We propose a two-layer control architecture for bilateral teleoperation with communication delays. The controller is structured with an (inner) performance layer and an (outer) passivity layer. In the performance layer, any traditional controller for bilateral teleoperation can be implemented. The passivity layer guarantees that, from the operator and environment perspective, the overall teleoperator is passive: The amount of energy that can be extracted from the teleoperator is bounded from below and the rate of increase of the stored energy in the teleoperator is bounded by (twice) the environment and operator supplied power. Passivity is ensured by modulating the performance layer outputs and by injecting a variable amount of damping via an energy-based logic that follows the innovative principle of energy duplication and takes into account the detrimental effects of time delays. In contrast to the traditional teleoperation approach, in which the master and slave controllers implement an as-stiff-as-possible coupling between the master and slave devices, our scheme is specifically designed for direct force-reflecting bilateral teleoperation: The slave controller mimics the operator action, whereas the master controller reflects the slave-environment interaction. We illustrate the performance of the two-layer approach in a challenging experiment with a round-trip communication delay of 300 ms while making and breaking contact with a stiff aluminum environment. Finally, we also compare our controller with the state of the art.

Remote control of vehicles is a difficult task for operators. Support systems that present additional task information may assist operators, but their usefulness is expected to depend on several factors such as 1) the nature of conveyed information, 2) what modality it is conveyed through, and 3) the task difficulty. In an exploratory experiment, these three factors were manipulated to quantify their effects on operator behavior. Subjects ( n = 15 ) used a haptic manipulator to steer a virtual nonholonomic vehicle through abstract environments, in which obstacles needed to be avoided. Both a simple support conveying near-future predictions of the trajectory of the vehicle and a more elaborate support that continuously suggests the path to be taken were designed (factor 1). These types of information were offered either with visual or haptic cues (factor 2). These four support systems were tested in four different abstracted environments with decreasing amount of allowed variability in realized trajectories (factor 3). The results show improvements for the simple support only when this information was presented visually, but not when offered haptically. For the elaborate support, equally large improvements for both modalities were found. This suggests that the elaborate support is better: additional information is key in improving performance in nonholonomic steering tasks.

In controlling teleoperation systems subject to communication delays, unstable behavior is often prevented by injecting damping. A proper perception of hardness is required to efficiently interact with an object, but it is unknown if and how this injected damping influences the perceived hardness of objects. To investigate the effect of damping on the perceived hardness of an object, 12 participants compared the hardnesses of lightly and heavily damped objects in a two-alternative forced choice experiment. Two tasks were investigated: an in-contact and a contact-transition task. For each task, 3 reference stiffnesses were used. Both force and position data were recorded. The results show that adding damping increases the perceived hardness of an object for an in-contact task, while it decreases perceived hardness for a contact-transition task. Movement and force data show that object indentation, mean and maximum velocity and adjusted rate-hardness, a new parameter defined in this paper, correlate with perceived object hardness. From a fundamental perspective, the results show that perceived hardness is influenced by damping in a task-specific way. Moreover, for designers of teleoperation systems the results provide insights for tuning and designing control architectures that properly reflect the desired hardness.