Visualisation of constrained predictive control of a liquid–liquid extractor

The extraction of aqueous oxalic acid into a mixture of tributyl phospate and dodecane in a pulsed column exhibited strong coupling between the two inputs, solvent feed-rate and pulsation frequency, and the two outputs, raffinate pH and bottom conductivity (an indication of flooding). A visualisation technique in which both the outputs and inputs and their constraints were represented on a phase plane proved useful to explain circuitous reponses and settling points that did not agree with setpoints. The visualisation is proposed as a useful real-time diagnostic tool which condenses the available information and creates easily recognisable patterns as a basis for tuning or problem identification.     

The active learning hypothesis of the job–demand–control model: an experimental examination

The active learning hypothesis of the job–demand–control model [Karasek, R. A. 1979. “Job Demands, Job Decision Latitude, and Mental Strain: Implications for Job Redesign.” Administration Science Quarterly 24: 285–307] proposes positive effects of high job demands and high job control on performance. We conducted a 2 (demands: high vs. low) × 2 (control: high vs. low) experimental office workplace simulation to examine this hypothesis. Since performance during a work simulation is confounded by the boundaries of the demands and control manipulations (e.g. time limits), we used a post-test, in which participants continued working at their task, but without any manipulation of demands and control. This post-test allowed for examining active learning (transfer) effects in an unconfounded fashion. Our results revealed that high demands had a positive effect on quantitative performance, without affecting task accuracy. In contrast, high control resulted in a speed–accuracy tradeoff, that is participants in the high control conditions worked slower but with greater accuracy than participants in the low control conditions.     

Supervisory control of air–fuel ratio in spark ignition engines

The problem of air–fuel ratio stabilization in spark ignition engines is addressed in this paper. The proposed strategy consists of proper switching among two control laws to improve quality of the closed-loop system. The first control law is based on an a priori off-line identified engine model and ensures robust and reliable stabilization of the system at large, while the second control law is adaptive, it provides on-line adaptive adjustment to the current fluctuations and improves accuracy of the closed-loop system. The supervisor realizes a switching rule between these control laws providing better performance of regulation. Results of implementation on two vehicles are reported and discussed.     

Thermodynamics of liquid Pb–In–Sn alloys determined by vapour pressure measurements

Application of Knudsen method for studies of liquid Pb–In and Pb–In–Sn alloys in temperatures 868–1200 and 848–1219 K, respectively, provided experimental data which made it possible to characterize thermodynamic properties of liquid phase of Pb–In and Pb–In–Sn systems. The produced experimental data were used in the optimization procedure aimed at determination of parameters of thermodynamic models of the Pb–In and Pb–In–Sn systems, linking the measured mass change rates with the thermodynamic properties of these systems. The model applied in this procedure uses equations proposed by Pelton and Bale, modified in the scope of this study. They provide an extension of the standard “dilute interaction parameter formalism” to non-dilute solutions. Parameters of the equations were calculated during optimization procedure using the least square method where the author’s experimental database was supplemented with the data which characterize molar enthalpies of mixing of both examined liquid alloys.     

Solution of an emergency air traffic control problem by differential dynamic programming†

An Air Traffic Control (ATC) problem in a case of emergency, when some of the airports become unoperational, is considered. The problem is first stated as a fully cooperative Non-zero-Sum Differential Game (NZDG) with perfect information. It is immediately reformulated as an optimal control problem. A computer programme, solving this problem numerically, has been developed. The programme is based on the Differential Dynamic Programming (DDP) algorithm. A numerical example is solved on the CDC CYBER-73 computer. The results are presented in a form understandable by laymen unfamiliar with the mathematical methods utilized in the solution.     

