http://www.computer.org/toh The IEEE Transactions on Haptics will address the science, technology and applications associated with information acquisition and object manipulation through touch. Haptic interactions relevant to this journal include all aspects of manual exploration and manipulation by humans, machines and interactions between the two, performed in real, virtual, teleoperated or networked environments. Research areas of relevance to this publication will include, but not be limited to, the following topics: a) Human haptic and multi-sensory perception and action b) Haptic interactions via passive or active tools and machines c) Devices that sense, enable, or create haptic interactions locally or at a distance d) Haptic rendering and its association with graphic and auditory rendering in virtual reality e) Algorithms, controls, and dynamics of haptic devices, users, and interactions between the two f) Human-machine performance and safety with haptic feedback g) Haptics in the context of human-computer interactions h)Systems and networks using haptic devices and interactions, including multi-modal feedback i) Application of the above, for example in areas such as education, rehabilitation, medicine, computer-aided design, skills training, computer games, driver controls, simulation and visualization en-us Sat, 25 May 2013 10:00:50 GMT http://csdl.computer.org/common/images/logos/toh.gif List of recently published journal articles http://www.computer.org/toh http://doi.ieeecomputersociety.org/10.1109/TOH.2013.3 Closed-loop force control can be used on haptic interfaces to mitigate the effects of mechanism dynamics. A single multi-dimensional force-torque sensor is often employed to measure the interaction force between the haptic device and the user's hand. The parallel haptic interface at the University of Colorado (CU) instead employs smaller one-dimensional force sensors oriented along each of the five actuating rods to build up a five-dimensional force vector. This paper shows that a particular manipulandum/hand partition in the system dynamics is induced by the placement and type of force sensing, and discusses the implications on force and impedance control for parallel haptic interfaces. The details of a "squaring down" process are also discussed, showing how to obtain reduced degree-of-freedom models from the general six degree-of-freedom dynamics formulation. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.3 http://doi.ieeecomputersociety.org/10.1109/TOH.2013.6 In this paper we present results from a study of prehensile human hand use during the daily work activities of four subjects: two housekeepers and two machinists. Subjects wore a head-mounted camera that recorded their hand usage during their daily work activities in their typical place of work. For each subject, 7.45 hours of video was analyzed, recording the type of grasp being used and its duration. From this data we extracted overall grasp frequency, duration distributions for each grasp, and common transitions between grasps. The results show that for 80% of the study duration the housekeepers used just five grasps and the machinists used ten. The grasping patterns for the different subjects were compared, and the overall top ten grasps are discussed in detail. The results of this study not only lend insight into how people use their hands during daily tasks, but can also inform the design of effective robotic and prosthetic hands. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.6 http://doi.ieeecomputersociety.org/10.1109/TOH.2013.1 Tactile displays are often used to present spatial cues about the environment, although the optimal configuration of a display used for spatial cuing is not known. The objective of the present set of experiments was to characterize the properties of surface waves induced by vibrotactile stimulation and to determine if the propagation of surface waves was a factor influenc-ing and the ability to localize a point of stimulation in a tactile display. Three sites on the body were tested: the palm of the hand, the forearm and the thigh. An accelerometer array was fabricated and used to measure the surface waves. The results indicated that there were significant differences between glabrous and hairy skin in terms of the frequency and amplitude of oscillation of the motor. Analyses of the motion of the surface waves across the skin indicated that they were markedly attenuated at 8 mm from the motor, but even at 24 mm the amplitude was still above perceptual threshold. The localization experiment indicated that subjects were much better at identifying the site of stimulation on the palm as compared to the forearm and thigh, and that the latter two sites were not significantly different. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.1 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.62 Human task performance with teleoperation systems is characterized by long task completion times, handling errors and excessive force application to objects in the remote environment. Haptic interfaces promise to address these challenges by providing the human user with sensory feedback from the remote environment that would otherwise be lacking. Up to now, only few attempts have been made to present current research efforts from a broader, more integrative perspective. To address this need, several meta-analyses were conducted which aimed at establishing the overall effectiveness of haptic interfaces in improving the critical performance aspects in teleoperation systems. In this context, the influence of potential moderator variables (i.e. virtual vs. real teleoperation setup; vibrotactile vs. kinaesthetic force feedback) as well as outcome-specific effects (i.e. force regulation ability; task completion time; performance errors) were investigated. