Robustness control for nonlinear systems based on homogeneous prescribed sliding mode control

This paper presents a new homogeneous control using dual sliding mode control, and robustness control using linear matrix inequality (LMI) constraints. The controller is applied for the severe disturbance. A sliding surface function, which relates to an exponential function and itself t-norm, is applied to save the energy consumption of the control system. The constraints related LMI are proposed with the matrices and vectors of the systems following the chosen matrices in control the energy for control. Solution of the constraints is also presented with new approach to save the time of calculation. In addition, the proof for the proposed controller is also presented by using the candidate Lyapunov function. In the input control function, the t-norm type is embedded to improve its performance in control disturbance. Besides of the t-norm, the modified sliding surface in the input control is also improve the energy for controlling. The combination of these robustness control elements would bring a new view for the design of control. The advantages of the controller are demonstrated via computer simulation for a seat suspension system. A magneto-rheological fluid seat suspension with its random disturbances is used. To prove the flexibility of the controller, the proposed approach is compared with an existing controller. The compared control has the same structure as shown in the proposed model. However, its design has a disadvantage in control the severe disturbance. The comparison between two controls is a clear view of distinct improvement. The results of simulations show that the controller provides better performance and stability of the system. The stability is also analyzed through the variation of the input control and power spectral density related energy consumption.

Effects of physical and chemical properties on the dissolution of sea salt

Salt plays a crucial role in human health. However, excess use of NaCl in food products can be harmful to health. One suggestion for this problem is optimization salt dissolution to increase the content of salt ions in the mouth. For this purpose, it is important to understand the solubility properties of salt crystals in saliva. The dissolving process is not only affected by the physical properties but also by the chemical composition of the salt. This study compared the solubility of four commercial grain salts in four regions in Vietnam (Bac Lieu, Thanh Hoa, Sa Huynh, Vung Tau), one flower salt in Sa Huynh and a control sample with two particle sizes 1 - 2 mm and 2 - 3 mm in a Saliva Artificial Gal – Fovet solution (SAGF). Dissolution was determined by analyzing microscopic images taken by the time and analysis by Bayesian and Partial Least Squared methods. The research evaluated the influence of physical properties (area, Feret's diameter, circularity, aspect ratio and solidity) and chemical compositions (sodium, potassium, magnesium, calcium and moisture content) on the dissolving process. Salt samples showed significant differences in physical and chemical properties by region. Morphological parameters are affected by conditions of salt crystallization that indicated through region of origin. Dissolution is evaluated through solubility coefficient, Sa Huynh flower salt and control salt have the highest solubility coefficient, simultaneously, it is also the smallest value of roundness and surface index. The projected area, magnesium and sodium content are the factors which strongly affecting on dissolution of salt samples. These results demonstrated the possibility to exploit these factors to adjust the solubility of salt as well as the perceived salinity over time.

Deformation behaviour of granular column reinforced by geosynthetic encasement

In Vietnam, the overpopulation and strong economic development require the synchronous development of infrastructure such as roads, urban areas, industrial parks, export processing zones, etc. With such requirements, the development of land fund for infrastructure construction is an indispensable need. Meanwhile, the appropriate land fund is very limited. Therefore, the land fund must be developed for areas with little value for agriculture, such as swamps, estuaries, and coastal areas, etc. These areas often have weak geological conditions; hence, to meet the requirements of infrastructure construction on the soft ground, it is necessary to carry out soil improvement to ensure load bearing capacity, total settlement, and consolidation settlement but still ensuring economic effectiveness. Beside several conventional methods widely used for soft soil improvement in order to increase bearing capacity and accelerate consolidation settlement of the ground, geosynthetic reinforced granular column is one of the new methods that has been applied to improving soft ground in designing practice in the recent years due to the many advantages of this method compared with other methods. In this paper, based on the unit cell model, the authors research on deformation behavior of granular column reinforced by geosynthetic encasement through the analytical analysis by varying external loadings corresponding to column diameter, stiffness of geosynthetic encasement. The settlements of a single geosynthetic encased granular column and load bearing capacity of the composite foundation are calculated on geological conditions of Ash Pond Area of Song Hau 1 Thermal Power Plant located in Hau Giang Province. The relationship between settlement and load bearing capacity with external loadings for different column diameters and geosynthetic stiffnesses are shown schematically. Other considerations related to factor of safety are also presented. The future researches are also proposed.

