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Lower-limb exoskeletons are promising applications of robotic rehabilitation for people with motor impairment. As current studies have tailored the design of gait trajectories for the target users, realizing a high-precision motion control is a critical issue for safe and effective assistance. The walking assistance involves unique characteristic phases that embody different physical constraints and requirements for assistance. Conventional methods often utilized gain-switching control for time-varying adaptation. However, despite their intuitiveness as well as simplicity, the control performance was unsatisfying due to unmodeled responses by human behavior and continuous interaction with the external environment. To tackle these challenges, this study proposes a hybrid control method applied to the disturbance observer that can provide robust robotic rehabilitation. The proposed method adaptively identifies the exoskeletal system as a hybrid nominal model and online exchanges model-based tracking controllers parallelly to the gait phase of a user. Furthermore, a unique filter named allowance filter is introduced to compensate for the plant dynamics, preventing instability of the inverted plant and realizing digital implementation. In this article, a practical user with complete paraplegia participated in the experiments for verification of the proposed methods. [ABSTRACT FROM AUTHOR]

Powered exoskeletons for people with complete paraplegia have been controlled based on predefined joint-reference trajectories. As the target users of such robots may not realize any voluntary movement, the human body is fully constrained and follows the movement of the powered exoskeleton joints. The predefined gait pattern, however, may or may not be adequate for every user because the gait pattern is resulting from complex interactions between the body segments and environment, as well as dynamic characteristics of the body segments. As all the persons and their body segments have different dynamic characteristics, therefore, a bespoke tuning of gait parameters is necessary in order to realize the natural gait motion, which is optimal for each user. In this article, an adaptive gait pattern adjustment method is proposed. The proposed method observes the ground contact timing, which is directly related to the adequacy of the gait pattern for the user wearing a robot. Based on the ground contact timing, the joint-reference trajectories are adjusted, which are parameterized by the trunk inclination angle. The proposed method iteratively calculates an appropriate trunk inclination angle from the information of ground contact timing. In this article, the derivation of the proposed method and its experimental verification with WalkON Suit, a powered exoskeleton, are introduced. The proposed algorithm successfully worked for two practical users with complete paraplegia, and the adapted gait patterns showed excessive performance in walking speed, oxygen consumption, palm force on crutches, etc. The results were also verified by winning both gold and bronze medals in the global competition, Cybathlon 2020, while accomplishing the best records among all the teams. [ABSTRACT FROM AUTHOR]

Novel mesoporous silicas rolled with silica sheets with 2D regular spacing were prepared using a self-assembled graphene oxide (GO) template formed by mixing GO with Pluronic123 (P123). Self-assembled GO templated mesoporous silicas (SGT-PMS) showed well-developed X-ray diffraction peaks with d-spacings of 9.8–10.8 nm depending on the amount of GO, indicating mesoporous structures. The specific surface areas increased from 603.8 to 861.2 m2g−1 on adding GO. The pore size distribution was in the range 5.1–5.8 nm and pore volume in the range 0.80–0.99 m3g−1. The SEM images of SGT-PMS showed irregular elliptical particles with various sizes. TEM images showed that the cross section of SGT-PMS particles comprises a roll of silica sheets with 2D regular spacing. The pore walls of SGT-PMS are firmer and thicker than those for PMS without GO as indicated by the corresponding intensities of Q3 and Q4 signals. These results were explained well by the self-assembled GO templating mechanism. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) was prepared by carbothermal reduction of a crystalline-layered sodium silicate (δ-Na2Si2O5)/carbon nanocomposite (LCN), which contained a stacked carbon film embedded with cobalt between the silicate layers. Subsequent sintering of this mixture for 3 h at 1000–1350°C resulted in the formation of graphitic carbon and SiC. Meanwhile, sintering without a cobalt catalyst resulted in the formation of graphitic carbon, regardless of the temperature. The use of a cobalt catalyst allowed the formation of a pure SiC phase at 1350°C. The formed SiC had an irregular worm-like morphology, with a particle size of ~5 µm. The Brunauer-Emmett-Teller surface areas of graphitic carbon and SiC were 28–150 and ~7.0 m2/g, respectively. We concluded that graphite and SiC were produced at this low sintering temperature because of the cobalt catalyst, which facilitated nanomixing of carbon and SiO2 by sandwiching the carbon films between the silicate layers. [ABSTRACT FROM AUTHOR]