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.62 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.53 This work contributes to the development of a common framework for the discussion and analysis of dexterous manipulation across the human and robotic domains. An overview of previous work is first provided along with an analysis of the tradeoffs between arm and hand dexterity. A hand-centric and motion-centric manipulation classification is then presented and applied in four different ways. It is first discussed how the taxonomy can be used to identify a manipulation strategy. Then, applications for robot hand analysis and engineering design are explained. Finally, the classification is applied to three activities of daily living (ADLs) to distinguish the patterns of dexterous manipulation involved in each task. The same analysis method could be used to predict problem ADLs for various impairments or to produce a representative benchmark set of ADL tasks. Overall, the classification scheme proposed creates a descriptive framework that can be used to effectively describe hand movements during manipulation in a variety of contexts and might be combined with existing object-centric or other taxonomies to provide a complete description of a specific manipulation task. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.53 http://doi.ieeecomputersociety.org/10.1109/TOH.2013.22 Haptic exploratory procedures (EPs) are prototypical hand movements that are linked to the acquisition of specific object properties. In studies of haptic perception, hand movements are often classified into these EPs. Here, we aim to investigate several EPs in a quantitative manner to understand how hand dynamics and contact forces differ between them. These dissimilarities are then used to construct an EP identification model capable of discriminating between EPs based on index finger position and contact force. The extent to which the instructed EPs were distinct, repeatable and similar across subjects was confirmed by showing that more that 95% of the analyzed trials were classified correctly. Finally, the method is employed to investigate haptic exploratory behavior during similarity judgments based on several object properties. It seems that discrimination based on material properties (hardness, roughness, and temperature) yields more consistent classification results compared to discrimination based on the acquisition of shape information. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.22 http://doi.ieeecomputersociety.org/10.1109/TOH.2013.21 Haptic perception of curvature depends largely on the kind of touch. An active and dynamic touch is considered to be the most natural way of exploring. In this study we have designed and evaluated a kinematic platform for curvature perception through active and dynamic touch. This platform can independently orient, elevate and translate a flat plate; by exploring forward and backwards along the flat plate with a finger, users can achieve shape feeling of extruded objects. The mechanism of platform and the way of touch have maximally respected the cues for curvature perception, especially the slip cue. Psychophysical evaluation demonstrated that the discrimination threshold of curvature for virtual shapes is close to that for real shapes; and the virtual shape is felt equally curved as the real one. The curvature perception of mono-convex surfaces was then expanded to perception of more complex surfaces: large textures, which have sinusoidal profile. The evaluation has accessed the correspondence between the virtual and real large textures. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.21 http://doi.ieeecomputersociety.org/10.1109/TOH.2013.20 This paper presents a new haptic rendering method for streaming point cloud data. It provides haptic rendering of moving physical objects using data obtained from RGB-D cameras. Thus real-time haptic interaction with moving objects can be achieved using non-contact sensors. This method extends `virtual coupling'-based proxy methods in a way that does not require pre-processing of points and allows for spatial point cloud discontinuities. The key ideas of the algorithm are iterative motion of the proxy with respect to the points, and the use of a variable proxy step size that results in better accuracy for short proxy movements and faster convergence for longer movements. This method provides highly accurate haptic interaction for geometries in which the proxy can physically fit. Another advantage is a significant reduction in the risk of 'pop through' during haptic interaction with dynamic point clouds, even in the presence of noise. This haptic rendering method is computationally efficient; it can run in real-time on available personal computers without the need for down-sampling of point clouds from commercially available depth cameras. