On the type of linear multivariable systems

Based on the prime factorization of transfer function matrices, alternative proofs of some basic properties of the type of linear multivariable systems [1] are given. Also, this leads to strengthening some results given in [1]. A connection is made between the system type and the Smith-McMillan form of the transfer function. An error in an example used in [1] is pointed out.     

Calculation of piecewise-constant control strategies for linear systems with retarded control

The letter presents a simple method of calculating piecewise-constant control strategies to transfer the state of a linear time-invariant system with retarded control from a given initial state xo to any desired state x(t*), provided that the system is controllable.     

A note on parameterization of the class of deadbeat controllers

The problem of parameterizing the class of deadbeat controllers for a given discrete-time system through the minimum number of parameters was solved by Schlegel [1]. This note shows how to utilize the above solution to study some problems in designing deadbeat controllers. First, an algorithm is developed to compute a controller which minimizes-in an average sense-a given objective function. Second, a necessary and sufficient condition is given for the existence of an output deadbeat controller. Finally, the problem of parameterizing the set of deadbeat controllers for those systems transformable to the phase-variable block-canonical form is reconsidered.     

A design procedure for multivariable regulators

A computational algorithm is presented for the design of a compensator for linear multivariable regulators. The compensated system is required to be structurally stable, in the sense of preserving output regulation and internal (loop) stability in the face of small parameter variations or uncertainties. The design technique is based on the internal model principle [1]. It is shown that the distance between the system transmission zeros and eigenvalues of the exogenous dynamics may be taken as a measure of the well-conditioning of the algorithm. The design algorithm is demonstrated by application to a two-area power system.     

Design and synthesis of novel di- and triblock amphiphilic polyelectrolytes: Improving salt-induced viscosity reduction of water solutions for potential application in enhanced oil recovery

In the present study, three different block copolymers based on styrene, tert-butyl methacrylate, and glycidyl methacrylate (GMA) were synthesized via sequential atom transfer radical polymerization. The addition of the GMA block was found to be best performed at 60°C. The polymers were then hydrolyzed and neutralized, to afford amphiphilic block copolymers, and the rheological properties of their aqueous solutions were measured, in order to investigate solution properties relevant for enhanced oil recovery, as a function of the polymer structure. It was observed that these polymers behave as thickening agents with shear thinning behavior. As expected, the polymers were sensitive to the presence of salt, as lower viscosities were recorded in saline water. However, the viscosity is less affected by high salinity, when compared to previously studied analogous diblock systems. In the best case, the viscosity only decreased by a factor of 1.8 upon salt addition whereas it decreased by a factor of 10 in previously reported non-GMA containing polymers. Finally, thermo-responsive behavior was found for one of the synthesized polymers. In particular, a hydrolyzed triblock poly[styrene-b-tert-butyl methacrylate-b-glycidyl methacrylate], which synthesis is reported here for the first time, showed a thermothickening behavior, promising for the intended application in oil recovery.     

New proof for the controllability criterion of linear systems with delay in control

A new proof is presented for the controllability criterion in linear systems with time delay in the control function. The control strategy is constructed in a way similar to that of Power.     

State regulation in linear discrete-time systems in minimum time

This paper presents an algorithm for computing a feedback law which guarantees that any initial state of the closed loop of a linear time-invariant discrete system will be driven to the origin in minimum finite time. The feedback law is constructed by solving a sequence of algebraic linear equations. The designer has considerable freedom in choosing the generalized eigenvectors which would allow the shaping of the transient response of the system. The algorithm offers, as a byproduct, a new and easy method for computing the so-called "generalized control form" of any controllable pair. Several examples are worked out to demonstrate the feasibility of the proposed method.     

Adaptive fuzzy APSO based inverse tracking-controller with an application to DC motors

This paper introduces the use of the adaptive particle swarm optimization (APSO) for adapting the weights of fuzzy neural networks (FNN) on line. The fuzzy neural network is used for identification of the dynamics of a DC motor with nonlinear load torque. Then the motor speed is controlled using an inverse controller to follow a required speed trajectory. The parameters of the DC motor are assumed unknown as well as the nonlinear load torque characteristics. In the first stage a nonlinear fuzzy neural network (FNN) is used to approximate the motor control voltage as a function of the motor speed samples. In the second stage, the above mentioned approximator is used to calculate the control signal (the motor voltage) as a function of the speed samples and the required reference trajectory. Unlike the conventional back-propagation technique, the adaptation of the weights of the FNN approximator is done on-line using adaptive particle swarm optimization (APSO). The APSO is based on the least squares error minimization with random initial condition and without any off-line pre-training. Simulation results are presented to prove the effectiveness of the proposed control technique in achieving the tracking performance.     

Identification and control of flexible civil structures with time delays

The identification of flexible civil structures as discrete-time mathematical models in a ready form for computer control is shown by using a simple identification technique and neglecting the noise problem. The use of a control mechanism for the purpose of modeling and also for the control of the flexible structure justifies the noise-free consideration. The effect of time delay during a control process on the dynamics and stability of the structural systems is shown in illustrative examples. The design of a feedback control law to compensate for the detrimental effect of time delay is given with an application to control the response of a flexible frame structure using a tendon control mechanism.