• Journal of Institute of Control, Robotics and Systems
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• v.12 no.6
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• pp.594-599
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• 2006

In this paper an anthropomorphic robot hand called SKKU Hand IIl is presented, which has a miniaturized fingertip tactile sensor. The thumb is designed as one part of the palm and multiplies the mobility of the palm. The fingertip tactile sensor, based on polyvinylidene fluoride (PVDF) and pressure variable resistor ink, is physically flexible enough to be deformed into any three-dimensional geometry. In order to detect incipient slip, a PVDF strip is arranged along the direction normal to the surface of the finger of the robot hand. Also, a thin flexible sensor to sense the static force as well as the contact location is fabricated into an arrayed type using pressure variable resistor ink. The driving circuits and the tactile sensing systems for the SKKU Hand II are embedded in the hand. Each driving circuit communicates with others using CAN protocol. SKKU Hand II is manufactured and its feasibility is validated through preliminary experiments.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.5
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• pp.142-149
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• 2009

This paper proposes and demonstrates novel flexible contact force sensing devices for 3-dimensional force measurement. To realize the sensor, polyimide and polydimethylsiloxane are used as a substrate, which makes it flexible. Thin-film metal strain gauges, which are incorporated into the polymer, are used for measuring the three-dimensional contact forces. The force sensor characteristics are evaluated against normal and shear load. The fabricated force sensor can measure normal loads up to 4N. The sensor output signals are saturated against load over 4N. Shear loads can be detected by different voltage drops in strain gauges. The device has no fragile structures; therefore, it can be used as a ground reaction force sensor for balance control in humanoid robots. Four force sensors are assembled and placed in the four corners of the robot's sole. By increasing bump dimensions, the force sensor can measure load up to 20N. When loads are exerted on the sole, the ground reaction force can be measured by these four sensors. The measured forces can be used in the balance control of biped locomotion system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.364-372
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• 2006

In this paper, we present a finger tip tactile sensor which can detect contact normal force as well as slip. The sensor is made up of two different materials, such as polyvinylidene fluoride (PVDF) known as piezoelectric polymer, and pressure variable resistor ink. In order to detect slip on the surface of the object, two PVDF strips are arranged along the normal direction in the robot finger tip and the thumb tip. The surface electrode of the PVDF strip is fabricated using silk-screening technique with silver paste. Also a thin flexible force sensor is fabricated in the form of a matrix using pressure variable resistor ink in order to sense the static force. The developed tactile sensor is physically flexible and it can be deformed three-dimensionally to any shape so that it can be placed on anywhere on the curved surface. In addition, a tactile sensing system is developed, which includes miniaturized charge amplifier to amplify the small signal from the sensor, and the fast signal processing unit. The sensor system is evaluated experimentally and its effectiveness is validated.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1808-1813
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• 2005

In this paper, we present the finger tip tactile sensor which can detect contact normal force as well as slip. The developed sensor is made of two different materials, such as polyvinylidene fluoride(PVDF) that is known as piezoelectric polymer and pressure variable resistor ink. In order to detect slip to surface of object, a PVDF strip is arranged along the normal direction in the robot finger tip and the thumb tip. The surface electrode of the PVDF strip is fabricated using silk-screening technique with silver paste. Also a thin flexible force sensor is fabricated in the form of a matrix using pressure variable resistor ink in order to sense the static force. The developed tactile sensor is physically flexible and it can be deformed three-dimensionally to any shape so that it can be placed on anywhere on the curved surface. In addition, we developed a tactile sensing system by miniaturizing the charge amplifier, in order to amplify the small signal from the sensor, and the fast signal processing unit. The sensor system is evaluated experimentally and its effectiveness is validated.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.161-166
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• 2001

The prototype of a tactile sensor with $4\times 4$ taxels using PVDF was fabricated. The electrode patterns of the thin Cu tape are attached to the 28${\mu}{\textrm}{m}$ thickness PVDF using conductive adhesive and covering the sensor using polyester film for insulation. The structure of the sensor is flexible and the fabrication procedure is easy relatively. Also the output characteristics of the sensor was nearly linear with 8% deviation. The signals of a contact pressure to the tactile sensor are sensed and processed through A/D converter, DSP system and personal computer. The reasonable performance for the detection of contact shape and force distribution was verified through the experiment.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1222-1228
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• 2002

This research is the development of a flexible tactile sensor array for service robots using PVDF (polyvinylidene fluoride) film for the detection of a contact state in real time. The prototype of the tactile sensor which has 8${\times}$8 array using PVDF film was fabricated. In the fabrication procedure, the electrode patterns and the common electrode of the thin conductive tape were attached to both sides of the 281$\mu\textrm{m}$ thickness PVDF film using conductive adhesive. The sensor was covered with polyester film for insulation and attached to the rubber base for a stable structure. The proposed fabrication method is simple and easy to make the sensor. The sensor has the advantages in the implementing for practical applications because its structure is flexible and the shape of the each tactile element can be designed arbitrarily. The signals of a contact force to the tactile sensor were sensed and processed in the DSP system in which the signals are digitized and filtered. Finally, the signals were integrated for taking the force profile. The processed signals of the output of the sensor were visualized in a personal computer, and the shape and force distribution of the contact object were obtained. The reasonable performance for the detection of the contact state was verified through the sensing examples.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.489.2-489.2
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• 2014

