How example "Perform SLAM Using 3D lidar point clouds"collects 3D lidar data?ud

When I was learning this routine, I didn't know how to collect the 3D Lidar data. Is it a 1*240 cell array formed by scanning 240 instances and then extracting their location attributes?

Answer 1

[Ryan Salvo]

Hi Wenjun,

For the Perform SLAM Using 3-D Lidar Point Clouds example, the lidar data stored in the pClouds MAT-file was collected on a Clearpath Husky robot moving around a parking garage. Each cell in the 1-by-240 cell array corresponds to a different timestep and each cell contains an n-by-3 matrix, where n is the number 3-D points in the captured lidar data, and the columns represent xyz-coordinates associated with each captured point.

Thanks,

Ryan

[Wenjun Li]

Hi Ryan Salvo,

Thank you for your patience!But I still have a question, does this robot scan 240 times, does each scan take a different time?I‘m looking forward to your reply,your answer will help me next step.Thank you so much!

Wenjun

[Ryan Salvo]

Hi Wenjun,

In the example, the lidar takes 240 successive scans, however, there is a varying number of points detected in each scan due to the number of obstacles in the immediate environment. That is why the scan for each timestep is logged in a different cell of the cell array. The scans take the same amount of time, however, successive scans are only accepted when the robot has moved a certain distance, specfied by the distanceMovedThreshold parameter.

Thanks,

Ryan

Answer 2

[Wenjun Li]

Hi Ryan,

Thank you for your patience!I still have a question,I can't understand why we need 240 successive scans.And I want to ask, can I record the .bag package multiple times to achieve the effect of the routine?We don't have a Husky robot in our lab yet, so I don't understand how the 240 successive scans were recorded.I'm looking forward to your reply.Please forgive my repeated interruptions.

Thank you,

Wenjun

[Ryan Salvo]

Hi Wenjun,

You do not need 240 successive scans, that is just the number of scans in the MAT-file provided in the example.

The example assumes that the provided lidar data is from a robot that is moving through a static space, so if you can re-create that when recording the BAG-file, then you should be able to use that data with the example.

Thanks,

Ryan

[Wenjun Li]

Hi Ryan,

I tried loading the recorded .bag package into the example today, and it works！ But the created occupancy map is not as dense as the example, so I plan to improve it tomorrow for the next path planning work. Thank you very much for your patience in answering my questions. Your answers have taught me a lot. I take the liberty to ask, if I have any questions in the future, can I ask you again?

Thank you,

Wenjun