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A novel tactile softness display for minimally invasive surgery
Abstract
The use of Minimally Invasive Surgery (MIS) in various types of surgical procedures has increased significantly in recent years. However, its scope is limited due mainly to the fact that this procedure does not currently provide tactile feedback without which the surgeon can neither feel nor palpate tissue. In this paper, we describe a new tactile display that reproduces these missing constituent properties of the tissue directly to the surgeon. The softness of different objects is regenerated based on the mechanical properties of those objects and fingertip pulp. The force–displacement non-linear behavior of several different materials is simulated using force feedback and a Proportional-Integral-Derivative (PID) controller for the linear actuator. Experimental tests show that the proposed tactile display can closely regenerate the feeling of softness for different objects by rendering the force–displacement curve to the surgeon’s hand.
... The work described in this paper has been partially supported by the STIFF-FLOP project grant from the European Communities Seventh Framework Programme under grant agreement 287728. 1 instrument and the patient internal body is essential to allow a surgeon to safely and efficiently carry out the operation. Numerous force and tactile sensors have been developed for measuring the interaction forces applied to the instrument's tip [7]- [15]. Current-based sensing method has been used to measure force in MIS [16]. ...
This paper presents a fiber-optic-based contact sensor for the body contact sensing of a flexible manipulator. The developed sensor is capable of providing both the magnitude of applied force and the contact location. A mathematical model of this sensor is developed. A sensor prototype is created and tested to illustrate the sensing principle of the proposed sensor. Sensor design and the fabrication procedure are presented. The developed sensor has a simple structure and is capable of working in high-electromagnetic interference environments. The sensor’s performance has been experimentally evaluated. Test results show that the proposed sensor has an accuracy of 83.50% for the force magnitude measurement and an average error of 10.23° for the contact angle measurement.
Purpose
– The purpose of this paper is to introduce a new tactile array sensor into the medical field to enhance current robotic minimally invasive surgery (RMIS) procedures that are still limited in scope and versatility. In this paper, a novel idea is proposed in which a tactile sensor array can measure rate of displacement in addition to force and displacement of any viscoelastic material during the course of a single touch. To verify this new array sensor, several experiments were conducted on a diversity of tissues from which it was concluded that this newly developed sensory offers definite and significant enhancements.
Design/methodology/approach
– The proposed array sensor is capable of extracting force, displacement and displacement rate in the course of a single touch on tissues. Several experiments have been conducted on different tissues and the array sensor to verify the concept and to verify the output of the sensor.
Findings
– It is shown that this new generation of sensors are required to distinguish the difference in hardness degrees of materials with viscoelastic behavior.
Originality/value
– In this paper, a new generation of tactile sensors is proposed that is capable of measuring indentation time in addition to force and displacement. This idea is completely unique and has not been submitted to any conference or journal.
In our former papers, we have proposed "Multi Primitive Tactile Stimulation" method for realizing a whole-palm-covering tactile display. Preparing two different kinds of tactile stimuli (primitives) within a unit area, we have realized various tactile sensations from a sharp-pin to a smooth surface by combination of them. In this paper, we propose another method for preparing multiple degree-of-freedom (DOF) tactile stimulations. That is temporal primitives. It is expected that we can activate two kinds of superficial mechanoreceptors selectively if we control the temporal pressure patterns of the stimuli precisely, using the difference of the frequency characteristics among the tactile mechanoreceptor types. We realized stable temporal stimuli by "Suction Pressure Stimulation" which was also proposed in the previous papers, and confirmed that we could realize multi DOF stimuli by the temporal primitives.
Detection of hard inclusions within soft tissue in robotic assisted minimally invasive surgery (MIS), also referred to as laparoscopic surgery, is of great importance, both in clinical and surgical applications. In clinical applications, surgeons need to detect and precisely identify the location and size of all growths, whether cancerous or benign, that are present within surrounding tissue in order to assess the extent and nature of any future treatment plan. In surgical applications, when any solid matter is being removed, it is important to avoid accidental injury to surrounding tissues and blood vessels since, were this to occur, it could then necessitate the need to resort to open surgery. The present study is aimed at developing a three-dimensional tactile display that provides palpation capability to any surgeon performing robotic assisted MIS. The information is collected from two force sensor/pressure matrices and processed with a new algorithm and graphi-cally rendered. Consequently, the surgeon can determine the presence, location, and the size of any hidden superficial tumor/artery by grasping the target tissue in a quasi-dynamic way. The developed algorithm is presented, and the results for various configu-rations of embedded tumor/arteries inside the tissue are compared with those of the finite element analysis.
