Multi-Phase Joint-Angle Trajectory Generation Inspired by Dog Motion for Control of Quadruped Robot.

Quadruped robots are receiving great attention as a new means of transportation for various purposes, such as military, welfare, and rehabilitation systems. The use of four legs enables a robustly stable gait; compared to the humanoid robots, the quadruped robots are particularly advantageous in improving the locomotion speed, the maximum payload, and the robustness toward disturbances. However, the more demanding conditions robots are exposed to, the more challenging the trajectory generation of robotic legs becomes. Although various trajectory generation methods (e.x., central pattern generator, finite states machine) have been developed for this purpose, these methods have limited degrees of freedom with respect to the gait transition. The conventional methods do not consider the transition of the gait phase (i.e., walk, amble, trot, canter, and gallop) or use a pre-determined fixed gait phase. Additionally, some research teams have developed locomotion algorithms that take into account the transition of the gait phase. Still, the transition of the gait phase is limited (mostly from walking to trot), and the transition according to gait speed is not considered. In this paper, a multi-phase joint-angle trajectory generation algorithm is proposed for the quadruped robot. The joint-angles of an animal are expressed as a cyclic basis function, and an input to the basis function is manipulated to realize the joint-angle trajectories in multiple gait phases as desired. To control the desired input of a cyclic basis function, a synchronization function is formulated, by which the motions of legs are designed to have proper ground contact sequences with each other. In the gait of animals, each gait phase is optimal for a certain speed, and thus transition of the gait phases is necessary for effective increase or decrease in the locomotion speed. The classification of the gait phases, however, is discrete, and thus the resultant joint-angle trajectories may be discontinuous due to the transition. For the smooth and continuous transition of gait phases, fuzzy logic is utilized in the proposed algorithm. The proposed methods are verified by simulation studies.

Palladium-Zeolite nanofiber as an effective recyclable catalyst membrane for water treatment.

Zeolite is an exciting natural material due to its unique capability of ammonium nitrogen (NH3N) adsorption in water. In this study, multifunctional hybrid composites of zeolite/palladium (Ze/Pd) on polymer nanofiber membranes were fabricated and explored for sustainable contaminant removal. SEM and XRD demonstrated that zeolite and palladium nanoparticles were uniformly distributed and deposited on the nanofibers. NH3N recovery rate was increased from 23 to 92% when palladium coated zeolite was embedded on the nanofiber. Multifunctional nanofibers of Ze/Pd membranes were able to adsorb NH3N on the zeolites placed on the surface of fibers and palladium catalysts were capable of selective oxidation of NH3N to N2 gas. The cycling of NH3N adsorption-oxidation, high flux, hydrophilicity, and flexibility of the membrane makes it a strong candidate for water treatment.

Three-dimensional (3D) palladium-zinc oxide nanowire nanofiber as photo-catalyst for water treatment.

Zinc Oxide Nano Wires (ZNWs) has been considered as a promising material for purification and disinfection of water and remediation of hazardous waste owing to its high activity and lower cost. In this study, three-dimensional (3D) structured palladium (Pd)/ZNWs were synthesized on the fabricated electrospun nanofibers and explored for enhancement of organic matter (OM) removal efficiency in water by suppressing electron-hole recombination during photocatalytic activity and increased surface area. The densely populated ZNWs were fabricated on the electrospun nanofiber by electroless plating (EP) and hydrothermal synthesis. In order to improve photocatalytic efficiency, a thin layer of Pd was coated prior to ZNWs growth to induce suppression of electron hole recombination produced during catalyst activity. The creation of a highly porous network of nanofibers decorated with ZNWs resulted in an increase of specific removal rate (SRR) of OM from 0.0249 to 0.0377 mg CODCr removed/mg ZNWs-hr when ZNW were grown on a Pd layer. It is believed that the demonstration of OM removal in the water through Pd/ZNWs membrane and enhanced photocatalytic activity under UV irradiation from layered structure can broaden potential applicability of Pd/ZNWs membranes for various photo catalytic water treatment.