Dynamic Model Displacement for Model-mediated Teleoperation

In this paper, we study and extend the concept of model-mediated teleoperation (MMT) for teleaction systems which provide live video feedback from the remote side with a time delay. In MMT, the haptic feedback is rendered locally on the operator side using a simple object surface model in order to keep the haptic control loop stable in the presence of communication delays. Because the live video from the remote side is received with delay, this results in a visual-haptic asynchrony for the displayed interaction events. In addition, sudden model parameter updates can lead to "model-jump" effects for the displayed haptic feedback. Both effects degrade the user experience and system performance. To address these issues, we propose an extension of MMT which we call model-displaced teleoperation (MDT) in this paper. In MDT, we adaptively shift the position of the local surface model to delay the haptic contact with the environment, thus compensating the visual-haptic asynchrony and avoiding the model-jump effect. As the haptic feedback is still rendered locally, the advantages of the MMT approach are retained and instabilities in the haptic interaction are avoided. In our experiments, we determine the optimal displacement compromise between visual-haptic asynchrony, the model-jump effect and perceived distance errors. Moreover, the subjective experience and objective task performance of the proposed MDT and the original MMT for a teleoperation setup with soft objects are evaluated. Our results show that the users prefer the MDT method compared to MMT once the communication delay between the teleoperator and the operator exceeds 50ms. In addition, the task error rate is reduced by about 50% and the subjects are better able to control their contact force for system delays larger than 50ms if the MDT method is employed.