A tactile display system is described which can produce ‘tac- tile movies’, that is, rapid sequences of tactile images refreshed at a rate of 700 Hz. The display uses an array of one hundred laterally moving skin contactors designed to create a time-varying programmable,strain field at the skin surface. The density of the array is of one contactor per millimeter square, resulting in a device with high spatial and temporal resolution. The paper describes the construction method,and the drive electronics. It also reports informally on initial test patterns and on the resulting tactile sensations.
This paper describes a wearable haptic display with small dimensions and low weight, that allows to simulate on the fingertip a wide range of contact forces. The device consists of two platforms: a static one, fixed on the back side of the finger, which supports three actuators and the mechanical instrumented system, and a mobile one, which interacts directly with the fingertip. The platforms are connected by three cables whose lengths and strains are regulated by the motors. Three force sensors, placed on the mobile platform, measure the actual forces applied to the finger. This work summarizes the design of the proposed display and presents a numerical model analysing the relationship between the forces registered at the fingertip and the platform's orientation and displacement. In order to validate the device an experiment of curvature discrimination has been carried out.
The design of a tactile shape display intended for Minimally Invasive Surgery (MIS) is pre-sented. It consists of 32 micro brushless motors arranged in a 4-by-8 configuration, and the total size is 27 mm × 20 mm × 18 mm. The main restrictive design parameter is the size of the display as it will be attached to a laparoscopic grasper. Modularity is also crucial since it might be desirable to do experiments with other pins or effectors attached to the actuators. The tactel (TACTile ELement) spacing is 2.7 mm with a tac-tel diameter of maximum 2.6 mm. The display is tested with respect to pin force, positioning accu-racy, bandwidth and stiffness. Results show that the tactels can provide an active force of 0.4-0.5 N at a frequency of close to 0.7 Hz at full excur-sion (3 mm). The testing also show that position-ing accuracy is approximately 40 µm, while the stiffness is close to 50 N/mm.
Tactile displays are used to provide tactile feedback in telemanipulation or virtual reality. One aim in fur-ther developments is the miniaturisation of tactile dis-plays for incorporation into data-and/or force feed-back gloves. This enables the combination of tactile and kinesthetic feedback. A main disadvantage of many tac-tile displays with a large number of stimulator elements is their large volume and structural rigidity. We pro-pose the use of electrostatic actuators with elastic di-electrics as tactile stimulator. Those actuators are flexible and show a high energy density. This paper describes the construction and function of such actua-tors. A possible actuator arrangement in a tactile dis-play and the controlling method is presented. Further the processing technology is shown.
It was previously suggested that the mechanical properties of the fingertip could be characterized by elasticity from dc to about 100Hz and by viscosity above this frequency. Using a specifically designed high mobility probe, we accurately measured the impedance of the fingertips of seven participants under a variety of conditions relevant to purposeful touch. Direct measurements vindicated previous indirect observations. We also characterized the dependency of the fingertip impedance upon normal load, orientation, and time.
We present a multi-finger 2-D haptic display device to potentially provide the opportunity of parallel processing of coarse haptic information, with the intended benefit of improving performance in 2-D haptic object recognition. Combined with a novel method for producing “texture” image representations, we found that multiple contacts does improve performance compared to a single contact in terms of both time and accuracy. However, we also found no benefit for additional contacts with only raised-line representations of objects. This suggests that the use of texture made a key contribution in improving performance from one to multiple fingers.
Virtual reality simulators seek to immerse users in realistic interactive environments. However, at present, while several provide kinesthetic feedback, most lack tactile feedback. Current means of tactile feedback do not generate enough force to the digits, deliver a non-intuitive sense of feedback and are too large or heavy to be used in hand-worn configurations. The tactile feedback system developed herein uses electroactive polymers to create light touch and vibratory sensation to the fingertips, and DC motors to constrict the distal digit. In essence, when current is passed through the electroactive polymer in the shape of a cantilever (7 mm long by 19 mm wide), it bends on its long axis, providing a forces of 25 mN. Vibratory feedback is created by varying input voltage with a sinusoidal waveform. To generate fingertip constriction, two DC motors cinch a wire attached to a rubber thimble. These hardware components are controlled by a computer running X3D software, an ISO standard for representing 3D graphics, which affords a virtual environment for the tracking of one's hand. Upon contact with a virtual object, the actuators generate prescribed forces or vibrations. With this setup, a series of human-subjects experiments will be conducted whereby the task is to contact and differentiate virtual spheres of differing stiffness. Experiment 1 will test the electroactive polymers to determine the threshold for recognizing light touch, Experiment 2 will test vibrational discrimination, and Experiment 3 will test the ability of the user to differentiate constriction forces.
