A disturbance reduction scheme for linear small delay systems with modeling uncertainties

Traditional underwater vehicles are limited in speed due to dramatic friction drag on the hull. A supercavitating vehicle exploits supercavitation to induce a gaseous cavity that contains most part of the vehicle and separates the vehicle hull from its surrounding water. Thus friction drag is substantially reduced. A supercavitating underwater vehicle can achieve very high speed, but also poses technical challenges in stability, control, and maneuvering due to various characteristics such as instability in open-loop dynamics, nonlinearity, cavity memory effect, etc. Among the existing literature on the control design for supercavitating vehicles, the cavity memory effect is often neglected to simplify system dynamics. In this paper, we take into account the cavity memory effect and model the supercavitating vehicle as a time-delay Quasi-Linear-Parameter-Varying system. Then a robust controller is designed to handle the switched, time-delay dependent behavior of the vehicle. The uncertainties considered in the presented control design include both parameter and planing force modeling uncertainties.

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A Review of Some Subtleties of Practical Relevance for Time-Delay Systems of Neutral Type

ISRN Applied Mathematics ◽

10.5402/2012/725783 ◽

2012 ◽

Vol 2012 ◽

pp. 1-46 ◽

Cited By ~ 38

Author(s):

Keqin Gu

Keyword(s):

Time Delay ◽

Neutral Type ◽

Distributed Delay ◽

Alternative Interpretation ◽

Smith Predictor ◽

Delay Systems ◽

Time Delay Systems ◽

Small Delay ◽

Parameter Variations ◽

Delay Feedback Control

This paper reviews some subtleties in time-delay systems of neutral type that are believed to be of particular relevance in practice. Both traditional formulation and the coupled differential-difference equation formulation are used. The discontinuity of the spectrum as a function of delays is discussed. Conditions to guarantee stability under small parameter variations are given. A number of subjects that have been discussed in the literature, often using different methods, are reviewed to illustrate some fundamental concepts. These include systems with small delays, the sensitivity of Smith predictor to small delay mismatch, and the discrete implementation of distributed-delay feedback control. The framework prsented in this paper makes it possible to provide simpler formulation and strengthen, generalize, or provide alternative interpretation of the existing results.

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Compared with PI, Fuzzy-PI and PSO-PI Controllers of Robotic Grinding Force Servo System

TELKOMNIKA Indonesian Journal of Electrical Engineering ◽

10.11591/tijee.v16i1.1589 ◽

2015 ◽

Vol 16 (1) ◽

pp. 65

Author(s):

Adnan Jabbar Attiya ◽

Yang Wenyu ◽

Salam Waley Shneen

Keyword(s):

Industrial Robot ◽

Servo System ◽

Pi Controller ◽

Grinding Force ◽

Delay Systems ◽

Step Response ◽

Robotic Grinding ◽

Comparison Results ◽

Modeling Uncertainties ◽

Optimal Gains

<p>By grinding process, when an industrial robot is used to finish a curved surface, both feed movement and contact force must controlled at the similar time in order that the grinding tool would machine the work-piece at the right position in right posture with required force. A passive wrist system is advanced, in this paper, to conform the shape of the machining propeller by altering its posture along with the surface. The proportional-integral (PI) controller, due to its simplicity, robustness, and affordable price, is extremely often used in practical applications, but it is effective for linear systems, as well as, the challenging task is to find its optimal gains. If the processes involved higher order and time delay systems, many intelligent controllers were appeared. In this paper, to cope with nonlinearities, improve the controller parameters and at the same time modeling uncertainties of grinding marine propeller surface, a PI torque controller is proposed such that its optimal gains are derived via a modern systems based on fuzzy logic theory and particle swarm optimization algorithm which are used to solve various engineering problems. Grinding force is controlled under Fuzzy-PI controller which is being assembled and compared with a PSO-PI controller to obtain which controller that provides grinding with higher quality. The compared controllers have been optimized together with the parameters of the Two-Phase Hybrid Stepping Motor. The suggested fuzzy rule function and PSO algorithm improve the response of the controlled system and searches a high-quality solution impressively. Simulation and comparison results are presented and that the proposed control systems are coping well with nonlinearities and uncertainties while find PI control parameter set effectively, the PSO-PI controller has a better control performance with improved step response for robotic grinding force servo system. These control methods was simulated using MATLAB/SIMULINK.</p>

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