Control policies for production-inventory systems with bounded input

In this paper nearly time-optimal control policies are derived for a class of linear time-invariant models of production-inventory systems which comprise a cascade of basic production-inventory subsystems with bounded input. The sub-optimal control policies are obtained by constructing the sampled-data model of the production-inventory system where the sampling period is chosen to give the maximum control input for the given shipping rate. The theory is illustrated by the presentation of the results of simulation studies which show the transient behaviour of two production-inventory subsystems in cascade.     

Types of flexibility in a single-machine production system

Flexibility is one of the most important aspects of production systems. In this paper, different approaches to this subject are summarized and it is argued that various aspects of flexibility can be unified in a hierarchical structure. A simple, one-machine system is used to obtain the 'volume flexibility' from the 'machine flexibility' in the context of the hierarchical structure of flexibility types.     

Moisture Sorption Isotherms of Dried Apricot, Fig and Raisin at 20 °C and 36°C

Isotherms were found to be of type I, typical of high sugar foods. Study on temperature dependence of isotherms showed that above water activities of 0.6, moisture content was higher at higher temperature. This was explained by endothermic dissolution of sugar at high water activities. Iglesias and Chirife, Halsey, BET and GAB equations were tested to fit the data. Monolayer moisture contents for the three foods were determined from BET and GAB equations. In both models, monolayer moisture was found to decrease with increasing temperature. Isosteric heat of sorption data from the isotherms at two temperatures, revealed that strength of interactions between water vapor and adsorbent increased with moisture content.     

An experimental stationary quadrotor with variable DOF

Unmanned air vehicles (UAV) and especially quadrotors have drawn great attention in recent years because of their maneuverability, ease of design and control. Most of the works concentrate mostly on control; yet, design and communication are also some sub-topics. In this research, a stationary, four rotor air vehicle with limited/controlled degree of freedom is constructed so that various control algorithms and their changing effects with varying vehicle dynamics can be studied on the ground for safety purposes. Ascending/descending, pitch/yaw/roll motions can be limited/controlled by setting the vehicle’s degree of freedom mechanically, resulting better net observability of the control algorithms on the vehicle’s dynamic performance. Design, in terms of mechanics, mechatronics and software is presented and the usability of the system is shown. Parallel self tuning fuzzy PD + PD control is applied to the system for preliminary studies and results are discussed. Inspite of the sensor noise, satisfactory pitch/roll/yaw control is achieved.     

A statistical approach for ground cover modelling according to the spectral brightness

The mixture of three normal distributions is proposed as a model for an area that we call a ‘class’ in a region according to the spectral brightness of three different band (pixel) values in remote sensing. The parameters in a mixture of three normal distributions arc estimated by the method of moments for grouped data. Newton-Raphson iteration method is used for estimating the parameters where all parameters are unconstrained. The method of finding suitable starting values for Newton-Raphson iterations is also given. A computer program is developed for this purpose.     

Pole assignment problem: a structural investigation

Based on the structure of a closed-loop system under a specified feedback pattern, a qualitative analysis of the problem of pole assignability is considered. The problem is first formulated algebraically, in terms of the relation p = g(f) between the vector p of the closed-loop characteristic polynomial coefficients and the vector f of the non-zero elements of the feedback matrix. Then, translation to the structural framework is achieved by means of two theorems which give graph-theoretical sufficient conditions for solvability. These structural conditions also guarantee genericity of pole assignability.