—Enabling haptic interaction with non-solid materials, such as liquids or sediments, could expand possibilities for exploration of virtual or remote environments, which would e.g enable training divers and astronauts in simulators. To allow application of natural investigation procedures in such scenarios, haptic interfaces with several degrees of freedom (DOF) are necessary, which allow the interaction with a variety of solid objects as well as different surrounding mediums. The goal of this work is to develop an algorithm for a high-DOF hand exoskeleton as haptic interface connected to five points on the human hand, that enables the perception of virtual fluids by rendering the fluids’ prominent proprioceptive characteristic (viscosity). To allow simultaneous rendering of virtual solid objects of varying stiffness, a high update rate should be maintained. To quantify human perception of the rendered fluid, two user studies are carried out. The first investigates the ability to perceive fluids of low viscosity such as water, while the second deals with the discrimination ability for higher viscous virtual fluids. For virtual fluids with low viscosity, it is found that a linear relationship exists between the rendered and perceived viscosity with a scaling factor of 2. Fluids with high viscosity (> 10 Pa s) can be discriminated well, achieving similar values for the Weber fractions (w = 0.3) as are found in real interactions with fluids. The results of both experiments prove that properties of fluids rendered using simplified models to allow high update frequencies (833 Hz) can still be discriminated by human users.

Haptic Shared Control (HSC) can improve operator performance during teleoperation. HSC uses assistive forces on the master device to guide the operator's control input towards a reference trajectory. However, the reference trajectory might be incorrect due to inaccuracies in the sensed or modeled environment and thus not match the intended trajectory of the operator, resulting in force conflicts that can potentially reduce performance. This paper describes the design and evaluation of a haptic shared controller whose reference trajectory adapts in real-time to resort force conflicts. Different adaptive controllers have been designed and compared in simulation. The final controller is built on a Task Parameterized Gaussian Mixture Model and adapts using an Incremental Gaussian Mixture Model. The controller is evaluated in an experiment (n=16) where subjects performed a planar teleoperation task that involved moving the slave through a narrow corridor. The subjects were assisted by HSC with a correct reference (cHSC), HSC with a wrong reference (wHSC), HSC with a wrong reference that adapts in real-time (waHSC) and a manual condition.
The waHSC condition was expected to result in lower control effort, compared to wHSC, and induce better performance compared to wHSC and the manual condition.
Within-subjects results showed that waHSC decreases control effort compared to wHSC, while the performance remained similar. Manual control had better performance than wHSC and waHSC, and cHSC outperformed all other conditions.
Even though the conditions were tested in a balanced order, we observed a strong effect of the order of the conditions: between-subject results showed improved performance, lower control effort and better subjective results for waHSC over wHSC when wHSC was executed first. Upon first execution of waHSC, improved performance and self-reported satisfaction were realized for wHSC over waHSC. The results show that, in the event of a force conflict, an adaptive controller is a promising alternative to temporarily adjusting the HSC stiffness.

The Rubber Hand Illusion is an illusion in which
visual cues of stimulation on a fake hand are combined with
synchronous tactile cues on a participant’s hand, which can
induce a sense of bodily ownership of the fake hand. This
technique does not facilitate synchronous movement of the
hands, and asynchronous stimulation or movement can break the
illusion, thereby limiting potential benefits that bodily ownership
may have in practical applications such as telerobotic control.
This study aims to quantify to what extent a Virtual Reality
headset with hand tracking capabilities can be used to evoke a
rubber hand illusion, and to what extent the illusion strength
maintains during voluntary hand movement. Twelve subjects
were randomly presented with three conditions; the classic Rubber
Hand Illusion (RHI), serving as a baseline for comparison,
the static Virtual reality Rubber Hand Illusion (VRHI), the
virtual reality equivalent of the original experiment, and the
moving Virtual reality Rubber Hand Illusion (mVRHI), where
participants’ voluntary hand movements were tracked using
motion controllers, to generate simultaneous virtual hand motion.
Illusion strength was quantified subjectively, by a 27-question
questionnaire adapted from literature, and objectively, by measuring
proprioceptive drift; the distance between perceived hand
location and actual hand location. It was hypothesized that VRHI
and mVRHI would increase the strength of the illusion, compared
to RHI. A significant increase in proprioceptive drift was found
between the RHI and VRHI conditions. Questionnaire scores
in the ownership category were significantly higher for VRHI,
and the control category showed higher scores for mVRHI. In
conclusion, a higher embodiment was achieved during VRHI, but
mVRHI did not improve upon VRHI as expected.

