Kwangmok Jung

Development of Soft-Actuator-Based Wearable Tactile Display

As a major human sensory function, the implementation of the tactile sensation for the human-machine interface has been one of the core research interests for long time. In this paper, an innovative tactile display device based on the soft actuator technology is presented. Using electroactive polymer for the construction of the tactile display device, it can provide stimulation on the human skin without any additional electromechanical transmission. Softness and flexibility of the device structure, ease of fabrication, possibility for miniaturization, and low cost for mass production are the representative benefits of the presented device. Especially, the device application is open to many different purposes since the flexible structure offers the excellent adaptability to any contour of the human body. To prove its feasibility, a wearable device that can fit to the distal part of the human finger is presented and its performance is evaluated, experimentally.

Artificial annelid robot driven by soft actuators

The annelid provides a biological solution of effective locomotion adaptable to a large variety of unstructured environmental conditions. The undulated locomotion of the segmented body in the annelid is characterized by the combination of individual motion of the muscles distributed along the body, which has been of keen interest in biomimetic investigation. In this paper, we present an annelid-like robot driven by soft actuators based on dielectric elastomer. To mimic the unique motion of the annelid, a novel actuation method employing dielectric elastomer is developed. By using the actuator, a three-degree-of-freedom actuator module is presented, which can provide up-down translational motion, and two rotational degree-of-freedom motion. The proposed actuation method provides advantageous features of reduction in size, fast response and ruggedness in operation. By serially connecting the actuator modules, a micro-robot mimicking the motion of the annelid is developed and its effectiveness is experimentally demonstrated.

Investigations on actuation characteristics of IPMC artificial muscle actuator

Electromechanical response characteristics of ion-exchange polymer metal composite (IPMC), known as a material for artificial muscle actuators, varies extremely depending on the driving method. With respect to the power management the driving method is one of the important considerations though it has not been investigated sufficiently up to now. Its efficiency is critical to enhance the performance of an IPMC system, especially self-contained one. The primary objective of this paper is to investigate electromechanical response characteristics of the IPMC actuator according to driving methods. We begin with developing an equivalent electrical circuit model for the IPMC actuator using experimental data. Based on this model, discuss how the waveforms and frequencies of driving inputs have effect on the characteristic features of the IPMC actuator. Typically square, triangular and harmonic waves are applied as the driving waveform of the IPMC actuator. By employing Fourier techniques, the responses of the IPMC actuator on each input waveform are mathematically analyzed. From this study, we conclude that large consumption of current during actuation is caused by the high frequency components of the driving waveforms because the IPMC actuator has the characteristics of damped high pass filter. A desirable method of driving the IPMC actuator is proposed and its validity is experimentally confirmed.

Biomimetic soft actuator: design, modeling, control, and applications

A new biomimetic linear actuator named Antagonistically Driven Linear Actuator (ANTLA) that could be directly employed in both macro and microscale of robotic applications is introduced in the present work. The presented actuator provides cost effectiveness and simple fabrication process thanks to its plain construction. In addition to producing basic bidirectional rectilinear motions, the actuator is able to modulate its compliance that might be one of the critical elements of the actuator functionality for the biomimetic applications. For the test, the proposed actuator concept is fabricated and assembled in a microscale robot that generates annelid motion.

Effects of prestrain on behavior of dielectric elastomer actuator

Among ElectroActive Polymers (EAPs) the dielectric elastomer actuator is regarded as one of the most practically applicable in the near future. So far, its effect on the actuation phenomena has not been discussed sufficiently, although its strong dependency on prestrain is a significant drawback as an actuator. Recent observations clarifies that prestrain has the following pros and cons: prestrain plays an important role in generating large strain, whereas it rather contributes to the reduction of the strain. Prestrain provides the advantages of improving the response speed, increase of the breakdown voltage, and removing the boundary constraint caused by the inactive actuation area of the actuator. On the contrary, the elastic forces by prestrain makes the deformation smaller and the induced stress relaxation is severely detrimental as an actuator. Also, the permittivity decreases as prestrain goes up, which adds an adverse effect because the strain is proportional to the permittivity. In the present work, a comprehensive study on the effects of prestrain is performed. The key parameters affecting the overall performances are extracted and it is experimentally validated how they work on the actuation performance.

