Doik Kim

Synthesis of soluble polypyrrole of the doped state in organic solvents

Polypyrrole soluble in m-cresol and conditionally soluble in chloroform, dichloromethane or 1,1,2,2-tetrachloroethane was synthesized chemically by using dodecylbenzene sulfonic acid as the dopant and ammonium persulfate as the oxidant. The polymer was soluble in m-cresol and became soluble in the weakly poor solvents such as chloroform, dichloromethane and 1,1,2,2-tetrachloroethane when equal amounts of dodecylbenzene sulfonic acid and polymer were added to one of the solvents. Soluble polypyrrole showed the same spectra of FT-Raman scattering and UV-Vis light absorption as those of electrochemically polymerized polypyrrole. The intrinsic viscosity of the soluble polypyrrole in m-cresol was 0.17 dl/g. The solution of the polymer in chloroform was cast to a stiff film with a very smooth surface and the electrical conductivity of the film was 5 S/cm. The redox reactivity of the film was sustained for a long time in cyclovoltammetry.

Posture/Walking Control for Humanoid Robot Based on Kinematic Resolution of CoM Jacobian With Embedded Motion

This paper proposes the walking pattern generation method, the kinematic resolution method of center of mass (CoM) Jacobian with embedded motions, and the design method of posture/walking controller for humanoid robots. First, the walking pattern is generated using the simplified model for bipedal robot. Second, the kinematic resolution of CoM Jacobian with embedded motions makes a humanoid robot balanced automatically during movement of all other limbs. Actually, it offers an ability of whole body coordination to humanoid robot. Third, the posture/walking controller is completed by adding the CoM controller minus the zero moment point controller to the suggested kinematic resolution method. We prove that the proposed posture/walking controller brings the disturbance input-to-state stability for the simplified bipedal walking robot model. Finally, the effectiveness of the suggested posture/walking control method is shown through experiments with regard to the arm dancing and walking of humanoid robot.

Difference in doping behavior between polypyrrole films and powders

Abstract The differences in protonation and charge transfer behavior between polypyrrole (PPY) powders and films doped with inorganic acids, such as H2SO4 and HClO4, or bulky acids, such as dodecylsulfonic acid (DS), toluene-4-sulfonic acid (TSA), dodecylbenzensulfonic acid (DBSA) and poly(styrenesulfonic acid) (PSSA), were assessed quantitatively by the X-ray photoelectron spectroscopic (XPS) technique. PPY-dodecylsulfate and PPY-toluene-4-sulfonate films with [N + ] [N] ratio over 40% can be readily prepared electrochemically. Treatment of these salt films with a base results in the 25% deprotonated PPY. Reprotonation of the 25% deprotonated PPY films (containing 25% =N- units) by excess bulky acids readily results in complexes with surface [N + ] [N] ratios substantially above 50%. For deprotonated PPY films loaded with excess inorganic acids, and deprotonated PPY powders loaded with excess simple or bulky acids, the protonation level or [N + ] [N] ratio remains in the order of 25 to 30%. Raman and UV-Vis spectroscopies show little difference in structures of PPY formed chemically and electrochemically, but morphologies of cross sections of the simple and bulky anion-doped samples look different from each other. The enhanced charge transfer interaction in PPY-bulky anion films is probably attributable to the counter-ion-induced molecular ‘blending’ between the polymer and the dopant.

Studies of the overoxidation of polypyrrole

Resistometry, UV-Vis and Raman Spectroscopy have been employed as in-situ methods for the determination of the overoxidation potential of polypyrrole (PPy). These methods all show that the onset of overoxidation begins at potentials as low as 0.65V v Ag/AgCl for unsubstituted PPy. They also show a strong dependence of overoxidation potential on the pH of the supporting electrolyte, with an increase in stability at lower pHs.

On the walking control for humanoid robot based on the kinematic resolution of CoM Jacobian with embedded motion

This paper proposes the walking pattern generation method, the kinematic resolution method of CoM (center of mass) Jacobian with an embedded motion, and the walking controller design method for humanoid robots. First, the walking pattern is generated using the simplified model for bipedal robot. Second, the kinematic resolution of CoM Jacobian with embedded motion makes a humanoid robot balanced automatically during the movement of the all other limbs. Actually, it offers the ability of whole body coordination to the humanoid robot. Third, the walking controller is composed of the CoM controller minus the ZMP (zero momentum position) controller. Also, we show that the proposed walking controller brings the disturbance input-to-state stability (ISS) for the simplified bipedal walking robot model. Finally, the effectiveness of the proposed kinematic resolution method and walking controller is shown through experiments in regard to humanoid robot dancing and walking