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.20 http://doi.ieeecomputersociety.org/10.1109/TOH.2013.4 The goal of this study was to analyze the human ability of external force discrimination while actively moving the arm. We give an overview for the whole arm of just-noticeable differences (JNDs) for controlled movements separately executed for wrist, elbow and shoulder joints. With the results of this study a force feedback can be designed which is calibrated according to human force sensitivity. In the experiments presented, ten subjects performed a series of movements facing an opposing force. Force changes had to be detected in a two-alternative forced choice task. For each of the three joints, perceptual thresholds were measured as absolute thresholds (no reference force) using the QUEST procedure and three JNDs corresponding to three reference forces were chosen. Our results demonstrate that different Weber fractions are measured with respect to the joints. These were 0.11, 0.13 and 0.08 for wrist, elbow and shoulder, respectively. The minimum perceivable force on average was 0.04 N for all three joints. The results of this work will be used for delivering appropriate force feedback to a user wearing an exoskeleton in a tele-operation scenario. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.4 http://doi.ieeecomputersociety.org/10.1109/TOH.2013.8 For small stimuli, it has been shown that subjects are very accurate in distinguishing a cylinder with an elliptical cross-section from one with a circular cross-section. In such a task, both curvature and length are integrated effectively. Large cylinders are explored differently: either by one hand or by two hands sliding over the surface. However, the same cues are available. We investigated the integration of position and curvature in unimanual and bimanual exploration. In Experiment 1, curved surfaces were presented as part of a horizontal cylinder with a cross-section that was either a horizontally or a vertically elongated ellipse. We found that discrimination thresholds for unimanual exploration were significantly larger than for bimanual exploration. In Experiment 2, we found that position discrimination thresholds were independent of type of exploration (unimanual or bimanual) and surprisingly also independent of reference length. In Experiment 3, we found that discrimination thresholds for the position of the midsagittal plane were on average lower than the position discrimination thresholds found in Experiment 2. From these findings, we conclude that the lower thresholds in Experiment 1 for bimanual exploration compared to unimanual exploration are due to integration of curvature, not position or uncertainty of the midsagittal plane in unimanual exploration. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.8 http://doi.ieeecomputersociety.org/10.1109/TOH.2013.7 We introduce a novel dual-band haptic music player for real-time simultaneous vibrotactile playback with music in mobile devices. Our haptic music player features a new miniature dual-mode actuator that can produce vibrations consisting of two principal frequencies and a real-time vibration generation algorithm that can extract vibration commands from a music file for dual-band playback (bass and treble). The algorithm uses a “haptic equalizer” and provides plausible sound-to-touch modality conversion based on human perceptual data. In addition, we present a user study carried out to evaluate the subjective performance (precision, harmony, fun, and preference) of the haptic music player, in comparison with the current practice of bass-band only vibrotactile playback via a single-frequency voice-coil actuator. The evaluation results indicated that the new dual-band playback outperforms the bass-only rendering, also providing several insights for further improvements. The developed system and experimental findings have implications for improving the multimedia experience with mobile devices. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.7 http://doi.ieeecomputersociety.org/10.1109/TOH.2013.5 Haptic stimuli with directional content, e.g. navigational cues, may be difficult to use in handheld applications; the user's hand, where the cues are delivered, may not be aligned with the world, where the cues are to be interpreted. In such a case, the user would be required to mentally transform the stimuli between different reference frames. We examine the mental rotation of directional haptic stimuli in three experiments, investigating: 1. users' intuitive interpretation of rotated stimuli, 2. mental rotation of haptic stimuli about a single axis, and 3. rotation about multiple axes. We conclude that directional haptic stimuli are suitable for use in mobile applications, although users do not naturally interpret rotated stimuli in any one universal way. We find evidence of cognitive processes involving the rotation of analog, spatial representations. For small angles, these mental rotations come at little cost, but rotations with larger misalignment angles impact user performance. When considering the design of a handheld haptic device, hand pose must be carefully considered, as certain poses increase the difficulty of stimulus interpretation. All tested joint rotations impact task difficulty, but finger flexion and wrist rotation interact to greatly increase the cost of stimulus interpretation; such hand poses should be avoided when designing a haptic interface. