feat(hesai): software-based precise FoV limit & early publishing

[mojomex]

PR Type

• New Feature

Description

This PR introduces software-based FoV limits and early publishing for Hesai sensors.

Software-based FoV

Previously, configuring cloud_min_angle and cloud_max_angle would set the sensor's hardware filter to those values.
However, the hardware filter is using raw azimuths.
This lead to the scan having jagged edges (points missing in some channels, too many points in others).
For certain models, this affected areas of up to ~10deg on both edges of the FoV.

This PR improves upon this in the following way:

1. User sets cloud_min_angle and cloud_max_angle to the exact FoV they want the output pointcloud to have
2. Nebula retrieves sensor calibration file and computes appropriately over-sized* hardware-FoV
3. Nebula sends hardware-FoV to sensor (or validates it if setup_sensor == false)
4. The Nebula decoder cuts the scan at the exact edges defined via the parameters above

Early publishing

Previously, a scan was published once the packet after it was received. This was done because this made the scan completion check easier (could compare 2 azimuths according to some scan completion criterion).
For scans of 360deg, this is not a problem, as there is no time gap between the end of one scan and the beginning of the next.
However, for FoVs < 360deg, this approach increases latency unnecessarily: for an FoV of 180deg and 1 full rotation every 100ms, the additional latency of the finished pointcloud just "sitting there" is 50ms.

This PR improves upon this in the following way:

1. Swap the order of decoding and scan completion check: decode first, then check for completion
2. Check if the current packet completed the current scan, as opposed to whether the current packet is the first belonging to the next scan

Other

For testing this PR with AT128, I had to fix the LidarRange issue:

• fixes AT128 HW interface crashes on GetLidarRange #129

This was done by checking the sensor model before sending the LidarRange command.

Review Procedure

Check for the following FoVs

• 0 - 360 deg
• 90 - 270 deg
• 270 - 90 deg
  if the pointcloud in Rviz has clean edges at those angles for a 360 deg sensor such as OT128.

Check AT128 in the same way but with FoVs inside [30; 150].

Remarks

These two improvements have been combined into one PR as they are closely related and would require extra work to function independently.

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• Commits are properly organized and messages are according to the guideline
• (Optional) Unit tests have been written for new behavior
• PR title describes the changes

Post-Review Checklist for the PR Author

PR Author should check the checkboxes below before merging.

• All open points are addressed and tracked via issues or tickets

CI Checks

• Build and test for PR: Required to pass before the merge.

[mojomex]

🚧 Evaluation

Pointclouds are colored by relative point timestamp: red is 0 ms relative to the cloud timestamp, blue is 100 ms.

🟢 360deg rotational sensors

FoV Setting (min, max, cut)	Resulting pointcloud
0, 360, 0
0, 360, 180
0, 360, 360	Cut angle gets overridden with 0, result is the same as 0, 360, 0: Cut angle was set to 360 deg, overriding with canonical representation of 0 deg.
90, 270, 90
90, 270, 180
90, 270, 270
270, 90, 90
270, 90, 0
270, 90, 270

🟢 AT128 (120deg rotational sensor)

FoV Setting (min, max, cut)	Resulting pointcloud
30, 150, 30	Nebula rejects the parameter: Cannot cut scan right at the start of the FoV. Cut at the end instead.
30, 150, 31
30, 150, 90
30, 150, 149
30, 150, 150
45, 135, 45	Nebula rejects the parameter: Cannot cut scan right at the start of the FoV. Cut at the end instead.
45, 135, 46
45, 135, 90
45, 135, 134
45, 135, 135

[drwnz]

This was tested with 40P with the following issue:

• Setting cut angle out side of the range of FoV start and end, resulted in no error and also pointcloud output.
• Even if that was the case and the "cut" happens in the area outside of the FoV (which is kind of uneccesary but logically possible) and the actual observed point cloud is correct in terms of min and max angles.
• Example: cut 10, min 180, max 360: no warnings, output pointcloud is full 180 degree segment.

[mojomex]

@drwnz Thank you for the review!

I have addressed your comments and re-tested setting the cut_angle parameter to a value outside of the FoV.
Nebula now properly emits an error:

[INFO] [hesai_ros_wrapper_node]: OnParameterChange
[ERROR] [hesai_ros_wrapper_node]: Cannot cut scan outside of the FoV.
[WARN] [hesai_ros_wrapper_node]: OnParameterChange aborted: Could not set SensorConfiguration

The fix is in this commit: 2e42bd0

[drwnz]

I left a few more comments, nothing urgent.
I haven't gone through the tests except for verifying that they passed.

[drwnz]

Ready to go, great work!