Effects of Time Delay, Packet Loss and Quality of Force Feedback on Human Operating Performance in Teleoperation

Kurzfassung

In teleoperation systems with force feedback the operator is exposed to a variety of system specific influences. Amongst them is time delay, the loss of data packets in transmission and the quality of force feedback. The objective of this thesis was the investigation of the effects of these three influencing factors on the human operating performance, when using a teleoperation system. Two human subject studies were conducted, whereby the first focused on the effect of packet loss and the second on time delay and the quality of force feedback. Five different tasks were conducted with a teleoperation system in order to deduce statements about the human operating performance in different types of tasks. Several parameters were used as indicators of the human oper-ating performance, which were dependent on the tasks executed with the teleoperation system. This objective data acquisition was supplemented with the acquisition of mental workload as a subjective parameter. The experimental design was balanced in terms of different aspects in order to keep the influence of sequence-, learning- and fatigue-effects as minimal as possible. The used teleoperation system consisted of a biaxial robot with stylus and a joystick with force feedback. The different parameters of each of the five experimental tasks was statistically analyzed. No systematic effects of packet loss on the performance of the operator nor his mental workload was found for the investigated packet loss rates. In terms of time delay, its deteriorating effect, which is known from literature, emerged for most of the parameters. It was unusual that an increase of time delay lead to an improvement of the human operating performance for one parameter in three experimental tasks, when the corresponding tasks were performed without force feedback. The operator's mental workload increased with rising time delay. In regards to the quality of force feedback, it was found that the human operating performance mainly improved for all experimental tasks, if force feedback was provided. A small difference in terms of the human operating performance was found for two of the three investigated qualities of force feedback, which were ascribed to different system configurations. Adding or removing force feedback did not influence the operator's mental workload. In the end, the practical implications in terms of the optimization of teleoperation systems in the development process and the limitations of the conducted human subject studies are summarized. Finally, further research questions were suggested.