Fuzzy bang–bang relay control of a single-axis active magnetic bearing system

Active magnetic bearings (AMB) are presently being utilized in various classes of rotating machinery. Although the rotor-AMB systems are open loop unstable, they are easily stabilized using feedback control schemes of which the PID controller is the most commonly used. The PID controller is however only effective at the vicinity of the rotor’s equilibrium position where the dynamics of the rotor-AMB system is linearized. Significant deviation of the rotor’s motion from this equilibrium position may occur due to large imbalance forces. In this situation, the nonlinearity in AMBs, which arises from the relationship between the electromagnetic force, coil current and air gap, may render the PID controller ineffective. For the control of nonlinear systems, artificial intelligence techniques such as fuzzy and hybrid techniques are effective. In this paper, a new fuzzy controller is proposed for the control of a single-axis AMB system. This controller is based on the bang–bang scheme, which is an old but effective technique to control nonlinear systems in optimal time. The performance of the proposed integrated fuzzy bang–bang relay controller (FBBRC) was found to be superior to that of the optimized PD controller and the conventional fuzzy logic controller. Comparison of the FBBRC with the fuzzy logic controller cascaded with a hard limiter (FBBC) relay revealed almost equal performance. High frequency chattering was however observed in the steady-state response of the FBBC. Such chattering is known to cause instability and distortion in the amplifiers that are used to supply current to the magnetic bearing actuators.     

Human–machine collaboration through vehicle head up display interface

This work introduces a novel design for an automotive full-windshield head-up display (HUD) interface which aims to improve the driver’s spatial awareness and response times under low visibility conditions. To fulfil these requirements, we have designed and implemented a working prototype of a human–machine interface (HMI). Particular emphasis was placed on the prioritisation and effective presentation of information available through vehicular sensors, which would assist, without distracting, the driver in successfully navigating the vehicle under low visibility conditions. The proposed interface is based on minimalist visual representations of real objects to offer a new form of interactive guidance for motorway environments. Overall, this work discusses the design challenges of such a human–machine system, elaborates on the interface design philosophy and presents the outcome of user trials that contrasted the effectiveness of our proposed HUD against a typical head-down display (HDD).     

Prediction of flow pattern of gas–liquid flow through circular microchannel using probabilistic neural network

The present study attempts to develop a flow pattern indicator for gas–liquid flow in microchannel with the help of artificial neural network (ANN). Out of many neural networks present in literature, probabilistic neural network (PNN) has been chosen for the present study due to its speed in operation and accuracy in pattern recognition. The inbuilt code in MATLAB R2008a has been used to develop the PNN. During training, superficial velocity of gas and liquid phase, channel diameter, angle of inclination and fluid properties such as density, viscosity and surface tension have been considered as the governing parameters of the flow pattern. Data has been collected from the literature for air–water and nitrogen–water flow through different circular microchannel diameters (0.53, 0.25, 0.100 and 0.050 mm for nitrogen–water and 0.53, 0.22 mm for air–water). For the convenience of the study, the flow patterns available in literature have been classified into six categories namely; bubbly, slug, annular, churn, liquid ring and liquid lump flow. Single PNN model is unable to predict the flow pattern for the whole range (0.53 mm–0.050 mm) of microchannel diameter. That is why two separate PNN models has been developed to predict the flow patterns of gas–liquid flow through different channel diameter, one for diameter ranging from 0.53 mm to 0.22 mm and another for 0.100 mm–0.05 mm. The predicted map and their transition boundaries have been compared with the corresponding experimental data and have been found to be in good agreement. Whereas accuracy in prediction of transition boundary obtained from available analytical models used for conventional channel is less for all diameter of channel as compared to the present work. The percentage accuracy of PNN (～94% for 0.53 mm ID and ～73% for 0.100 mm ID channel) has also been found to be higher than the model based on Weber number (～86% for 0.53 mm ID and ～36% for 0.05 mm ID channel).     

A parameter-varying filtered PID strategy for air–fuel ratio control of spark ignition engines

In this paper, a new synthesis method is presented to control air–fuel ratio (AFR) in spark ignition engines to maximize the fuel economy while minimizing exhaust emissions. The major challenge in the control of AFR is the time-varying delay in the control loop which restricts the application of conventional control techniques. In this paper, the time-varying delay in the system dynamics is first approximated by Padé approximation to render the system dynamics into non-minimum phase characteristics with time-varying parameters. Application of parameter-varying dynamic compensators is invoked to retrieve unstable internal dynamics. The associated error dynamics is then utilized to construct a filtered PID controller combined with a parameter-varying dynamic compensator to track the desired AFR command using the feedback from the universal exhaust gas oxygen sensor. The proposed method achieves desired dynamic properties independent of the matched disturbances. It also accommodates the unmatched perturbations due to the dynamic compensator features. The results of applying the proposed method to experimental numerical data demonstrate the closed-loop system stability and performance against time-varying delay, canister purge disturbances and measurement noise for both port fuel injection engines and lean-burn engines.     