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.5 http://doi.ieeecomputersociety.org/10.1109/TOH.2013.2 To design effective vibrotactile actuators or display algorithms, an understanding of the perceived intensity (strength) of their vibrations is essential. This paper aims to build a robust model for the perceived intensities of mobile device vibrations, which can be used by engineers and application designers. We carried out two psychophysical experiments using absolute magnitude estimation procedures. In Exp. I, we investigated the effects of vibration direction and device weight on the perceived intensity of mobile device vibrations. Only the vibration direction was found to be a statistically significant factor, showing the highest perceived intensities along the height direction of a mobile device. In Exp. II, we measured the perceived intensities of vibrations with various amplitudes and frequencies along the three vibration directions. Then, for each direction, a psychophysical magnitude function and equal sensation contours were constructed based on Stevens’ power law. In addition, we found a monotonic relationship between the physical power of vibration absorbed by the hand and the resulting perceived intensity. This suggests that the former, which is greatly easier to acquire in practice, is a reliable predictor of the latter. We expect that the results of this study can provide knowledge about the perceptual strength of vibrations that engineers and applications developers will find useful. http://doi.ieeecomputersociety.org/10.1109/TOH.2013.2 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.73 A teleoperation system consists of a teleoperator, a human operator, and a remote environment. Conditions involving system and controller parameters that ensure the teleoperator passivity can serve as control design guidelines to attain maximum teleoperation transparency while maintaining system stability. In this paper, sufficient conditions for teleoperator passivity are derived for when position error based controllers are implemented in discrete-time. This new analysis is necessary because discretization causes energy leaks and does not necessarily preserve the passivity of the system. The proposed criterion for sampled-data teleoperator passivity imposes lower bounds on the teleoperator's robots dampings, an upper bound on the sampling time, and bounds on the control gains. The criterion is verified through simulations and experiments. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.73 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.74 Various psychophysical methods have been used to study human haptic perception, although the selection of a particular method is often based on convention, rather than an analysis of which technique is optimal for the question being addressed. In this review, classical psychophysical techniques used to measure sensory thresholds are described as well as more modern methods such as adaptive procedures and those associated with signal detection theory. Details are provided as to how these techniques should be implemented to measure absolute and difference thresholds and factors that influence subjects' responses are noted. In addition to the methods used to measure sensory thresholds, the techniques available for measuring the perception of suprathreshold stimuli are presented. These scaling methods are reviewed in the context of the various stimulus and response biases that influence how subjects respond to stimuli. The importance of understanding the factors that influence perceptual processing is highlighted throughout the review with reference to experimental studies of haptic perception. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.74 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.64 Tactile sensing and force reflection have been the subject of considerable research for tumor localization in soft-tissue palpation. The work presented in this paper investigates the relevance of force feedback during tactile sensing for tumor localization using an experimental setup close to one that could be applied for real Robotics-Assisted Minimally Invasive Surgery (RAMIS). The setup is a teleoperated (master-slave) system facilitated with a state-of-the-art minimally invasive probe with a rigidly mounted tactile sensor at the tip and an externally mounted force sensor at the base of the probe. The objective is to capture the tactile information and measure the interaction forces between the probe and tissue during palpation and to explore how they can be integrated to improve the performance of tumor localization. To quantitatively explore the effect of force feedback on tactile sensing tumor localization, several experiments were conducted by human subjects to locate artificial tumors embedded in the ex vivo bovine livers. The results show that using tactile sensing in a force-controlled environment can realize on average 57% decrease in the maximum force and 55% decrease in the average force applied to tissue while increasing the tumor detection accuracy by up to 50% compared to the case of using tactile feedback alone. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.64 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.72 This study investigates how controllability of force is influenced by concurrent vibrotactile feedback that is generated proportionally to the applied force. Three different models to provide tactile feedback are introduced: amplitude- and frequency modulation and granular synthesis. Then, an experiment investigating the effect of the feedback models on force control is reported. The tactile feedback conditions were compared to each other and to a condition with no feedback in a force repetition and a force hold tasks. In the force repetition task, all the feedback conditions yielded significantly better accuracy compared to no feedback condition. In the force hold task, there was no difference in the accuracy between the conditions including the no feedback condition. The results suggest that dynamic vibrotactile feedback assists the force control in force repetition tasks. