Tae-Heon Yang

Development of a miniature pin-array tactile module using elastic and electromagnetic force for mobile devices

In these days, tactile sensation using a vibration motor is recently receiving attention for immersive interaction with mobile devices. However, the vibration motor is not enough to provide detailed texture or small-scale shape. In order to generate various and exiting tactile sensation, this paper presents a new tactile actuator with a solenoid, a permanent magnet and an elastic spring. This paper also proposes a miniature tactile module with the proposed actuators. On constructing a miniature tactile module, we separate the elastic springs in the actuators into several layers to minimize the contactors gap without decreasing the performance of the tactile module. We conduct experiments to investigate each contactors output force and the frequency response of the proposed tactile module. Each contactor can generate enough output force to stimulate humans mechanoreceptors. Moreover, since the contactors are actuated in a wide range of frequency, the proposed tactile module can generate various tactile sensations.

Small and lightweight tactile display(SaLT) and its application

This paper presents a small and lightweight tactile display system and describes its capabilities with respect to spatial and temporal tactile feedback. Each tactile display module is comprised of a 4×4 piezoelectric ultrasonic actuator array with a spatial resolution of 1.5mm and a temporal resolution of 20Hz. The objective of this research is to build a small and lightweight tactile display system such that the system, including the display modules and complete controller parts, will be wearable by a user. It was found that the developed tactile display module can display both spatial and temporal information with less power consumption.

Application of magnetorheological fluids for a miniature haptic button: Experimental evaluation

This study investigates a miniature haptic button actuated by magnetorheological fluids with the aim of conveying kinesthetic information or realistic button sensations to users for small electronic devices. To this end, a prototype haptic button that creates varying kinesthetic sensations was designed and constructed. The design focus was to maximize the resistive force generated by magnetorheological fluids in a given size by using multiple operating modes of the fluids. In order to evaluate the performance of the prototype, a test setup consisting of a microstage and a precision load cell was constructed. Using the setup, the resistive force of the prototype button was measured by changing the indented depth and the input current. The results show that the force rate (defined as the ratio of the difference between the maximum force and the minimum force to the maximum force) is over 72% for all indented depths (up to 1.5 mm). This change is sufficient to create various button sensations, indicating that the proposed haptic button can offer a range of resistive force change that can be conveyed to human operators.

Compact Tactile Display for Fingertips with Multiple Vibrotactile Actuator and Thermoelectric Module

In this paper, a compact tactile display which consists of multiple vibrotactile actuators with 4-different vibrotactile unbalanced masses and a Peltier thermoelectric module is proposed. By stimulating 2 different sensory channels including mechanoreceptors and thermoreceptor simultaneously, surface texture and material composition can be displayed using the implemented device. 3 experiments were conducted for the performance evaluation of the proposed device through discriminating various patterned textures. Experimental results show that the developed device can be used to display surface texture and temperature together and suggest the possibility of implementing a small-sized, multi-fingered tactile display device.

A new subminiature impact actuator for mobile devices

This paper presents a new subminiature impact type actuator which creates the haptic sensation in a mobile device. Recently, linear resonance actuators (LRA) are widely used. One of the key differences between an LRA and a traditional eccentric motor is that the LRA generates the vibrotactile sensation through resonance for minimizing response time. The strategy of operation near the resonant frequency, however, brought a new issue for creating vibrotactile sensation which can be strong enough to feel in arbitrary frequency. In order to achieve this issue, we adopt an unstable structure to amplify impact force and to reduce response rate. Due to the impact with fast rising and falling time in the proposed impact actuator, the available strong impact vibration is created over wide frequency range from 0Hz to 100Hz. The impact vibration generated from the proposed actuator is suitable for reproducing realistic button sensation and creating various vibration patterns in mobile devices.

Mechatronics Technology in Mobile Devices

Recently, haptics research has grown into an interdisciplinary field, covering perception, psychophysics, virtual reality, mechanism design, and control. Haptics research is considered to have originated from teleoperator systems. In these initial explorations, increasing the transparency level of the mechanical master/slave manipulator system was the main issue. As computer graphics technology has emerged to realize a wide range of virtual reality applications, the development of control technologies and haptic master device designs have adapted to focus mainly on interaction with virtual environments. Numerous breakthroughs in visual, sound, and haptic modeling technologies enable the real-time display of contact with virtual objects, including capabilities such as shape deformation and reactive force. There have been attempts to model and display the fine details of touched surfaces to enhance virtual presence. Research in neuroscience and psychophysics has led to discoveries in the human perceptual processes underlying haptic sensations. Drawing on this understanding, researchers have begun to examine efficient methods of building tactile display units that are capable of rendering feelings of roughness, softness, and temperature.

SaLT: Small and lightweight tactile display using ultrasonic actuators

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.

TAXEL: Initial progress toward self-morphing visio-haptic interface

This paper proposes a new interactive interface TAXEL, which aims at developing a reconfigurable self-morphing visio-haptic interface. We first present the overall architecture and concept of a self-morphing visuo-haptic interface. Key hardware components are developed and tested, including three tactile actuators using a piezoelectric active linear actuator, a passive MR fluid actuator, and a thin film-type actuator, respectively, and a flexible visual display based on the light-waveguide technology. Using the developed components, a tactile platform that includes a 8×16 array of the linear actuators is implemented for a proof of concept. A rendering engine is also designed for the tactile platform with emphasis on the use of haptic feedback together with GUI. We also carried out a user study with virtual button simulation as a benchmark to evaluate the performance of the TAXEL tactile platform. Lastly, an integrated system with a visual display is demonstrated along with several application examples.

Trend & prospects of haptic technology in mobile devices

Through researches defining tactile feeling on touched surfaces, researchers have begun to examine how to design effective tactile actuators and displays. In this paper, we present the state-of-the-art in tactile actuators and modules for mobile device applications. This paper focuses on tactile actuators such as solenoid actuators, piezo-actuators, electroactive polymers, ultrasonic actuators and MR fluids. The characteristics of actuators are presented and compared. Various tactile modules using the actuators are examined. In addition, the ultimate goal of haptics is discussed.

Mechanical and psychophysical performance evaluation of a haptic actuator based on magnetorheological fluids

This study presents a miniature haptic actuator (10 mm (L) × 10 mm (W) × 6.5 mm (H)) based on magnetorheological fluids, which is designed to provide realistic touch sensations to users. Its primary goals are to evaluate mechanical or actuation performances of the prototype magnetorheological actuator and to assess its effectiveness in conveying haptic sensations to users by conducting the psychophysical experiments. The mechanical performance study evaluated the prototype’s output forces from haptic perspectives using a dynamic test frame. The psychophysical experiments studied human subjects’ perceptions on haptic sensations produced by the prototype. The mechanical test results show that the magnetorheological actuator is capable of generating a wide range of frequency-dependent output forces (from 1.5 N to nearly 9 N). The psychophysical experiments show that the actuator offers various kinesthetic and vibrotactile sensations to human operators. Overall, the results suggest a feasibility of using the magnetorheological haptic actuator in real-world applications, such as a haptic keypad and functional buttons in small consumer electronics and hand-held devices.