A laboratory evaluation of two graphical displays for space manipulator positioning tasks

Abstract

A space manipulator is a lightweight robotic arm mounted on a space station or a spacecraft.If the manipulator is manually controlled from a remote site (teleoperation), the pictures front camras in the neighbourhood of the manipulator are the only aids the hurnan operator can use.Besides, manipulator dynamics and the possible prsence of tirne delays in the control loop also complicate manual control.In space manipulator positioning tasks, the manipulator hand (the end-effector) has to be positioned accurately in front of a known (physical) target.Here, the human operator can only use the camra picture from a camra attached to the end-effector.In that picture, hardly any spatial eues are prsent.Therefore, it is difiicult to assess the attitude of the end-effector relative to the target.This paper valutes two graphical camra overlays that visualise the actual end-effector attitude.The first overlay, the lndicator Display, shows the exact position and orientation of the end-effector with a set of smart two-dimensional display indicators.In the second overlay, the spatial Pyramid Display, spatial information is presented by means of the intersections of three spatial graphical objects.The results of man-machine experiments show that the positioning task can be performed remarkably fast with both displays.Also, it appears that at the end of the task, the 'Pyramid operator' is more aware of the actual manipulator environment than the 'lndicator operator'.