Center for Mass and Related Quantities

Daejeon, South Korea

Center for Mass and Related Quantities

Daejeon, South Korea

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Yang T.-H.,Center for Mass and Related Quantities | Koo J.-H.,Miami University Ohio | Kim S.-Y.,Korea University of Technology and Education | Kwon D.-S.,KAIST
Review of Scientific Instruments | Year: 2017

Haptic display units have been widely used for conveying button sensations to users, primarily employing vibrotactile actuators. However, the human feeling for pressing buttons mainly relies on kinaesthetic sensations (rather than vibrotactile sensations), and little studies exist on small-scale kinaesthetic haptic units. Thus, the primary goals of this paper are to design a miniature kinaesthetic actuator based on Magneto-Rheological (MR) fluid that can convey various button-clicking sensations and to experimentally evaluate its haptic performance. The design focuses of the proposed actuator were to produce sufficiently large actuation forces (resistive forces) for human users in a given size constraint and to offer a wide range of actuation forces for conveying vivid haptic sensations to users. To this end, this study first performed a series of parametric studies using mathematical force models for multiple operating modes of MR fluid in conjunction with finite element electromagnetism analysis. After selecting design parameters based on parametric studies, a prototype actuator was constructed, and its performance was evaluated using a dynamic mechanical analyzer. It measured the actuator’s resistive force with a varying stroke (pressed depth) up to 1 mm and a varying input current from 0 A to 200 mA. The results show that the proposed actuator creates a wide range of resistive forces from around 2 N (off-state) to over 9.5 N at 200 mA. In order to assess the prototype’s performance in the terms of the haptic application prospective, a maximum force rate was calculated to determine just noticeable difference in force changes for the 1 mm stoke of the actuator. The results show that the force rate is sufficient to mimic various levels of button sensations, indicating that the proposed kinaesthetic actuator can offer a wide range of resistive force changes that can be conveyed to human operators. © 2017 Author(s).

Park W.-H.,Korea University of Technology and Education | Yang T.-H.,Center for Mass and Related Quantities | Kim B.-G.,Yeonhap Precision Co. | Kim S.-Y.,Korea University of Technology and Education
2015 IEEE International Conference on Consumer Electronics, ICCE 2015 | Year: 2015

This paper proposes a new thin and flexible vibrotactile module based on an electroactive polymer with 3×3 actuating cells. Since all components of the proposed module are flexible, the proposed module can be easily embedded into commercial mice having any shape. An experiment is conducted to investigate that the proposed module can generate enough force to stimulate human's mechanoreceptors with wide frequency range. © 2015 IEEE.

Kim S.,KAIST | Hong S.,KAIST | Hong S.,Argonne National Laboratory | Choi Y.-Y.,KAIST | And 3 more authors.
Electrochimica Acta | Year: 2013

An autocatalytic electro-less plating of nickel is attempted to replace an electroless impregnation-reduction (IR) method in ionic polymer-metal composite (IPMC) actuators to reduce cost and processing time. Because nucleation time of Pd-Sn colloids is the determining factor of overall processing time, we used the nucleation time as our control parameter. To optimize nucleation time and investigate its effect on the performance of IPMC actuators, we analyzed the relationship between the nucleation time, interface morphology and electrical properties. The optimized nucleation time was 10 h. The trends of the performance and electrical properties as a function of nucleation time were attributed to the fact that the Ni penetration depth was determined by the minimum diffusion length of either Pd-Sn colloids or reducing agent ions. The Ni-IPMC actuators can be fabricated less than 14 h processing time without deteriorating performance of the actuators, which is comparable to Pt-IPMC prepared by IR method.

Ryu S.,KAIST | Koo J.-H.,Miami University Ohio | Yang T.-H.,Center for Mass and Related Quantities | Pyo D.,KAIST | And 2 more authors.
Journal of Intelligent Material Systems and Structures | Year: 2016

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. © The Author(s) 2015.

Pyo D.,KAIST | Yang T.-H.,Center for Mass and Related Quantities | Ryu S.,KAIST | Han B.-K.,KAIST | And 2 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

This paper presents a novel impact-resonant actuator (IRA) that can increase a degree of reality and a sense of immersion by providing a delicate haptic sensation. In current mobile devices, eccentric rotary motor and linear resonant actuators are widely used for haptic feedback, but they provide only simple vibration response to a user's on-screen touch. Varied vibration patterns cannot be generated due to their limited working frequency range. Also, it is hard to create crisp vibrotactile sensation which can mimic the sensation of pressing a button due to their slow response time and long residual vibration. To overcome the limitations of conventional actuators, the proposed actuator generates impact vibration, operating at a wide frequency range from 0 Hz to 190 Hz with a fast response time and very short residual vibration. Moreover, stronger impact force can be generated effectively near the resonant frequency. © 2012 Springer-Verlag.