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.72 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.71 Development of tactile displays to enhance palpation of lumps during robot-assisted minimally invasive surgery (RMIS) is challenging due to size and weight constraints, motivating a pneumatic actuation strategy. This work describes the quantitative and psychophysical assessment of an air-jet tactile display that creates a lump percept by directing pressurized air through an aperture onto the finger. The air pressure and aperture size are meant to control the hardness and size, respectively, of the perceived lump. Jet impingement pressure and flow rate were measured by capacitive tactile sensors and mass flow meters at varying aperture sizes and pressures. The air-jet pressure profile width evolves as jet theory predicts and is largely independent of supply pressure (and therefore jet exit velocity). The method of constant stimuli was used to determine the just noticeable differences (JNDs) for the air pressure and aperture size. Qualitative results indicate that subjects perceive the stimulus as a "lump-like" shape. Pressure JNDs ranged from 19.6-24.4 kPag and aperture size JNDs ranged from 0.50-0.66 mm. No significant correlation exists between the supply pressure and changes in perceived lump size. However, pressure JNDs show significant (p < 0.001) inverse correlation with aperture size, with improved discrimination at larger apertures, where a greater finger-pad area is stimulated. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.71 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.70 Haptic technology has been widely employed in applications ranging from teleoperation and medical simulation to art and design, including entertainment, flight simulation and virtual reality. Today there is a growing interest among researchers in integrating haptic feedback into audiovisual systems. A new medium emerges from this effort: haptic-audiovisual (HAV) content. This paper presents the techniques, formalisms and key results pertinent to this medium. We first review the three main stages of the HAV workflow: the production, distribution and rendering of haptic effects. We then highlight the pressing necessity for evaluation techniques in this context and discuss the key challenges in the field. By building on existing technologies and tackling the specific challenges of the enhancement of audiovisual experience with haptics, we believe the field presents exciting research perspectives whose financial and societal stakes are significant. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.70 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.63 Six-degree-of-freedom (6-DOF) haptic rendering for fine manipulation in narrow space is a challenging topic because of frequent constraint changes caused by small tool movement and the requirement to preserve the feel of fine-features of objects. In this paper, we introduce a configuration-based constrained optimization method for solving this rendering problem. We represent an object using a hierarchy of spheres, i.e., a sphere-tree, which allows faster detection of multiple contacts/collisions among objects than polygonal mesh and facilitates contact constraint formulation. Given a moving graphic tool as the avatar of the haptic tool in the virtual environment, we compute its quasi-static motion by solving a configuration-based optimization. The constraints in the 6-D configuration space (C-space) of the graphic tool is obtained and updated through on-line mapping of the non-penetration constraint between the spheres of the graphic tool and those of the other objects in the three dimensional physical space, based on the result of collision detection. This problem is further modeled as a quadratic programming optimization and solved by the classic active-set methods. Our algorithm has been implemented and interfaced with a 6-DOF Phantom Premium 3.0. The experimental results show both the high efficiency and stability of haptic rendering by our method for complex scenarios. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.63 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.55 Haptic technology, providing force cues and creating a programmable interface, can assist users in more accurately using an interface. This paper investigates haptic assistance in combination with auditory feedback instead of visual feedback. A user test is carried out in which participants select fundamental frequencies from a continuous range to play brief musical melodies. Two control conditions are compared with two detent-based haptic assistance conditions. The detents gently guide the users toward locations of equal tempered fundamental frequencies. Results from the user test confirm improved accuracy brought about by the detents. It is further helpful to provide regulation of the strength of haptic assistance in real time, allowing the user to remain always in control. This concept motivated the force-sensitive detent condition, which enables the user to adjust the strength of the haptic assistance in real time by changing the downward force applied to the haptic device. The work implies that users of graphical user interfaces could similarly benefit from force-sensitive detents and more generally real-time regulation of the strength of haptic assistance. