Haptic Probe Research Articles

Haptic Edge Detection Through Shear.

Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals.

An optimization method for penalty-based six-degrees-of-freedom haptic rendering system

We present an optimization method which is based on generalized penetration depth computation algorithm to resolve the pop-through problem in six degrees of freedom haptic rendering system. Our optimization method can handle any type of object to object haptic interaction and produce high fidelity haptic feedback for general polygonal models with tens of thousands triangles near ideal haptic update rate 1000Hz. The algorithm in our method is mainly based on a continuous collision detection method, using a contact-space projection technique which can compute the realtime contact configurations and record the position of visual semantic haptic probe, moreover, combined with iterative local optimization on the contact space and using a constraint method to minimum the local optimization result. The experiment results show our method can resolve the pop-through phenomenon in penalty-based haptic rendering system and can get the realistic force and torque feedback. We successfully integrated the method into a six degree of freedom haptic device.

Surface point location by walking algorithm for haptic visualization of triangulated 3D models

Haptic devices are nowadays gaining popularity because of their increasing availability. These special input/output devices provide, unlike mouse or keyboard, a native 3D manipulation, especially a more precise control and a force interaction. With more accurate description of the model, haptics can achieve more realistic force feedback. Therefore, triangulated surface models are often used for an authentic interpretation of 3D models. A common task in haptic visualization using triangulated surface models is to find a triangle which is in the collision trajectory of the haptic probe. Since the render rate of the haptic visualization is relatively high (usually about 1kHz), the task becomes highly non-trivial for complex mesh models, especially for the meshes which are changing over time. The paper presents a fast and novel location algorithm able to find the triangle which is close to the haptic probe and in the direction of the probe motion vector. The algorithm has negligible additional memory requirements, since it does not need additional searching data structures and uses only the information usually available for triangulated models. Therefore, the algorithm could handle even triangular meshes changing over time. Results show that the proposed algorithm is fast enough to be used in haptic visualization of complex-shaped models with hundreds of thousands of triangles.

Haptic discrimination of virtual surface slope

We report the difference thresholds of the slope of a virtual surface rendered via a force---feedback haptic interface with the body frontal plane as a reference. The factors varied in experiments were the stiffness of a virtual plane, the lateral velocity with which the haptic probe scanned the plane, the length of a scanning interval, the movement direction of the probe to the body frontal plane (toward or away from the body), and lateral scanning direction (left-to-right or right-to-left). Measured slope thresholds ranged from 8.33° to 12.74° and were generally higher than or similar to previously published thresholds for haptic orientation or angle discrimination. The results suggested that haptic slope discriminability was independent of surface stiffness and lateral scanning velocity. Slope discrimination was largely affected by the lateral scan distance, indicating that the terminal difference of probe normal position can be an important sensory cue. In terms of scan direction, inward or rightward scans resulted in better slope discrimination than outward or leftward scans, respectively. These thresholds and findings have implications for haptics applications that involve geometric model modification or simplification of virtual objects while preserving their perceptual properties.

An Anticipative Control Approach and Interactive GUI to Enhance the Rendering of the Distal Robot Interaction with its Environment during Robotized Tele-Echography

Performing a robotized telemedicine act via specific networks brings forth the issue of transparency in order to enable the operator, e.g. the medical ultrasound specialist, to safely and accurately perform bilateral tele-operation tasks despite the long time delays inherent to the communication link. To counter these effects, two strategies are combined to improve, at the operator site, the rendering of the interactions between the remote robotic systems with its environment (i.e. the patient), and the control of the robot’s orientation at the operator site. The first approach is the development of a new control architecture based on an internal model providing an anticipated value of the distant environment stiffness; it is complemented with a graphic user interface (GUI) which provides the expert with the real-time relative position of the haptic probe with the robot’s end effector for better tele-operated control. These combined strategies provide the expert with an improved interactive tool for tele-diagnosis.

Hybrid Rugosity Mesostructures (HRMs) for fast and accurate rendering of fine haptic detail


 
 
 Thehapticrenderingofsurfacemesostructure(finerelieffeatures)indensetrianglemeshesrequires special structures, equipment, and high sampling rates for detailed perception of rugged models. Low cost approaches render haptic texture at the expense of fidelity of perception. We propose a faster method for sur- face haptic rendering using image-based Hybrid Rugosity Mesostructures (HRMs), paired maps with per-face heightfield displacements and normal maps, which are layered on top of a much decimated mesh, effectively adding greater surface detail than actually present in the geometry. The haptic probe’s force response algorithm is modulated using the blended HRM coat to render dense surface features at much lower costs. The proposed method solves typical problems at edge crossings, concave foldings and texture transitions. To prove the well- ness of the approach, a usability testbed framework was built to measure and compare experimental results of haptic rendering approaches in a common set of specially devised meshes, HRMs, and performance tests. Trial results of user testing evaluations show the goodness of the proposed HRM technique, rendering accurate 3D surface detail at high sampling rates, deriving useful modeling and perception thresholds for this technique.
 
