Creating Realistic Virtual Textures from Contact Acceleration Data.

Modern haptic interfaces are adept at conveying the large-scale shape of virtual objects, but they often provide unrealistic or no feedback when it comes to the microscopic details of surface texture. Direct texture-rendering challenges the state of the art in haptics because it requires a finely detailed model of the surface's properties, real-time dynamic simulation of complex interactions, and high-bandwidth haptic output to enable the user to feel the resulting contacts. This paper presents a new, fully realized solution for creating realistic virtual textures. Our system employs a sensorized handheld tool to capture the feel of a given texture, recording three-dimensional tool acceleration, tool position, and contact force over time. We reduce the three-dimensional acceleration signals to a perceptually equivalent one-dimensional signal, and then we use linear predictive coding to distill this raw haptic information into a database of frequency-domain texture models. Finally, we render these texture models in real time on a Wacom tablet using a stylus augmented with small voice coil actuators. The resulting virtual textures provide a compelling simulation of contact with the real surfaces, which we verify through a human subject study.

Evaluation of Tactile Feedback Methods for Wrist Rotation Guidance.

Tactile motion guidance systems aim to direct the user's movement toward a target pose or trajectory by delivering tactile cues through lightweight wearable actuators. This study evaluates 10 forms of tactile feedback for guidance of wrist rotation to understand the traits that influence the effectiveness of such systems. We present five wearable actuators capable of tapping, dragging across, squeezing, twisting, or vibrating against the user's wrist; each actuator can be controlled via steady or pulsing drive algorithms. Ten subjects used each form of feedback to perform three unsighted movement tasks: directional response, position targeting, and trajectory following. The results show that directional responses are fastest when direction is conveyed through the location of the tactile stimulus or steady lateral skin stretch. Feedback that clearly conveys movement direction enables subjects to reach target positions most quickly, though tactile magnitude cues (steady intensity and especially pulsing frequency) can also be used when direction is difficult to discern. Subjects closely tracked arbitrary trajectories only when both movement direction and cue magnitude were subjectively rated as very easy to discern. The best overall performance was achieved by the actuator that repeatedly taps on the subject's wrist on the side toward which they should turn.

Tool Contact Acceleration Feedback for Telerobotic Surgery.

Minimally invasive telerobotic surgical systems enable surgeons to perform complicated procedures without large incisions. Unfortunately, these systems typically do not provide the surgeon with sensory feedback aside from stereoscopic vision. We have, thus, developed VerroTouch, a sensing and actuating device that can be added to Intuitive Surgical's existing da Vinci S Surgical System to provide auditory and vibrotactile feedback of tool contact accelerations. These cues let the surgeon feel and hear contact with rough textures as well as the making and breaking of contact with objects and other tools. To evaluate the merits of this approach, we had 11 surgeons use an augmented da Vinci S to perform three in vitro manipulation tasks under four different feedback conditions: with no acceleration feedback, with audio feedback, with haptic feedback, and with both audio and haptic. Subjects expressed a significant preference for the inclusion of tool contact acceleration feedback, although they disagreed over which sensory modality was best. Other survey responses and qualitative written comments indicate that the feedback may have improved the subject's concentration and situational awareness by strengthening the connection between the surgeon and the surgical instruments. Analysis of quantitative task metrics shows that the feedback neither improves nor impedes the performance of the chosen tasks.