Use copra meal as a partial substitute for wheat flour in fiber-rich biscuits

Biscuits, which are loved by many consumers, often provide a high level of energy because they are rich in sugar, flour, fat and low in fiber. Fiber plays an important role in preventing constipation, cardiovascular diseases and obesity, so the current trend of manufacturers is to create high-fiber biscuit lines. Defatted copra meal (DCM) is a rich source of fiber and is added to biscuits to increase the fiber content of the cake. In this study, defatted copra meal, after being hydrolysed with the enzyme Cellulast1.5L (HDCM), will be used to replace wheat flour with different ratios, from 10% to 40%, in fiber rich biscuit recipe. The hydrolysis of DCM was carried out with an enzyme concentration of 5U/g dry matter, for 30 minutes. The obtained HDCM has a soluble fiber (SDF) content of 7.3% dry matter, an increase of 2.43 times compared to the DCM sample. At the same time, the ratio between insoluble fiber and soluble fiber (IDF/SDF) of HDCM also decreased by 2.64 times compared to this ratio of DCM. The chemical composition, hardness, physical and sensory parameters of biscuits were used to evaluate the effect of hydrolyzed copra meal replacement rate. When increasing the percentage of HDCM from 20-40%, the total fiber content of biscuits increased 1.7- 5.9 times compared with the control sample. The HDCM substitution rates of 20% and 30%, for biscuits with acceptable taste scores of 5.7 and 5.0, respectively, with total fiber content of 9.0 and 15.5%, respectively, are suitable for manufactures fiber-rich biscuits.

Combined cellulolytic and pectinolytic enzymes to increase the polyphenol extractability of coffee husks

Coffee husks (CHs) is a high biological activity by-product of the coffee bean industry, but currently, in Vietnam, it has not been used properly in the food industry. This study was conducted to investigate the combined cellulolytic and pectinolytic enzymes to increase the polyphenol extractability of coffee husks. The red ripe Robusta coffee cherries from Dăklak province, Vietnam were blanched, peeled and the coffee husks was then extracted. The effects of pectinase content (from 0 to 800 U/gCHs), cellulase content (from 0 to 800 U/gCHs), pH (from 3.0 to 5.0), temperature (from 40◦C to 60◦C), CHs: solvent ratio (from 1: 6 to 1:12) and extracted time (from 60 minutes to 120 minutes) on soluble solid content (SSC), total polyphenol content (TPC) and antioxidant activity were investigated. The appropriate conditions for the treatment were pectinase dosage of 600 U/gCHs, cellulase dosage of 400 U/gCHs, pH 4.0, temperature 50◦C, CHs:soluble ratio = 1:10 and incubation time of 60 min under which the SSC, TPC and antioxidant activity of extract were highest by 60.60.4 g/100g dry weight of CHs, 200.5 gGAE /100g dry weight of CHs, 1.5 +/- 0.1 mMTE/g dry weight of extract (according to DPPH assay) and 1.5 +/- 0.1 mMTE/g dry weight of extract (according to DPPH assay). From this result, it can be seen that the extracted solution from coffee husk is a potential source for the production of soft drinks with high antioxidant activity.

Comparative study of control techniques for three phase PWM rectifier

This paper studies and compare the performances of different control strategies of 3-phase active rectifier under different load and frequency conditions. There are three main control approaches to be investigated such as: Voltage Oriented Control (VOC), Direct Power Control (DPC) and Model Predictive Control (MPC). The traditional method VOC has been used widely in practice. Its control principle is available to many different grid-connected converter systems such as electric drive system, renewable energy conversion system. However, the problem of optimal design of the current regulators for the different operating conditions of the system is not an easy problem. The DPC and MPC methods then help to eliminate the disadvantages of the VOC. The MPC method has been now become much interesting since it offers a general solution to a multi-goal optimization problem. In the paper, the system structures and controller parameters are briefly presented. The main evaluation factors of the active rectifier are low input current distortion (THD), a unit input power factor and stable DC output voltage. Three methods are analyzed and verified using MATLAB software and measuring experiment on a real model. The obtained results show that the VOC method achieves stable quality under different load as well as the switching frequency conditions, while the MPC method may achieve good quality with a rather high switching frequency.

Algorithim to control output voltage and reduce the ripple of input current in quasi switched boost inverter

In recent years, the quasi -switched boost inverter uses widely in electrical systems. This paper proposes a method to control the AC output voltage and reduce the current ripple of the booster inductor in the quasi-switched boost inverter (QSBI). The proposed technique base on carrier pulse width modulation with two triangles with phase shifts 90◦. This technique uses the offset function to expand the modulation index and the algorithm for output voltage stabilization based on the adjustment of the boost ratio. The modulation index expansion will reduce the stress voltage on the switches by an average of 16.5% under the simulated conditions. The boost factor base on the short circuit time on the DC / DC booster and the inverter on the zero vectors. So, the duty ratio (of the boost DC / DC) can reduce by the short-circuit pulses that insert in the position of zero vectors, so the inverter is responsible for both boosting and inverting. The combination helps to reduce the current ripple on the boost inductor. Besides that, reducing the short-circuit ratio of DC / DC booster will also reduce the capacity of the booster switch and thereby reduce the production cost. The analysis clarifies the proposed technique. Simulations and experiments evaluate the proposed method.

