Multiple Lidar Calibration

Surface Registration

Aras AkbariDr.Liam Pedersen

LER (SEV) System Overview

SICK LMS 291 Lidar•70 Hz scan rate •180° range, •0.25° angular resolution

Hokuyo UTM-30LX Lidar•45 Hz scan rate •180° range, •0.25° angular resolution

Problem StatementPoint clouds from different lidars not well aligned using best estimates (digital level)

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Pos at time t

Laser pose WRT Robot

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Optimize

Problem Statement

Surface Registration

ICP: point To point matching

Finding the rotation, translation between two point clouds by solving the orientation problem using Horn's quaternion-based method.

Result :

Reason -> No point to point correspondences.

Terrain Problem The Terrains are different.

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∆t•Time difference •Pose estimator error

Surface Registration

Used Nelder Mead method to minimize the Mahalanobis distance between the corresponding points

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Where is the mean vector and ∑ is the covariance matrix of closets point to x in Pref

Solved globally

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Multiple Lidar Calibration

Calibrate lidar’s wrt primary:

Pose at time t

reference lidar point set (global coords)

adjusted lidar points (wrt rover) at time t

calibration correction

No calibration target required

But need some verticalrelief.

Question ?Question ?? Questions??