Tactile Actuator Research Articles

AIREAL

AIREAL is a novel haptic technology that delivers effective and expressive tactile sensations in free air, without requiring the user to wear a physical device. Combined with interactive computers graphics, AIREAL enables users to feel virtual 3D objects, experience free air textures and receive haptic feedback on gestures performed in free space. AIREAL relies on air vortex generation directed by an actuated flexible nozzle to provide effective tactile feedback with a 75 degrees field of view, and within an 8.5cm resolution at 1 meter. AIREAL is a scalable, inexpensive and practical free air haptic technology that can be used in a broad range of applications, including gaming, mobile applications, and gesture interaction among many others. This paper reports the details of the AIREAL design and control, experimental evaluations of the device's performance, as well as an exploration of the application space of free air haptic displays. Although we used vortices, we believe that the results reported are generalizable and will inform the design of haptic displays based on alternative principles of free air tactile actuation.

Systems to support relaxation by using tactile, acoustic and visual stimuli

There are indications that well-chosen tactile and acoustic stimuli may help people to relax. Technology can be used to apply such stimuli. In this paper, we present a technology platform that we have designed to support research into multi-sensory stimulation systems for the purpose of relaxation. One particular component in this platform is a novel tactile actuator array, the Touch Blanket. Besides technology, we also present the 'Breathe with the Ocean' concept, which defines a system to help a user to relax by providing an immersive experience. In this concept, an illusion of being present at an ocean shore is achieved by using multi-sensory stimuli. We describe three system prototypes, each implement the concept and also use our technology platform. All three systems provide tactile, acoustic and visual stimuli to a user. Results of the initial evaluation of these prototypes are presented.

Microfabrication of Three-Axis Tactile Feedback Actuator for Robot-Assisted Surgery

In this paper, we propose and demonstrate a three-axis tactile feedback actuator using pneumatic balloons for human perception applications such as robot-assisted surgery systems. A tactile actuator is composed of a center structure having four balloons, sidewalls with one lateral balloon on each sidewall, and a bottom structure supporting the center structure. We fabricated the proposed device using flexible poly(dimethylsiloxane) and hard polyurethane with final dimensions of 18 ×18 ×18 mm3. The four balloons on the center structure produce normal tactile display during pneumatic-pressure-assisted inflation. The lateral movement of the center structure driven by sidewall balloons generates a shear tactile display on fingertips. The center deflections of the circular and rectangular balloons were calculated and measured experimentally.

A Refreshable Braille Cell Based on Pneumatic Microbubble Actuators

A refreshable Braille cell as a tactile display prototype has been developed based on a 2 x 3 pneumatic microbubble actuator array and an array of commercial valves. The microbubble actuator acting as a Braille dot consists of a parylene corrugated diaphragm and an overcoated elastomer layer. Polyurethane (PU) and polydimethylsiloxane (PDMS) elastomer-based Braille cells were fabricated and compared in terms of their displacement-pressure characteristics, force-displacement characteristics, dynamic response, and hysteresis of elastic deformation. Both PU- and PDMS-based pneumatic Braille cells demonstrate satisfactory properties against the static and vibrational tactile display requirements. The displacement of the PU-based Braille dot is 0.56 mm at a 0.2-Hz operating frequency, and the generated force is 66 mN at a 100-kPa applied pressure. The strong hysteresis observed in microbubble actuators made with PU elastomer is resolved by the use of PDMS elastomer. The refreshable Braille cell was also designed to meet the criteria of lightness and compactness to permit portable operation. The design is scalable with respect to the number of tactile actuators while maintaining fabrication simplicity.

