Multi input–single output models identification of tower bridge movements using GPS monitoring system

In this paper, RTK-GPS system was used for movement data collection. Two identification models namely; Multi input–single output (MISO) robust fit regression and Neural Network Auto-Regression Moving Average with eXogenous input (NNARMAX) models were used for the identification of these data. The analysis of test results indicate that: (1) the NNARMAX [4 4 1 1] and [5 4 1 5] models defined by taking into account the results of robust regression analysis estimate structural movements more accurately than the NNARMAX [0 1 0 0] model, and (2) the robust fit regression models have good capacities for mapping relationship of applied loads effects factors and displacements of tower. However, temperature and humidity effects on the entire modal shapes are insignificant and (3) the traffic loads are the main factor affects tower bridge displacement.     

H∞ output-feedback fuzzy proportional-integral control of fully delayed input/output systems

This paper presents the output-feedback fuzzy proportional-integral (PI) controller design for uncertain nonlinear systems with both fully delayed input and output. Based on the Takagi–Sugeno (T–S) fuzzy model representation, the output-feedback PI control is realized via parallel distributed PI compensation and novel LMI gain design. Although the T–S fuzzy PI controller is simple, asymptotic output regulation is assured to overcome the effect of uncertainty, state delay, and full input/output delays. When considering disturbance and measurement noise, the control performance is achieved by robust gain design. Furthermore, state observers and bilinear matrix inequality conditions are removed in this paper. Finally, time-delay Chua׳s circuit system and a continuous-time stirred tank reactor are taken as applications to show the expected performance.     

Input–output finite-time stabilization of linear systems with finite-time boundedness

The paper presents linear system Input–Output Finite-Time Stabilization (IO-FTS) method under Finite-Time Boundedness (FTB) constraint. A state feedback controller is designed, via Linear Matrix Inequalities (LMIs), to guarantee the system both IO-FTS and FTB. The proposed methods are applied to the guidance design of a class of terminal guidance systems to suppress disturbances with IO-FTS method and FTB constraints simultaneously satisfied. The simulation results illustrate the effectiveness of the proposed methods.     

Study of performance and emission characteristics of IC engines by using diesel–water emulsion

Due to the shortage of petroleum products and its increasing cost, efforts are on to develop alternate fuels, especially diesel oil, for partial or full replacement. Also, internal combustion engines generate undesirable emissions during combustion process. The emissions exhausted in to the surroundings pollute the atmosphere and causes several problems. The emissions of concern are: unburnt hydrocarbons, oxides of carbon, and oxides of nitrogen (NO_X). Advanced diesel fuel formulations offer significant emission reductions to new and older in-use engines every time the fuel tank is filled. The addition of water to diesel fuel lowers particulate emissions by serving as diluents to the key combustion intermediates that lead to particulate formation. The incorporation of water also reduces NO_X emissions by lowering the peak combustion temperatures through high heat of vaporization. When using water blend diesel, the engine fuel system recognizes the liquid as diesel fuel because the water droplet is encapsulated within a diesel fuel. In this experiment, we have used single cylinder four-stroke engine and the water-blend diesel emulsion is used and the diesel emission test, emulsion emission test, and various gases has been analyzed; smoke meter test is also conducted for various rate of loads. The test results from the engine fuelled with water-blend diesel showed reduction in emissions as compared to that of engine fuelled with conventional diesel. The better emissions in the CI engine using water-blend diesel is due to the incorporation of water which reduces NO_X emissions by lowering the peak combustion temperatures. Water-blend fuel enhances fuel atomization by micro-explosion. The addition of water to diesel fuel lowers particulate emissions by serving as diluents to the key combustion intermediates that lead to particulate formation     

Temperature–friction characteristics of used lubricant from two-stroke cross-head marine diesel engines

It is now quite apparent that, in a two-stroke, cross-head marine diesel engine, the lubrication regime in the contact between piston ring and cylinder liner at the top dead centre (TDC) is of a boundary type. Therefore, the tribological performance of a system to simulate the real contact should be assessed under conditions closely resembling the operating engine environment. In the reality of engine operation, the lubricant is often contaminated by fuel and products of combustion, hence the need to study the temperature–friction characteristics of this actual lubricant under the conditions of boundary lubrication.In this paper, an oil taken from the drainage system of the engine was used. A five times heating and cooling test methodology was employed to assess tribological performance of a model contact lubricated with the actual oil. The model contact was formed by a pin sliding over a plate both made of materials used in two-stroke, cross-head marine diesel engines.Experiments showed that the general trend in temperature–friction characteristics of the used oil is similar to that of a new oil. However, the level of friction in the contact lubricated with an used oil is significantly higher than that for a new oil.     

