Real-time model-based obstacle detection for the NASA Ranger Telerobot

Abstract

This paper describes the approach and algorithms developed for real-time model-based obstacle detection and distance computation for the NASA Ranger Telerobotic Flight Experiment. Objects of interest, such as manipulator arms or the ranger vehicle and solar arrays, are modeled using a small set of component types: edges, polygonal faces and cylindrical links. Link positions are computed using standard forward kinematics, and distances between object components are computed directly using equations derived from geometry. Prioritized lists of potential obstacles for each manipulator link eliminate needless distance computations and assure that the most likely obstacles are checked, even if the computation is terminated early due to real-time constraints. A test program, utilizing a 3D graphical simulation and providing a graphical user interface for operator control, has been developed and used to test and demonstrate obstacle detection. An earlier paper (1996) described how the obstacle detection results are utilized for collision avoidance.