Raffaele Mascella

Optimal Control Algorithms for Second Order Systems

Proportional Integral Derivative (PID) controllers are widely used in industrial processes for their simplicity and robustness. The main application problems are the tuning of PID parameters to obtain good settling time, rise time and overshoot. The challenge is to improve the timing parameters to achieve optimal control performances. Remarkable findings are obtained through the use of Artificial Intelligence techniques as Fuzzy Logic, Genetic Algorithms and Neural Networks. The combination of these theories can give good results in terms of settling time, rise time and overshoot. In this study, suitable controllers able of improving timing performance of second order plants are proposed. The results show that the PID controller has good overshoot values and shows optimal robustness. The genetic-fuzzy controller gives a good value of settling time and a very good overshoot value. The neural-fuzzy controller gives the best timing parameters improving the control performances of the others two approaches. Further improvements are achieved designing a real-time optimization algorithm which works on a genetic-neuro-fuzzy controller.

Revised Gravitational Search Algorithms Based on Evolutionary-Fuzzy Systems

The choice of the best optimization algorithm is a hard issue, and it sometime depends on specific problem. The Gravitational Search Algorithm (GSA) is a search algorithm based on the law of gravity, which states that each particle attracts every other particle with a force called gravitational force. Some revised versions of GSA have been proposed by using intelligent techniques. This work proposes some GSA versions based on fuzzy techniques powered by evolutionary methods, such as Genetic Algorithms (GA), Particle Swarm Optimization (PSO) and Differential Evolution (DE), to improve GSA. The designed algorithms tune a suitable parameter of GSA through a fuzzy controller whose membership functions are optimized by GA, PSO and DE. The results show that Fuzzy Gravitational Search Algorithm (FGSA) optimized by DE is optimal for unimodal functions, whereas FGSA optimized through GA is good for multimodal functions.

Fuzzy algorithm control effectiveness on drum boiler simulated dynamics

The optimal control of parameters in a system assumes an important role in industrial processes. Models based on boiler-turbine plant are proposed in various applications. The target of this paper is to apply intelligent techniques on a boiler simulator to improve the speed and precision of control. In order to release such task, genetic-fuzzy controllers able of tuning the time duration of specific boiler drum signals, are designed. The results show good precision and relevant speed of control system improving the control performances of classical control structures.

On efficient balanced codes over the mth roots of unity

Let /spl Phi//sub m//spl sube/ /spl Copf/ be the set of all mth roots of unity, m/spl isin/ IN. A balanced code over /spl Phi//sub m/ is a block code over the alphabet /spl Phi//sub m/ such that each code word is balanced; that is, the complex sum of its components (or weight) is equal to 0. Let B/sub m/(n) be the set of all balanced words of length n over /spl Phi//sub m/. In this correspondence, it is shown that when m is a prime number, the set B/sub m/(n) is not empty if, and only if, m divides n. In this case, the minimum redundancy for a balanced code over /spl Phi//sub m/ of length n is. On the other hand, it is shown that when m=4, the set B/sub 4/(n) is not empty if, and only if, n is even, and in this case, the minimum redundancy for a balanced code over /spl Phi//sub 4/ of length n is. Further, this correspondence completely solves the problem of designing efficient coding methods for balanced codes over /spl Phi//sub m/, when m=4. In fact, it reduces the problem of designing efficient coding schemes for balanced codes over /spl Phi//sub 4/ to the design of efficient balanced codes over the usual bipolar alphabet /spl Phi//sub 2/={-1,+1}.

Neural network and fuzzy system for the tuning of Gravitational Search Algorithm parameters

Abstract A good trade-off between exploration and exploitation to find optimal values in search algorithms is very hard to achieve. On the other hand, the combination of search methods may cause computational complexity increase problems. The Gravitational Search Algorithm (GSA) is a swarm optimization algorithm based on the law of gravity, where the solution search process depends on the velocity of particles. The application of intelligent techniques can improve the search performances of GSA. This paper proposes the design of a Neuro and Fuzzy Gravitational Search Algorithm (NFGSA) to achieve better results than GSA in terms of global optimum search capability and convergence speed, without increasing the computational complexity. Both the algorithms have the same computational complexity O(nd), where n is the number of agents and d is the search space dimension. The main task of the designed intelligent system is to adjust a GSA parameter on a revised version of GSA. NFGSA is compared with GSA, a Plane Surface Gravitational Search Algorithm (PSGSA) and a Modified Gravitational Search Algorithm (MGSA). The results show that NFGSA improves the optimization performances of GSA and PSGSA, without adding computational costs. Moreover, the proposed algorithm is better than MGSA for a benchmark function and achieves similar results for two test functions. The analysis on the computational complexity shows that NFGSA has a better computational complexity than MGSA, because NFGSA has complexity O(nd), whereas MGSA has complexity O((nd)2).

