Haptic Contact Research Articles

Touching Images: Photography, medical imaging and the incarnation of light

The late twentieth century development in digital imaging technologies has led to claims that we are in the midst of both a transformation of representation and a reconfiguration of vision. This essay considers the ways in which photography's structural reliance on light has shaped our understanding of representation, and the ways in which that understanding might be extended and reshaped through the digital imaging technologies of ultrasound, MRI and CT. Operating through a sonic and haptic mediation of the body, these imaging technologies cannot be contained within the realm of light, vision and visible reality. As such, they bring into play an alternative reading of the ways in which reality may be imaged — an alternative which calls upon touch as much as sight in determining the referentiality and indexicality of an image and its relationship to the real. The indexicality of photography is premised on light's “magical transfer” of the real into representation. Harboured within this understanding of the photograph's relation to the referent is a desire for a material, haptic contact with that reality. Is light the only possible agent of the “magical transfer” between reality and representation? Or can indexicality and referentiality be refounded within a tactile relation, based not on light's transcendent illumination, but on the physical contact between the world and its image?

Somatosensory driven interpersonal synchrony during rhythmic sway

Spontaneous synchrony emerges between individuals performing together rhythmic activities while communicating by means of sensory feedback. In this study, we examined the nature of interpersonal synchrony mediated by light fingertip contact when individuals sway rhythmically in the sagittal plane. The effect of traditional dance expertise on interpersonal synchrony was investigated. Sixty participants (30 dancers, 30 novices) formed three types of couples (10 expert couples, 10 novice couples, 10 mixed couples) and performed a rhythmical sway task (40s) that was either self or metronome paced (frequency: 0.25Hz). Cross spectral analysis of the center of pressure (CoP) displacement signals revealed that during self-paced sway fingertip contact evoked a decrease of the dominant sway frequency difference between partners, an increase in the coherence between the sway signals and a concentration of relative phase angles towards the in-phase (0°–20°) region. In metronome paced sway however, only expert dancers were able to benefit from haptic contact to further improve interpersonal synchrony. These findings suggest that haptic contact can stabilize the spontaneous coordination dynamics of two persons performing rhythmic sway together. The strength of the emerged synchrony depends on the individuals’ expertise to integrate tactile and auditory information about sway.

Hand shaping using hapsis resembles visually guided hand shaping

The reach-to-grasp movement is composed of a number of movement elements including hand transport, hand shaping, and grasping. These movement elements are featured in grasping when it is guided by vision, when it is guided by haptic input from the non-reaching hand or other body parts, and when it is guided by off-line perceptual (remembered) knowledge. An unanswered question is how is the reach-to-grasp movement achieved when all information about the target must be acquired by the grasping hand? The answer to this question was obtained by asking participants to reach for three randomly presented food items that varied in size: an orange slice, a small round donut ball, or a blueberry. In order to constrain the grasping pattern, participants were asked to pick up an item with the intention of placing it in the mouth. Thus, in the unsighted condition, participants did not know which item they were reaching for until they made haptic contact with it. Hand transport, shaping, and grasping were examined using frame-by-frame video analysis and linear kinematics. These measures showed that in unsighted reaching, hand transport first served to establish haptic contact between either the second or third digit and the target. After haptic identification of the target, the hand and/or grasping digits adjusted their trajectory, reshaped, and reoriented for grasping. A comparison of haptically guided grasping and visually guided grasping indicated that the two were very similar. This similarity is discussed in relation to contemporary ideas concerning the neural mechanisms that guide hand use.

Adaptive stiffness estimation for compliant robotic manipulation using stochastic disturbance models

To achieve haptic telepresence and proper contact behaviour, the control action of a robotic manipulator must be designed with respect to contact parameters. Unfortunately, it is hard to know these parameters exactly in unknown or partly known environments. In this case, contact instability and poor dynamic accuracy can arise due to the presence of modelling errors in the control design. To overcome these problems, online estimation of the relevant contact parameters can be performed, with corresponding adaptation of control laws. This article presents an algorithm for online stiffness estimation for compliant robotic manipulation based on the extended state-space representation of the system and force signals. No position or velocity measurements are required. The algorithm, supported by theoretical analysis, uses offline data concerning several stiffness mismatch scenarios and, through a least square error analysis, computes an estimate of the stiffness value. Simulation results are presented, with fast and accurate estimation even in the presence of noise, highlighting the merits of the method.