Batch fabrication of optical actuators using nanotube–elastomer composites towards refreshable Braille displays

This paper reports an opto-actuable device fabricated using micro-machined silicon moulds. The actuating component of the device is made from a composite material containing carbon nanotubes (CNTs) embedded in a liquid crystal elastomer (LCE) matrix. We demonstrate the fabrication of a patterned LCE-CNT film by a combination of mechanical stretching and thermal cross-linking. The resulting poly-domain LCE-CNT film contains ‘blister-shaped’ mono-domain regions, which reversibly change their shape under light irradiation and hence can be used as dynamic Braille dots. We demonstrate that blisters with diameters of 1.0 and 1.5 mm, and wall thickness 300 µm, will mechanically contract under irradiation by a laser diode with optical power up to 60 mW. The magnitude of this contraction was up to 40 µm, which is more than 10% of their height in the ‘rest’ state. The stabilization time of the material is less than 6 s for both actuation and recovery. We also carried out preliminary tests on the repeatability of this photo-actuation process, observing no material or performance degradation. This manufacturing approach establishes a starting point for the design and fabrication of wide-area tactile actuators, which are promising candidates for the development of new Braille reading applications for the visually impaired.

A new tactile stimulator using a planar coil type actuator

In this study, we developed a new tactile stimulator using a planar coil type actuator. The newly developed system consists of three units, which are control unit, drive unit, and planar coil type actuator. The control unit of this simulator controls stimulation frequency, intensity, time, and channel. The drive unit amplifies the stimulation signal to drive the actuator. Mechanical tactile stimulation of vibration and normal indentation can be made by modulating the planar coil type actuator and the arrangement of the permanent magnet. Even though the developed stimulator is simple, it has a wide frequency range of 0–400Hz with 40 levels, and intensity modulation of 256 levels. Stimulation intensity does not change due to frequency change. The transient response time is about 100μs. The advantages of this actuator also include safety and usefulness. The performance of this tactile actuator was tested using a dummy finger made of silicone rubber.

Traffic flow harmonization in expressway merging

Steering a vehicle is a task increasingly challenging the driver in terms of mental resources. Reasons for this include the increasing volume of road traffic and a rising quantity of road signs, traffic lights, and other distractions at the roadside (such as billboards), to name a few. The application of Advanced Driver Assistance Systems, in particular if taking advantage of Ambient Intelligence (AmI) technology, can help to increase the perceptivity of a driver, leading as a direct consequence to more relaxed mental stress of the same. One situation where we see potential in the application of such a system are merging areas on the expressway where two or more varying traffic streams converge into a single one. In order to reduce cognitive liabilities (in this work expressed as panic or anger), drivers are exposed to while merging, we have developed two behavioral rules. The first ("increased range of perception") enables drivers to change early upstream into a spare lane, allowing the merging traffic to join into mainline traffic at reduced conflicts, the second ("inter-car distance management" in the broader area of merging) provide drivers with recommendations of when and how to change lanes at the best. From a technical point of view, the "VibraSeat" a in-house developed car seat with integrated tactile actuators, is used for delivering information about perception range and inter-car distances to the driver in a way that does not stress his/her mental capabilities. To figure out possible improvements in its application in real traffic and at a meaningful scale, cellular automaton---based simulation of a specific section of Madrid expressway M30 was performed. Results from the data-driven simulation experiments on the true to scale model indicate that AmI technology has the potential to increase road throughput or average driving speed and furthermore to decrease the panic of drivers while merging into an upper (the main) lane.

Design of a Tactile Instrument to Measure Human Roughness Perception in a Virtual Environment

This paper presents the experimental results on the measurement of human texture perception in virtual environments. The experiment is conducted with a haptic tactile instrument that provides sensations of rough textures directly to the fingertip of the users. It consists of a brush and a DC motor. The brush rubs directly against the user's fingertip. Simulated texture is felt through an aperture on the tactile actuator where the users place their fingertip. The speed and direction of the brush are varied to control the roughness of the virtual surface and to determine the effect of either variable on perceived roughness. The actuator is designed to be attached to an existing force feedback device in order to create an interface that can provide force feedback and tactile feedback. The magnitudes of rough textures are measured through this device by comparing the virtual textures with real sandpapers of different grit sizes. Through human factor testing, it is found that the direction of rotation has negligible effects on roughness perception when the time gap between two consecutive stimuli is as large as 10 s. However, when the time gap is reduced to 0.5 s, the effects of direction become prominent. The just noticeable difference with respect to speed is found to decrease as the base speed of the brush increases. The results also show that although each subject's perception of roughness is biased using various sandpapers, the measured data is divided between two trends. One group of users perceives the roughness to increase with increasing speed, while the other group perceives the roughness to decrease.