Braille display device using soft actuator

Tactile sensation is one of the most important sensory functions along with the auditory sensation for the visually impaired because it replaces the visual sensation of the persons with sight. In this paper, we present a tactile display device as a dynamic Braille display that is the unique tool for exchanging information among them. The proposed tactile cell of the Braille display is based on the dielectric elastomer and it has advantageous features over the existing ones with respect to intrinsic softness, ease of fabrication, cost effectiveness and miniaturization. We introduce a new idea for actuation and describe the actuating mechanism of the Braille pin in details capable of realizing the enhanced spatial density of the tactile cells. Finally, results of psychophysical experiments are given and its effectiveness is confirmed.

Development of enhanced synthetic elastomer for energy-efficient polymer actuators

In this paper, a new material, called a synthetic elastomer, is presented as a means of actuation. The material displays enhanced performances in terms of electrical as well as mechanical aspects such as dielectric constant, elastic strength and stress relaxation. We begin by developing synthesis procedures for the material, which result in its general recipe with chemical composition. In addition, the effects of respective chemical constituents are studied with regard to the electrical and mechanical characteristics of the actuator. Finally, experimental tests are performed to evaluate the actuation performance of the material, and its advantages are clarified by conducting comparative studies with other existing materials.

Wearable Fingertip Tactile Display

Tactile sensation is one of the most important sensory functions for human perception of objects. Recently, there have been many technical challenges in the field of tactile sensing as well as tactile display. In this paper, we propose an innovative tactile display device based on soft actuator technology with electroactive polymer (EAP). This device offers advantageous features over existing devices with respect to intrinsic flexibility, softness, ease of fabrication and miniaturization, high power density, and cost effectiveness. In particular, it can be adapted to various geometric configurations because it possesses structural flexibility, so it can be worn on any part of the human body such as finger, palm, and arm etc. It can be extensively applied as a wearable tactile display, a Braille device for the visually disabled, and a human interface in the future. A new design of the flexible actuator is proposed and its basic operational principles are discussed. In addition, a wearable tactile display device with 4times5 actuator array (20 actuator cells) is developed and its effectiveness is confirmed

Wearable tactile display based on soft actuator

Tactile sensation is one of the most important sensory functions for human perception of objects. Recently, there have been many technical challenges in the field of tactile sensing as well as tactile display. In this paper, we propose an innovative tactile display device based on soft actuator technology with electroactive polymer (EAP). This device offers advantageous features over existing devices with respect to intrinsic flexibility, softness, ease of fabrication and miniaturization, high power density, and cost effectiveness. In particular, it can be adapted to various geometric configurations because it possesses structural flexibility, so it can be worn on any part of the human body such as finger, palm, and arm etc. It can be extensively applied as a wearable tactile display, a Braille device for the visually disabled, and a human interface in the future. A new design of the flexible actuator is proposed and its basic operational principles are discussed. In addition, a tactile display device with 10times10 actuator array (100 actuator cells) is developed and its effectiveness is confirmed

Microrobot actuated by soft actuators based on dielectric elastomer

In this paper a microrobot, mimicking annelid animals like the earthworm, is presented. The robot is composed of several ring-like segments. Each segment is able to generate three degree-of-freedom motions such as pan/tilt/up-down respectively, and it is actuated by three soft actuators located equidistantly along the circumferential direction. The soft actuator, called antagonistically-driven linear actuator (ANTLA), is based on polymer dielectrics and has muscle-like characteristics capable of performing motions such as forward/backward/controllable compliance. In this paper, the basic concept of the actuator is briefly reviewed and the robot, including the ring-like segment, is explained in detail with demonstrations.