 

The effect of sub-threshold forces on human performance in multi-modal computer-aided design

In traditional CAD (computer-aided design) systems, the manipulation of points and lines is often difficult because designers manipulate virtual objects through their vision system. Nowadays, designers can explore and manipulate virtual objects in haptic-enabled CAD systems using haptic devices. Haptic devices can present force feedbacks to pull or push the users’ hands into desirable targets. Of course the intent is for the user to experience the same sensations in the virtual realm as they would in the real world. Thus, sub-threshold forces, which cannot be perceived by users, should be incorporated in the control of users’ movements. As a result, our attention is directed to study the effect of sub-threshold forces on the accuracy of movement in a haptic-enabled virtual reality (VR) system. In this study, our goal is to manipulate users’ hands using controlled forces such that users cannot notice the forces. With this in mind, we have constructed a haptic-enabled virtual environment (VE) to carry out a multi-modal Fitts’ type task. In the task, subjects could see the position of the haptic probe in the VE where forces were applied on their hands. Basically, the accuracy of subjects was measured using a performance index when the intensity and direction of forces changed. A psychophysical method was utilized to ensure that the forces were below the force threshold of the human force perception. Results indicate that the accuracy is affected by the intensity and direction of sub-threshold forces even when users are allowed to control their actions through visual feedbacks.

Effects of haptic feedback, stereoscopy, and image resolution on performance and presence in remote navigation

Traditionally, the main goal of teleoperation has been to successfully achieve a given task as if performing the task in local space. An emerging and related requirement is to also match the subjective sensation or the user experience of the remote environment, while maintaining reasonable task performance. This concept is often called “presence” or “(experiential) telepresence,” which is informally defined as “the sense of being in a mediated environment.” In this paper, haptic feedback is considered as an important element for providing improved presence and reasonable task performance in remote navigation. An approach for using haptic information to “experientially” teleoperate a mobile robot is described. Haptic feedback is computed from the range information obtained by a sonar array attached to the robot, and delivered to a user's hand via a haptic probe. This haptic feedback is provided to the user, in addition to stereoscopic images from a forward-facing stereo camera mounted on the mobile robot. The experiment with a user population in a real-world environment showed that haptic feedback significantly improved both task performance and user-felt presence. When considering user-felt presence, no interaction among haptic feedback, image resolution, and stereoscopy was observed, that is, haptic feedback was effective, regardless of the fidelity of visual elements. Stereoscopic images also significantly improved both task performance and user-felt presence, but high-resolution images only significantly improved user-felt presence. When considering task performance, however, it was found that there was an interaction between haptic feedback and stereoscopy, that is, stereoscopic images were only effective when no force feedback was applied. According to the multiple regression analysis, haptic feedback was a higher contributing factor to the improvement in performance and presence than image resolution and stereoscopy.

Development of a new instrument for examination of stiffness in the breast using haptic sensor technology

Detection of breast cancer and regular monitoring of the response to neoadjuvant chemotherapy are important issues for large numbers of women. To address these needs, we developed a new instrument for examination of stiffness of the breast using haptic sensor technology. The instrument consists of a 64-element tactile sensor array designed to visualize haptic information within the breast. It was demonstrated in both basic and clinical studies that the hardness of breast cancer lesions larger than 10 mm located at depths less than 20 mm could be detected using this novel haptic probe. We expect that the proposed instrument will be useful for the detection and follow-up of treatment and to predict the response to neoadjuvant chemotherapy.

Haptic Rendering of Dynamic Volumetric Data

With current methods for volume haptics in scientific visualization, features in time-varying data can freely move straight through the haptic probe without generating any haptic feedback the algorithms are simply not designed to handle variation with time but consider only the instantaneous configuration when the haptic feedback is calculated. This article introduces haptic rendering of dynamic volumetric data to provide a means for haptic exploration of dynamic behaviour in volumetric data. We show how haptic feedback can be produced that is consistent with volumetric data moving within the virtual environment and with data that, in itself, evolves over time. Haptic interaction with time-varying data is demonstrated by allowing palpation of a CT sequence of a beating human heart.

Haptic Teleoperation of a Mobile Robot: A User Study

The problem of teleoperating a mobile robot using shared autonomy is addressed: An onboard controller performs close-range obstacle avoidance while the operator uses the manipulandum of a haptic probe to designate the desired speed and rate of turn. Sensors on the robot are used to measure obstacle-range information. A strategy to convert such range information into forces is described, which are reflected to the operator's hand via the haptic probe. This haptic information provides feedback to the operator in addition to imagery from a front-facing camera mounted on the mobile robot. Extensive experiments with a user population both in virtual and in real environments show that this added haptic feedback significantly improves operator performance, as well as presence, in several ways (reduced collisions, increased minimum distance between the robot and obstacles, etc.) without a significant increase in navigation time.