On-line collision avoidance for the Ranger telerobotic flight experiment

This paper describes an online approach to whole-arm collision avoidance for the NASA Ranger Telerobotic Flight Experiment. Using a geometric world model, minimum distances and nearest points between parts of the active dexterous 7-DOF manipulator and potential obstacles are computed by the Ranger obstacle detection software. Obstacle data is then used to compute virtual repulsive forces which perturb the operator-commanded manipulator Cartesian motions in order to avoid collisions. The virtual forces are computed at the tool-tip for end-effector position perturbation, at the wrist for end-effector orientation perturbation, and on the upper and lower arm links for arm angle perturbation. The paper also describes the software development environment, utilizing a 3D graphical simulation and providing a graphical user interface for display and operator command. Results of several test runs illustrating end-effector position and orientation perturbation, as well as arm angle perturbation, are presented