Horowitz Method Research Articles

La1−xCexMn1−yCoyO3 perovskite oxides: Preparation, physico-chemical properties and catalytic activity for the reduction of diesel soot

La1−xCexMn1−yCoyO3 catalysts were prepared by the “glucose method”. The structures and physico-chemical properties for these catalysts were characterized using X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR), H2-temperature-programmed reduction (H2-TPR) and O2-tempreature-programmed desorption (O2-TPD). Results showed that cerium substitution at the A-site in LaMnO3 produced a CeO2 phase. The cobalt can be introduced into the B-site in La0.8Ce0.2MnO3 at any substitution ratio because of the similar ionic radii between cobalt and manganese. The catalytic activity for soot combustion in air was evaluated using a TG/DTA analyzer. Cerium substitution at A-site enhances the catalytic activity, while cobalt substitution at B-site inhibits the catalytic activity. The activation energy for soot combustion was calculated using the Horowitz method. The activation energy for non-catalytic soot combustion was 164.1 kJ mol−1. The addition of catalysts decreased the activation energy by about 26–63 kJ mol−1. Among the applied catalysts, Ce20Mn exhibited the lowest activation energy (101.1 kJ mol−1).

Non-linear inverse compensation of an SI engine by system identification for robust performance control

Treating non-linear systems as equivalent time-invariant systems with associated uncertainty is often excessively conservative and significantly reduces the achievable robust performance. This paper presents a method for reducing the associated uncertainty of non-linear uncertain single-input single-output systems based on Horowitz's method for non-linear quantitative feedback theory. The new method implements a non-linear compensator based on an approximate causal inversion of an identified nominal model. The inverse system compensator reduces the uncertainty associated with the linear time-invariant equivalent system. The method is applied and experimentally validated on the idle speed dynamics of an automotive SI engine system using an electric dynamometer.

Thermal decomposition of metal-doped carbons

The effects of different concentrations of metals (Ni, Cu, Cd, Zn) on the reactivity of carbon towards air were studied by means of TG and DTA. It was observed that these metals are capable of decreasing the ignition temperature and increasing the mass loss. Activation energies calculated by Horowitz's method revealed that these metals promote the combustion of active carbon.

Robust noniterative synthesis of ill-conditioned plants

Ill-conditioned plants with delays are generally difficult to control. Skogestad, Morari and Doyle (1988) applied the mu method to achieve synthesis and analysis of such a problem. An alternative synthesis using the Horowitz method for MIMO uncertain feedback systems is applied to the same example. An economical bandwidth solution was achieved without iterations. Design details and simulations are presented. >

An algorithm for the adaptation of a robust controller to reduced plant uncertainty

A robust fixed parameter controller, with prefilter F and feedback compensator G designed according to the Horowitz method, for a minimum phase uncertain plant P, is considered. The uncertainty is defined as a compact set п 0 in the parameter space. Assume that it becomes known that the actual plant parameter uncertainty is п 1 ⊂ п 0 . This paper presents an algorithm that changes the parameters of F and G in such a way that the closed loop behaviour stays within the original specifications while lowering the “cost of feedback”. The algorithm is simple to use, and few calculations are needed to apply it.

An Algorithm for Adaptation of a Robust Controller to Reduced Plant Uncertainty

Given a robust fixed parameter controller, with prefilter F, and feedback compensator G, designed according to the Horowitz method, for a Minimum Phase SISO plant P with large uncertainty, defined by a compact set π in the parameter space. Assume it is known that the actual plant parameter uncertainty is π1 C.π, an algorithm that changes the parameter of F and G in such a way that the closed loop behaviour stays within the original tolerances while lowering the ‘cost of feedback’ is presented. The algorithm is simple to use and very few calculations are needed to apply it.

Estimation of the intrinsic kinetic constants in the immobilized enzyme system

Abstract The effect of mass transfer resistance on the reaction kinetics of immobilized glucose isomerase was studied, using a commercially available enzyme Swetase (Nagase Co., Japan). The effective diffusivity of glucose in the support matrix of Swetase was first determined experimentally with the Horowitz method. Using the concept of effectiveness factor encountered in reaction kinetics, a method for estimating the intrinsic kinetic parameters for immobilized glucose isomerase from reaction rates of the enzyme system was proposed. Knowing these intrinsic kinetic parameters along with the diffusivity of glucose within the enzyme particle, we can simulate Swetase's behavior in a CSTR, with a mathematical model. The simulated results compared very well with experimental values, indicating that the methods for determining enzyme kinetic parameters and substate diffusivity within the enzyme system were quite reliable.

Design of Nuclear Reactor Control Systems by the Horowitz Method

In this paper, the Horowitz method is first introduced for the design of nuclear reactor control systems. Then an experimental boiling water reactor (EBWR) is considered. The system can be designed to meet all the specifications, although it has twenty-eight parameters with each of-them having a quite large range of variation. For varifying the design, computer simulations are given.

Root locus analysis of a high-gain linear system with variable coefficients; Application of Horowitz's method

An extension of Horowitz's root-locus compensation design method is presented for analyzing and designing a high-gain linear system having variable coefficients. Rules for positioning the far-out poles of such a system based upon known specifications are established. These rules, when applicable, permit a high-gain system capable of handling large variations in the loop gain parameter to be successfully designed.