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We investigate the effect of adding cutaneous cues to kinesthetic feedback on the perception of a virtual object's hardness. A cutaneous haptic interface is designed to deliver hardness information to a user's fingertip along with a force-feedback interface, and the corresponding rendering strategy is implemented. Two sets of experiments are conducted to evaluate the proposed approach for hardness perception using one-finger touch and two-finger grasp. Experimental results indicate that the addition of cutaneous feedback can make the virtual surface feel significantly harder than the nominal stiffness delivered by force-feedback alone. In addition, the perceived hardness is significantly affected by the rate of hardness rendered with a cutaneous interface for the nominal stiffness $K= {{0.3}}$ and 0.5 N/mm. For two-finger grip, the effect of a virtual object's thickness has a significant effect on the perceived hardness measured in stiffness. When the perceived hardness is converted to Young's modulus, the effect of thickness is insignificant. [ABSTRACT FROM AUTHOR]

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Haptic perception is an important modality in reinforcing the presence of virtual or remote targets, but providing haptic feedback of dynamic environments still remains a challenging task. We address the issue of haptic telepresence systems by improving and integrating two independent approaches: real-time haptic rendering of unstructured spatial data and collaborative interaction with a remote partner. Contact with physical constraints is directly estimated from streaming point-cloud data without surface reconstruction, and haptic guidance cues that restrict or promote the users motion can be provided by both predefined triggers and gesture-based input from a helper. Through a user study with a proof-of-concept prototype, the authors show that the proposed approach significantly improves the performance of remote exploration tasks while enabling stable haptic interaction with real-world spatial data. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Image & Graphics is the property of Editorial Office of Journal of Image & Graphics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, we extend ideas of machine learning to the domain of data-driven haptic rendering. The proposed approach facilitates the processing of high-dimensional haptic interaction signals, which so far proved too difficult for existing data-driven methods. The key idea is to construct a compact feature space in the frequency domain which allows for efficient data reduction via a feature selection process. First, in a recording stage, extensive force and displacement datasets are acquired in automated measurements on deformable sample objects. These data are then transformed into a dimensionally reduced, compact frequency space representation. Next, feature-based learning is carried out in this feature space to significantly reduce the size of the original dataset. Based on this, time-domain haptic models capable of real-time performance are finally generated to encode the forces arising from bimanual object interactions. The presented processing chain is generally applicable and extendable to more complex interactions with even higher-dimensional data. The resulting haptic models are directly usable for data-driven haptic rendering. We illustrate the improved performance in comparison with previously existing data-processing approaches. [ABSTRACT FROM AUTHOR]

The kinematic serial chain configuration of a finger modulates the frictional properties during tactile exploration tasks. This paper analyzes and subsequently models the effects of the entire finger during sliding operations on a surface. Qualitative and quantitative study of finger movement patterns with postures, sliding directions, and contact angles first indicate the effect of finger stiffness on contact mechanics. A “stiffness ellipse” is subsequently modeled to incorporate finger pose effects, and then coupled with the lumped mass-spring-damper model of the finger pad to estimate resultant contact forces. The performance of the proposed model is verified by comparing with experimental results obtained from 10 subjects. The proposed model could estimate the general tendencies of contact forces with change in postures (Extended and Flexed), sliding directions (proximal and distal), and contact angles ($20^{\circ }$ , $40^{\circ }$ , and $60^{\circ }$ ). The experimental results indicates that finger stiffness significantly modulates the contact forces, stick-slip frequency, preloading duration, and initial spike during sliding. Introduction of finger posture effects could explain the change in finger normal force during tactile exploration tasks. The proposed haptic rendering model can be used to give a more natural user feedback in virtual fingertip-surface interactions. [ABSTRACT FROM AUTHOR]

Stable control of haptic interfaces is one of the most important challenges in haptic simulations, because any instability of a haptic interface can cause it to get far from the realistic sense. In this paper, the control strategies employed for a stable haptic rendering in an interactive virtual control laboratory are presented. In this interactive virtual laboratory, there are different scenarios to teach the control concepts, in which a haptic interface is used in the two cases of force control and position control. In this regard, two control strategies are employed to avoid instability. An energy-compensating controller is utilized to remove energy leakage. Besides, a fuzzy impedance control is used along with the energy-compensating controller for the position control scenarios. The results obtained indicate the proposed approaches practically guarantee the stability of the haptic interface for an educational application in practice. [ABSTRACT FROM AUTHOR]

