CO2 bubble absorption enhancement in methanol-based nanofluids

In this study, the nanoparticles (i.e. SiO₂ and Al₂O₃ nanoparticles) and methanol are combined into SiO₂/methanol and Al₂O₃/methanol nanofluids to enhance the CO₂ absorption rate of the base fluid (methanol). The absorption experiments are performed in the bubble type absorber system equipped with mass flow controller (MFC), mass flow meter (MFM) and silica gel (which can remove the methanol vapor existing in the outlet gases). The parametric analysis on the effects of the particle species and concentrations on CO₂ bubble absorption rate is carried out. The particle concentration ranges from 0.005 to 0.5 vol%. It is found that the CO₂ absorption rate is enhanced up to 4.5% at 0.01 vol% of Al₂O₃/methanol nanofluids at 20 °C, and 5.6% at 0.01 vol% of SiO₂/methanol nanofluids at −20 °C, respectively.     

Time-efficient and complete coverage path planning based on flow networks for multi-robots

Complete coverage path planning (CCPP), specifically, the efficiency and completeness of coverage of robots, is one of the major problems in autonomous mobile robotics. This study proposes a path planning technique to solve global time optimization. Conventional algorithms related to template-based coverage can minimize the time required to cover particular cells. The minimal turning path is mostly based on the shape and size of the cell. Conventional algorithms can determine the optimum time path inside a cell; however, these algorithms cannot ensure that the total time determined for the coverage path is the global optimum. This study presents an algorithm that can convert a CCPP problem into a flow network by exact cell decomposition. The total time cost to reach the edge of a flow network is the sum of the time to cover the current cell and the time to shift in adjacent cells. The time cost determines a minimum-cost path from the start node to the final node through the flow network, which is capable of visiting each node exactly once through the network search algorithm. Search results show that the time-efficient coverage can obtain the global optimum. Simulation and experimental results demonstrate that the proposed algorithm operates in a time-efficient manner.     

Sliding mode controls of double-pendulum crane systems

This study focuses on the design of robust nonlinear controllers based on both conventional and hierarchical sliding mode techniques for double-pendulum overhead crane systems. In the first approach, a first-order sliding surface is provided and a proper control scheme is generated to stabilize the surface. In the second approach, two levels of sliding surfaces are proposed and the control scheme is designed based on the stability of the second-level surface. We also prove the stability of the first-level sliding surface. To verify the quality of the proposed controllers, simulation for a particular type of overhead crane systems is implemented. Simulation results show that all state trajectories asymptotically converged to desired values.     

Passivity-based Nonlinear Control for a Ballbot to Balance and Transfer

International Journal of Control, Automation and Systems - Ballbot is a robot that can transfer to a given position while maintaining a self-balanced upright posture on a spherical ball. This paper...     

Simulation and experimental methods for media transport system: Part II,effect of normal force on slippage of paper

Many daily appliances for examples copiers, printers and ATMs contain the media transport system (MTS) and the slippage between the medium in the MTS deteriorates the performance quality of the whole system The slippage of the medium in the MTS is affected by many parameters including the friction coefficient between the feeding rollers and the medium, the velocity of the feeding rollers, and the normal force exerted on the medium by feeding rollers This paper focuses on the effect of the normal force on the slippage while the medium is being fed For this purpose, we developed a two-dimensional simulation model for a paper feeding system. Using the simulation model, we calculated the slippage of the paper for different normal forces We have also constructed a testbed of the paper feeding system to verify the simulation results Experimental results are compared with the simulation resultsKey Words: Media Transport System, Slippage, Normal Force, Friction Coefficients, Paper Modeling

     

Model-based reference trajectory generation for tip-based learning controller

The non-minimum phase characteristic of a flexible manipulator makes tracking control of its tip difficult The level of the tip tracking performance of a flexible manipulator is significantly affected by the characteristics of the tip reference trajectory as well as the characteristics of the flexible manipulator system This paper addresses the question of how to best specify a reference trajectory for the tip of a flexible mampulator to follow in order to achieve the objectives of reducing tip tracking error, residual tip vibration, and the required actuation effort at the manipulator joint A novel method of tip-based learning controller for the flexible manipulator system is proposed in the paper, where a model of the flexible manipulator system with a command shaping filter is used to generate a smooth and realizable tip reference trajectory for a tip-based learning controller     

Adaptive sliding mode control of overhead cranes with varying cable length

An overhead crane transports cargoes of various weights and volumes depending on the operation case. Friction factors characterized by damped coefficients are changeable in terms of the operating environment. In this study, an adaptive version of the sliding mode control of a crane system is developed in the case of no priori knowledge of the payload mass and damped elements. Using two inputs, namely, trolley driving force and cargo lifting force, the proposed adaptive robust controller simultaneously executes four duties, including tracking the trolley, hoisting the cargo, keeping the cargo swing small during transient state, and completely eliminating the payload angle at steady destination. Numerical simulations and experiments are conducted to investigate the quality of the proposed controller. The results show that the proposed controller works well and all system responses are asymptotically stabilized.     

Seeing the electroporative uptake of cell-membrane impermeable fluorescent molecules and nanoparticles

This paper presents direct visualization of uptake directionality for cell-membrane impermeant fluorescent molecules and fluorescence-doped nanoparticles at a single-cell level during electroporation. To observe directly the uptake direction, we used microchannel-type electroporation that can generate a relatively symmetric and uniform electric field. For all the image frames during electroporation, fluorescence intensities that occurred at cell membranes in both uptake directions toward the electrodes have been sequentially recorded and quantitatively analyzed pixel by pixel. In our experiments, we found that fluorescent molecules, even not labeled to target biomolecules, had their own uptake direction with different intensities. It is also observed that the uptake intensity toward the cell membrane had a maximal value at a certain electric voltage, not at the highest value of voltages applied. The results also imply that the uptake direction of fluorescence-doped nanoparticles can be determined by a net surface charge of uptake materials and sizes in the electroporative environments. In summary, we performed a quantitative screening and direct visualization of uptake directionality for a set of fluorescent molecules and fluorescence-doped nanoparticles using electric-pulsation. Taking a closer look at the uptake direction of exogenous materials will help researchers to understand an unknown uptake phenomenon in which way foreign materials are inclined to move, and furthermore to design functional nanoparticles for electroporative gene delivery.     

A novel modified analytical method and finite element method for vibration analysis of cable-driven parallel robots

Journal of Mechanical Science and Technology - Cable-driven parallel robots (CDPRs) are vulnerable to vibration due to the inevitable flexible properties of the cables. Thus, vibration analysis is...     

Partial Feedback Linearization Double-loop Control for a Pseudo-2D Ridable Ballbot

International Journal of Control, Automation and Systems - A ridable ballbot has unstable underactuated dynamics with nonholonomic velocity constraints and input coupling case. Such a robot can...