There is a distinction between environmental and social interactions as humans interpret the world. Environmental interactions are based on weighted sensory estimates formed on integrated redundant information. Trust is a heuristic used in social interactions. As social interactions and technology interrelate, social factors become influences on the environmental estimates. Hence trust could influence our sensory estimates.

The optimal sensory weights for the sensory estimates are determined with a Maximum Likelihood Estimate based on the reliability of the sensory information.

The objective of this research is to find evidence that trust influences sensory weighting on the level of sensory integration, believing that human-machine interaction will benefit from a better understanding of sensory weighting.

We hypothesised that information on the reliabilities of the sensory cues, while not changing these, will cause participants to reweigh the sensory information. Reweighing sensory information when the reliability of the sensory cue has not changed contradicts the Maximum Likelihood Estimation prediction.

An experiment was conducted in which participants performed a target-hitting task with a haptic device. The target was hidden, yet participants were presented with a visual and haptic cue to deduct the location of the target. Although both cues were not of equal reliability, the participants created the optimal sensory estimate by sensory integration.

The results showed that trust influenced sensory weighting.
Since the outcome of the Maximum Likelihood Estimation model was challenged by the occurrence of sensory reweighting because of trust, it is recommended to extend the model with a factor trust.

Epiretinal Membrane Peeling (EMP) is a common vitreoretinal surgery in clinic. Over the past twenty years, telerobotics has been developed to assist retinal surgeons. Robot-assisted surgery can aid the surgeon by motion scaling and filtering out natural hand tremor. However, the additive precision has yet to relieve the surgeon from the burdensome task entirely, and teleoperation comes with a downside of extending execution time.

One of the complicating factors in robot-assisted EMP surgery is the limited depth perception afforded by the binocular microscope, which increases the risk of inadvertent contact of the surgical tool with the retina. Recently, PRECEYES has introduced an intraoperative sensor that measures the distance to the surface of the retina to their surgical system. The master device is capable of force feedback, which can be employed to transmit distance information to the surgeon without extra burden to the already visually overwhelmed task.

This study aims to design and evaluate haptic assistance for teleoperated EMP based on noisy distance sensor. Sixteen subjects with non-medical background participated in the human factors experiment performing a simulated vitreoretinal surgery by using a 3-DoF haptic master device controlling a simulated slave robot. All subjects performed two experimental conditions (with and without haptic assistance) in a balanced order. The experimental result shows that, with haptic assistance, the overall puncture rate reduces from 9.6% to 2.8% and peeling forces are stabilized significantly. Which indicates that the proposed method utilizes distance information in a promising way, thus reducing the difficulty of the teleoperated task.

Humans can compensate rapidly to unforeseen errors and circumstances while performing motor tasks. These tasks are exposed to sensory and motor noise and delays originated from the biological system characteristics, as well as to varying surrounding environments while performing movements. Therefore, uncertainty of the estimate of limb position arises. Error estimates during movement and displacements after a mechanical perturbation are compensated by relying on proprioceptive feedback from the body. Moreover, the motor system can rely on co-contraction as it increases the amplitude of the short latency stretch reflex, which plays an important role in minimizing the effects of disturbances. This study examines the influence of position, velocity, and pre-perturbation background muscle activity in the decision process of avoiding obstacles in the environment after a mechanical perturbation while performing a reaching task. After the perturbation, participants had to choose between two strategies: going in between or around the obstacles to reach an end target. Position of the hand, velocity, and EMG activity of four muscles in the shoulder and elbow were compared at different time epochs between both strategies. No significant differences were found in muscle activity pre-perturbation and lateral position before and up to 100ms after perturbation onset. Significant difference in lateral velocity was found 50ms after perturbation onset between the two strategies. Online corrections to avoid obstacles after a mechanical perturbation are modulated by the lateral velocity of the limb.