The impact of light fingertip touch on haptic cortical processing during a standing balance task

Availability of fingertip touch onto a stable surface reduces body sway for subjects standing with eyes closed. This is largely associated with sensory feedback from the fingertip when mechanical load is limited. Here, it is possible that the central nervous system facilitates cortical sensory processing to augment feedback to control upright stance. To test this, we compared cortical sensory excitability between tasks with and without light finger touch while standing. Subjects stood in tandem on a force plate with eyes closed while lightly touching a stable surface with the index finger. This was, in two different studies, compared to: (1) no haptic contact or (2) light touch on an object not referenced to balance. Throughout testing, the median nerve was stimulated and electroencephalography was used to measure somatosensory evoked potentials (SEPs). As expected, availability of stable light touch reduced medial-lateral COP sway. Peak amplitudes for SEP components revealed reduced P100 (48%), but increased P50 (31%), N140 (80%), and P200 (20%) during stable touch versus no touch. The modulation of P50 and N140 was no longer present when comparing stable to control (touch), which suggested that attending to touch on either surface, regardless of stability reference, accounted for these changes. Conversely, P200 was increased (19%) when touching the stable surface. Our data show SEP modulation during a standing balance task related to hand contact. Facilitation of P200 in particular may indicate task-specific regulation of the cortical representation of fingertip afferent input when it is relevant to providing stable cues for static balance control.

Combining Contact Models With Perceptual Data Reduction for Efficient Haptic Data Communication in Networked VEs

In cooperative networked virtual environments, haptic rendering enables joint haptic interaction with virtual objects and, thus, shared touch experiences among multiple users. In case of an underlying packet-based communication network (e.g., the Internet), minimizing the end-to-end delay, with the goal of preventing instability of the involved control loops, results in high packet rates. Previously proposed perceptual data reduction approaches address this challenge and satisfy the strict delay constraints. However, significantly increased packet rates still occur during contact events. We present a novel event-based coding scheme based on a distributed haptic-rendering framework that integrates model-based distributed haptic rendering with perceptual data reduction. We also present a comprehensive haptic contact model for signals with multiple degrees of freedom. Furthermore, we show that the integration of event-triggered force transient models from event-based haptics into our local contact model is instrumental for generating convincing haptic feedback. Psychophysical experiments reveal that the approach presented herein allows us to push the data reduction performance beyond what is normally achievable by perceptual data reduction schemes alone while significantly improving the quality of haptic contact feedback.

Human Factors in Haptic Contact of Pliable Surfaces

This paper considers relevant human factors to interact with a pliable body in a teleoperation surgical environment. Our aim is to identify the human capabilities, in terms of penetration depth and responsiveness, in a task of pliable surface contact, where surgeons are required to adopt a specific behavior immediately after the contact. A psychophysical experiment is conducted using virtual surfaces rendered with two different force-feedback devices. The results show that impact velocity affects performance in surface contact perception. In a second experiment where different postures are used, we examine whether the previous results hold for the particular ergonomic configuration employed. The results show that posture affects performance especially in expert users. Our findings underscore the importance of understanding the interplay of human perceptual parameters in the surgical teleoperation framework.