The planar type flexible piezoelectric energy harvesters (PEH) based on PbZr0.52Ti0.48O3 (PZT) thin films on the flexible substrates are demonstrated to convert mechanical energy to electrical energy. The planar type energy harvesters have been realized, which have an electrode pair on the PZT thin films. The PZT thin films were deposited on double side polished sapphire substrates using conventional RF-magnetron sputtering. The PZT thin films on the sapphire substrates were transferred by PDMS stamp with laser lift-off (LLO) process. KrF excimer laser (wavelength: 248nm) were used for the LLO process. The PDMS stamp was attached to the top of the PZT thin films and the excimer laser induced onto back side of the sapphire substrate to detach the thin films. The detached thin films on the PDMS stamp transferred to adhesive layer coated on the flexible polyimide substrate. Structural properties of the PZT thin films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). To measure piezoelectric power generation characteristics, Au/Cr inter digital electrode (IDE) was formed on the PZT thin films using the e-beam evaporation. The ferroelectric and piezoelectric properties were measured by a ferroelectric test system (Precision Premier-II) and piezoelectric force microscopy (PFM), respectively. The output signals of the flexible PEHs were evaluated by electrometer (6517A, Keithley). In the result, the transferred PZT thin films showed the ferroelectric and piezoelectric characteristics without electrical degradation and the fabricated flexible PEHs generated an AC-type output power electrical energy during periodically bending and releasing motion. We expect that the flexible PEHs based on laser transferred PZT thin film is able to be applied on self-powered electronic devices in wireless sensor networks technologies. Also, it has a lot of potential for high performance flexible piezoelectric energy harvester.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.390-390
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• 2000

This research is the development of a skin-type tactile sensor for service robot using PVDF film for the detection of the contact state. The Prototype of the tactile sensor which has 8$\times$8 taxels was fabricated using PVDF film In the fabrication procedure of the sensor, the electrode patterns and common electrode of the thin conductive tape were attached to the both side of the 28 micro meter thickness PVDF film using conductive adhesive. The sensor was covered with polyester film for insulation and attached to the rubber base for making stable structure. The signals of a contact pressure to the tactile sensor were sensed and processed in the DSP system in which the signals were digitized and filtered. Finally, the signals were integrated for taking the force profile. The processed signals of the output of the sensor were visualized in PC, the shape and force distribution of the contact object were obtained. The reasonable performance for the detection of contact state was verified through the experiment.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1524-1525
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• 2007

A flexible tactile sensor module based on polyimide matrix integrated with sensing elements and pluggable terminals connector was fabricated by polymer micromachining technology for robotic applications. The tactile sensor arrays are composed of $4{\times}4$, $8{\times}8$ and $16{\times}16$ sensing elements connected with pluggable terminals connector, respectively. Especially, both the tactile sensor array and the pluggable terminals are formed in the sensor module during the fabrication process. The fabricated tactile sensor module is measured continuously in the normal force range of $0{\sim}1N$ with tactile sensor auto-evaluation system. The value of resistance is relatively increased linearly with normal force in the overall range. The variation rate of resistance is about 2.0%/N in the range of $0{\sim}0.6N$ and 1.5%/N in the range of $0.6{\sim}1N$. Also, the flexibility of the sensing module is adequate to be placed on any curved surface as cylinder because the matrix consists of polymer and metal thin film.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.100-108
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• 2019

In this paper, a new stacked element pressure sensor has proposed for heartbeat and respiration measurement. This device can be directly attached to an individual's chest; heartbeat and respiration are detected by the pulsatile vibration and deformation of the chest. A key feature of the device is the simultaneous measurement of heart rate and respiration. The structure of the sensor consists of two stacked elements, in which one element includes one polyvinylidene fluoride (PVDF) thin film bonded on polydimethylsiloxane (PDMS) substrate. In addition, for the measurement and signal processing, the electric circuit and the filter are simply constructed with an OP-amp, resistance, and a capacitor. One element (element1, PDMS) maximizes the respiration signal; the other (element2, PVDF) is used to measure heartbeat. Element1 and element2 had sensitivity of 0.163V/N and 0.209V/N, respectively, and element2 showed improved characteristics compared with element1 in response to force. Thus, element1 and element2 were optimized for measuring respiration heart rate, respectively. Through mechanical and vivo human tests, this sensor shows the great potential to optimize the signals of heartbeat and respiration compared with commercial devices. Moreover, the proposed sensor is flexible, light weight, and low cost. All of these characteristics illustrate an effective piezoelectric pressure sensor for heartbeat and respiration measurements.