Ryu S.,KAIST | Koo J.-H.,Miami University Ohio | Yang T.-H.,Center for Mass and Related Quantities | Pyo D.,KAIST | And 2 more authors.
ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2014 | Year: 2014

This paper presents design and testing of a haptic keypad system using an array of haptic actuators. The research goals are to construct a prototype haptic keypad system using haptic actuators and to evaluate the performance of the prototype keypad for haptic rendering. To this end, an MR haptic actuator was designed and fabricated such that it can convey realistic force feedback to users. To demonstrate haptic applications of the MR actuator, a haptic keypad system was constructed, which consists of following components: (1) 3 × 3 array of haptic actuators, (2) 3 × 3 array of force sensing resistors (FSR), (3) a controller including a micro-processor, a current amplifier and a wireless communication module, (4) a graphic display unit with PC. After constructing a prototype keypad system, a haptic rendering technology was employed to interface the hardware keypad system with test software (virtual environment). The prototype system enabled human operators to interact with the target contents in a virtual environment more intuitively. The evaluation results show a feasibility of applications of MR fluids-based haptic actuators in real-world mobile applications. © 2014 by ASME.

Pyo D.,KAIST | Yang T.-H.,Center for Mass and Related Quantities | Ryu S.,KAIST | Kwon D.-S.,KAIST
Sensors and Actuators, A: Physical | Year: 2015

In this study, a novel linear impact-resonant actuator was proposed for mobile device applications. The most significant issue in mobile haptic actuators is the ability to provide various vibrotactile and alert functions despite their size and power consumption limitations. This study aimed to achieve fast and strong impact vibrations over a wide frequency range, including the resonant frequency, which decoupled the intensity and frequency of the vibration to achieve both fruitful vibrotactile feedback and strong alarming vibration. To accomplish this, a new mechanism was proposed that can amplify the impact force at the end of the stroke and increase the speed of the response. The magnetic flux path was optimized using an equivalent magnetic circuit model to maximize the electromagnetic force. The performance of a prototype actuator (11 mm × 9 mm × 3.2 mm) was evaluated in terms of the response time and vibration acceleration amplitude under an input power of 0.3 W. The experimental results clearly showed that the proposed actuator could create a vibration acceleration that was greater than 2 g over a frequency range of 1-210 Hz with a fast response of 4 ms and extremely short residual vibration. In addition, a stronger impact force of around 3 g could be generated near the resonant frequency of 190 Hz. © 2015 Elsevier B.V. All rights reserved.

Choi Y.-Y.,KAIST | Choi Y.-Y.,Chung - Ang University | Park M.,KAIST | Hong J.,Center for Mass and Related Quantities | No K.,KAIST
20th IMEKO World Congress 2012 | Year: 2012

We demonstrated a facile route to fabricate ferroelectric poly(vinylidene fluoridetrifluoroethylene), P(VDF-TrFE), nanodots from spincoated thin films. Importantly, the discrete P(VDFTrFE) nanodots possessed high degree of β-phase [F(β) > 60%] when compared to the fraction of β- phase in thin films [F(β) = 51%]. P(VDF-TrFE) nanodots of 51.4 ± 10.6 nm in height and 172.75 ± 40.5 nm in diameter displayed superior piezoresponse values (18.1 ± 3.3 pm/V) and a low coercive voltage (2.4 ± 0.5V). This offers our rationale for a great promise in non-volatile memories, infrared sensor arrays and artificial skin applications. Copyright © (2012) by the International Measurement Federation (IMEKO).

Ryu S.,KAIST | Koo J.-H.,Miami University Ohio | Yang T.-H.,Center for Mass and Related Quantities | Pyo D.,KAIST | And 2 more authors.
Journal of Intelligent Material Systems and Structures | Year: 2015

This article presents a novel design of a miniature haptic actuator based on magnetorheological fluids for mobile applications with the aim of providing various haptic sensations to users in mobile devices. The primary design goal for a haptic actuator for mobile applications is to miniaturize its size while achieving large forces and low power consumption. To this end, this study proposes to design the actuator's piston head (or plunger) in cone shape and activate multiple modes of magnetorheological fluids. A prototype actuator was designed and fabricated based on a simulation model. Using a dynamic test frame, the performance of the prototype actuator was evaluated in terms of the force (resistive force) produced by the prototype. The results show that the small actuator (10 mm × 10 mm × 6.5 mm) produced a maximum resistive force of about 5 N and the force rate of nearly 80% at 0.3 W. This change in resistive force or the force rate is sufficient to provide several steps of force variation that is explicitly perceivable for operators, depending on the input power. The results demonstrate a feasibility of using the proposed actuator's applications in mobile devices, conveying realistic haptic sensations to users. © SAGE Publications.

Song H.W.,Center for Mass and Related Quantities | Lee J.-T.,Center for Mass and Related Quantities
International Journal of Precision Engineering and Manufacturing | Year: 2015

The importance of a runner’s start was briefly discussed in short distance athletic sports. The main research theme in this field has mainly been the relationship between the starting signal and the response speed of leg muscles. Records in short distance athletic sports have been improved by training athletes to increase their response speed. However, the improvements in records have also been due to the athlete’s speed at starting time; thus, there is another way to improve race times through the starting speed. Starting speed is related to the kicking force against the starting blocks at the start. The objectives of this research were to present an equipment for measuring forces acting upon a starting block at the start and to optimize the starting conditions for each athlete. To achieve these objectives, a starting block with Wheatstone bridge type strain gauges which could measure, in normal and horizontal directions, the propulsion forces acting on the starting blocks at a starting point in real-time, was developed and showed an uncertainty below 0.4%. The use of this block is expected to correct the posture of each athlete and record important sports dynamics data for each athlete. © 2015, Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.

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