Laser Rangefinder Calibration for a Walking Robot

Abstract

In rugged terrain, walking robots that select footholds can be more mobile and more energy efficient than machines that roll on wheels or crawl on tracks. To achieve these footholds requires calibration of the terrain sensors with respect to the walking mechanism. We present an implemented technique to calibrate scanning laser rangefinders to legged robots. The procedure accommodates two scanners, one manufactured by Erim and the other by Perceptron, and two walkers, a one-legged robot and a six-legged robot. The technique acquires two sets of corresponding three-dimensional points and identifies the rigid transformation that maps one onto the other with least squared error, i.e., it solves the absolute orientation problem. We report experimental results with the two different scanners and vehicles. For the Erim and the one-legged robot, the technique achieves an accuracy of 6?2 cm with a precision no lower than 2? cm. for the Perceptron and the Ambler, the accuracy is 2? cm with a precision no lower than 2? cm. These results have proven to be satisfactory for constructing terrain maps and using them to select footholds during our rough terrain walking experiments.