Capacitance wire-mesh sensor applied for the visualization of three-phase gas–liquid–liquid flows

This short communication describes the application of a capacitance wire-mesh sensor for the investigation of a gas–liquid–liquid three-phase flow in a laboratory setup. Experiments with air, silicone oil and water are performed first in static and second in dynamic flow conditions. The capacitance mesh sensor is capable of generating images of the cross-sectional distribution of relative permittivity values, which in turn is an indication to the phases present in the multiphase mixture. Initial tests show that the sensor is a valuable tool to investigate three-phase flows, which are very common in the oil industry.     

A modified NARMAX model-based self-tuner with fault tolerance for unknown nonlinear stochastic hybrid systems with an input–output direct feed-through term

A modified nonlinear autoregressive moving average with exogenous inputs (NARMAX) model-based state-space self-tuner with fault tolerance is proposed in this paper for the unknown nonlinear stochastic hybrid system with a direct transmission matrix from input to output. Through the off-line observer/Kalman filter identification method, one has a good initial guess of modified NARMAX model to reduce the on-line system identification process time. Then, based on the modified NARMAX-based system identification, a corresponding adaptive digital control scheme is presented for the unknown continuous-time nonlinear system, with an input–output direct transmission term, which also has measurement and system noises and inaccessible system states. Besides, an effective state space self-turner with fault tolerance scheme is presented for the unknown multivariable stochastic system. A quantitative criterion is suggested by comparing the innovation process error estimated by the Kalman filter estimation algorithm, so that a weighting matrix resetting technique by adjusting and resetting the covariance matrices of parameter estimate obtained by the Kalman filter estimation algorithm is utilized to achieve the parameter estimation for faulty system recovery. Consequently, the proposed method can effectively cope with partially abrupt and/or gradual system faults and input failures by the fault detection.     

Study of the slow-fast preamplifier input parameter’s effects on output image for LYSO scintillator with PS-PMT based animal PET

We developed a small animal positron emission tomography with four detector heads, each one composed of 2 × 2 cm² of pixilated LYSO matrix of 10 × 10 crystals, 2 × 2 mm wide and 10 mm deep coupled to position sensitive photomultiplier (PS-PMT, Hamamatsu R8900U-00-C12). Anger-type logic discretized positioning circuit (DPC) multiplexed readout connected to PMT of each head. The fast-slow preamplifier is used in the fabricated animal PET. We showed that the input capacitance of the preamplifier (the capacitance in the output node of the resistive network) has a direct effect on output image. Image broadening, peak to valley ratio and the geometry distortion of crystal illustration are studied for different input capacitance of preamplifier. The input capacitance of 1 nF resulted in the best image by keeping all the parameters at the proper level with no geometry distortion at the edge of the image.     

Influence of the electromagnetic gap in gas–magnetic bearings on the output characteristics of high-speed rotor systems

The electromagnetic gap in gas–magnetic bearings has a considerable influence on the output load and rigidity characteristics of high-speed rotor systems, as shown by experiments and simulation.     

Refined reconstruction of liquid–gas interface structures for stratified two-phase flow using wire-mesh sensor

Wire-mesh sensors (WMS), developed at HZDR [4], [13], are widely used to visualize two-phase flows and measure flow parameters, such as phase fraction distributions or gas phase velocities quantitatively and with a very high temporal resolution. They have been extensively applied to a wide range of two-phase gas–liquid flow problems with conducting and non-conducting liquids. However, for very low liquid loadings, the state of the art data analysis algorithms for WMS data suffer from the comparably low spatial resolution of measurements and from boundary effects, caused by e.g. flange rings – especially in the case of capacitance type WMS. In the recent past, diverse studies have been performed on two-phase liquid–gas stratified flow with low liquid loading conditions in horizontal pipes at the University of Tulsa. These tests cover oil–air flow in a 6-inch ID pipe and water–air flow in a 3-inch ID pipe employing dual WMS with 32×32 and 16×16 wires, respectively. For oil–air flow experiments, the superficial liquid and gas velocities vary between 9.2 m/s≤ν_SG≤15 m/s and 0.01 m/s≤ν_SL≤0.02 m/s, respectively [2]. In water–air experiments, the superficial liquid and gas velocities vary between 9.1 m/s≤ν_SG≤33.5 m/s and 0.03 m/s≤ν_SL≤0.2 m/s, respectively [17], [18]. In order to understand the stratified wavy structure of the flow, the reconstruction of the liquid–gas interface is essential. Due to the relatively low spatial resolution in the WMS measurements of approximately 5 mm, the liquid–gas interface recognition has always an unknown uncertainty level. In this work, a novel algorithm for refined liquid–gas interface reconstruction is introduced for flow conditions where entrainment is negligible.     