The Stiles–Crawford effect of the first kind and the full-field electroretinogram (ERG)

Electroretinography (ERG) can be used to quantify the directional sensitivity of the retina to incident stimuli. We have developed a rapid technique to derive a global measurement of the Stiles–Crawford effect of the first kind (SCE I) using the full-field flash ERG using artificial pupils. Three opaque haptic contact lenses were designed to direct stimuli along the photoreceptor axes with a single central aperture or obliquely through double apertures of equivalent area (4.5 mm2) separated horizontally by 3.0 and by 5.5 mm. ERGs recorded using an HK loop electrode to a series of white flashes ranging from sub-threshold to 2000 cd s/m2 were presented in a ganzfeld bowl. Sensitivity was compared using the luminance:response functions for the ERG a-wave and b-wave amplitudes. The b-waves of the ERGs showed a shift in sensitivity between the central mid and outer apertures requiring stronger flashes for threshold, semi-saturation and saturation for the more peripheral apertures. The ERG a-waves did not demonstrate a significant sensitivity shift. Small apertures are suitable for generating oblique stimulation of photoreceptors for ERG recordings. The method described gives a global measure of the SCE I that may be useful when time or cooperation is limited. Apertures reduce the available light and positioning is less precise than with Maxwellian view systems. Thus, physical apertures in contact lenses may not be suitable for positioning stimuli on small retinal regions.

The Island: Work, Tourism and the Biopolitical

This paper reflects on the biopolitical implications for tourists and workers of enclavic tourist resorts. I contend that the concept of ‘the Island’ captures very well the metaphorical, but also the functional proximity between many tourist ‘islands’ and other past and contemporary forms of encampment and seclusion. I will thus explore the relationship between the idea of ‘the Island’ in tourism and the production and reproduction of what are supposedly docile bodies and minds. I will suggest that in the island-like resort, the docile bodies of the tourist and of the worker come into contact and interact in very particular ways, marked by the distinct nature of the context that hosts their encounter. The space of that encounter is a very interesting haptic contact zone in the production of the tourist experience, a zone where ideas about life, class, habitus, gender, sexuality, the body, etc. are negotiated and where the very concept of work is questioned and may take unpredictable expressions. This is a space that the capitalist production of leisure tries to manage, tame and possibly reduce to a minimum but, paradoxically, this is also a space without which the endless re-enactment of the tourist performance in that place (a re-enactment that constitutes the very foundation of any tourist resort) would simply be impossible.

Haptic two-finger contact with textiles

Real-time cloth simulation involves many computational challenges to be solved, particularly in the context of haptic applications, where high frame rates are necessary for obtaining a satisfying experience. In this paper, we present an interactive cloth simulation system that offers a compromise between a realistic physics-based simulation of fabrics and a haptic application meeting high requirements in terms of computation speed. Our system allows the user to interact with the fabric using two fingers. The required performance of the system is achieved by introducing an intermediate layer responsible for the simulation of the small part of the surface being in contact with the fingers. Additionally we separate the possible contact situations into different cases, each being individually handled by a specialised contact algorithm.

Auditory contact cues improve performance when grasping augmented and virtual objects with a tool

This experiment investigated the roles of haptic and auditory contact information for the control and execution of reaching to grasp augmented (physical plus graphic) and virtual (graphic only) objects of different sizes using a tool. Haptic contact information was present when grasping augmented objects only. In half of the trials, auditory cues were provided when contact was made between the tip of the tool and the target object. Transport and grasp kinematics, as well as on spatial errors at the end of the movement were examined. Providing auditory cues at contact led to faster movements; moreover, when haptic information was not available (when grasping virtual objects), auditory cues improved spatial accuracy. Movement times increased as the object size decreased for the augmented objects, when haptic information was available, and also for the virtual objects when auditory contact cues were provided, thus following Fitts' law. However, movement times were similar for all object sizes when neither haptic nor auditory contact information was provided. These results emphasize the importance of contact information when grasping with a tool, and the benefits of auditory contact cues for improving performance.

