Variable structure control with chattering reduction of a generalized T-S model

In this paper, a fuzzy logic controller (FLC) based variable structure control (VSC) is presented. The main objective is to obtain an improved performance of highly non-linear unstable systems. New functions for chattering reduction and error convergence without sacrificing invariant properties are proposed. The main feature of the proposed method is that the switching function is added as an additional fuzzy variable and will be introduced in the premise part of the fuzzy rules; together with the state variables. In this work, a tuning of the well known weighting parameters approach is proposed to optimize local and global approximation and modelling capability of the Takagi-Sugeno (T-S) fuzzy model to improve the choice of the performance index and minimize it. The main problem encountered is that the T-S identification method can not be applied when the membership functions are overlapped by pairs. This in turn restricts the application of the T-S method because this type of membership function has been widely used in control applications. The approach developed here can be considered as a generalized version of the T-S method. An inverted pendulum mounted on a cart is chosen to evaluate the robustness, effectiveness, accuracy and remarkable performance of the proposed estimation approach in comparison with the original T-S model. Simulation results indicate the potential, simplicity and generality of the estimation method and the robustness of the chattering reduction algorithm. In this paper, we prove that the proposed estimation algorithm converge the very fast, thereby making it very practical to use. The application of the proposed FLC-VSC shows that both alleviation of chattering and robust performance are achieved.

Oxygen extended sooting index of FAME blends with aviation kerosene

The use of biofuels in the aviation sector has economic and environmental benefits. Among the options for the production of renewable jet fuels, hydroprocessed esters and fatty acids (HEFA) have received predominant attention in comparison with fatty acid methyl esters (FAME), which are not approved as additives for jet fuels. However, the presence of oxygen in methyl esters tends to reduce soot emissions and therefore particulate matter emissions. This sooting tendency is quantified in this work with an oxygen-extended sooting index, based on smoke point measurements. Results have shown considerable reduction in the sooting tendency for all biokerosenes (produced by transesterification and eventually distillation) with respect to fossil kerosenes. Among the tested biokerosenes, that made from palm kernel oil was the most effective one, and nondistilled methyl esters (from camelina and linseed oils) showed lower effectiveness than distilled biokerosenes to reduce the sooting tendency. These results may constitute an additional argument for the use of FAME’s as blend components of jet fuels. Other arguments were pointed out in previous publications, but some controversy has aroused over the use of these components. Some of the criticism was based on the fact that the methods used in our previous work are not approved for jet fuels in the standard methods and concluded that the use of FAME in any amount is, thus, inappropriate. However, some of the standard methods are not updated for considering oxygenated components (like the method for obtaining the lower heating value), and others are not precise enough (like the methods for measuring the freezing point), whereas some alternative methods may provide better reproducibility for oxygenated fuels.

Impact of introducing longer and heavier vehicles on regional consumer price index and Spanish road freight transport system

This paper applies an integrated modeling approach to the case of Spain; the approach is based on a random utility-based multiregional input-output model and a road transport network model for assessing the effect of introducing longer and heavier vehicles (LHVs) on the regional consumer price index (CPI) and on the transportation system. The approach strongly supports the concept that changes in transport costs derived from the LHV allowance as well as the economic structure of regions have direct and indirect effects on the economy and on the transportation system. Results show that the introduction of LHVs might reduce prices paid by consumers for a representative basket of goods and services in the regions of Spain and would also lead to a reduction in the regional CPI. In addition, the magnitude and extent of changes in the transportation system are estimated by using the commodity-based structure of the approach to identify the effect of traffic changes on traffic flows and on pollutant emissions over the whole network.

Reduction of critical mass in a chemotaxis system by external application of a chemoattractant

In this paper we study non-negative radially symmetric solutions of a parabolic-elliptic Keller-Segel system. The system describes the chemotactic movement of cells under the additional circumstance that an external application of a chemo attractant at a distinguished point is introduced.