Asymmetric order-doubling and robust state estimation for uncertain nonminimum phase systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (leaves 145-148).by Muralidhar Ravuri.Ph.D

Grating Motor Control

A monochromator is a part of a spectrometer in which the grating scans the different wavelengths over the exit slit. A full spectrum is generated as the grating scans over a predefined interval. The grating must accelerate to a set speed very fast, then keep the speed constant over a predefined interval, and break to reverse the scan. On top of this come disturbances from an optical filter, causing vibrations in the housing, which can be seen in the spectra if not corrected for in the control algorithm. A model-based control system composed of Proportional-Integral (PI) control, and Iterative Learning Control (ILC), is implemented on a Field-Programmable Gate Array, using LabVIEW. The proposed controller shows promising results, with closed loop rise time within given bounds, and reduced disturbance effects

An algebraic approach to the estimation of the order of FIR filters from complete and partial magnitude and phase specifications

Published versio

Discretization of complex-order differintegrals

This paper deals with the discretization of integrals and derivatives (i.e., differintegrals) of complex order. Several methods for the discretization of the operator s, where y = u+jv is a complex value, are proposed. The concept of conjugated-order differintegral is also presented. The conjugated-order operator allows the use of complexorder differintegrals while still resulting in real time responses and real transfer functions. The performance of the resulting approximations is evaluated both in the time and frequency domains.N/

Resource-aware motion control:feedforward, learning, and feedback

Controllers with new sampling schemes improve motion systems’ performanc

Fast Adaptive Robust Differentiator Based Robust-Adaptive Control of Grid-Tied Inverters with a New L Filter Design Method

In this research, a new nonlinear and adaptive state feedback controller with a fast-adaptive robust differentiator is presented for grid-tied inverters. All parameters and external disturbances are taken as uncertain in the design of the proposed controller without the disadvantages of singularity and over-parameterization. A robust differentiator based on the second order sliding mode is also developed with a fast-adaptive structure to be able to consider the time derivative of the virtual control input. Unlike the conventional backstepping, the proposed differentiator overcomes the problem of explosion of complexity. In the closed-loop control system, the three phase source currents and direct current (DC) bus voltage are assumed to be available for feedback. Using the Lyapunov stability theory, it is proven that the overall control system has the global asymptotic stability. In addition, a new simple L filter design method based on the total harmonic distortion approach is also proposed. Simulations and experimental results show that the proposed controller assurances drive the tracking errors to zero with better performance, and it is robust against all uncertainties. Moreover, the proposed L filter design method matches the total harmonic distortion (THD) aim in the design with the experimental result