Last Updated: Sep 19th, 2018 - I will be updating my original post as people correct me and I learn new things.

Well, I am next off to monkey around with LIDAR technology and interestingly there is not one single document available that can explain different LIDAR technologies available for PixHawk "or" Pixhawk compatible devices, what each device does, limitations, programmability etc. 


I will attempt to take a shot at what I have learned so far but I would like the community to chime in so we can have a consolidated document for future reference. Just like a wiki page.

LIDAR = A detection system that works on the principle of radar, but uses light from a laser.

Applications:

1D - Range Finders. Typically work in combination with FC such as PixHawk.
2D - Short Range Obstacle detection.
3D - Used for surveying, mapping and point clouds. A method that measures the distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a sensor. Differences in laser return times and wavelengths can then be used to make digital 3-D representation of the target. 

LIDAR Types: So it appears there are two types of LIDAR sensors as far as the technology goes behind it.

1. traditional LIDAR sensors
2. Time of Flight (ToF) - More to come later...

SETUP:

So what are the components of an overall LIDAR system/solution?

Well, first you need to decide what the LIDAR will do in the real life world. That will determine the type of LIDAR sensor you will need for your fixed wing aircraft or the copter you are planning to use.

Do you really need a flight controller like PixHawk? the answer is NO BUT it depends on the application. If the application is rangefinder or does object avoidance, Pixhawk along with Mission planner can support such application on a drone.


If you are going to use the LIDAR for Mapping or analysis, that's whole new setup but do you really need a flight controller for such LiDAR to work? My understanding is NO, as long as we can provide LIDAR with the position of the aircraft using a separate GPS and IMU for processing data.

LIDAR SENSORS - Bufete :)

I am planning to put a power point presentation at the end which will consolidate all the tips, discussions here for future reference. Thanks for joining the discussion.

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Replies to This Discussion

@laser Developer - Good observations on your part and I totally agree on the business challenges associated with the evolution of new concepts vs. disappearance of new LiDAR concepts as there is no market for such things.

In the US and other parts of the world, what drives new technology to be available for public use is our Defence budgets. Military demands, they adopt it and then later on same technology becomes available for the public sector. I can give 100's of such cases. I guess one has to come up with a strong military application first.

I will continue to look for more documents. I have called meetings with some key LiDAR developers in the US and Europe and let's see what I learn from them. I will keep everyone posted.

I will post video tests of the Benewake when it's all ready to go.

I fly an off the shelf drone to determine average canopy height then add 8 to 12 feet in mission planner.

iSkyMaster said:

@Jimmy Oliver - As long as you promise to send all of us a bag full of California Almonds, Cherry jams we are all in it :)

I think I understand what you meant by LiDAR move at the speed of light. I think you meant the laser source is travelling at speed of light, But the LiDAR sensor scanning is a derivative of two moving components. The aircraft speed and the housing that controls the movement of the laser source (if the laser source is rotating for scanning)

I have seen Randy video before. He is great! is he located in Japan?

That said if I make a bold guess here the key LiDAR sensor parameters one should look for are;

1. Distance limit.
2. Refresh rate, which directly defines the maximum speed an aircraft can fly before senor starts to lose its accuracy.
3. The processing speed of the IMU to process incoming data and can store it for real-time or future processing.
4. Other soft parameters will be;

     a) Lens type used.
     b) Stepping accuracy of the laser rotating source to catch the reflective beam on time.

For what you are trying to accomplish, I doubt any off the shelf solution will work in a plug and play mode without any customization.

You are trying to solve two challenges:

1. Maintain absolute height - which is easy to accomplish.
2. Push drone to predefined push limit in advance if one tree height is higher than others.

How about this approach? First, you scan the playing field in 3D. Develop a Geo Map of the area which I am assuming will help you to predetermine the different heights of the trees, and then you construct a flight plan accordingly?

Has anyone ever thought of using a blimp? Slow and steady probably more viable for pollination application.

@Jimmy Oliver - do you have any videos to share?

I have lots of videos. Are you saying video of LIDAR? I am attaching one as we speak and will fly tomorrow. Pollination of cherry orchard. I cannot share video at this time. The company wants to unveil at trade show.

