x 8' tunnel, using one Sick TIM551. Very light weight and very good results.

We only went for TOF camera's, to increase our sweep resolution for mapping.

http://www.sick.com/us/en-us/home/products/product_news/laser_measu...
Jasper Pons January 22, 2015 at 6:16am

very nice idea, thanks for this article. We are using a lightware range finder on our indoor drone autopilot for height detection at 40 times per second, we are struggling with infrared and sonar on the forward facing one, to detect the warehouse racking at at 2m. we didnt want to put another laser rangefinder facing forwards due to the weight, but it looks like we will have to. we might be able to use one which can sweep down and up using your servo method.

the one we are using is here:

http://www.lightware.co.za/shop/en/laser-rangefinders/33-sf10a.html
LightWare - Laser Developer January 21, 2015 at 12:09pm

@Robert, great feedback. If you now try to visualize an ideal solution, what comes to mind?

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