Surface studies of pristine and surface-modified polypyrrole films

Polypyrrole (PPY) films having high conductivity were synthesized electrochemically in acetonitrile at low temperature and low current density. Pristine, deprotonated, and ozone-pretreated PPY films were subjected to either thermally induced or near-UV-light-induced graft copolymerization with acrylic acid (AAc), or sodium salt of 4-styrenesulfonic acid (NaSS). Surface structures and redox states of the pristine, deprotonated, reprotonated, and surface-modified polypyrrole films were studied by angle-dependent X-ray photoelectron spectroscopy (XPS). The morphology of the PPY surface after modification by graft copolymerization was revealed by atomic force microscopy (AFM). The results showed that the density of surface grafting decreased with ozone pretreatment. Surface grafting of the two polymeric acids also gave rise to a self-protonated surface structure. A substantial proportion of the grafted protonic acid groups at the surface remained free for further surface functionalization. The surface characteristics, in particular the charge-transfer interactions and the changes in the intrinsic redox states of the substrate films, associated with the external protonation and surface self-protonation processes were also discussed.

Real-Time Walking Pattern Generation Method for Humanoid Robots by Combining Feedback and Feedforward Controller

This paper focuses on real-time walking pattern generation for humanoid robots with linear inverted pendulum model (LIPM). In general, there are many issues in generating proper walking patterns of center of mass and zero moment point (ZMP) with the LIPM since the LIPM has two drawbacks such as instability and non-minimum phase property. For resolving these difficulties, the paper proposes a new real-time approach by combining a feedback and a feedforward controller. The feedback controller employs a pole placement method which shifts the poles of the LIPM in order to improve system stability. The feedforward controller utilizes advanced pole-zero cancelation by series approximation method (APZCSA) for reducing non-minimum phase property which occurs by an unstable zero and is not able to be dealt with by the feedback controller. In addition, the APZCSA improves the tracking error induced by finite series approximation. Using the two controllers, the proposed method makes the transfer function of overall walking pattern generation system approximately unity and consequently generates a stable walking pattern which follows a desired ZMP according to walking path. The efficiency of the proposed method is verified by walking pattern planning examples and experiments with the humanoid robot MAHRU-R.

Design and implementation of IMU-based human arm motion capture system

This paper presents the design of a generic inertial measurement unit (IMU) module for motion capture system. The module consists of 32-bit microcontroller with gyroscope, accelerometer, and magnetometer to provide orientation estimation of human limbs. An orientation estimation algorithm that compensates magnetic distortion is implemented. Our main contribution is on the sensor network which is low cost but high speed. We developed a serial-chain network for sensors interconnection in which UART communication is used. We also consider frame alignment issue in developing human arm motion capture to improve tracking accuracy. A simple frame calibration method is implemented and tested.

Characterization of the Hokuyo UBG-04LX-F01 2D laser rangefinder

This paper presents a characterization of the Hokuyo UBG-04LX-F01 laser rangefinder (LRF). The Hokuyo LRFs are suitable for a small mobile robot due to their small size and light weight. In particular, the scan frequency of Hokuyo UBG-04LX-F01 is higher than those of the previous LRFs in its price range. However, there is no research on characterizing this LRF for the convenience of practical use. Therefore, this paper characterizes the Hokuyo UBG-04LX-F01 and analyzes the effect of the target properties, such as incidence angle, color, brightness, and material, by measuring the distance to a target. The experimental results show that the measurement error is strongly influenced by the incidence angle and the brightness of the target surface. From the experimental results, a calibration model is also proposed to measure the accurate distance to a target.

Speaker localization using the TDOA-based feature matrix for a humanoid robot

Research on human-robot interaction has recently been getting increasing attention. In the research field of human-robot interaction, speech signal processing in particular is the source of much interest. In this paper, we report on a speaker localization system with six microphones for a humanoid robot called MAHRU of KIST and propose a time delay of arrival (TDOA)-based feature matrix with its algorithm based on the minimum sum of absolute errors (MSAE) for sound source localization. The TDOA-based feature matrix is defined as a simple database matrix calculated from pairs of microphones installed on a humanoid robot. To verify the solid performance of our speaker localization system for a humanoid robot, we present the various experimental results for the speech sources at all directions within 5 m distance and the height divided into three parts.