Fotis N. Koumboulis

Robust triangular decoupling with application to 4WS cars

The necessary and sufficient conditions for the problem of robust triangular decoupling are established for the case of a linear time-invariant system with a nonlinear uncertain structure. The general analytic expressions of the feedback matrices and the robust triangularly decoupled closed-loop system are derived. For the solution of the problem of robust triangular decoupling with simultaneous Hurwitz invariability, sufficient conditions are established. Finally, all of the above results are successfully applied to control four-wheel steering (4WS) cars.

Input-output decoupling for linear systems with nonlinear uncertain structure

Abstract In this paper the problem of input-output decoupling for linear systems with nonlinear uncertain structure, via an independent of the uncertainties static state feedback law, is studied and solved for the first time. The necessary and sufficient conditions for the problem to have a solution are established. The general analytical expressions of the feedback matrices and the decoupled closed loop system are derived. The decoupled closed loop system structural properties of pole assignment, stabilizability are also studied. All above results are successfully applied to control the longitudinal motion of an aircraft.

Feedback controlling against chaos

Abstract A P–D (Proportional plus Derivative) feedback controller is proposed for the control of chaotic dynamic systems. Using this feedback law the design requirement of command matching is satisfied independently of the perturbations of the initial conditions of the dynamic plant. The problem is solved for all nonlinear systems having independent inputs and independent performance variables. The controller is implemented without knowledge of the system’s initial conditions and thus it is independent of their perturbations.

On Kalman's controllability and observability criteria for singular systems

The controllability and observability properties of a singular system are extensively studied. The definitions of controllability,R-controllability, and impulse controllability are introduced via characteristics of the original state vector. Analogous definitions are presented for the case of observability. The criteria established for controllability and observability are simple rank criteria related to the Markov parameters from the inputs to the states and from the initial conditions to the outputs, respectively. The present results can be considered as the direct extension of Kalmans controllability and observability criteria to the case of singular systems. Finally, the controllability and observability subspaces are derived from the image and the kernel of the controllability and the observability matrices, respectively.

Meeting transfer function requirements via static measurement output feedback

Abstract The important transfer function design problems of input-output decoupling, exact model matching and disturbance rejection, via static measurement output feedback, are studied for the case of generalized state space systems. Necessary and sufficient conditions for the solvability of these problems are established. The general analytical expressions of the respective controller matrices are derived. The above results are also extended to cover the combined problem of disturbance rejection with simultaneous decoupling and the problem of disturbance rejection with simultaneous exact model matching.

Indirect adaptive neural control for precalcination in cement plants

Control of the precalcination degree in the precalciner of cement plants is a problem of great importance due to its effect to the quality of the clinker, the consumed energy and the byproducts of the whole cement pyroprocess. Divergence of the desired precalcination degree of the raw mix may cause increased carbon monoxide production which is a significant pollution factor that under certain circumstances may lead to explosive gas mixtures. The basic inputs of the precalciner are the temperature and pressure of the tertiary air, temperature and mass flow rate of the raw mix, and the mass flow rate of the fuel, namely pulverized coal. From these inputs, the coal mass flow rate is the only actuatable one. The outputs of the precalciner are the calcinated raw mix, characterized by its mass flow rate, temperature and degree of precalcination, and the abgasses consisting of oxygen, carbon monoxide, carbon dioxide, water and nitrogen, characterized by their temperature and the concentrations of the above elements. Some of the variables of the process, namely the raw mix and coal mass flow rates, the raw mix temperature, the temperature and pressure of the tertiary air and abgasses, and the oxygen concentration in them, can be measured by appropriate sensors. The rest variables can be computed from the measurable variables after appropriate approximations. In this paper, the precalcination degree is controlled via a dynamic controller that regulates the abgasses temperature. The parameters of the controller are computed on the basis of a polynomial neural network that identifies off-line the variations (around nominal values) of the real industrial measurements of the variables of the process. The results are illustrated via simulations of the closed loop system where it is shown that the abgasses temperature is set to a desired level while a desirable precalcination degree is derived.

Block decoupling of generalized state space systems

Abstract The problem of input-output block decoupling of generalized state space systems, via a regular static state feedback law, is studied for the first time. The necessary and sufficient conditions for the problem to have a solution are established. The necessary and sufficient conditions for block decoupling with simultaneous stabilizability, and the necessary and sufficient conditions for block decoupling with simultaneous arbitrary assignment of the system poles are established.

Robust disturbance rejection with simultaneous robust input-output decoupling

Abstract The problem of robust disturbance rejection with simultaneous robust input-output decoupling of linear systems with nonlinear uncertain structure is solved. The controller is static and independent of the uncertainties. The necessary and sufficient conditions for the problem to have a solution via state feedback are established. The general analytical expressions of the feedback matrices and the decoupled closed-loop system are derived. The closed-loop system structural properties of pole assignment and stabilizability are studied.

Output feedback decoupling of linear systems with nonlinear uncertain structure

Abstract The problem of input-output decoupling for linear systems with nonlinear uncertain structure, via an independent of the uncertainties static output feedback law, is solved. The necessary and sufficient conditions for the problem have a solution are established. The general analytical expressions of the feedback matrices and the decoupled closed loop system, are derived.

Adaptive asymptotic disturbance attenuation for a permanent magnet DC motor

The problem of speed control of a permanent magnet DC motor with unknown parameters and unknown external load torque is formulated in the form of an adaptive control problem based on the design requirement of asymptotic command following with simultaneous asymptotic disturbance attenuation. The adaptive design scheme is indirect and it is based on RLS (recursive least squares) identification. The key point of the disturbance attenuation approach is to identify the system without knowledge, estimation or measurement of the unknown disturbance. This way the variations of the disturbance influence the estimation of the system parameters and consequently the choice of the controller parameters. The identification can be initialized on the basis of arbitrary initial estimation. The present results are successfully applied to a 75 Watt DC motor (35NT2R82-426SP) where a significantly varying external torque and rotor voltage noise of about 1% are considered to be applied. The present design scheme is compared to those of a traditional open loop feeding system and a PID (or PI, or P) controller designed on the basis of the first Ziegler-Nichols method.