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.55 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.54 We developed a compact Tactile Imaging (TI) system to guide the clinician or the self-user for non-invasive detection of breast tumors. Our system measures the force distribution based on the difference in stiffness between a palpated object and an abnormality within. The average force resolution, force range, and the spatial resolution of the device are 0.02 N, 0-4 N and 2.8 mm, respectively. In order to evaluate the performance of the proposed TI system, compression experiments were performed to measure the sensitivity and specificity of the system in detecting tumor-like inclusions embedded in tissue-like cylindrical silicon samples. Based on the experiments performed with 11 inclusions, having 2 different sizes and 2 different stiffnesses located at 3 different depths, our TI system showed an average sensitivity of 90.8 ± 8.1% and an average specificity of 89.8 ± 12.7%. Finally, manual palpation experiments were performed with 12 human subjects on the same silicon samples and the results were compared to that of the TI system. The performance of the TI system was significantly better than that of the human subjects in detecting deep inclusions while the human subjects performed slightly better in detecting shallow inclusions close to the contact surface. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.54 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.52 In this paper, we propose an approach to the control of linear teleoperation systems under time delays. Unlike traditional delay-robust control systems which guarantee passive communication channel through the transmission of wave variables, the new approach uses the concept of absolute stability for the physically expressive Lawrence's four-channel structure for transmitting the standard power variables, i.e. force and position. By incorporating kinesthetic performance requirements, we derive an absolutely stable four-channel controller that is transparent when time delay is negligible. Experimentally, the study evaluates and compares the performance of the proposed controller with that of a benchmark wave variable-based controller. The results indicate contact stability for large delays, a lack of position drift, and improved position and force tracking in both the free motion and rigid contact regimes for small delays. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.52 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.38 This paper proposes a directional torque feedback technique for mobile devices that creates brief unbalanced torque by suddenly starting to rotate a stationary flywheel and then stopping it soon after. The experimental results show that a twisting sensation was induced effectively with angular velocity profiles that include sudden starts. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.38 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.31 Two-interval two-alternative forced-choice discrimination experiments were conducted separately for sinusoidal and triangular textured surface gratings from which amplitude (i.e., height) discrimination thresholds were estimated. Participants (group sizes: n = 4 to 7) explored one of these texture types either by fingertip on real gratings (Finger-real), by stylus on real gratings (Stylus-real), or by stylus on virtual gratings (Stylus-virtual). The real gratings were fabricated from stainless steel by an electrical discharge machining process while the virtual gratings were rendered via a programmable force-feedback device. All gratings had a 2.5-mm spatial period. On each trial, participants compared test gratings with 55, 60, 65, or 70 μm amplitudes against a 50-μm reference. The results indicate that discrimination thresholds did not differ significantly between sinusoidal and triangular gratings. With sinusoidal and triangular data combined, the average (mean ± standard error) for the Stylus-real threshold (2.5 ± 0.2 μm) was significantly smaller (p < 0.01) than that for the Stylus-virtual condition (4.9 ± 0.2 μm). Differences between the Finger-real threshold (3.8 ± 0.2 μm) and those from the other two conditions were not statistically significant. Further studies are needed to better understand the differences in perceptual cues resulting from interactions with real and virtual gratings. http://doi.ieeecomputersociety.org/10.1109/TOH.2012.31 http://doi.ieeecomputersociety.org/10.1109/TOH.2012.19 In teleoperation, haptic feedback allows the human operator to touch the remote environment. Yet it is only partially understood to what extent the quality of haptic feedback contributes to human-in-the-loop task performance. This paper presents a human factors experiment in which teleoperated task performance and control effort are assessed for a typical (dis-)assembly tasks in a hard-to-hard environment, well-known to the operator. Subjects are provided with four levels of haptic feedback quality: no haptic feedback, low-frequency haptic feedback, combined low- and high-frequency haptic feedback and the best possible - a natural spectrum of haptic feedback in a direct-controlled equivalent of the task. Four generalized fundamental subtasks are identified, namely i) Free-Space Movement Tasks, ii) Contact Transition Task, iii) Constrained Translational Tasks and iv) Constrained Rotational Task. The results show that overall task performance and control effort are primarily improved by providing low-frequency haptic feedback (specifically by improvements in Constrained Translational and Constrained Rotational Tasks), while further improvement the haptic feedback quality yields only http://doi.ieeecomputersociety.org/10.1109/TOH.2012.19 http://www.computer.org/portal/site/toh/ IEEE Transactions on Haptics http://www.computer.org/portal/site/toh/