Carboxylated-graphene–Mn2O3 (G-COOMn) nanocomposites were grown as Mn2O3 nanowires on graphene sheets by a one-step thermal method using graphene oxide–COOH (G-COOH) and Mn(NO3)2. Graphene oxide (G) was prepared by the Hummers method by using graphite flakes as a starting material. G-COOH sheets were synthesized using G and chloroacetic acid (Cl–CH2–COOH). G, G-COOH, and G-COOMn were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, 13C-nuclear magnetic resonance, and Raman spectroscopy. The electrochemical properties of the fabricated G-COOMn supercapacitor were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests. The obtained results showed that the asymmetric supercapacitor had electrochemical capacitance performance within the potential range 0–0.7 V. The supercapacitor delivered a specific capacitance of ∼300 F g−1 at a current density of 50 mA cm−2. The method used in this work provides an easy and straightforward approach for depositing Mn2O3 nanowires on graphene sheets and may be readily extended to the preparation of other classes of hybrids based on G sheets for use in specific technological applications. [ABSTRACT FROM AUTHOR]

The preparation and structural characterization of a transparent poly(vinyl chloride)–octyltriethoxysilane-Jilin Davy Faraday-Layered solid #1 nanocomposite is reported. H +-Jilin Davy Faraday-Layered solid #1 (H 4Ti 2Si 8O 22) was prepared by proton exchange of layered Na +-Jilin Davy Faraday-Layered solid #1 (Na 4Ti 2Si 8O 22). The octyltriethoxysilane-Jilin Davy Faraday-Layered solid #1, in a siloxane-pillared form, was obtained by hydrolysis of the H +-Jilin Davy Faraday-Layered solid #1–dodecylamine–octyltriethoxysilane in pure water. In addition, the poly(vinyl chloride)–octyltriethoxysilane-Jilin Davy Faraday-Layered #1, as an organic–inorganic nanocomposite, was prepared using a poly(vinyl chloride) resin and Na +-Jilin Davy Faraday-Layered solid #1, H +-Jilin Davy Faraday-Layered solid #1 or octyltriethoxysilane-Jilin Davy Faraday-Layered #1 in tetrahydrofuran. The prepared organic–inorganic nanocomposite, as an interlayer space expander, was confirmed by XRD, SEM, EDS, TGA and TEM. The poly(vinyl chloride)–octyltriethoxysilane-Jilin Davy Faraday-Layered #1 nanocomposite showed a larger interlayer distance (~6.74 nm) than octyltriethoxysilane-Jilin Davy Faraday-Layered solid #1 (2.95 nm), H +-Jilin Davy Faraday-Layered solid #1 (0.92 nm) and Na +-Jilin Davy Faraday-Layered solid #1 (1.08 nm). [ABSTRACT FROM AUTHOR]

Mesoporous silica (MSPN12) was prepared by nonionic surfactant micelle–templated gelation of sodium silicate (Na2SiO3) and fluorosilicic acid (H2SiF6) in aqueous solution, characterized by a range of instrumental techniques, and tested as a support for Ni and Rh catalysts in the partial oxidation of methane (POM). Calcined and sintered MSPN12 exhibited well-defined d00l-spacings (3.5–4.39 nm), narrow pore distributions (2.4–3.1 nm), and large specific surface areas (552–1,246 m2 g−1), and was found to be highly thermally stable. Microscopic imaging revealed that MSPN12 comprised spherical particles with a uniform diameter of ~0.7 µm, with each particle featuring firm and regular honeycomb-type pores. MSPN12-loaded Ni and Rh maintained stable POM activity at 700 °C during almost 100 h on stream, which were comparable to those for the commercial Rh(5)/Al2O3 catalyst in terms of methane conversion and H2 formation selectivity. Thus, the combination of structural stability and favorable physicochemical properties resulted in good POM performance. [ABSTRACT FROM AUTHOR]