In this paper, we introduce a novel, self-sensing technique for dielectric elastomer (DE) actuators which will adequately
measure the in-situ impedance variation of the DE under a deformation. A standard signal processing technique was
introduced to accurately mix and extract actuating and sensing signals. Although the technique is limited to the
actuation-bandwidth of several tens of Hz, its practical use for applications and tests is attractive. With the proposed
technique, the self-sensing actuation system was effectively demonstrated without using auxiliary sensors. The proposed
technique is useful for many attractive robotic applications including space-limited micro-actuation systems and multi-DOF systems that use hyper redundant manipulators.
The purpose of this study is to develop a novel thermokinetically-driven actuator technology based on the
physics of metal hydrides (MH's). A metal hydride absorbs and desorbs hydrogen due to the imposed
temperature swing(s). The MH can also work as an effective thermally-driven hydrogen compressor
producing more than 5,000 psia net pressure swing. The MH actuation system can be built in a simple
structure, exhibits high power, produces soft actuating, and is essentially noiseless. Moreover, it is much
more powerful and compact than conventional pneumatic systems that require bulky auxiliary systems. It is
our belief that the MH actuators are useful for many emerging industrial, biorobotic, and civil structural
applications. In this paper, we report the recent preliminary experimental results for a laboratory-prototyped
MH actuation system. In particular, the dynamic response characteristics, enhanced controllability,
thermodynamic performances, and reliability of the metal hydride actuator were studied in order to estimate
the actuation capability of the MH actuator. A unique design of the MH actuator was created. It encases a
so-called "porous metal hydride (PMH)" in the reactor to effectively achieve desirable performance by
improving overall thermal conductance.
This paper presents a new artificial muscle actuator produced from
dielectric elastomer, called Tube-Spring Actuator(TSA). The new
actuator construction includes two steps: the first part is a
cylindrical actuator manufactured with dielectric elastomer and
the second is a compressed spring inserted inside the tube. An
inner spring is used to maximize the axial deformation while
constraining the radial one. This unique design enables linear
actuation with the largest strain of active length up to 14%
without any additional means. As a result this actuator was
applied to a robot hand. This study lays the foundation for the
future work on dielectric polymer actuator.
A new material, called synthetic rubber in this paper, is proposed
as a material for artificial muscle actuator based on dielectric
elastomer. The presented material displays enhanced electrical as
well as mechanical characteristics in terms of higher dielectric
constant, elastic strength and lower stress relaxation. Several
experiments are performed to evaluate actuation performance of the
material. Also, its advantages are proved by conducting
comparative studies with the other existing materials.
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.
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.
In this paper, we present a novel actuation method employing dielectric elastomer and a micro--inchworm robot actuated by the proposed method. Different from the previous approaches adopting pretensions of dielectric elastomer, the method depends solely on the deformation caused by the Maxwell stress, and thus, their critical problem such as stress relaxation as time goes on is cleared, though the amount of deformation is largely reduced. In addition, the proposed actuation method provides advantageous features of reduction in size, speed of response, ruggedness in operation. Using the actuator, a three-degree-of-freedom actuator module is developed, which can provide up-down, and two rotational degree-of-freedom motion. In the application of the proposed actuation method, a micro-robot mimicking the motion of an inchworm is developed.
In this paper we present a packaged actuator to be applied for
micro and macro robotic applications. The actuator is based on polymer dielectrics, and intrinsically has musclelike characteristics capable of performing motions such as forward/backward/controllable compliance. The actuator is featured in several aspects such as simplicity and lightness in weight, cost-effectiveness, multiple DOF-actuation, and digital interface. In this paper, its basic concepts are briefly introduced and the issues about design, fabrication and applications are discussed.
A new biomemetic actuator is proposed. The actuator realizes bidirectional actuation since it is with a stretched film antagonistically configured with compliant electrodes. Also, it is distinguished from existing actuators with respect to the controllability of its compliance. Bidirectional actuation and compliance controllability are important characteristics for the artificial muscle actuator and the proposed one accomplishes these requirements without any mechanical substitute or complicated algorithms. In this paper its basic concepts and working principles are introduced with static and dynamic analysis. Control strategies for displacement as well as stiffness are introduced, and experimental results are given to confirm the effectiveness of the proposed methods. In addition, an example of robotic actuating devices is given to confirm the usefulness of the proposed actuator.
In this paper first we address experimental works to investigate basic characteristics of IPMC actuators which have not been discussed sufficiently yet. Surface conductivity, displacement and force features are discussed. Also a new actuator is proposed called Artificial Musclelike Linear Actuator (AMuLA) inspired from the actuation principles of the human. The actuator is a linear actuator simulating the mechanical behavior of myofilaments that are the basic units of the human muscle. Multiple IPMC's and electrodes are utilized to mimic the motion of muscles and as a result, musclelike linear motions can be realized. The prototype of AMuLA is introduced and its performance is evaluated.