Haptic rendering in virtual environment provides a powerful training and validation tool for assembly of bolted joints that require accurate assembly forces. This work proposes a staged haptic rendering approach for virtual assembly (VA) of bolted joints. Firstly, by analyzing the stress condition during the actual assembly process, four consecutive stages, namely navigation stage, transition stage, linearity stage, and yield stage, are identified. Then, the force rendering model is set up. Moreover, a prototype VA system is developed to implement and test the approach. Two groups of experiments on a two-stage gear reducer are conducted to verify the feasibility of the approach and evaluate the prototype’s performance. The results have shown that the force calculated by the proposed approach is consistent with the actual assembly and the evaluators are highly positive on the immersion and the guiding ability of the VA process with the haptic rendering provided. [ABSTRACT FROM AUTHOR]

During the last decade, haptics has been a new emerged and interesting subject for many researchers, which can be classified into three topics such as human haptics, machine haptics and computer haptics. Haptic rendering is the most important technology for computer haptics, which means the process of calculating the force or tactile feedback to give the user a sense of touch or interaction with the virtual object. This paper provides a detailed and comprehensive survey of the methods and technologies for haptic rendering in the past 5 years, mainly from 2010–2015, including haptic rendering for rigid–rigid interaction, haptic rendering for rigid–deformable interaction, haptic rendering for rigid–fluid interaction, haptic rendering for image- and video-based interaction, and texture and tactile rendering. The main research efforts and the typical algorithms are discussed, and the new ideas and research progresses are investigated, then the conclusions and future directions are summarized. [ABSTRACT FROM AUTHOR]

This article presents a new data-driven model design for rendering force responses from elastic tool deformation. The new design incorporates a six-dimensional input describing the initial position of the contact, as well as the state of the tool deformation. The input-output relationship of the model was represented by a radial basis functions network, which was optimized based on training data collected from real tool-surface contact. Since the input space of the model is represented in the local coordinate system of a tool, the model is independent of recording and rendering devices and can be easily deployed to an existing simulator. The model also supports complex interactions, such as self and multi-contact collisions. In order to assess the proposed data-driven model, we built a custom data acquisition setup and developed a proof-of-concept rendering simulator. The simulator was evaluated through numerical and psychophysical experiments with four different real tools. The numerical evaluation demonstrated the perceptual soundness of the proposed model, meanwhile the user study revealed the force feedback of the proposed simulator to be realistic. [ABSTRACT FROM AUTHOR]

In this paper, we present a robotic surface display that physically imitates the orientation of virtual 3D geometry touched through a 2D flat screen. The proposed approach renders the surface orientation of 3D geometry such that users can tactually obtain relative geometric information, which plays a significant role in the process of real-world haptic object perception. Taking advantage of the planar aspect of touch surfaces, the system constructs a rotation matrix to control the pose of a surface with minimal mechanical movements with given partial geometric information (i.e., normal vector at the point of touch). To evaluate the proposed rendering scheme, we conducted a geometric task (two alternative forced choices) with a set of hand-sized cylindrically curved geometries in which participants were asked to identify which of the two surfaces they perceived as being more curved. Curvatures with the same polarities (i.e., convex-convex and concave-concave) were employed in the study and psychometric curves estimated to obtain the threshold of the curvature difference and to validate the proposed rendering scheme. Possible applications of the proposed system and its limitations are also presented. [ABSTRACT FROM PUBLISHER]

What are the technological bottlenecks in virtual assembly simulations with haptic feedback? To tackle this question, we present an evaluation study in which real feedback modalities are gradually replaced by synthetic ones. In particular, the effects of the following factors on the user performance and perception during virtual assemblies are analyzed: ($i$ ) a visual feedback system consisting of an nVisor head-mounted display, ($ii$ ) our haptic device HUG suited for unscaled upper-body movements, and ($iii$ ) our novel six-DoF constraint-based haptic rendering algorithm. Besides that, the influence of ( $iv$ ) real collision sounds is also examined to a lesser extent. The experimental assembly scenario consisted of three variations of peg-in-hole tasks which were performed by a total of $N = 24$ participants in a within-design study. The mentioned three synthetic factors ( $i$ )-( $iii$ ) gradually replaced in five degrees or steps the real feedback sources, ending up in completely virtual assembly simulations. For each of the degrees, three objective variables (completion time, collision forces, and muscular effort) and five subjective ratings (related to the perception of realism and the workload) were recorded and statistically analyzed. In order to explain subjective perception also with objective measures, reaction times of a secondary audio task performed in parallel with the assembly exercises were recorded, too. While previous works have mainly focused on differences of completion time between real and virtual manipulations, our results show how all of the mentioned twelve performance and perception indicators are influenced by each of the four varied feedback factors, building a multi-modality relationship function that maps our or similar systems and expected user responses. In general, the haptic feedback modality turned out to have the largest impact on the dependent variables, particularly the HUG interface, whereas audio cues seemed to be less significant. We quantify these previous and further qualitative statements within the domain defined by the used systems. Moreover, the relationship of our insights with related other work is discussed, and their projections are outlined. [ABSTRACT FROM PUBLISHER]