fix: imu scale estimation covariance limit for stability

[SergioReyesSan]

Description

This PR fixes an issue in the IMU scale estimation where the covariance matrix (specifically non-diagonal terms) would increase significantly when the vehicle is stationary or moving straight/ slow turning for extended periods. This growth caused instability in scale estimation and triggered MRM.

Parent Issue:

• Link

How was this PR tested?

The fix was validated using Rosbags directly from the vehicle, with prolonged, slow turns causing no updates to the imu scale estimate. Furthermore, a Rosbag containing an NDT pose anomaly (which previously caused system instability due to high accumulated covariance) was tested; the system now remains stable after the fix.

decay coefficient and threshold to estimate scale parameters, also changed to increase scale estimation stability.

No needed changes on this version of Autoware launch, since it uses the default values.

Related links

Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 18.04%. Comparing base (54af299) to head (f536089).

Files with missing lines	Patch %	Lines
...autoware_imu_corrector/src/gyro_bias_estimator.cpp	0.00%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #12562       +/-   ##
===========================================
- Coverage   18.64%   18.04%    -0.60%     
===========================================
  Files        1918        5     -1913     
  Lines      131362      615   -130747     
  Branches    44502      257    -44245     
===========================================
- Hits        24489      111    -24378     
+ Misses      86760      406    -86354     
+ Partials    20113       98    -20015     

Flag	Coverage Δ
daily	?
full-suite	18.04% <0.00%> (-0.59%)	⬇️

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