A solid hydraulically amplified piezoelectric microvalve

We report a piezoelectrically driven and hydraulically amplified axial polymer microvalve. The microvalve is normally open and is assembled primarily with stereolithographically fabricated polymer components. An incompressible elastomer is used as a solid hydraulic medium to convert the small axial displacement of a piezoelectric actuator into a large valve head stroke while maintaining a large blocking force. Also, the axial design of the microvalve enables densely packed valve arrays. One application of this microvalve is in pneumatic tactile displays, which operates against gas pressure up to approximately 90 kPa and switching speed between 1 and 200 Hz. The current valve design has a maximum static hydraulic amplification ratio of 5 at 30 V driving voltage and a maximum valve head stroke of 37 µm at 150 V. Under a 94.4 kPa differential pressure, the flow rate of the valve and the closing voltage measure are 785 mL min−1 and 150 V, respectively. The function of the microvalve as an on–off switch for a pneumatic microbubble tactile actuator is demonstrated.

Rendering edge enhancement tactile phenomenon by friction variation in dynamic touch

Variable friction tactile displays have been recently used to render virtual textures and gratings. Neural basis of perceptual mechanism of detection of edge-like features resulting in discrimination of virtual gratings during active touching these tactile actuators is studied using a finite-element biomechanical model of human fingertip. The predicted neural response of the mechanoreceptors, i.e. the computed strain energy density at the location of selected mechanoreceptors as a measure of neural discharge rate of the corresponding receptors, to local reduction of friction between fingerpad and surface are shown to exhibit a similar shape as the edge enhancement phenomenon, particularly in a sudden burst at the boundary of variable friction regions. This phenomenon is supposed to account for the illusion of virtual edges rendered through the modification of contact forces. The presence of this sudden burst under varied model parameters was investigated. It was shown that while the appearance of this phenomenon in simulation results was invariant to model parameters, associated alteration of the edge enhancement ratio might be considered for the purpose of the tuning of the variable friction tactile display.

Results from Empirical Testing of the System for Tactile Reception of Advanced Patterns (STRAP)

The System for Tactile Reception of Advanced Patterns (STRAP) is capable of displaying complex information through tactile actuators on a user's torso. Non-verbal communication requirements from a Military Operations in Urban Terrain (MOUT) task and tactile design guidelines resulted greater than 60 distinct tactile symbols for communication and a context free grammar. This empirical evaluation is the first step in validating the STRAP system as a complement to traditional communication methods such as military hand and arm signals and radio. Nine participants were trained on the entire tactile language to a 90% criterion and were asked to utilize a small subset of the vocabulary while completing room clearing tasks using a virtual desktop simulation. The results show no significant difference in room clearing performance when haptic versus verbal communications were provided, indicating that the STRAP system shows promise as a complementary communication device. Improvements to both the tactile display and symbols are discussed as a means to improve recognition of haptic commands and overall system utility.

Design of Dynamic Vibrotactile Textures.

This paper describes a method for creating virtual textures without force feedback by using a simple motion sensor and a single vibrotactile actuator. It is based on wavetable synthesis driven by the user's hand movements. The output of the synthesis is rendered with the tactile actuator attached in a hand-held box together with the motion sensor. The method provides a solution for creating tangible properties for virtual objects which can be explored by pointing at them with the sensor-actuator device. The study introduces 12 virtual textures which were based on three different envelope ridge lengths, two spatial densities, and were either regularly or irregularly organized. To evaluate the role of each design parameter in the perception of the texture, a series of experiments was conducted. The perceived similarity was assessed in a pairwise comparison test and the outcome was analyzed by using multidimensional scaling. The analysis revealed that envelope ridge length and spatial density were distinguishable design parameters while regularity was not. The textures were also rated according to five attribute scales previously determined in the pilot experiment. The results show that ridge length and spatial density influence perceived roughness and flatness similarly as with real textures.