The dynamic response of the fingerpad plays an important role in the tactile sensory response and precision manipulation, as well as in ergonomic design. This paper investigates the dynamic lumped element response of the human fingerpad in vivo to a compressive load. A flat probe indented the fingerpad at a constant velocity, then held a constant position. The resulting force (0-2 N) increased rapidly with indentation then relaxed during the hold phase. A quasilinear viscoelastic model successfully explained the experimental data. The instantaneous elastic response increased exponentially with position, and the reduced relaxation function included three decaying exponentials (with time constants of approximately 4 ms, 70 ms, and 1.4 s) plus a constant. The model was confirmed with data from sinusoidal displacement trajectories.
In this paper, we propose a large-area tactile display by controlling suction pressure. This research is based on our discovery of tactile illusion that pulling a skin through a hole with air suction causes a sensation as if something like a stick is pushing the skin. This illusion implies that our mechanoreceptors are insensitive to the sign of stress (negative or positive), i.e. we detect not stress directly but strain energy. There are two key concepts to realize our tactile display. One is the tactile illusion mentioned above and the other is "multi primitive tactile stimulation." We explain our approach to produce various tactile sensations from a sharp edge to a plane surface with a simple structure of display device based on air pressure control, and report the experimental results.
In this paper we propose a new method for displaying touch sensation by controlling suction pressure. We discovered a tactile illusion that pulling skin through a hole with suction pressure causes a feeling as if a stick is pushing the skin. This illusion is considered to be caused by the insensitivity of our mechanoreceptors to signs of stress (negative or positive) that are sensitive to the strain energy. Our tactile display is based on the key concept of this illusion and that of "multi-primitive stimulation." We show that a simple structure of a sparse stimulator array produces various tactile sensations from a sharp edge to a smooth plane surface.
A new concept for the realization of a refreshable Braille cell is presented. An electrothermally controlled microactuator that exploits the hydraulic pressure due to the volumetric expansion of melted paraffin wax is described. The paraffin wax is contained within a bulk micromachined silicon container. The container is sealed using an elastic diaphragm of silicone rubber. The container is heated using gold microheaters located on an underlying glass substrate. All the layers used to make up the containers are bonded together using an overglaze paste. The complete 3 ,times, 2 dot Braille cell has air gaps between containers, to prevent unwanted actuation by means of heat leakage from adjacent containers. The prototype Braille cell measures 7 ,times, 8.5 ,times, 2 mm and its raised dots are held in equilibrium by pulsed actuation voltages. To maintain a dot height at 50% of its maximum, a duty factor of more than 0.8 was found, with an average power of 0.30 W ( Hz). The total actuation time for a dot on an up/down cycle was sim50 s. The dot height increases with an increasing duty factor with a fixed PRF, and increases with decreasing PRF with a fixed duty factor. A stable maximum dot height was achieved by reducing the cooling time. hfillhbox[1381]
Many applications in teleoperation and virtual reality call for the implementation of e#ective means of displaying to the human operator information on the softness and other mechanical properties of objects being touched. The ability of humans to detect softness of di#erent objects by tactual exploration is intimately relatedtoboth kinesthetic and cutaneous perception, and haptic displays should be designed so as to address such multimodal perceptual channel. Unfortunately, accurate detection and replication of cutaneous information in all its details appears to be a formidable task for current technology, causing most of today's haptic displays to merely address the kinesthetic part of haptic information. In this paper we investigate the possibility of surrogating detailed tactile information for softness discrimination, with information on the rate of spread of the contact areabetween the #nger and the specimen as the contact force increases. Devices for implementing such a perceptu...
Haptic interfaces that include tactile shape displays must correlate small-scale shape information with finger position. High temporal bandwidth of the display actuators is required to provide realistic sensation during rapid finger motions. To characterize finger speeds during surgical palpation, we performed an experiment where subjects used the tip of the index finger to search for 4 mm lumps embedded in flat rubber models. The models were 15 to 25 mm thick soft silicone rubber with mechanical characteristics approximating lung or breast tissue. Average fingertip speed while in contact with the rubber was approximately 38±16 mm/s (mean ± standard deviation), and average maximum speed was 90±31 mm/s. While moving between contact intervals, the average finger tip speed was approximately 76±18mm/s, and average maximum speed was 146±37 mm/s. There were no significant speed differences between experienced surgeons and subjects who had no medical training. The results indicate that a 30 Hz bandwidth is necessary for shape displays used in haptic interfaces for lump localization in surgery. A shape display design meeting this specification is also presented.