On efficient second-order spectral-null codes using sets of m 1 -balancing functions

A new efficient coding scheme is given for second-order spectral-null (2-OSN) codes. The new method applies the Knuths optimal parallel decoding scheme for balanced (i.e., 1-OSN) codes to the random walk method introduced by Tallini and Bose to design 2-OSN codes. If k ∈ IN is the length of a 1-OSN code then the new 2-OSN coding scheme has length n = k+r ∈ IN with an extra redundancy of r ≳ 2 log2 k + (1/2) log2 log2 k - 0.674 check bits. The whole coding process requires O(n log n) bit operations and 0(n) bit memory elements.

On efficient high-order spectral-null codes over the m-ary alphabet

Abstract Let be the set of all words of length N over the m-polar alphabet Φ m ={−(m−1),−(m−3),…,+(m−3),+(m−1)}, having a q-th order spectral-null at zero frequency. Any subset of is a spectral-null code of length N and order q. This paper gives an equivalent formulation of in terms of codes over the m-ary alphabet ℤ m ={0, 1,…, m−1}, derives a recursive expression for the cardinality of , shows combinatorial properties of , gives new simple ways to obtain systematic m-ary q-th order spectral-null codes, and finally, presents new efficient recursive design methods to encode k m-ary information digits into second-order spectral-null codes over ℤ m of length N(k)=n(k)+N(⌈log m n(k)(n(k)−1)/2⌉+1), whose implementing algorithm requires T=O(mk log m k) m-ary digit operations and S=O(k) m-ary digit storing elements.

On balanced codes over the m-th roots of unity, m=4

This paper completely solves the coding problem for balanced codes over /spl Phi//sub m/, when m = 4. In fact, it reduces the problem of designing efficient coding schemes for balanced codes over /spl Phi//sub 4/ to the design of efficient balanced codes over /spl Phi/4 = {-1,+1}. In particular, the paper proposes efficient constructions for balanced codes over /spl Phi//sub 4/ with k information digits and r=2log/sub 4/k -log/sub 4/s(k) + /spl Theta/(1), check digits, where s(k) is any function such that 1/spl les/s(k)/spl les/k. Such balanced codes can be implemented with T=O(klogk:+ ks(k)) digit operations, by storing A=O(k+s/sup 3/(k)) memory digits. The paper also shows that the minimum redundancy for a balanced code over /spl Phi//sub 4/ of length n is r/sub min/ /spl ap/ Iog/sub 4/n+0.326.

Efficient Non-Recursive Design of Second-Order Spectral-Null Codes

A new efficient design of second-order spectralnull (2-OSN) codes is presented. The new codes are obtained by applying the technique used to design parallel decoding balanced (i.e., 1-OSN) codes to the random walk method introduced by some of the authors for designing 2-OSN codes. This gives new non-recursive efficient code designs, which are less redundant than the code designs found in the literature. In particular, if k ∈ IIN is the length of a 1-OSN code then the new 2-OSN coding scheme has length n = k + r ∈ IIN with an extra redundancy of r ≃ 2 log2 k + (1/2) log2 log2 k - 0.174 check bits, with k and r even and n multiple of 4. The whole coding process requires O(k log k) bit operations and O(k) bit memory elements.

A note on generalized Fibonacci numbers

Abstract Starting from the simplest recurrence relations of second order, in this paper are suggested direct solutions obtained from a generalization of Pascal’s Triangle. With some binomial formulas, it isn’t necessary anymore to calculate roots of associated equations, and the extension of parameters’ definition field to the complex field can be done without any difficulty. The general cases in which the coefficients are functions of an integer variable are studied, too.