Tiny Feel: A New Miniature Tactile Module Using Elastic and Electromagnetic Force for Mobile Devices

For tactile feedback in mobile devices, the size and the power consumption of tactile modules are the dominant factors. Thus, vibration motors have been widely used in mobile devices to provide tactile sensation. However, the vibration motor cannot sufficiently generate a great amount of tactile sensation because the magnitude and the frequency of the vibration motor are coupled. For the generation of a wide variety of tactile sensations, this paper presents a new tactile actuator that incorporates a solenoid, a permanent magnet and an elastic spring. The feedback force in this actuator is generated by elastic and electromagnetic force. This paper also proposes a tiny tactile module with the proposed actuators. To construct a tiny tactile module, the contactor gap of the module is minimized without decreasing the contactor stroke, the output force, and the working frequency. The elastic springs of the actuators are separated into several layers to minimize the contactor gap without decreasing the performance of the tactile module. Experiments were conducted to investigate each contactor output force as well as the frequency response of the proposed tactile module. Each contactor of the tactile module can generate enough output force to stimulate human mechanoreceptors. As the contactors are actuated in a wide range of frequency, the proposed tactile module can generate various tactile sensations. Moreover, the size of the proposed tactile module is small enough to be embedded it into a mobile device, and its power consumption is low. Therefore, the proposed tactile actuator and module have good potential in many interactive mobile devices.

Effects of multi-directional vibrotactile feedback on vestibular-deficient postural performance during continuous multi-directional support surface perturbations

Single-axis vibrotactile feedback of trunk tilt provided in real-time has previously been shown to significantly reduce the root-mean-square (RMS) trunk sway in subjects with vestibular loss during single-axis perturbation. This research examines the effect of multi-directional vibrotactile feedback on postural sway during continuous multi-directional surface perturbations when the subjects' eyes are closed. Eight subjects with vestibular loss donned a multi-axis feedback device that mapped body tilt estimates onto their torsos with a 3-row by 16-column array of tactile actuators (tactors). Tactor row indicated tilt magnitude and tactor column indicated tilt direction. Root-mean-square trunk tilt, elliptical fits to trunk sway trajectory areas, percentage of time spent outside a no vibrotactile feedback zone, RMS center of pressure, and anchoring index parameters indicating intersegmental coordination were used to assess the efficacy of the multi-directional vibrotactile balance aid. Four tactor display configurations in addition to the tactors off configuration were evaluated. Subjects had significantly reduced RMS trunk sway, significantly smaller elliptical fits of the trajectory area, and spent significantly less time outside of the no feedback zone in the tactors on versus the tactors off configuration. Among the displays evaluated in this study, there was not an optimal tactor column configuration for standing tasks involving continuous surface perturbations. Furthermore, subjects performed worse when erroneous information was displayed. Therefore, a spatial resolution of 90 degrees (4 columns) seems to be as effective as a spatial resolution of 22.5 degrees (16 columns) for control of standing.

Results from Pilot Testing a System for Tactile Reception of Advanced Patterns (STRAP)

This paper presents pilot study results on the learnability and effectiveness of the System for Tactile Reception of Advanced Patterns (STRAP) that is capable of displaying complex information through tactile actuators on the user's torso. Information requirements from dismounted soldier communications and tactile design guidelines resulted in 56 distinct tactile symbols. To facilitate cognitive demands for decoding, information presentation was formalized by developing construction rules for tactile symbols and a context-free grammar for compilation of tactile sentences. The pilot study outlined trained two participants on the tactile language. Results showed they were able to reach 90% criterion in less than 3.5 hours. Furthermore, once learned, participants were able to receive and comprehend complex commands comprised of multiple tactile symbols under varying levels of workload with some success.