Recent developments in the field of robotics, smart materials, micro actuators and mechatronics have opened a new frontier for innovation and development in millimeter scale actuators for use in medical robotics. In this paper a novel design idea for developing a millimeter scale actuator is presented for actuating the end effector of a robot performing minimally invasive surgery (MIS). This actuator is designed by combining D.C motor and shape memory alloy (SMA) actuator in series. The designed actuator is 5mm in diameter and 40mm in length and is used to actuate 10mm long needle driver jaws, while generating a force of 15N and a gripping force of 5.5N.
The thirteen chapters of this book are introduced by a preface and followed by five appendices. The main chapter headings are: motion and forces at a point of contact; line loading of an elastic half-space; point loading of an elastic half-space; normal contact of elastic solids - Hertz theory; non-Hertzian normal contact of elastic bodies; normal contact of inelastic solids; tangential loading and sliding contact; rolling contact of elastic bodies; rolling contact of inelastic bodies; calendering and lubrication; dynamic effects and impact; thermoelastic contact; and rough surfaces. (C.J.A.)
We demonstrate display of artificial tactile feeling using large displacement MEMS actuator arrays. Each actuator consists of a piezoelectric actuator and hydraulic displacement amplification mechanism (HDAM) that encapsulates incompressible liquid in a micro-chamber with two flexible polymer membranes. In prior work, we experimentally applied the actuator arrays to an efficient vibrational Braille code display. In this paper, we investigated the artificial tactile feeling projected onto the fingertip in contact with the display while the actuation pattern was controlled both temporally and spatially. The arrays could successfully display “rough” and “smooth” tactile feeling distinctly when the vibrational frequency of the individual actuator and switching time of the lines of actuators were controlled.
This paper presents a thermopneumatic actuator to build large tactile displays as well as a smart activation circuitry to study and improve its performance. Since the main drawback of large tactile screens in the market is their cost, this proposal is intended to reduce the price because of the simplicity of the actuator and the potential low cost assembling. A small display with 4 x 4 taxels and 2.54mm of distance between centres has been built to show the viability of the proposal. Furthermore, a smart actuation strategy is implemented where the heater element (a diode) is also used as sensor in a feedback control loop that improves the dynamic response. Such strategy consists in sensing the voltage drop in the diode to measure its temperature, thus it can be heated up quickly without being destroyed because power supply is decreased once the target temperature is reached. We have measured rise times around 2 seconds and fall times around 4 seconds, while the maximum force and stroke are above 10grams (0.1N) and 1mm respectively. The obtained results are good, specially to implement a large tactile screen. Power consumption is high, but it could be lower if latching mechanisms are used to keep the taxel active without power supply.
Haptic perception and display of softness are important parts of the haptic display technique, which is currently the frontier in teleoperation systems and human-computer interaction. A portable softness display device is developed for this study. The device can quickly change the displayed stiffness by controlling the deformable length of the elastic element. Ideally, when a human operator's fingertip presses the device, one will feel as if he/she actually pressed a soft object. A virtual softness display system based on the softness display device is also developed, which mainly includes geometric modeling of virtual objects, collision detection, and deformation modeling. The system can provide visual and haptic feedback, synchronously allowing operators to manipulate objects in the virtual environment. The Gauss deformation model is proposed to simulate the deformation of virtual objects. Based on the feature of haptic interaction, an extensible software architecture based on the Model-View-Controller pattern and plugin is given. Based on the simulation results, the softness display system is found to be efficient and credible.
Robot-ass: vied surgery is characterized by a total loss of haptic feedback requiring surgeons to rely solely on vi vim! cues A pneumatically driven balloon actuator array suitable for mounting on robotic surgical mower controls has been developed to provide haptic feedback to surgeons The actuation at rays consist of a molded polydimethylsiloxane substrate with cylindrical channels and a spin coated silicone that forms the array of balloons Preliminary human perceptual studies have demonstrated that balloon diameters greater than 1 0 mm may provide effective haptic feedback to the index finger Before conducting further human perceptual teas refinements of the fabrication process and performance data of the actuator are required Balloons with diameters ranging between 1 5 mm and 4 0 nun were fabricated with film thicknesses of 200 mu m and 300 mu m Inflation pressure versus balloon deflection tests and cyclic actuation tests were performed to characterize each balloon type The results demonstrated a high linearity between inflation pressure and balloon deflection (R-2 > 0 93) and negligible hysteresis effects between inflation and deflation over 100 000 cycles The studies indicated that 300 mu m films are optimal for 3 0 mm and 4 0 mm diameter balloons and 200 mu m films are optimal for 1 5 mm 2 0 mm and 2 5 mm diameter balloons Due to its compact size and high performance the described pneumatic actuator can provide sensory input that is otherwise unavailable during robotic surgery [DOI 10.1115/1.2996593]
Purpose
Robotic surgery is limited by the lack of haptic feedback to the surgeon. The addition of tactile information may enable surgeons to feel tissue characteristics, appropriately tension sutures, and identify pathologic conditions. Tactile feedback may also enable expansion of minimally invasive surgery to other surgical procedures and decrease the learning curve associated with robotic surgery. This paper aims to explore a system to provide tactile feedback.
