Hyungpil Moon

Knitted Fabrics Made from Highly Conductive Stretchable Fibers

We report knitted fabrics made from highly conductive stretchable fibers. The maximum initial conductivity of fibers synthesized by wet spinning was 17460 S cm(-1) with a rupture tensile strain of 50%. The maximum strain could be increased to 490% by decreasing the conductivity to 236 S cm(-1). The knitted fabric was mechanically and electrically reversible up to 100% tensile strain when coated by poly(dimethylsiloxane). The normalized resistance of the poly(dimethylsiloxane)-coated fabric decreased to 0.65 at 100% strain.

A transparent and stretchable graphene-based actuator for tactile display

A tactile display is an important tool to help humans interact with machines by using touch. In this paper, we present a transparent and stretchable graphene-based actuator for advanced tactile displays. The proposed actuator is composed of transparent and compliant graphene electrodes and a dielectric elastomer substrate. Since the electrode is coated onto the appointed region of the substrate layer by layer, only the area of the dielectric elastomer substrate with electrodes bumps up in response to the input voltage, which consequently produces actuation. The actuator is proven to be operable while preserving its electrical and mechanical properties even under 25% stretching. Also, the simple fabrication of the proposed actuator is cost-effective and can easily be extended to multiple arrays. The actuator is expected to be applicable to various applications including tactile displays, vari-focal lenses etc.

Modularized in-pipe robot capable of selective navigation Inside of pipelines

In this paper we present an in-pipe robot, called MRINSPECT V (Multifunctional Robotic crawler for In-pipe inSPECTion V), which is under development for the inspection of pipelines with a nominal 8-inch inside diameter. To travel freely in every pipeline element, the robot adopts a differential driving mechanism that we have developed. Furthermore, by introducing clutches in transmitting driving power to the wheels, MRINSPECT V is able to select the suitable driving method according to the shape of the pipeline and save the energy to drive in pipelines. The robot aiming for autonomous navigation is configured with four modules serially connected. Two active driving modules are located in front and rear of the system, respectively. Passive modules are linked between the driving modules. This module-based robot can fit to narrow and winding pipelines by using the novel mechanism such as the specially designed module-joints. In this paper, the critical points in the design and construction of the proposed robot are described with the preliminary results of experiments that yield good mobility and increased efficiency.

Iterated filters for bearing-only SLAM

This paper discusses the importance of iteration when performing the measurement update step for the problem of bearing-only SLAM. We focus on an undelayed approach that initializes a landmark after only one bearing measurement. Traditionally, the extended Kalman filter (EKF) has been used for SLAM, but the EKF measurement update rule can often lead to a divergent state estimate due to its inconsistency in linearization. We discuss the flaws of the EKF in this paper, and show that even the well established inverse-depth parametrization for bearing-only SLAM can be affected. We then show that representing the bearing-only update as a numerical optimization problem (solved with an iterative approach such as Gauss-Newton minimization) prevents divergence of the Kalman filter state and produces accurate SLAM results for a bearing-only sensor. More specifically, we propose the use of an iterated Kalman filter to resolve the issues normally associated with the EKF measurement update. Two outdoor mobile robot experiments are discussed to compare algorithm performance.

A small biomimetic quadruped robot driven by multistacked dielectric elastomer actuators

A kind of dielectric elastomer (DE) material, called ‘synthetic elastomer’, has been developed based on acrylonitrile butadiene rubber (NBR) to be used as a dielectric elastomer actuator (DEA). By stacking single layers of synthetic elastomer, a linear actuator, called a multistacked actuator, is produced, and used by mechatronic and robotic systems to generate linear motion. In this paper, we demonstrate the application of the multistacked dielectric elastomer actuator in a biomimetic legged robot. A miniature robot driven by a biomimetic actuation system with four 2-DOF (two-degree-of-freedom) legged mechanisms is realized. Based on the experimental results, we evaluate the performance of the proposed robot and validate the feasibility of the multistacked actuator in a locomotion system as a replacement for conventional actuators.

