Vibol Yem

Vibrotactile and pseudo force presentation using motor rotational acceleration

Linear vibration actuators such as the Force Reactor from Alps Electric Co. or the Haptuator from Tactile Labs Inc. are actively used to present numerous tactile sensation to the fingertip. They have high responsiveness compared with conventional eccentric rotating mass vibration motors, and are also able to produce pseudo-haptic illusions when asymmetric signals are applied. However, this type of actuator has certain design challenges, such as resonance via the spring attached to the vibration mass, and limited acceleration amplitude at low frequency because of the limited travel distance of the mass. In our study, we propose a new haptic presentation method using the rotational motors counterforce that occurs during acceleration. We use the rotor of motor itself as the vibration mass, so the mass can move indefinitely without limitation. This paper reports on the use of a DC motor as a vibration actuator. The results show that the response time of a DC motor is about 3 ms, which is faster than current linear vibration actuators. The peak amplitude of vibration is at a low frequency (about 40 Hz). We also found that a DC motor is able to provide a rotational pseudo-force sensation. The combination of vibration and pseudo-force produced by a single motor allows a wide range of haptic presentation to the fingertips.

FinGAR: combination of electrical and mechanical stimulation for high-fidelity tactile presentation

It is known that our touch sensation is a result of activities of four types of mechanoreceptors, each of which responds to different types of skin deformation; pressure, low frequency vibration, high frequency vibration, and shear stretch. If we could selectively activate these receptors, we could combine and present any types of tactile sensation. This approach has been studied but not fully achieved. In our study, we developed FinGAR (Finger Glove for Augmented Reality), in which we combined electrical and mechanical stimulation to selectively stimulate these four channels and thus to achieve high-fidelity tactile sensation. The electrical stimulation with array of electrodes presents pressure and low frequency vibration with high spatial resolution, while the mechanical stimulation with DC motor presents high frequency vibration and shear deformation of the whole finger. Furthermore, FinGAR is lightweight, simple in mechanism, easy to wear, and does not disturb the natural movement of the finger, all of which are necessary for general-purpose virtual reality system.

Hand-Skill Learning Using Outer-Covering Haptic Display

During hand-skill learning, it is important for the learner to manipulate a tool with the appropriate amount of force. Haptic training systems in which a tool is directly actuated are therefore undesirable due to the fact that the force applied to the tool is assisted by an actuator. We report a method in which we have replaced guiding by a tool with an outer-covering haptic display in which a guidance sensation was imparted to the back of a learner’s hand. To show the effectiveness of this approach for hand-skill learning, we conducted experiments with comparisons to two existing methods: a haptic guidance system in which the tool is directly actuated and a visual information guidance system.

Wearable tactile device using mechanical and electrical stimulation for fingertip interaction with virtual world

We developed “Finger Glove for Augmented Reality” (FinGAR), which combines electrical and mechanical stimulation to selectively stimulate skin sensory mechanoreceptors and provide tactile feedback of virtual objects. A DC motor provides high-frequency vibration and shear deformation to the whole finger, and an array of electrodes provide pressure and low-frequency vibration with high spatial resolution. FinGAR devices are attached to the thumb, index finger and middle finger. It is lightweight, simple in mechanism, easy to wear, and does not disturb the natural movements of the hand. All of these attributes are necessary for a general-purpose virtual reality system. User study was conducted to evaluate its ability to reproduce sensations of four tactile dimensions: macro roughness, friction, fine roughness and hardness. Result indicated that skin deformation and cathodic stimulation affect macro roughness and hardness, whereas high-frequency vibration and anodic stimulation affect friction and fine roughness.

Comparative Evaluation of Tactile Sensation by Electrical and Mechanical Stimulation

An electrotactile display is a tactile interface that provides tactile perception by passing electrical current through the surface of the skin. It is actively used instead of mechanical tactile displays for tactile feedback because of several advantages such as its small and thin size, light weight, and high responsiveness. However, the similarities and differences between these sensations is still not clear. This study directly compares the intensity sensation of electrotactile stimulation to that of mechanical stimulation, and investigates the characteristic sensation of anodic and cathodic stimulation. In the experiment, participants underwent a 30 pps electrotactile stimulus every one second to their middle finger, and were asked to match this intensity by adjusting the intensity of a mechanical tactile stimulus to an index finger. The results showed that anodic stimulation mainly produced vibration sensation, whereas cathodic sensation produced both vibration and pressure sensations. Relatively low pressure sensation was also observed for anodic stimulation but it remains low, regardless of the increasing of electrical intensity.

Development of Wearable Outer-Covering Haptic Display Using Ball Effector for Hand Motion Guidance

An outer-covering haptic display (OCHD) is a device that imparts a guiding force sensation to the back of a learner’s hand and guides the learner to manipulate a tool. Our previous study found that OCHD provides a skin deformation sensation and is able to guide a learner with less drive force than the alternative method where the tool is directly actuated. In this study, we developed a wearable outer-covering haptic display (wOCHD) for hand motion, with two ball effectors to deform the skin and provide a guiding information in four axes of motion.

Assisting hand skill transfer of tracheal intubation using outer-covering haptic display

Various systems for hand tool skill training have been developed in the domain of haptic displays. These systems typically present force to a learners palm by directly actuating the tool. However, this approach is sometimes ineffective because learners have difficulty sensing the haptic feedback from the tool when they are holding it tightly. Thus, we propose a different approach (OCHD) that effectively guides the learners hand by presenting force to the back of his/her hand as if an instructor is holding it. A preliminary experiment showed that OCHD effectively guides users with less actuator drive force than cases where the tool is directly actuated.

HapTONE: haptic instrument for enriched musical play

This paper describes a novel music entertainment system that draws on auditory, tactile and visual senses. HapTONE presents players with high-fidelity vibrotactile sensations, not only after pressing the keyboard but also during the pressing operation itself. We developed keyboard type instrument that composed of key unit which is structured a vibrator and a distance sensor. This instrument reproduces the touch sensation of a keyboard, stringed, wind, percussion or non-musical instrument. We describe three applications of HapTONE that include: 1) the accurate replication of percussion instruments; 2) playing of pseudo-stringed instruments, and 3) synchronized vibration with animation. HapTONE is a musical entertainment system for players themselves using auditory, tactile and visual senses.

Expression of 2DOF Fingertip Traction with 1DOF Lateral Skin Stretch

To reproduce the sensation of rubbing on a surface, we need to laterally stretch the skin of the fingertip with two degrees of freedom (2DOF). Unfortunately, it is difficult to develop a compact 2DOF device for the fingertip because at least two actuators are required. However, if we can perceive the rubbing sensation regardless of the skin stretching direction, a device with 1DOF is sufficient. This study used a lateral skin deforming device with 1DOF, and evaluated the realism of the sensation. We found that even when the direction of skin stretch was opposite or perpendicular to the finger movement, users still perceived it as natural.

Pseudo force presentation to multiple fingers by asymmetric rotational vibration using a motor: Consideration in grasping posture

It is known that a pseudo force sensation of pulling in one direction is generated by presenting an asymmetrical vibration stimulus with different accelerations in a round trip. The present study employed a similar phenomenon using the asymmetric rotational vibration of a direct-current motor to present the pseudo force sensation to multiple fingertips. We investigated the frequency characteristics of this phenomenon for two fingers (i.e., the thumb and index finger) in a grasping posture, showing that vibration at a frequency around 30 Hz is optimal. We experimentally found that the equivalent physical force that this illusion generates is 10 to 30 grams, with large variance among participants in the study.