Abstract
In recent years, control system problems involving non linearities are important concerns in the framework of automation industries. Actuators with non-linear behavior such as saturation, dead zone, relay, backlash etc. may be responsible for poor control performance in the system. The analysis of these non-linearities is an important task for a control system engineer. Moreover the methods of analyzing these non-linearities are time consuming and non-generic. This paper presents simple and systematic approach for analyzing such kind of non-linearities using user-friendly MATLAB tool “Nonlintool”. This tool saves the time as well as provides visual effects for analysis. Main contribution of this paper is to show how user friendly MATLAB tool “Nonlintool” can extensively be used for quicker and wider interpretation of results based on describing function models. The novelty of this paper lies in analyzing all kinds of non-linearities along with their impact on stability of the nonlinear system. The performance has been evaluated for varying conditions of magnitude and gain of the system as well as on various transfer function models. The results of stability analysis, for which only standard transfer function model is considered, are presented here.
Highlights
Every real control system is non linear and nonlinear system analysis is an important issue in modern control system engineering
This paper presents an application of user-friendly MATLAB tool “Nonlintool” using describing function models
MATLAB based GUI tool -‘nonlintool’ is easy and effective for studying the nonlinear control system based on proven graphical methods like DF, PPT, and Zames’ circle criteria
Summary
Every real control system is non linear and nonlinear system analysis is an important issue in modern control system engineering. The computer aided tool offers user friendly computational platform to analysis and design of nonlinear control system [4,5,6,7]. Role of these tools is to serve information about stability analysis and behavior of nonlinear systems. The hard nonlinearities are the part of both mechanical subsystems (friction, backlash, hysteresis) and the control system (saturation, hysteresis) These nonlinearities can cause both desirable and undesired phenomena where their most significant manifestation is the existence of limit cycles. Limit cycles play an important role in nonlinear systems, provided that many control loops with common nonlinearities like relay, hysteresis, and saturation can present them. Results have been evaluated and presented here for the standard non linearities and the standard transfer function model
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