Behavior of fluid lubricant and air–oil interface of operating FDBs due to operating condition and seal design

This paper investigated the behavior of fluid lubricant and air–oil interface of operating fluid dynamic bearings (FDBs) by using two-phase flow analysis of air and oil to describe the oil sealing mechanism of operating FDBs. The two-phase flow of fluid lubricant and air was analyzed by using the Navier–Stokes equation and the volume of fluid method of a multi-phase flow. The proposed numerical method was verified by the numerical result of the Reynolds equation and the experimental result of the prior researcher. This research also discussed the effect on the oil leakage of the operating FDBs due to the existence of inward pumping groove, tapering angle and initial position of fluid.     

Principles of transparency for autonomous vehicles: first results of an experiment with an augmented reality human–machine interface

Cognition, Technology & Work - Highly automated driving allows the driver to temporarily delegate the driving task to the autonomous vehicle. The challenge is to define the information that...     

Lattice Boltzmann simulation of liquid–gas flows through solid bodies in a square duct

The lattice Boltzmann method for two-phase immiscible fluids with large density differences proposed by Inamuro et al. [T. Inamuro, T. Ogata, S. Tajima, N. Konishi, A lattice Boltzmann method for incompressible two-phase flows with large density differences, J. Comput. Phys. 198 (2004) 628–644] is applied to the problem of liquid–gas flows through solid bodies in a square duct. A wetting boundary condition is introduced so that partial wetting on solid surfaces is realized to agree with Cahn theory. Using this method, we investigate the characteristics of wettability in terms of dynamic contact angles between two fluids and a solid wall. Also, we carry out simulations of liquid–gas rising flows through solid bodies in a square duct. It is found from these simulations that the present method can be useful for the problems of liquid–gas flows through complicated geometries.     

Viscous flow and colloid transport near air–water interface in a microchannel

In order to understand the transport behavior of colloids near an air–water interface (AWI), two computational methods are applied to simulate the local water flow field near a moving AWI in a 2D microfluidic channel. The first method is a mesoscopic multicomponent and multiphase lattice Boltzmann (LBM) model and the second is the macroscopic, Navier–Stokes based, volume-of-fluid interface tracking method. In the LBM, it is possible to predict the dynamic contact angles after the static contact angle is correctly set, and the predicted dynamic contact angles are in good agreement with previous observations. It is demonstrated that the two methods can yield a similar flow velocity field if they are applied properly. The flow field relative to AWI depends on the direction of the flow, and exhibits curved streamlines that transport fluid between the center of the channel and the wall region. Using the obtained flow, the motion of sub-micron colloids in a de-ionized water solution is then studied by a Lagrangian approach. The observed colloid trajectories are in qualitative agreement with our visualizations using a confocal microscope.     

Effect of temperature and helium ratio for performance of thermal flying control in air–helium gas mixture

This paper proposes advanced approach able to calculate the gas properties with the temperature of binary gas mixture using the diffusion-based diameter and investigates the performance of thermal flying control for different temperature and fraction ratio at head disk interface. It is found that because of the combined effects of mean free path, thermal conductivity and viscosity, the heat transfer coefficient increases with the increase of fraction of ratio, while it decreases with the increase of temperature reversely. In addition, the pole-tip protrusion increases substantially with increase of the fraction ratio. And in higher temperature, it linearly decreases more.     