Design/methodology/approach
A pneumatic balloon‐based system has been developed to provide tactile feedback to the fingers of the surgeon during robotic surgery. The system features a polydimethyl siloxane actuator with a thin‐film silicone balloon membrane and a compact pneumatic control system. The 1.0 × 1.8 × 0.4 cm actuators designed for the da Vinci system feature a 3 × 2 array of 3 mm inflatable balloons.
Findings
The low‐profile pneumatic system and actuator have been mounted directly onto the da Vinci surgical system. Human perceptual tests have indicated that pneumatic balloon‐based tactile input is an effective means to provide tactile information to the fingers of the surgeon.
Research limitations/implications
Application of a complete tactile feedback system is limited by current force sensing technologies.
Originality/value
The actuators have been designed such that they can be mounted directly onto the hand controls of the da Vinci robotic system, and are scalable such that they can be applied to various robotic applications.
A spatial electrocutaneous display for sensory sub stitution is being designed. The display will be used to feed back sen sory signals from trans- femoral prostheses to amputees. The aim is to impro ve their walking perform- ance. Two experiments have been performed to optimise the display parameters for dynamic, cyclic signals, which are common during walking. From these experiments it became clear that healthy subjects w ere capable of discerning ar- tificially generated disturbed knee angle patterns from undisturbed patterns. This shows that the electrocutaneous display has the cap ability to feed back signals from a transfemoral prosthesis.
Tangible interface is a newly defined concept, which provides effective and seamless interaction between a human as a subjective existence and a cyberspace as an objective existence. As one of the tangible interface, tactile interface is essential for many exploration and manipulation tasks in the tangible space. In this paper, we suggest a design of an integrated tactile sensor-display system that enables both of tactile sensing and display with kinesthetic force, pressure distribution, and vibration. A human-like tactile sensing system with PVDF strips and a display system with bimorph actuators have been developed and integrated in the tangible space. In the demonstration scenario of haptic navigation in the tangible space, the developed tactile sensing to display system is successfully experimented
Manual palpation of tissue and organs during a surgical procedure provides clinicians with valuable information for diagnosis and surgical planning. In present-day robotassisted minimally invasive surgery systems, lack of perceptible haptic feedback makes it challenging to detect a tumor in an organ or a calcified artery in heart tissue. This study presents an automated tissue property estimation method and a real-time graphical overlay that allow an operator to discriminate hard and soft tissues. We first evaluate experimentally the properties of an artificial tissue and compare seven possible mathematical tissue models. Self-validation as well as cross-validation confirm that the Hunt-Crossley model best describes the experimentally observed phantom tissue properties and is suitable for our purpose. Second, we present the development of a system in which the phantom tissue is palpated using a teleoperated surgical robot, and the stiffness of the Hunt-Crossly model is estimated in real time by recursive least squares. A real-time visual overlay representing tissue stiffness is created using a hue-saturation-luminance representation on a semi-transparent disc at the tissue surface. Hue depicts the stiffness at a palpated point and saturation is calculated based on distance from the point. A simple interpolation technique creates a continuous stiffness color map. In an experiment, the graphical overlay successfully shows the location of an artificial calcified artery hidden in phantom tissue.
This paper investigates the use of elastomeric dielectric materials with compliant electrodes as a means of actuation. When a voltage is applied to the electrodes, the elastomeric films expand in area and compresses in thickness. The strain response to applied electric fields was measured for a variety of elastomers. A nonlinear, high-strain, Mooney–Rivlin model was used to determine the expected strain response for a given applied field pressure. Comparing this analytical result to with experimentally measured strains, we determined that the electrostatic forces between the free charges on the electrodes are responsible for the observed response. Silicone polymers have produced the best combination of high strain and energy density, with thickness strains up to 41% and elastic energy densities up to 0.2 MJ/m3. Response times of 2 ms have been experimentally measured. This paper also reports recent progress in making highly compliant electrodes. We have shown, for example, that gold traces fabricated in a zig-zag pattern on silicone retain their conductivity when stretched up to 80%, compared to 1–5% when fabricated as a uniform two-dimensional electrodelayer. Optimal loading of dielectric elastomers can have a significant impact on performance: and the paper describes techniques which that can increase output up to a factor of 5 compared to neutral loading conditions. Lastly, the paper briefly discusses the performance of various actuators that use dielectric elastomer materials. The technology appears to be well-suited to a variety of small-scale actuator applications.