Trying to determine what this video means. I have the unit and am just wondering if the "2.5" meters that the drone stays at in terrain mode can be adjusted. The example of flying up the hill is exactly what I need to do. I am not sure if the LIDAR just pushes up just enough to avoid. Hard to interpret the Chinese instructions as usual. Video link below.

Benewake Lidar

yes, LIDAR does exactly what shown in the video.

Jimmy Oliver said:

Trying to determine what this video means. I have the unit and am just wondering if the "2.5" meters that the drone stays at in terrain mode can be adjusted. The example of flying up the hill is exactly what I need to do. I am not sure if the LIDAR just pushes up just enough to avoid. Hard to interpret the Chinese instructions as usual. Video link below.

Benewake Lidar

 Do you think its possible to provide the GPS and accelerometer information from Pixhawk and do the post processing of LIDAR Data for Precise PointCloud afterwards??

Im interested in this because i dont understand why LIDAR IMUs are so expensive, it seems to me that Pixhawk 2.1 can provide accurate enough information (to my understanding LIDAR IMUs only provide attitude and GPS position) to work with LIDAR... <0.02 degrees?

Please let me know your thoughts on this matter!

Daniel

Chris Anderson said:

Yes, for mapping/scanning the Lidar works independently of the flight controller and often has its own GPS and/or IMU for more accurate recording. 

Lidars only work with the FC in the case of obstacle avoidance or (common in cars, rare with drones) SLAM. 

-c

iSkyMaster said:

Thanks, Chris. I will add it to the list.

I am still struggling to understand the correlation between liDAR and FC.

So for options 1,2,3,4,5,6 I can understand the function of the FC, but for 6,7,8 is it safe to assume that LiDAR for mapping works independent of FC and uses its own GPS perhaps or not even needed?

Is there wiring diagram I can look at for LiDAR mapping solutions.

Chris Anderson said:

Daniel,

1. As far as passing GPS data and Accelerometer info from Pixhawk to any other device can be simply done via I2C interface of the Pixhawk. read this thread 

https://diydrones.com/forum/topics/how-to-get-gps-and-sensor-data-v...

2. How you will store the data for future processing will require an additional solution.

3. I remember one Canadian company that is providing a LiDar solution with a development kit for further customization. Give them a call. https://leddartech.com/


Daniel Domit said:

 Do you think its possible to provide the GPS and accelerometer information from Pixhawk and do the post processing of LIDAR Data for Precise PointCloud afterwards??

Im interested in this because i dont understand why LIDAR IMUs are so expensive, it seems to me that Pixhawk 2.1 can provide accurate enough information (to my understanding LIDAR IMUs only provide attitude and GPS position) to work with LIDAR... <0.02 degrees?

Please let me know your thoughts on this matter!

Daniel

Chris Anderson said:

Yes, for mapping/scanning the Lidar works independently of the flight controller and often has its own GPS and/or IMU for more accurate recording. 

Lidars only work with the FC in the case of obstacle avoidance or (common in cars, rare with drones) SLAM. 

-c

iSkyMaster said:

Thanks, Chris. I will add it to the list.

I am still struggling to understand the correlation between liDAR and FC.

So for options 1,2,3,4,5,6 I can understand the function of the FC, but for 6,7,8 is it safe to assume that LiDAR for mapping works independent of FC and uses its own GPS perhaps or not even needed?

Is there wiring diagram I can look at for LiDAR mapping solutions.

Chris Anderson said:

Thanks! 

Do you think a raspberry pi would be too slow to store that info? What about the NVidia TX2?

I will look at the documentation you sent, thanks a lot. 

By any chance you know softwares to do the post processing of the point cloud, or can you point me in any direction how to post-process after storing all the info?

Thanks,


Daniel

You are trying to figure out a solution while providing piece part information about what are your overall objectives are? very difficult to guide you in the right direction.

Is it a school project or a commercial development effort?

Wha are you scanning, for how long, what is the overall objective here? do you have an engineering background?

You will just go in circles this way and people will confuse the hell out of you this way.

Provide complete project details else, else not sure how to help.

there are 100's companies providing solutions to process raw data. Simply google it.

Daniel Domit said:

Thanks! 

Do you think a raspberry pi would be too slow to store that info? What about the NVidia TX2?

I will look at the documentation you sent, thanks a lot. 

By any chance you know softwares to do the post processing of the point cloud, or can you point me in any direction how to post-process after storing all the info?

Thanks,


Daniel

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