Time delay and communication bandwidth limitation on telerobotic control

Remote teleoperation allows humans to extend their capabilities to environments too dangerous for biological organisms. The communication between the operator and the robot needs to be fast in order to accommodate quick interaction with the environment. However, certain remote environments, such as deep-sea and space operations, impose restrictions on the communication link which limits the available bandwidth. In addition, as the distance increases, the communication between the operator and robot is further handicapped by significant time delays. The difficulties of controlling a robotic system remotely with long time delays and limited communication bandwidth are investigated. Four subjects performed a manipulator positioning task, controlling a simulated seven-joint manipulator under various time delay and communication rates. Results confirm performance degradation for 1.5, 3, and 6-second round trip delays. Compared to no delay, the time to complete the task increased between 160% and 480%. Limiting the communication bandwidth from 20 Hz also degraded performance, but not as severely as time delay. Only a 36% increase in completion time occurred when the bandwidth was reduced by a factor of eight to 2.5 Hz. A novel predictive display was introduced which dramatically decreased completion times to levels similar to no delay being present.