Robust integral of neural network and precision motion control of electrical–optical gyro-stabilized platform with unknown input dead-zones

Parametric uncertainty associated with unmodeled disturbance always exist in physical electrical–optical gyro-stabilized platform systems, and poses great challenges to the controller design. Moreover, the existence of actuator deadzone nonlinearity makes the situation more complicated. By constructing a smooth dead-zone inverse, the control law consisting of the robust integral of a neural network (NN) output plus sign of the tracking error feedback is proposed, in which adaptive law is synthesized to handle parametric uncertainty and RISE robust term to attenuate unmodeled disturbance. In order to reduce the measure noise, a desired compensation method is utilized in controller design, in which the model compensation term depends on the reference signal only. By mainly activating an auxiliary robust control component for pulling back the transient escaped from the neural active region, a multi-switching robust neuro adaptive controller in the neural approximation domain, which can achieve globally uniformly ultimately bounded (GUUB) tracking stability of servo systems recently. An asymptotic tracking performance in the presence of unknown dead-zone, parametric uncertainties and various disturbances, which is vital for high accuracy tracking, is achieved by the proposed robust adaptive backstepping controller. Extensively comparative experimental results are obtained to verify the effectiveness of the proposed control strategy.     

Novel method for fabrication of room temperature polypyrrole–ZnO nanocomposite NO2 sensor

Nanocomposites of polypyrrole (PPy) and zinc oxide (ZnO) nanoparticles (NPs) were prepared by spin coating method. These nanocomposites were characterized by Fourier transform infrared (FTIR), Field emission scanning electron microscope (SEM), Atomic force microscopy (AFM), Transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV–vis techniques, which proved the polymerization of pyrrole monomer and the strong interaction between polypyrrole and ZnO NPs. The nanocomposites were used for gas sensing to CH₃OH, C₂H₅OH, NH₃, H₂S and NO₂ at room temperature. It was revealed that PPy–ZnO nanocomposites with different ZnO weight ratios (10%, 20%, 30%, 40% and 50%) could detect NO₂ at low concentration with very higher selectivity and sensitivity at room temperature than the reported PPy. The PPy–ZnO nanocomposites responded to NO₂ at concentration as low as 10 ppm. PPy–ZnO nanocomposite containing ZnO (50%) showed the maximum sensitivity 38% with 92.10% stability to 100 ppm NO₂ gas at room temperature. The sensing mechanism of PPy–ZnO nanocomposites to NO₂ was presumed to be the effects of p–n junction between PPy and ZnO.     

Review of human–robot coordination control for rehabilitation based on motor function evaluation

As a wearable and intelligent system, a lower limb exoskeleton rehabilitation robot can provide auxiliary rehabilitation training for patients with lower limb walking impairment/loss and address the existing problem of insufficient medical resources. One of the main elements of such a human–robot coupling system is a control system to ensure human–robot coordination. This review aims to summarise the development of human–robot coordination control and the associated research achievements and provide insight into the research challenges in promoting innovative design in such control systems. The patients’ functional disorders and clinical rehabilitation needs regarding lower limbs are analysed in detail, forming the basis for the human–robot coordination of lower limb rehabilitation robots. Then, human–robot coordination is discussed in terms of three aspects: modelling, perception and control. Based on the reviewed research, the demand for robotic rehabilitation, modelling for human–robot coupling systems with new structures and assessment methods with different etiologies based on multi-mode sensors are discussed in detail, suggesting development directions of human–robot coordination and providing a reference for relevant research.     