This paper presents a thermopneumatic micropump fabricated by micromachining. The micropump consists of a p+ silicon diaphragm, a micro heater and a pair of nozzle/diffuser. The thermopneumatic actuator of this paper is characterized by a corrugated diaphragm, which is more flexible than a flat one. The diaphragm is driven by the air cavity pressure variation caused by the ohmic heating and the natural cooling. If the diaphragm of the micropump vibrates, the fluid flows in one direction through a nozzle/diffuser. The experimental result illustrates that the deflection of the corrugated diaphragm is about three times that of the flat one. The maximum flow rate of the micropump with the corrugated diaphragm is about 14 μl/min at 4 Hz when the input voltage and duty ratio are 8 V and 40%, respectively.
This paper presents a 2-DOF controlled softness display and its application to a tactile tele-presentation system. It has been reported that softness feelings can be displayed by reproducing contact area, or contact width, on a fingertip. Several softness displays based on the contact area control have been reported in past studies, but all of them had only one degree-of-freedom (DOF) for their contact area control. Resultantly, the reproduced contact area was symmetric, which could only produce uniform surface feelings. In some practical deformable surfaces, however, the contact conditions are not uniform over fingertip surfaces; for example, if there is a small lump beneath a soft deformable surface, resultant contact area can become asymmetric. To reproduce such asymmetric contact conditions, a softness display should have more controlled DOFs. This paper reports our trial to realize a multi-DOF controlled softness display. As a first step, this particular paper describes a 2-DOF controlled display. The display has two DC motors which independently control both sides of the contact area. Resultant asymmetric contact area can facilitate, e.g., discrimination of lump location in soft deformable surfaces. The display was integrated into a tactile tele-presentation system together with a contact width sensor, which measures asymmetric contact condition. Using the tele-presentation system, discriminations of lump location are demonstrated.
We have constructed a tactile shape display which can be used to convey small-scale shapes in teleoperation and virtual environments. A line of 10 pins spaced 2 mm on center are each actuated with a shape memory alloy wire. A combination of careful mechanical design and liquid cooling allows a simple proportional controller with constant current feed-forward to achieve 40 Hz bandwidth. To quantify the value of increased bandwidth, an experiment involving a prototypical search task has been conducted using the display. A digital filter limited the frequency response of the display to three cutoff frequencies: 1, 5 and 30 Hz. Subjects were able to complete the search more than six times as quickly with 30 Hz bandwidth than with 1 Hz.
2nd Ed Bibliogr. na konci kapitol
This paper describes the design and performance of a prototype remote palpation instrument with tactile feedback for laparoscopic surgery. Psychophysical experiments aiming at comparing palpation with and without tactile feedback are also described. The remote palpation instrument is designed to provide the surgeon with information about size and contact force distribution. The instrument consists of a tactile sensor and a tactile display, both of which are small enough to fit onto a conventional laparoscopic grasper. Static tests showed that hardness, size and shape were successfully rendered by the tactile display. Dynamic testing showed that the bandwidth is suboptimal, but at low frequencies the output from the remote palpation instrument is useful. For the psychophysical testing, nine subjects were asked to discriminate hardness and size of objects with and without tactile feedback. The results indicated that the instrument with tactile feedback can be helpful for hardness discrimination, although the difference between the two instruments was not statistically significant for neither hardness nor size. Comparisons with earlier, similar experiments showed that the quality of the grasper and size of the forceps affected the results, indicating that there is a great potential for improving laparoscopic graspers in general.