Elasticity modeling and estimation for haptic contact using a DD‐robot

PurposeTo propose a new haptic modeling and contact analysis algorithm (modified long element method (MLEM)) to efficiently model deformation, to estimate elasticity, and to provide the characterization of contact with deformable objects, which is important in teleoperation and haptic system.Design/methodology/approachWidely used finite element method for haptic rendering and visualization of deformable objects has limitations in real‐time applications because of its massive calculations and the absence of physical modeling. Using long elements method (LEM), the authors propose the MLEM which is capable of real‐time deformation rendering and elasticity estimation with reliable physical modeling. The authors applied MLEM to a simple haptic system composed of the three‐link SNU DD‐robot and a force‐feedback joystick.FindingsAn efficient, real‐time haptic modeling for deformable objects has been developed. MLEM provides physically accurate deformation modeling in real time, and estimates the elasticity of objects at contact, providing contact characterization based on material properties.Research limitations/implicationsMLEM has been applied to SNU DD‐robot, and displayed real‐time haptic visualization in 2D space. It can be applied easily to any haptic system with force sensors, and may have impacts on the applications of teleoperation, robot‐aided surgery and human‐robot interaction.Originality/valueThis paper offers a practical tool to the engineers in the haptics field for visualization of deformation. The efficient algorithm of MLEM can be placed on any haptic system with force sensors, and will improve the efficiency and accuracy of teleoperated haptic systems with real‐time analysis of haptic contact.

Shrinking Upper and Lower Eyelid Skin with a Novel Radiofrequency Tip

Many subjects wish to have tightening of eyelid skin but are reluctant to undergo aesthetic blepharoplasty surgery. We wanted to perform a small pilot study to test the efficacy and safety of a 0.25-cm(2) monopolar radiofrequency tip in a prospective noncomparative study as a novel nonsurgical method to safely tighten upper and lower eyelid skin in subjects of differing ethnicity and sex. Twenty adult subjects were enrolled in this prospective pilot study. All received symmetrical monopolar radiofrequency treatments in multiple passes to the pretarsal, preseptal, and lateral orbital skin. All subjects wore a protective plastic haptic contact lens to protect their vision during the radiofrequency treatment. (Haptic contact lenses fit over the entire anterior surface of the globe from superior to inferior and medial to lateral fornix. The purpose of using such a large contact lens was to protect the globe itself from radiofrequency energy.) Standardized color digital photography with eyes both open and closed was taken on each visit. Treatment efficacy was evaluated by both the expert observer and the subject at each visit. RESULTS At 6-month follow-up, according to the expert observer, 26 upper lids (87%) showed 25% or more tightening. Twenty lower lids (67%) showed 25% or more tightening. Two subjects (3.33%) had 51% to 75% upper lid tightening at 6 months. There were no adverse events beyond one subject with minimal corneal epithelial punctate defects on the treatment day. These resolved over several hours. The use of this new tip was shown to be safe. Effectiveness at shrinking eyelid skin was at best mild to moderate.

Grasping at ‘thin air’: multimodal contact cues for reaching and grasping

Two experiments investigated the effects of haptic, auditory and graphic contact cues on reaching to grasp augmented objects (physical and graphic) and virtual objects (graphic only) of various sizes. In Experiment 1, auditory contact cues were presented either to enhance or to replace natural haptic contact cues in grasping. In Experiment 2, graphic contact cues were presented alone or in combination with auditory cues, and were provided either to enhance or to replace haptic contact information. Visual information of the hand was not available. Experiment 1 showed that enhancing haptic contact information with redundant auditory cues (augmented object) led to faster movement times than haptic cues alone. When haptic information was not available (virtual object), it could be replaced to some extent by auditory contact cues. In Experiment 2 movement times were fastest when both auditory and graphic cues were provided, and slowest when no contact cues were provided. Further, movement times were scaled to target width when reaching to grasp augmented objects, thus following Fitts' law. In contrast, movement times showed a less pronounced decrease with increasing object size for virtual objects. However, even in the absence of haptic information, movement times showed a more pronounced scaling to object size when auditory contact cues were provided. These results emphasize the importance of contact information, especially haptic and auditory information, for planning and control of reaching and grasping.

