In Hyuk Kim

Robust Cascade Control of Electric Motor Drives Using Dual Reduced-Order PI Observer

This paper addresses the problem of preserving the nominal performance of a conventional cascade controller for electric motor drives in the presence of parameter uncertainties and external disturbances. Practical reduced-order proportional-integral (PI) observers are incorporated with predesigned PI controllers in order to enhance the robust performance of current and speed controllers. A unified analysis based on the singular perturbation theory is presented to confirm the desired approximation of the augmented system with the PI observers to the nominal closed-loop system. The validity of the proposed dual observer-based control scheme is tested via computer simulations and experiments using a dc motor system. Both results verify that the proposed controller can be used effectively to recover the nominal performance of the conventional cascade scheme for electric motor drives.

Regulation of a DC/DC Boost Converter Under Parametric Uncertainty and Input Voltage Variation Using Nested Reduced-Order PI Observers

DC/DC boost converters are known for presenting highly nonlinear and nonminimum phase properties. This paper combines a predesigned cascade controller and nested reduced-order proportional-integral observers (PIOs) to maintain the desirable voltage regulation performance of the cascade controller for a dc/dc boost converter subject to load change, parametric uncertainties, unmodeled dynamics, and input voltage variations. In the proposed cascade controller design, the fast inner current loop adopts proportional-integral control and the slow outer voltage loop employs integral-proportional control based on a linearized model at a single nominal operating point. Unified theoretical analysis is performed by applying singular perturbation theory, which confirms the desired approximation of the augmented system with the PIOs to the nominal closed-loop system using the cascade controller without accounting for the uncertainties. The validity of the proposed observer-based control scheme is tested via computer simulations and comparative experiments using a laboratory prototype. Both results show that the closed-loop performance remains nearly nominal under load change, parametric uncertainties, unmodeled dynamics, and input voltage variations, confirming the effectiveness of the proposed controller.

Robust cascade control of DC/DC boost converter against input variation and parameter uncertainties

A DC/DC boost converter is a highly nonlinear system and subject to various uncertainties, such as load change, input voltage variation, and parametric uncertainties. In order to achieve a robust performance for the converters current and voltage output responses against the uncertainties, this paper proposes the use of a robust cascade controller based on a reduced-order proportional-integral observer (PIO). In the proposed design, a cascade approach is adopted, where an integral-proportional (IP) controller and a proportional-integral (PI) controller are constructed to set a nominal, desired dynamic response for the closed-loop system. A theoretical analysis, based on the singular perturbation theory, is presented, to confirm the desired approximation of the augmented system with the PIO to the nominal system without the uncertainties. Simulation results suggest that the additional compensation using dual PIOs can be effectively used to improve the robust performance against load change, input voltage variation, and parametric uncertainties.

LuGre model-based adaptive robust control of 1 DOF mechanical systems using only position measurement

In a large number of mechanical systems, both structured and unstructured uncertainties often degrade control performance. Among the structured uncertainties, friction force is a common cause of motion control performance degradation. In order to improve the motion control performance in the presence of various uncertainties, this paper presents the LuGre friction model based adaptive robust control (ARC) scheme combined with a reduced order proportional-integral (PI) observer. The reduced order PI observer is utilized to estimate unstructured disturbances as well as the velocity information. Comparative computer simulations are carried out to test the performance of the proposed controller.

A robust finite-time convergent multiple integral observer against input disturbance and measurement noise

This paper deals with the design of a robust finite-time convergent observer for linear systems in the presence of unknown input disturbance and measurement noise. In order to achieve the robust estimation performance and ensure the finite-time convergence, the proposed observer is constructed by combining a multiple integral observer with a hybrid system framework. Computer simulations are carried out to test the performance of the proposed observer against parameter uncertainties and an input disturbance as well as measurement noise.

Design of a Speed Controller for Vertical One-Link Manipulator Using Internal Model-based Disturbance Observer

This paper deals with a robust speed control problem of a vertical one-link manipulator in the presence of parameter uncertainties and unknown input disturbance. Uncertain load weight causes an additional sinusoidal disturbance in the rotation of the link. In order to improve the robustness against parameter uncertainties and external input disturbances, this paper employs an internal model-based disturbance observer approach. Comparative computer simulations are performed to test the performance of the proposed controller. The simulation results show the enhanced performance of the proposed method.

ROBUST CASCADE CONTROL OF ELECTRIC MOTOR DRIVES USING PI OBSERVERS

This paper presents a new practical control structure for electric motor drives under parameter uncertainty. Since the conventional PI-type controller requires accurate information on the motor parameters and load conditions to achieve the desired performance, a reduced-order observerbased perturbation estimator has been proposed with the PI controller to preserve the nominal performance of the conventional method. Analysis on the robust performance of the perturbation observer is presented by using the singular perturbation theory. Both computer simulations and experimental results verify that the proposed controller can be used effectively as an additional compensator to the PI-type cascade scheme for electric motor drives.