Development of Wall Climbing Robot System by Using Impeller Type Adhesion Mechanism

In this paper, we present a wall climbing robot system, called “LARVA”, developed for visual inspection of structures with flat surfaces. The robot has two differential driving wheels with a suspension and an adhesion mechanism. The adhesion mechanism is composed of an impeller and two–layered suction seals. It is designed to provide sufficient adhesion force and be controlled so that the robot can move freely on various wall surfaces. The static and aerodynamic modeling of the adhesion mechanism is given and the analysis of the adhesion mechanism, air leakage, and inner flow are carried out to be useful for the design as well as the control. Finally, the performances of the robot are experimentally verified on several kinds of walls and its feasibility is validated.

Directly printed stretchable strain sensor based on ring and diamond shaped silver nanowire electrodes

In this study, we fabricated a stretchable Silver nanowires (Ag NWs)/PDMS composite strain sensor with arbitrary micro-pattern electrodes using dispensing nozzle printing. In order to ensure a mechanically stable design, we proposed two types of electrodes: patterns of overlapped rings and diamonds. We also demonstrated that the electrical resistance could be modified according to the printing speed because the number of conductive fillers was proportional to the liquid ejection time. We also conducted static simulation for the two geometries to study the effect of the patterns when the strain sensor is stretched. We achieved highly stretchable strain sensor (up to 60% strain) with a suitable electrode design. Based on experimental results, it is expected that directly drawn electronic skin (E-skin) via the printing method can be fabricated with multifunctional sensing abilities in the near future.

In-pipe robot navigation based on the landmark recognition system using shadow images

In this paper, we present an autonomous in-pipe robot navigating system using vision-based landmark recognition. We propose to use special features of the pipelines (such as elbows or branches) as landmarks by recognizing the shadows of the elbows and branches. To obtain consistent shadow images, the in-pipe robot equips with specially designed illuminator. By analyzing the shadow, the robot can easily identify these landmarks, detect the direction of the passage, and adaptively traverse through while continuously updating the map. The effectiveness of the proposed method is verified by real experiments using the in-pipe robot MRINSPECT V for inspecting inside of the miniature urban 8-inch gas pipeline structure.

A robotic finger driven by twisted and coiled polymer actuator

Previous studies reported that a twisted and coiled polymer actuator (TCA) generates strong force and large stroke by heating. Nylon 6,6 is known to be the most suitable polymer material for TCA because it has high thermal expansion ratio, high softening point and high toughness which is able to sustain gigantic twisting. In order to find the optimal structure of TCA fabricated with silver-coated nylon sewing threads, an equipment for twist-insertion (structuralization), composed of single DC motor, a slider fabricated by 3D printer and a body frame, is developed. It can measure the behaviors of TCAs as well as fabricate TCAs with desired characteristics by structuralizing fibers with controlled rotation per minutes (RPM) and turns. Comparing performances of diverse structures of TCAs, the optimal structure for TCA is found. For the verification of the availability of the optimal TCA, a TCA-driven biomimetic finger is developed. Finally, we successfully demonstrate the flexion/extension of the finger by using the actuation of TCAs.

Central pattern generator based reflexive control of quadruped walking robots using a recurrent neural network

This paper presents a novel Central Pattern Generator (CPG) model for controlling quadruped walking robots. The improvement of this model focuses on generating any desired waveforms along with accurate online modulation. In detail, a well-analyzed Recurrent Neural Network is used as the oscillators to generate simple harmonic periodic signals that exhibit limit cycle effects. Then, an approximate Fourier series is employed to transform those mentioned simple signals into arbitrary desired outputs under the phase constraints of several primary quadruped gaits. With comprehensive closed-form equations, the model also allows the user to modulate the waveform, the frequency and the phase constraint of the outputs online by directly setting the inner parameters without the need for any manual tuning. In addition, an associated controller is designed using leg coordination Cartesian position as the control state space based on which stiffness control is performed at sub-controller level. In addition, several reflex modules are embedded to transform the feedback of all sensors into the CPG space. This helps the CPG recognize external disturbances and utilize inner limit cycle effect to stabilize the robot motion. Finally, experiments with a real quadruped robot named AiDIN III performing several dynamic trotting tasks on several unknown natural terrains are presented to validate the effectiveness of the proposed CPG model and controller.