Synthesis of fixed-order controllers for control systems with long transmission lines

The doctoral dissertation "Synthesis of Fixed-Order Controllers for Control Systems with Long Transmission Lines" refers to the problem of fixed-order controller design when hydraulic executive bodies (drives) with long transmission lines, which are described by mathematical models of high order, should be controlled. It consists of seven chapters. Chapter I points out the need for and significance of research on systems with displacement control because of a lot of advantages in relation to the systems with damping control, especially from the aspect of energy efficiency. As these systems are described by mathematical models of high order, the dissertation indicates the necessity of finding a methodology for design of controllers with fixed structure and low order for control of these systems for the purpose of improving the quality of operation of hydraulic and electro-hydraulic executive bodies with long transmission lines. Chapter II provides an overview of research results in the field of hydraulic and electro-hydraulic control systems with long transmission lines as well as results in the field of control theory Chapter III, through a comprehensive methodological approach, presents forms of mathematical model of flow of working fluid in long transmission lines, from the simplest to the most complex ones. The models are shown through matrix dependences and combination of hyperbolic functions and they are presented in tables. Frequent characteristics of the adopted models as well as their analysis in the frequency domain are presented with real values of parameters. Chapter IV develops the methodology of design of P controllers in the system of pump-controlled motor with a long transmission line. The methodology of P controller design was carried out by the root locus of the closed loop where the performances were also included through the specification of relative stability of the system, which implies an a priori given location of poles of transmission function of the closed loop in a complex plane determined on the basis of known requirements. It was shown that the designed controller gave good performances even during variation of the parameters in the system components (for instance: the viscosity coefficient and the module of compressibility which considerably change with the change of temperature and pressure). By using the possibilities offered by computers and software, a simple graphical method for design of the P controller, which often sati