The experiments reported here are part of an investigation of the spatial neural mechanisms underlying tactile sensation. The first step in such an investigation must be a broad, accurate characterization of tactile spatial discrimination. More particularly, the investigation requires specification of the discrimination behavior that depends strictly on spatial neural mechanisms. The results of four experimental designs are reported here. No single experiment, taken in isolation, provides a basis for ascertaining which aspects of spatial discrimination are based on spatial information in the neural discharge patterns rather than on intensive or temporal information. Taken together, the results of the four experiments provide a consistent basis for examining the neural mechanisms underlying tactile spatial discrimination. Experiment I, a modified two-point limen test, showed that subjects could reliably discriminate between one and two 0.5-mm-diameter points even when there was no separation between the two points. The result demonstrated a high level of spatial resolution but discrimination may have been based on any of a number of neural codes. The contact area and the overall dimensions of the two stimuli being compared were different and, therefore, discrimination may have been based on a difference in number of active fibers, in total number of impulses, or in the spatial patterning of the afferent discharge evoked by the single- and double-point stimuli. In experiment II an attempt was made to eliminate contact area and overall dimensions as variables between the stimuli being discriminated. Subjects were required to discriminate between stimuli with an without gaps. The overall dimensions of the stimuli were constant and much larger than the gaps. The d' function was constant for small gaps and then rose steeply (d' = 0.86 for gaps, g, ranging from 0.2 to 0.6 mm; d' = 4.25 (g - 0.55) for g > 0.7 mm). d' is defined here as the separation between two unit-normal (σ2 = 1.0) distributions that would, with an appropriate discrimination boundary, produce discrimination judgments with the same probabilities as those observed experimentally. Gap size at threshold (p = 0.75) equaled 0.87 mm. Some ambiguity arises in the interpretation of these results. Neurophysiological experiments have shown that one major mechanoreceptive fiber class is very sensitive to edges. Subjects may have discriminated between stimuli on the basis of the increased discharge evoked by edges when gaps were present. Experiment III was designed to hold overall size, contact area, and edge content constant between stimuli. Subjects were required to discriminate between square-wave gratings (equal gaps and bars) that were oriented along or across the axis of the finger. Subjects could not discriminate grating orientation until the gaps exceeded 0.5 mm (d' = 0.0 for gaps < 0.5 mm). For gaps greater than 0.5 mm (spatial periods > 1.0 mm) the d' function rose steeply with a slope of 4.0 SD units per millimeter gap size (d' = 4.0 (g - 0.5)). Gap size at threshold (p = 0.75) equaled 0.84 mm. Neurophysiological studies have shown that some primary afferents are sensitive to grating orientation. Subjects may have discriminated the stimuli on the basis of differences in discharge rate evoked by the gratings with different orientations. The results of each of the preceding experimental designs provided simple measures of spatial resolution but they allowed the possibility that they were based on nonspatial neural cues. Experiment IV, a tactile letter-recognition task, yielded results that could not readily be explained by any nonspatial neural mechanisms. Subjects' performance was as good or better than predictions based on the results of experiments II and III, indicating that the results of those experiments were not based on some simple nonspatial mechanism. On the basis of information measures, 3.0-mm letters were discriminated at a level midway between chance and perfect discrimination behavior.
The fingertip pulp modulates the force transmitted to the underlying musculoskeletal system during finger contact on external bodies. A model of the fingertip pulp is needed to represent the transmission of forces to the tendons, muscles, and bone during these contacts. In this study, a structural model of the in vivo human fingertip was developed that incorporates both the material inhomogeneity and geometry. Study objectives were to determine (1) if this fingertip model can predict the force-displacement and force contact area responses of the in vivo human fingertip during contact with a flat, rigid surface, and (2) if the stresses and strains predicted by this model are consistent with the tactile sensing functionality of the in vivo human fingertip. The in vivo fingertip pulp was modeled as an inflated, ellipsoidal membrane, containing an incompressible fluid, that is quasi-statically compressed against a flat, frictionless surface. The membrane was assigned properties of skin (Veronda and Westmann, 1970) and when inflated, possessed dimensions approximating those of a human fingertip. Finite deformation was allowed. The model was validated by the pulp force-displacement relationship obtained by Serina et al. (1997) and by measurements of the contact area when the fingertip was pressed against a rigid surface with contact forces between 0.25 and 7.0 N. Model predictions represent the experimental data sufficiently well, suggesting that geometry, inhomogeneous material structure, and initial skin tension appear to represent the nonlinear response of the in vivo human fingertip pulp under compression. The predicted response of the fingertip pulp is consistent with its functionality as a tactile sensor.
A new electrostatic tactile display is proposed to realize compact tactile display devices that can be incorporated with virtual reality systems. The tactile display of this study consists of a thin conductive film slider with stator electrodes that excite electrostatic forces. Users of the device experience tactile texture sensations by moving the slider with their fingers. The display operates by applying two-phase cyclic voltage patterns to the electrodes. The display is incorporated into a tactile telepresentation system to realize explorations of remote surface textures with real-time tactile feedback. In the system, a PVDF tactile sensor and a DSP controller automatically generate voltage patterns to present surface texture sensations through the tactile display. A sensor, in synchronization with finger motion on the tactile display, scans a texture sample and outputs information about the sample surface. The information is processed by a DSP and fed back to the tactile display in real time. The tactile telepresentation system was evaluated in texture discrimination tests and demonstrated a 79 percent correct answer ratio. A transparent electrostatic tactile display is also reported in which the tactile display is combined with an LCD to realize a visual-tactile integrated display system.