Design of New Micro Actuator for Tactile Display

In order to provide the realistic tactile sensation in a pin-array tactile display for a hand-held device, we need to consider the pins’ gap, the pins’ stroke, the output force, and the working frequency of the tactile display. This paper presents a new small-scale actuator with a solenoid, a permanent magnet, and a elastic spring for a tactile display. The feedback force of this actuator is generated by the interaction among a solenoid, a permanent magnet, and a elastic spring. We separate the elastic springs into several elastic plates in order to considerately minimize the pins’ gap of tactile display without decreasing the pins’ stroke, the output force, and the working frequency of the displays. In the proposed tactile actuator, a micro-pin is actuated to satisfy the above specification (the pins’ gap, the output force, and the working frequency). Hence, a tactile display with the proposed tactile actuators provides realistic cutaneous sensation to human operators.

Development of vibrating insoles

The objective of this study was to describe the development of vibrating insoles. Insoles, providing a subsensory mechanical noise signal to the plantar side of the feet, may improve balance in healthy young and older people and in patients with stroke or diabetic neuropathy. This study describes the requirements for the tactors, (tactile actuators) insole material and noise generator. A search for the components of vibrating insoles providing mechanical noise to the plantar side of the feet was performed. The mechanical noise signal should be provided by tactors built in an insole or shoe and should obtain an input signal from a noise generator and an amplifier. Possible tactors are electromechanical tactors, a piezo actuator or the VBW32 skin transducer. The Minirator MR1 of NTI, a portable MP3 player or a custom-made noise generator can provide these tactors with input. The tactors can be built in foam, silicone or cork insoles. In conclusion, a C2 electromechanical tactor, a piezo actuator or the VBW32 skin transducer, activated by a custom-made noise generator, built in a cork insole covered with a leather layer seems the ideal solution.

Toward Low-Cost Highly Portable Tactile Displays with Shape Memory Alloys

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 tactile actuator consists of an antagonist arranged pair of miniature NiTi SMA helical springs capable of developing a 300 mN pull force at 1.5 Hz bandwidth by using simple forced-air convection. The proposed concept allows the development of 200 g weight tactile instruments of compact dimensions which can be easily carried by a visually disabled user. A detailed technical description of the SMA active element, tactile actuator and tactile display is presented and discussed. Preliminary perceptual results confirm the effectiveness of the display on information transmission.

2A2-F11 触覚バイオフィードバックに基づく歩行リハビリ支援システム : 第3報 : 全訓練相に適用可能な足底圧呈示インタフェースの設計(リハビリテーションロボティクス・メカトロニクス)

We newly propose a locomotion rehabilitation system for stroke patients based on tactile-biofeedback that provides foot contact pressures on the paralytic side onto the body of their non-paralytic side. The earlier system composed of foot pressure detecting interface and providing one has two problems: One is moving cycle which takes too long to use it in walking practice. The other is limitation of provided region. It can be only put on forearm. To resolve these issues, we replace tactile stimulation-providing actuator with proportion control solenoids to improve moving cycle. In addition, a new design method using panel structure (composed of Common part and Custom one) is adopted, to put on to every region. Using the new interface, we carried out psychology physics experiments to investigate region order. The result indicates the order of identifiability is back→Hipper arm→shoulder→waist, which will be useful for clinical tests to stroke patients.

Display of Holistic Haptic Sensations by Combined Tactile and Kinesthetic Feedback

This article presents conceptual as well as experimental work toward the display of holistic haptic sensations in telepresence and virtual environment applications. (In this context holistic is understood in the sense of “not neglecting an essential component.”) In contrast to most existing developments, the presented haptic humansystem interface is a combination of dedicated subsystems for both kinesthetic and tactile display. With respect to the mechanical coupling of both subsystems, we propose two basic approaches. One is based on a parallel kinematic system setup and forms the conceptual basis of a multifingered experimental feedback device generating vibrotactile, thermal, and wrist/finger kinesthetic stimuli. Another is to demonstrate the potential to reduce the design complexity of tactile display subsystems in haptic human-system interfaces with a serial kinematic structure. For verification purposes, a tactile actuator array providing spatially distributed tactile shape display on a single fingertip has been combined with a single-fingered kinesthetic display. Each of the investigated combined haptic systems features significant functional advances compared to existing developments. The usability of our systems has been demonstrated in haptic exploration and object identification experiments in virtual environments.