Research of decentralized loop automation simulation in distribution network using MALAB/SIMULINK

Nowadays, technologies are rapidly developing, automation is omnipresent in our life. In the power system, automation technology solutions have been applied gradually and widely to meet the requirements of reliability. Before, when a fault occurs on the distribution network, the fault locating, isolating and grid restoring are still being done manually, so a large number of customers that are not in the fault zone still suffer outage for a long time. Distribution Automation System was developed to solve this problem. Currently, with the development of information technology, the Decentralized Loop Automation (DLA) in the distribution network is carried out by communication between the protective devices in the grid. Communication between devices can be done using time-control rules, using GOOSE messages, wifi or according to protocol IEC 61850. In addition, the protective devices can be connected to the control center to create a Centralized Loop Automation (CLA) in the distribution network. The paper considers the DLA solution with the time-control rules for a simple grid. Time-control rules models and simulation results were performed on MATLAB/ SIMULINK software. The paper proposed a user interface for DLA solution with many different failure cases, especially considering the protection coordination in case of doubles failure. The results of the paper show that DLA can isolate faults automatically and restore the grid in a short time, and these results can be developed as an experimental simulation in the future.

Identifying the drivers of liking for texture attributes of Vietnamese sausage

Vietnamese sausage (cha lua), a pork processing food with a characteristic chewy and crunchy texture, are widely consumed in Vietnam. However, there are not many established researchs on hedonic and sensory attributes for this product, especially about the texture attributes. The goal of this study was to investigate consumer's preference as well as identify the drivers of liking for texture of Vietnamese sausage. Eight samples were prepared with various ratio of lean meat, lard and starch to cover a wide range of different texture of Vietnamese sausage. Sixty eight consumers then evaluated these eight samples, rating texture liking on nine-point scale and answering a checkall- that-apply (CATA) question, which consisted of 16 different texture attributes of Vietnamese sausage. The consumers were also asked to check all the approriate attributes to describe their ideal products. The ANOVA and post –hoc test showed samples which had recipes with high lard ratio (20-25%) and low meat ratio (70%) had a significant higher liking scores, while the samples which had recipe with high meat ratio (90%) had the lowest liking scores. The Cochran's Q test showed that 12 attributes had different choice frequency between samples, suggesting the texture of Vietnamese sausage is complex and diverse. The CA results showed all the samples without stach were associated with large air holes, while samples which high meat ratio (80%) were associated with hardness. The ideal Vietnamese sausage product was associated with fattiness, juiciness, springiness and brittleness. Finally, the results of penalty analysis showed that chewy, firm, and elastic attributes had positive impacts on the liking score for Vietnamese sausage products, while attributes that exhibit heterogeneity, such as large air hole and grainy, significantly reduced the liking score of the product. This suggested the importance of mechanical texture attributes and homogenity on the consumer's preference of the Vietnamese sausage.

Hydrodynamic studies on liquid-liquid two phase flow separation in microchannel by computational fluid dynamic modelling

Microfluidic systems undergo rapid expansion of its application in different industries over the few decades as its surface tension-dominated property provides better mixing and improves mass transfer between two immiscible liquids. Synthesis of biodiesel via transesterification of vegetable oil and methanol in microfluidic systems by droplet flow requires separation of the products after the reaction occurred. The separation technique for multiphase fluid flow in the microfluidic system is different from the macro-system, as the gravitational force is overtaken by surface force. To understand these phenomena completely, a study on the hydrodynamic characteristics of two-phase oil-methanol system in microchannel was carried out. A multiphase Volume of Fluid model was developed to predict the fluid flow in the microchannel. An inline separator design was proposed along with its variable to obtain effective separation for the oil-methanol system. The separation performance was evaluated based on the amount of oil recovered and its purity. The capability of the developed model has been validated through a comparison of simulation results with published experiment. It was predicted that the purity of recovered oil was increased by more than 46% when the design with side openings arranged at both sides of the microchannel. The highest percentage recovery of oil from the mixture was simulated at 91.3% by adding the number of side openings to ensure the maximum recovery. The oil that was separated by the inline separator was predicted to be at 100% purity, which indicates that no methanol contamination throughout the separation process. The purity of the separated product can be increased by manipulating the pressure drop across the side openings. Hence, it can be concluded that the separation in a large diameter microchannel system is possible and methodology can be tuned to achieve the separation goal. Finally, the simulation results showed that the present volume of fluid model had a good agreement with the published experiment.