Investigation on pressure drop characteristic and mass transfer performance of gas–liquid flow in micro-channels

Pressure drop characteristics and mass transfer performance of gas–liquid two-phase flow in micro-channels with different surface wettabilities were experimentally investigated. Side-entry T micro-channel mixers made of glass and polydimethylsiloxane were tested. Frictional pressure drop was found to decrease as the hydrophobicity of the channel surface increased. The flow patterns observed in the experiment were classified as slug flow and continuous gas phase flows. The modified Hagen–Poiseuille equation and Lockhart–Martinelli model were developed to predict the pressure drop for these two types of flow, respectively. The effect of surface wettability was heuristically incorporated in the present models which can correlate well the experimental results. Mass transfer performance was studied by the physical absorption of oxygen into de-ionized water. The results show that the volumetric mass transfer coefficients in hydrophobic micro-channels are generally higher than those in hydrophilic ones. The empirical correlations of overall volumetric mass transfer coefficients were proposed.     

The active disturbance rejection control of the rotating disk–beam system with boundary input disturbances

This paper deals with the stabilisation of the rotating disk–beam system, where the control ends of beam and disk are suffered from disturbances, respectively. The active disturbance rejection control (ADRC) approach is adopted in investigation. The disturbances are first estimated by the extended state observers, and the observer-based feedback control laws are then designed to cancel the disturbances. When the angular velocity of the disk is less than the square root of the first nature frequency of the beam, it is shown that the feedback control laws are robust to the external disturbances, that is, the vibration of the beam can be suppressed while the disk rotating with a desired angular velocity in presence of the disturbances. Finally, the simulation results are provided to illustrate the effectiveness of ADRC approach.     

Rapid stabilisation of an Euler–Bernoulli beam with the internal delay control

ABSTRACT

In this paper, we are concerned with rapid stabilisation of an Euler--Bernoulli beam with internal delayed control. Herein we introduce a new approach of the feedback control design from the system equivalence point of view. The design approach can be divided into several steps. First, we construct a target system of the desired stability. Second, we select a suitable integral transform that transforms the present system to the target system. In this procedure, one can get a corresponding feedback control. Third, we find a transform that transforms the target system to the present system, which provides the equivalence of both systems. Finally, we prove that the two transforms are bounded linear operators in an appropriate Hilbert space.     

Efficient numerical integration of an elastic–plastic damage law within a mixed velocity–pressure formulation

This study focuses on numerical integration of constitutive laws in numerical modeling of cold materials processing that involves large plastic strain together with ductile damage. A mixed velocity–pressure formulation is used to handle the incompressibility of plastic deformation. A Lemaitre damage model where dissipative phenomena are coupled is considered. Numerical aspects of the constitutive equations are addressed in detail. Three integration algorithms with different levels of coupling of damage with elastic–plastic behavior are presented and discussed in terms of accuracy and computational cost. The implicit gradient formulation with a non-local damage variable is used to regularize the localization phenomenon and thus to ensure the objectivity of numerical results for damage prediction problems. A tensile test on a plane plate specimen, where damage and plastic strain tend to localize in well-known shear bands, successfully shows both the objectivity and effectiveness of the developed approach.     

Selectively modified microfluidic chip for solvent extraction of Radix Salvia Miltiorrhiza using three-phase laminar flow to provide double liquid–liquid interface area

Radix Salvia Miltiorrhiza, a famous herb medicine is widely used in China and limitedly used in USA, Japan, and other countries for the treatment of cardiovascular and cerebrovascular diseases. This herb medicine has two groups (non-polar and polar) of active ingredients with distinct clinical effects, and thus theses ingredients should be separately used to enhance therapeutic efficacy and reduce side effect. In this article, as an alternative of conventional mechanical shaking and separatory funnel, laminar flow extraction in microfluidic chip is proposed to separate the two kinds of herb ingredients. Compared with conventional methods, microfluidic chip provides continuous extraction, less labor intensity, and better performance. Furthermore, we employ three-phase laminar flow to provide double liquid–liquid interface area, circumventing the low efficiency of two-phase laminar flow. Therefore, the extraction ratio is dramatically improved to 92% (tanshinone IIA). To predict the extraction ratio, a straightforward theoretical model is also established and agrees well with the experimental results. This microfluidic chip would be a powerful technical platform for handling complicated natural products.