Cutting on Triangle Mesh: Local Model-Based Haptic Display for Dental Preparation Surgery Simulation

A new method to realize stable and realistic cutting simulation using an impedance display haptic device and microcomputer is presented in this paper. Material removal or cutting simulation is a critical task in dental preparation surgery simulation. In this paper, a piecewise contact force model is proposed to approximately describe the cutting process. Challenging issues of minimizing the difference between the cutting simulation and haptic contact simulation are analyzed. The proposed contact-based simulation method is developed for a one-dimensional cutting task and can be expanded to three-dimensional cases. Local model-based multirate simulation cutting architecture is proposed and force control of the haptic device is decoupled from the cutting simulation loop, which can both ensure high fidelity of dynamical simulation as well as maintain stability of the haptic device. The cutting operation is realized using spherical and cylindrical shaped tools. An experiment based on the Phantom desktop proves that fidelity in one-dimensional cutting can be realized and stability in three-dimensional cutting can be ensured using the force-filtering method.

Stabilization and Destabilization of Perception-Action Patterns Influence the Self-Organized Recruitment of Degrees of Freedom.

The recruitment of an additional biomechanical degree of freedom in a unimanual rhythmic task was explored. Subjects were asked to synchronize adduction or abduction of their right index finger with a metronome, the frequency of which was increased systematically. In addition, haptic contact on or off the metronome beat was provided. Results showed that the pattern exhibiting the highest intrinsic stability recruited the vertical plane more than did the less stable one. Moreover, presence and location of haptic contact modulated coordination stability and therefore induced changes in the recruitment of the vertical plane. Thus, a trade-off was shown between coordination stability on the horizontal plane and recruitment of the vertical one. These findings suggest that recruitment of degrees of freedom is governed by general principles of coordination dynamics.

Haptic information stabilizes and destabilizes coordination dynamics.

Goal-directed, coordinated movements in humans emerge from a variety of constraints that range from 'high-level' cognitive strategies based on perception of the task to 'low-level' neuromuscular-skeletal factors such as differential contributions to coordination from flexor and extensor muscles. There has been a tendency in the literature to dichotomize these sources of constraint, favouring one or the other rather than recognizing and understanding their mutual interplay. In this experiment, subjects were required to coordinate rhythmic flexion and extension movements with an auditory metronome, the rate of which was systematically increased. When subjects started in extension on the beat of the metronome, there was a small tendency to switch to flexion at higher rates, but not vice versa. When subjects were asked to contact a physical stop, the location of which was either coincident with or counterphase to the auditory stimulus, two effects occurred. When haptic contact was coincident with sound, coordination was stabilized for both flexion and extension. When haptic contact was counterphase to the metronome, coordination was actually destabilized, with transitions occurring from both extension to flexion on the beat and from flexion to extension on the beat. These results reveal the complementary nature of strategic and neuromuscular factors in sensorimotor coordination. They also suggest the presence of a multimodal neural integration process - which is parametrizable by rate and context - in which intentional movement, touch and sound are bound into a single, coherent unit.

Fingertip contact suppresses the destabilizing influence of leg muscle vibration.

Touch of the hand with a stationary surface at nonmechanically supportive force levels (<1 N) greatly attenuates postural sway during quiet stance. We predicted such haptic contact would also suppress the postural destabilization caused by vibrating the right peroneus brevis and longus muscles of subjects standing heel-to-toe with eyes closed. In experiment 1, ten subjects were tested under four conditions: no-vibration, no-touch; no-vibration, touch; vibration, no-touch; and vibration, touch. A hand-held physiotherapy vibrator (120 Hz) was applied approximately 5 cm above the malleolous to stimulate the peroneus longus and brevis tendons. Touch conditions involved contact of the right index finger with a laterally positioned surface (<1 N of force) at waist height. Vibration in the absence of finger contact greatly increased the mean sway amplitude of the center of pressure and of the head relative to the no-vibration, no-touch control condition (P < 0.001). The touch, no-vibration and touch-vibration conditions were not significantly different (P > 0.05) from each other and both had significantly less mean sway amplitude of head and of center of pressure than the other conditions (P < 0.01). In experiment 2, eight subjects stood heel-to-toe under touch and no-touch conditions involving 40-s duration trials of peroneus tendon vibration at different duty cycles: 1-, 2-, 3-, and 4-s ON and OFF periods. The vibrator was attached to the subject's leg and remotely activated. In the no-touch conditions, subjects showed periodic postural disruptions contingent on the duty cycle and mirror image rebounds with the offset of vibration. In the touch conditions, subjects were much less disrupted and showed compensations occurring within 500 ms of vibration onset and mirror image rebounds with vibration offset. Subjects were able to suppress almost completely the destabilizing influence of the vibration in the 3- and 4-s duty cycle trials. These experiments show that haptic contact of the hand with a stable surface can suppress abnormal proprioceptive and motor signals in leg muscles.