Experimental method of fabrication of a matched metal–dielectric structure for a sensor based on the effect of frustrated total internal reflection

An experimental method of fabrication of a sensor based on a metal–dielectric structure (Al + ZnS) and optimization of its characteristics is described. The coefficient of light reflection (p-polarization) from the aluminum layer is studied as a function of the layer thickness for different angles of incidence at the wavelength of 532 nm. Based on calculations, which are qualitatively consistent with experimental results, a structure consisting of matched layers of aluminum and zinc sulfide is fabricated; this structure has a higher angular resolution than the aluminum film with no dielectric coating. The detection limit of angular measurements by the sensor based on this structure is estimated as 2.6 · 10^-5 RIU (refraction index units).     

Temperature-mediated structural evolution of vapor–phase deposited cyclosiloxane polymer thin films for enhanced mechanical properties and thermal conductivity

Polymer-derived ceramic(PDC) thin films are promising wear-resistant coatings for protecting metals and carbon-carbon composites from corrosion and oxidation.However,the high pyrolysis temperature hinders the applications on substrate materials with low melting points.We report a new synthesis route for PDC coatings using initiated chemical vapor deposited poly(1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane)(pV₃D₃) as the precurs or.We investigated the changes in siloxane m...     

Method of calculating the cross-wind speed at the entrance aperture of an adaptive system based on Shack–Hartmann wavefront sensor measurements

This paper presents a method for calculating the cross-wind speed at the entrance aperture of an adaptive system from the coordinates of the energy centers of gravity of the focal spots measured by a Shack–Hartmann wavefront sensor. The range of applicability of the method are determined for data obtained in an experiment on an atmospheric path depending on the intensity of turbulent distortions and the optical parameters of the sensor.     

Application of dfb diode laser sensor to reacting flow (II) —liquid-gas 2-phase reacting flow—

Diode laser sensor is conducted to measure the gas temperature in the liquid-gas 2-phase counter flow flame. C₁₀H₂₂ and city gas were used as liquid fuel and gas fuel, respectively. Two vibrational overtones of H₂O were selected and measurements were carried out in the spray flame region stabilized the above gaseous premixed flame. The path-averaged temperature measurement using diode laser absorption method succeeded in the liquid fuel combustion environment regardless of droplets of wide range diameter. The path-averaged temperature measured in the post flame of liquid-gas 2-phase counter flow flame showed qualitative reliable results. The successful demonstration of time series temperature measurement in the liquid-gas 2-phase counter flow flame gave us motivation of trying to establish the effective control system in practical combustion system. These results demonstrated the ability of real-time feedback from combustor inside using the non-intrusive measurement as well as the possibility of application to practical combustion system. Failure case due to influence of spray flame was also discussed.     

Optimization of surface treatment to enhance fiber–matrix interface and performance of composites

Oxidation treatment with concentrated HNO₃ was employed to the carbon fabric (CF) for various time intervals (30–180 min) to observe the effect of treatment on two simultaneous processes involved viz. improvement in its adhesion with the matrix and reduction of fiber strength which in turn is responsible for change in the performance properties of composites. Seven composites with untreated and acid treated CF were developed based on the polyetherimide (PEI) matrix and evaluated for adhesive wear properties under various loads (200–600 N) against mild steel disc. 90 min treated CF composite indicated the best tribological properties and showed 30% reduction in specific wear rate (K₀) and 23% in coefficient of friction (μ) respectively at 600 N load. Treatment beyond this time proved detrimental for improvement in properties. Field emission scanning electron microscopy (FE-SEM) showed increase in roughness with treatment time, while atomic force microscopy (AFM) studies indicated substantial increase in roughness value. Scanning electron microscopy (SEM) of worn surfaces supported the wear mechanisms and improvement in adhesion between fiber and matrix.     

On the role of sliding load and heat input conditions in friction stir processing on tribology of aluminium alloy–alumina surface composites

ABSTRACT

Aluminium (AA5083)-alumina surface composites are prepared by friction stir processing in two conditions of heat input. The low heat (LH) input conditions is achieved at a rotational speed of 710?rpm and a traverse speed of 100?mm/min, and high heat (HH) input conditions are achieved at a rotational speed of 1400?rpm and a traverse speed of 40?mm/min. The tribological characteristics of aluminium alloy, friction stir processed (FSPed) alloy and FSPed surface composites against steel ball are studied at 5, 10 and 20?N load. While no significant influence is found on frictional behaviour, wear resistance of FSPed composites is superior to FSPed alloys. FSPed composites fabricated at HH input conditions exhibited improved wear resistance as compared to LH input condition. Adhesion and delamination are dominant wear mechanisms at 20?N. Debris particles are reduced in size and hydroxidated in sliding of surface composites.