Baek-chul Kim

A dual axis shear force film sensor for robotic tactile applications

Sensing and delivering tactile information is of interest not only in robotic researches but in most of broad sensor technology areas since along with olfactory it is one of the most difficult sensory information to detect and transfer. Most of the tactile sensors developed are using either brittle ceramic base material or bulky electromagnetic material. Although those tactile sensors provides some advantages like a certain level of accuracy in terms of the applied force measurement and reliable fabrication methods such as MEMS, there is still a significant drawback due to its brittle material characteristics. Especially for biomimetic applications the material flexibility might be the major concern in order to achieve the application objectives. In the present work, a multi-axis force sensor using polymeric material are developed. The sensor has ability to differentiate applied force directions such as normal and tangential and it to be deployed as an massive array so that a set of tactile sensors can be easily organized. Having the material flexibility, the present work successfully demonstrates a tactile sensor array affixed on a human-hand-like robot finger tip.

Smart material actuators for micro optical zoom lens driving systems

Micro-optical system designs for slim mobile device are presented. Evaluations on advantages and the drawbacks in terms of mechanical actuation performance of smart materials such as conducting polymer, co-polymer, and dielectric elastomers are provided for the efficient optical system driving actuation. In addition the present work makes an attempt to optimize fabrication process for each possible smart material candidate.

Design of slip detection sensor for artificial skin

A tactile sensor for slip detection is necessary for human- like grasping in robot hand. This paper reports a capacitive tactile slip sensor that can detect slip on the surface of the sensor structure. The newly developed capacitive slip sensor uses acrylo-nitrile butadiene rubber (NBR) as substrate. The presented sensor device in this paper has fingerprint - like structures that are similar with the role of the humans fingerprint. Movement of the structure that attached on surface of substrate arise capacitance changes, and these are used to detect slip. We carried out slip experiment by prototype of capacitive slip sensor and slip was successfully detected.

Development of a Dry Actuation Conducting Polymer Actuator For Micro-Optical Zoom Lenses

The objective of the present work is to demonstrate the efficiency and feasibility of NBR (Nitrile Butadiene Rubber) based conducting polymer actuator that is fabricated into a micro zoon lens driver. Unlike the traditional conducting polymer that normally operates in a liquid, the proposed actuator successfully provides fairly effective driving performance for the zoom lens system in a dry environment. And this paper is including the experiment results for an efficiency improvement. The result suggested by an experiment was efficient in micro optical zoom lens system. In addition, the developed design method of actuator was given consideration to design the system.

Highly sensitive resistive type single-axis tactile sensor with liquid pocket

In this paper, we propose the resistive type tactile sensor with a liquid pocket. The tactile sensor with polymer substrate has two components which are the sensing element and the structural part. The sensing part is surrounded by PDMS (Sylgard 184) which is relatively solid. To make the sensor more sensitive, we design the upper part of the sensing element in a shape of half-sphere filled with a liquid (silicone oil). When the force is applied to the sensor, the liquid pressure increases and evenly presses down the sensing element to deform. The size of sensor is 7 x 3 x 1 mm including the wiring part. The good sensitivity (0.012 S/kPa-1) of the fabricated sensor is experimentally verified.

Biomimetic Actuator and Sensor for Robot Hand

To manufacture a robot hand that essentially mimics the functions of a human hand, it is necessary to develop flexible actuators and sensors. In this study, we propose the design, manufacture, and performance verification of flexible actuators and sensors based on Electro Active Polymer (EAP). EAP is fabricated as a type of film, and it moves with changes in the voltage because of contraction and expansion in the polymer film. Furthermore, if a force is applied to an EAP film, its thickness and effective area change, and therefore, the capacitance also changes. By using this mechanism, we produce capacitive actuators and sensors. In this study, we propose an EAP-based capacitive sensor and evaluate its use as a robot hand sensor.

Dual-axis hybrid tactile sensor

Robotic grasping requires not only force and touch sensors but also flexibility of such sensors because most of the sensors are attached to the finger tip. Many studies are underway in such sensors using polymer because polymer is flexible and affordable. Polydimethylsiloxane (PDMS) is one of widely used substances because it is very stable physically and chemically. The principle of the capacitive force sensor using polymer is as follows; capacitance values will be changed by changes in the thickness of the dielectric elastomer under normal force or changes in the overlapping area of electrodes under shear force. The force and moment are measured by such changes. Conventional one-axis capacitive type force sensors measure normal or tangential force from one pair of electrodes. The increased number of electrodes can be used for multi-axis force sensors at the cost of the size of the sensor and resolution of the sensor. In this paper, we propose a dual-axis capacitive and resistive hybrid-type force sensor using dielectric elastomer with only one pair of electrodes. The electrodes are made with thermal evaporator. With only one pair of electrodes, the normal force is measured from the change of capacitance and resistance values and the shear force is measured from the change of only capacitance values. Experimental results verify the effectiveness of the proposed dual-axis hybrid type force sensor.

Multi-axis flexible force sensor for tactile display

In this study, we were the development and calibration of new complex sensor which is similar to tactile sensing of human due to can be measured normal and shear force by using newly developed synthetic elastomer and conductive silicone. The developed sensor can sense pressing force by capacitance changes as thickness changes by applied normal force in surface. And this sensor can sense by using capacitance change as an electrode area change when applied shear force. The capacitance change is measured by CDC(capacitance to digital converter integrated circuits) and the data is transmitted to user interface of a Host PC though microcontroller system constructed for signal processing. To verify the performance of the sensor, we constructed a calibration system and accurately analyzed the applied force.

A Flexible Tactile Capacitive Sensor for Slip Detection

A tactile sensor for slip detection is necessary for humanlike grasping in robot hand. This paper reports a capacitive tactile slip sensor that can detect slip on the surface of the sensor structure. The newly developed capacitive slip sensor uses acrlyro-nitrile butadien rubber (NBR) as substrate. The presented sensor device in this paper has fingerprint -like structures that are similar with the role of the human’s fingerprint. Movement of the structure that attached on surface of substrate arise capacitance changes, and these are used to detect slip. We carried out slip experiment by prototype of capacitive slip sensor and slip was successfully detected.Copyright

A method of determining flow stress and friction factor using an inverse analaysis in ring compression test

An inverse analysis been applied to obtain the flow stress of the material. In this method, a ring-shaped specimen is compressed between two flat tools. This procedure employs, as the object function of inverse analysis, the balance of measured loads and reaction forces calculated by using rigid-plastic finite element method. The balance is explicit scalar function of flow stress which is a function of some unknown constants. For minimizing the balance, Newton-Raphon scheme is used. The friction factor, m, between flat tools and the specimen is determined by using friction area-divided method. The proposed method allows an accurate identification by avoiding the usual assumptions made in order to convert experimental measures into stress-strain relation. In this paper, the proposed method is numerically tested. A commercial pure aluminum was selected, as an example, to apply the method and the results are compared with stress-strain relation obtained by experiments.