Is anterior chamber lens implantation after intracapsular cataract extraction safe in rural black patients in Africa? A pilot study in KwaZulu-Natal, South Africa.

There are an estimated 16 million people blind from cataract world-wide. In many areas the routine operation is intracapsular cataract extraction (ICCE). The role of modern anterior chamber (AC) intraocular lenses (IOLs) is being explored, and they have been shown to be safe and successful in Asia. Are they equally safe in rural black African populations? One hundred black patients aged 50 years and over who attended Edendale Hospital were enrolled in a pilot study of insertion of AC IOLs after ICCE. They were followed up for 6 months. With financial remuneration, the follow-up rate at 8 weeks increased from the usual 30% to 72%. At 6 months, 67% of eyes achieved a correlated visual acuity of 6/18 or better. Thirty per cent had persistent uveitis, 16% had peripheral anterior synechiae beyond the points of haptic contact, and 5% had an intraocular pressure greater than 21 mmHg. A randomised trial comparing ICCE with AC IOL and extracapsular cataract extraction with posterior chamber IOL is probably not justified at this time in this population. However, there may be wide variations in the reaction of the eyes of different African ethnic groups to IOLs. In view of the successful use of AC IOLs in Asian eyes, further pilot studies of AC IOLs may be warranted in other parts of Africa where ICCE is the routine procedure.

Experimental study of different intraocular lens designs implanted in the bag after capsulorhexis

Objective: To analyze experimentally in cadaver eyes several models of commercially available posterior chamber intraocular lenses (IOLs) to determine their stability, fixation, and behavior in the capsular bag in relation to their overall size, optic diameter, shape, material, and haptic configuration.Setting: Eye Bank and Department of Ophthalmology, University General Hospital of Alicante, Spain.Methods: Thirty-three IOLs of different sizes, shapes, and designs, divided in two series and five groups, were implanted successively in 31 cadaver eyes. All the proceedings were videotaped, and measurements were made on the television screen with the picture static. Main outcome measures were the diameters of the lens, the empty capsular bag, and the capsulorhexis; capsular distension by the IOL haptics; extent of haptic arc of contact with the capsular equator; and IOL mobility in the bag.Results: The stability of and stretching caused by the IOLs varied greatly depending on their overall size, haptic flexibility, and the extent of the arc of haptic contact with the capsular equator. Lenses between 13.5 and 14.0 mm had good stability but stretched the capsule excessively. The J-loop haptic configuration produced a spindle-shaped bag deformity that might come in contact with the ciliary processes in the physiologic eye. Among IOLs designed for in-the-bag implantation after capsulorhexis, the two smaller than 12.0 mm were unstable, permitting excessive mobility in the capsular bag. Except for IOLs with a 5.0 mm optic, all 12.0 mm IOLs had reasonable stability, little or no mobility within the capsular bag, and good short-term centering. Lenses with a broad angulation at the haptic-optic junction, to about 90 degrees, achieved the largest arc of contact with the equator and behaved as lenses with larger optics. The Pharmacia 808 performed best.Conclusion: After capsulorhexis and extracapsular cataract extraction, 12.0 mm, poly(methyl methacrylate), one-piece IOLs with modified C-shaped loops, 90 degree angulation at the haptic-optic junction, and an optic diameter between 6.0 and 6.5 mm performed best in the capsular bag.