In this paper, multi-fingered tactile display modules are proposed. Each tactile display module is comprised of a 4 times 4 piezoelectric ultrasonic actuator array with a spatial resolution of 1.5 mm and a temporal resolution of 20 Hz. The objective of this research is to build a small and lightweight tactile display system so that the system including the display modules and complete controller parts is wearable by a user. It was found that various types of texture information can be generated using a static indentation or through the vibration of each pin. Three tactile display modules were utilized for interaction with a 3D virtual environment. As the developed tactile display modules consume less power and are connected wirelessly to a host PC, the system is applicable to various types of texture representation systems.
This paper presents a new concept of low-cost, high-resolution, lightweight, compact and highly-portable tactile display. The prototype consists of an array of 8 × 8 upward/downward independent moveable pins based on shape memory alloy (SMA) technology. Each actuator is capable of developing a 320 mN pull force at 1.5 Hz bandwidth by using simple forced-air convection. The proposed concept allows the development of 60 g weight tactile devices of compact dimensions easily carried in the user's hand. SMA active element, tactile actuator and tactile display are presented and discussed.
As a major human sensory function, the implementation of the tactile sensation for the human-machine interface has been one of the core research interests for long time. In this paper, an innovative tactile display device based on the soft actuator technology is presented. Using electroactive polymer for the construction of the tactile display device, it can provide stimulation on the human skin without any additional electromechanical transmission. Softness and flexibility of the device structure, ease of fabrication, possibility for miniaturization, and low cost for mass production are the representative benefits of the presented device. Especially, the device application is open to many different purposes since the flexible structure offers the excellent adaptability to any contour of the human body. To prove its feasibility, a wearable device that can fit to the distal part of the human finger is presented and its performance is evaluated, experimentally.
Many surgical procedures are now performed using the techniques of
minimally invasive surgery (MIS), in which unnecessary trauma is limited
by reducing the size of incisions to less than about 1 cm or by using
catheters or endoscopes threaded through vessels, the gastrointestinal
tract, or other tubular structures. Micromechatronic technologies have
great potential to allow access to regions now inaccessible, or to
enhance the surgeon's abilities in applications where current minimally
invasive techniques do not permit the full range of human dexterity and
perception. Key needs and applications in MIS are identified, and
relevant technologies, methods, and systems issues in mechatronics are
discussed. The authors' millirobotic system for MIS of the abdomen is
used as an example
In this paper, we quantify several perceptual capabilities of the human tactile system needed for teletaction. We develop a model of a teletaction system based on predicted subsurface strain. Psychophysics experiments measure the amplitude resolution of the human tactile system, the effects of shear stress on grating orientation discrimination, and the effects of viscoelasticity (creep and relaxation) on tactile perception for static touch. The results are used to determine teletaction system design parameters. We find that 10% amplitude resolution is sufficient for a teletaction system with a 2 mm elastic layer and 2 mm tactor spacing. 1 INTRODUCTION Information about texture, local compliance, and local shape is important in applications such as telesurgery or handling of fragile objects in telerobotics. Figure 1 shows a general configuration of a teletaction system. A teletaction system is defined to be a system that senses tactile information from the environment and displays tha...
Haptic interfaces that include tactile shape displays must correlate small-scale shape information with finger position. High temporal bandwidth of the display actuators is required to provide realistic sensation during rapid finger motions. To characterize finger speeds during surgical palpation, we performed an experiment where subjects used the tip of the index finger to search for 4 mm lumps embedded in flat rubber models. The models were 15 to 25 mm thick soft silicone rubber with mechanical characteristics approximating lung or breast tissue. Average fingertip speed while in contact with the rubber was approximately 3816 mm/s (mean standard deviation), and average maximum speed was 9031 mm/s. While moving between contact intervals, the average finger tip speed was approximately 7618 mm/s, average maximum speed was 14637 mm/s. There were no significant speed differences between experienced surgeons and subjects who had no medical training. The results indicate that ...
Philadelphia: Saunders
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Towards the optimisation of spatial electrocutaneous display parameters for sensory substitution. In: 7th Annual conf. of the international functional electrical stimulation society
- Vos Wk Buma Dg
- Veltink
- Ph
Vos WK, Buma DG, Veltink PH. Towards the optimisation of spatial electrocutaneous display parameters for sensory substitution. In: 7th Annual conf. of the international functional electrical stimulation society, Ljubljana, Slovenia; 2004.
The material properties of the elastomers for the second experiment
- Fig
Fig. 27. The material properties of the elastomers for the second experiment.