Auto-tuning of PID controller according to fractional-order reference model approximation for DC rotor control

This paper presents a stochastic, multi-parameters, divergence optimization method for the auto-tuning of proportional–integral–derivative (PID) controllers according to a fractional-order reference model. The study aimed to approximate the step response of the real closed-loop flight control system to the response of a theoretical reference model for a smoother and more precise flight control experience. The proposed heuristic optimization method can auto-tune a PID controller without a precise plant model. This is very advantageous when dealing with model and parameter uncertainties in real control application and practice. Experimental study confirms the reference model driven auto-tuning of the DC rotor prototype.     

Modification of Harris hawks optimization algorithm with random distribution functions for optimum power flow problem

Neural Computing and Applications - Harris hawks optimization (HHO) algorithm, which is inspired from Harris hawks hunting strategy, uses uniform random numbers in the optimization process. This...     

Mineral contents of 34 species of edible mushrooms growing wild in Turkey

Mineral contents of 34 species of wild mushrooms, growing particularly in the central Anatolia region in Turkey, were determined by inductively coupled plasma atomic emission spectrometry (ICP‐AES). All mushrooms contained high amounts of Al, Ca, Fe, K, Mg and P. The highest potassium level was 45189.4 mg kg^?1 for the species Coprinus micaceus, whereas the lowest K content was 9973.8 mg kg^?1 in Polyporus squamosus. Among the wild mushrooms, the highest lead level was 5.4 mg kg^?1 in the species Helvella leucomelano. Iron contents of mushrooms were found in similarly small percentages in all the species analysed, ranging from 338.3 mg kg^?1 in Russula delica to 8994.71 mg kg^?1 in Helvella spadicea. Phosphorus content ranged from 2095.6 mg kg^?1 in Polyporus squamosus to 22799.0 mg kg^?1 in Helvella spadicea. Magnesium was found to be high, ranging from 458.1 mg kg^?1 in Rhizopogon luteolus to 4254.9 mg kg^?1 in Morchella esculenta. This study attempts to contribute to knowledge of the human nutritional properties of these mushroom species, and may be useful for the evaluation of dietary information. Copyright © 2006 Society of Chemical Industry     

Possible heat‐tolerant wheat cultivar improvement through the use of flag leaf gas exchange traits in a Mediterranean environment

BACKGROUND: Flag leaf traits are associated with performance of wheat (Triticum aestivum L.) genotypes in heat‐stress environments. Fifteen cultivars were evaluated during 3 years with two sowing dates under irrigated conditions so as to examine the relationship between the flag leaf traits and performance in a Mediterranean environment. RESULTS: It became possible to assess a heat susceptibility index (HSI) for each cultivar by altering the sowing date, exposing the crops to different temperatures. The cultivars showed significant differences for all measured traits except canopy temperatures and chlorophyll fluorescence, though not all were consistent. Excluding two cultivars that differed in development, yield, grain number, harvest index and leaf A_n (net CO₂ assimilation rate), g_s (stomatal conductance to water vapor), m_c (apparent mesophyll conductance of CO₂) and ash content were negatively associated with HSI, whereas leaf area and width were positively associated. Traits showing the best correlation with HSI were A_n, followed by area, g_s, m_c, width and ash content. High A_n was associated with smaller leaf size. CONCLUSION: It is worthwhile to select high ear grain number and harvest index. In addition, flag leaf gas exchange traits and ash content can be used as complementary selection criteria after the possible pleiotropic associations of these traits with leaf size are clarified. Copyright © 2008 Society of Chemical Industry     

Random metric space of fuzzy numbers

In this paper, we introduce the concept of a random metric (RM) space of fuzzy numbers and establish some of its basic properties. In this approach, the distance between two fuzzy numbers is considered as a certain measurable function. Using this concept, we also obtain some convergence relations for a sequence of fuzzy numbers. Finally, we investigate a boundedness property for a subset of such an RM space.     

A numerical investigation for robust stability of fractional-order uncertain systems

This study presents numerical methods for robust stability analysis of closed loop control systems with parameter uncertainty. Methods are based on scan sampling of interval characteristic polynomials from the hypercube of parameter space. Exposed-edge polynomial sampling is used to reduce the computational complexity of robust stability analysis. Computer experiments are used for demonstration of the proposed robust stability test procedures.     

Classical controller design techniques for fractional order case

This paper presents some classical controller design techniques for the fractional order case. New robust lag, lag-lead, PI controller design methods for control systems with a fractional order interval transfer function (FOITF) are proposed using classical design methods with the Bode envelopes of the FOITF. These controllers satisfy the robust performance specifications of the fractional order interval plant. In order to design a classical PID controller, an optimization technique based on fractional order reference model is used. PID controller parameters are obtained using the least squares optimization method. Different PID controller parameters that satisfy stability have been obtained for the same plant.     

Frequency response computation of fractional order interval transfer functions

The paper present extensions of some results developed in the parametric robust control to fractional order interval control systems (FOICS). Computation of the Bode and Nyquist envelopes of FOICS are studied. Using the geometric structure of the value set of fractional order interval polynomials (FOIP), a technique is proposed for computing the Bode and Nyquist envelopes of transfer functions whose numerator and denominator polynomials are fractional order polynomials with interval uncertainty structure. The results obtained are useful for the analysis and design of FOICS. Numerical examples are included to illustrate the benefit of the method presented.