Jeevamma Jacob

Repetitive controller for periodic disturbance rejection in motor-gear transmission system

In control systems, disturbance or reference inputs invariably include a significant periodic component with a known period. Repetitive controllers are those control elements that strategically reduce or nullify the effect of these repeating signals. In motor gear transmission system, the tooth-to-tooth error manifests as periodic disturbance. Repetitive control has by now proved as an effective control scheme for improving periodic disturbance attenuation performance. This paper aims to formulate the repetitive controller design for the Motor-Gear system as an optimization problem with an LMI (Linear Matrix Inequality) constraint on the free parameter of the bandwidth of the filter and demonstrate the effect of such a controller through MATLAB simulation. The filter is used to cater to the stability requirements of the system with the repetitive controller incorporated with it. The form of the repetitive controller is based on a single parameter determined by the fundamental period of the disturbance. It is demonstrated through the results that the repetitive controller indeed reduces the periodic disturbances. Also as the bandwidth is increased, stability is found to be at stake whereas the disturbance rejection is affected if the bandwidth is reduced.

Damping of interarea oscillations using SSSC and STATCOM with supplementary controllers

The paper investigates the effect of Static Synchronous Series Compensator (SSSC) and Static Synchronous Compensator (STATCOM) on damping interarea oscillations. Supplementary controllers for each of the flexible ac transmission system (FACTS) devices are developed. An objective function is formulated for tuning the controller parameters of the FACTS devices. The optimization is done based on the promising technique- Particle Swarm Optimisation (PSO). The performances of the proposed controllers are evaluated in a multimachine power system.

Composite control of flexible link flexible joint manipulator

This paper presents composite control of flexible link flexible joint manipulator for precise position tracking and vibration suppression control simultaneously. The dynamic model of the manipulator has been developed using Lagrangian mechanics and Assumed Modes Method (AMM). The link has been considered as an Euler-Bernoulli beam subjected to a small angular displacement. A computed torque (CT) control is used for the position control and a Linear Quadratic Regulator (LQR) is designed for vibration control. It is verified through numerical simulations that the proposed composite control suppresses the joint and link vibrations of the manipulator satisfactorily, while achieving perfect trajectory tracking.

A decoupled reference generation algorithm for harmonic, reactive power and current unbalance compensation in three-phase systems

In this paper a decoupled reference generation algorithm for harmonic, reactive power and current unbalance compensation is presented. The proposed method has the advantage that it generates the reference for compensation which is immune to supply voltage distortions and ensures that the source has to deliver only the fundamental active component of the load current. It also ensures that the source current after compensation is balanced and at unity power factor. Matlab simulation of the proposed method and a comparison of reference generation by the existing methods have been done and presented in this paper for establishing the validity and practicability of the proposed method.

Novel Two Degree of Freedom Model Matching Controller for Desired Tracking and Disturbance Rejection

A control scheme is proposed in the present paper that introduces Two Degree of Freedom (2-DOF) controller to eliminate the effect of disturbances while tracking the desired trajectory, for Two-Input Two-output (TITO) systems, by implementing an original method that infuses three techniques such as the model order reduction, optimization and the approximate model matching techniques. From authors’ knowledge, first time in literature, the objective of this kind of a proposed method is to accomplish a single low order 2-DOF controller, which can handle desired tracking and disturbance rejection simultaneously, using AGTM/AGMP matching method combined with optimization technique. The desired specifications for achieving the set-point tracking may be encompassed inside what resembles a transfer function matrix. This method is directed at ensuring that the closed loop system is stabilized by implementing a 2-DOF controller while also guaranteeing that it is capable of exhibiting the specified performance standards. This method is cost-effective, computationally simple, easy to implement and can be used for the design without any restriction in the structure/order of the model closed loop transfer function or 2-DOF controller. The efficacy of the proposed methodology is realized when it is performed on coupled tank process.

Novel two degree of freedom model matching controller for set-point tracking in MIMO systems

Abstract A control scheme is proposed in this paper that introduces a two degree of freedom (2-DOF) controller for tracking the desired trajectory of a multi-input multi-output (MIMO) system, by implementing an original method that infuses three techniques, such as the model order reduction, optimization and the approximate model matching techniques. The desired specifications for achieving set-point tracking may be embodied in the form of a transfer function matrix. The proposed method not only ensures the stability of the closed loop system with designed 2-DOF controller, but also satisfies the required performance criteria. This method is cost-effective, computationally simple, easy to implement and can be used in the design without any restrictions in the structure/order of the models closed loop transfer function or 2-DOF controller. Simulation results demonstrate the effectiveness of the developed method.

Power system stabilizer for single machine infinite bus system for robustness against inertia constant variations

Now a days the complexity of power systems increases drastically because of the growth of industries and domestic consumers. One of the major problems that can arise, in the contest of this growth, is low frequency oscillation, which can adversely affect stability of system. Power System Stabilizer (PSS) is generally used to repress the low frequency oscillation. It improves the system dynamic stability. PSS generates component of electrical torque in phase with the rotor speed variation. Variations in system inertia constant, significantly play a role in causing the low frequency oscillations, which in turn affect the power system frequency. The inertia constant also affects the manner in which a disturbed system regains its steady state. So in order to achieve a good frequency stability for single machine infinite bus(SMIB) system, it is important to have a robust PSS which can attain robustness against variations in inertia constant. This paper elucidates the design of the PSS for a simplified SMIB model using robust controller and robustness of the system against parameter variation in inertia constant. The ensuing Robust Power System Stabilizer (RPSS) ensures the stability and has superior oscillation damping capacity against system inertia constant.

Quasi-LPV modelling and control of TRMS

Twin rotor multi input multi output system (TRMS) is laboratory setup of helicopter with two degrees of freedom (DOF). High non-linearity, cross-coupling between axes and difficulty in measuring variables makes its control a challenging task. Nonlinear systems can be modelled as linear parameter varying (LPV) system by hiding nonlinearities with in scheduling parameters. LPV model enables application of linear like control methods to nonlinear systems with guaranteed time robustness and stability.

Elevation and hovering control of TRMS via H ∞ optimization technique

This paper proposes a plausible solution to the robust control problem of stabilizing the twin rotor multi input multi output system (TRMS) using H∞ control techniques. The proposed H∞ control technique optimizes the output error of TRMS compared with a reference plant. Computer simulations yield marked improvements in the results of this work over former results published. The controlled plant exhibits stable responses in hovering positions at the set pitch and yaw angles. Control and sensor singularities are corrected at design stage. The optimization technique proposed in this paper can be referred in controlling the autonomous rotorcrafts of this class.

Robust PSS design using H ∞ loop shaping method over variations in inertia constant of SMIB system

Low frequency oscillations are one of the major problems which can adversely affect stability of power system. In order to repress this problem; usually a power system stabilizer is used. Performance of Conventional Power System Stabilizer (CPSS) will degrade due to any deviation from its quiescent operating state. Variations in system inertia constant; significantly play a role in causing the low frequency oscillations; which in turn affect the power system frequency. The inertia constant also affects the manner in which a disturbed system regains its steady state. So a robust PSS is required to achieve a good frequency stability for single machine infinite bus (SMIB) system; which can attain robustness against variations in inertia constant. This paper elucidates the; H∞ loop shaping method to design a PSS for a simplified Heffron-Phillips model of SMIB system. Designed robust PSS ensures the robustness of the system against parameter variation in inertia constant. It also ensures the stability and has superior oscillation damping capacity against system inertia constant.