  A misalignment of LiDAR as low as a few degrees could cause a significant
error in obstacle detection and mapping that could cause safety and quality
issues. In this paper, an accurate inspection system is proposed for estimating
a LiDAR alignment error after sensor attachment on a mobility system such as a
vehicle or robot. The proposed method uses only a single target board at the
fixed position to estimate the three orientations (roll, tilt, and yaw) and the
horizontal position of the LiDAR attachment with sub-degree and millimeter
level accuracy. After the proposed preprocessing steps, the feature beam points
that are the closest to each target corner are extracted and used to calculate
the sensor attachment pose with respect to the target board frame using a
nonlinear optimization method and with a low computational cost. The
performance of the proposed method is evaluated using a test bench that can
control the reference yaw and horizontal translation of LiDAR within ranges of
3 degrees and 30 millimeters, respectively. The experimental results for a
low-resolution 16 channel LiDAR (Velodyne VLP-16) confirmed that misalignment
could be estimated with accuracy within 0.2 degrees and 4 mm. The high accuracy
and simplicity of the proposed system make it practical for large-scale
industrial applications such as automobile or robot manufacturing process that
inspects the sensor attachment for the safety quality control.
