scispace - formally typeset
Search or ask a question
Topic

Describing function

About: Describing function is a research topic. Over the lifetime, 1742 publications have been published within this topic receiving 26702 citations.


Papers
More filters
Proceedings ArticleDOI
04 Jun 2014
TL;DR: Simulation and experiments are presented to verify the feasibility and effectiveness of the proposed relay feedback identification method from integer order systems to a class of linear fractional order systems.
Abstract: The relay feedback approach has been used to identify integer order models. Fractional order systems are usually identified by many other approaches. Yet, using the relay feedback to identify a fractional order system has not been reported. This paper investigates this interesting and useful topic by means of extending the relay feedback identification method from integer order systems to a class of linear fractional order systems. Equations are derived for model parameter calculation. Simulation and experiments are presented to verify the feasibility and effectiveness of the proposed approach. I. INTRODUCTION data or need much knowledge of the system to be identified; hence, they lack the vitality in industry. In this paper, the identification of a fractional order plus dead time (FOPDT) model in frequency domain using the relay feedback approach is proposed. The describing function method is utilized as a tool to obtain the system information at the self-sustained oscillation point. Compared with the integer order systems, the difference lies in the equations for computing the model parameters, especially the fractional order, α. Thus, the major contribution of this paper is to generalize the equations for integer order models to fractional order models, which further reveals that the equations for IO systems are particular cases of those for FO systems. Simulation and experiments based on relay feedback tests at multiple frequency points are presented to demonstrate the proposed method. The benefits and limitations of this method are commented and the identification error is briefly discussed. The rest of the paper is organized as follows. First, the proposed method is elaborated through math derivations; then the implementation procedure of the method is demon- strated in simulation and an experiment, respectively; finally, the advantages, limitation and potential improvement are commented.

16 citations

Journal ArticleDOI
TL;DR: In this paper, an analysis for the transfer functions of a particular pulsewidth modulator and power-stage subsystem that has been widely used in practical switching-mode dc regulator systems is presented.
Abstract: An analysis is presented for the transfer functions of a particular pulsewidth modulator and power-stage subsystem that has been widely used in practical switching-mode dc regulator systems. The switch and filter are in a ?buck? configuration, and the switch is driven by a constant-frequency, variable duty-ratio, push-pull magnetic modulator employing square-loop cores. The two transfer functions considered are that with modulator control signal as input and that with line voltage as input. For ac signal,the corresponding describing functions (DF) are derived. It is shown thatcurrent-source drive to the modulator extends the control DF frequency response over that with voltage drive, and that complete cancellation of the effects of line variations can be obtained at dc, but not for ac. Experimental confirmation of the analytical results for the control DF are presented.

16 citations

Proceedings ArticleDOI
21 May 1995
TL;DR: A multiple term lead-lag controller is designed and implemented to quench the limit cycle and improve the rise time of the force control by more than an order of magnitude.
Abstract: The characteristics and the nonlinear dynamics of a high performance hydraulic actuator produced by ASI Inc. are described and modeled. When a feedback is applied for the regulation of output force, a limit cycle is observed. The existence of the limit cycle can a priori be attributed to one, or to a combination of, the four dominant nonlinear effect that were identified in these actuators. In order to pinpoint its origin, successive approximations are made to apply the describing function principle, so as to predict the onset of the limit cycle as function of the feedback gain. Given the experimental data, this method allows us to attribute beyond any doubt its origin to the electromagnetic hysteresis in the valve, which is based on jet-pipe technology. A multiple term lead-lag controller is designed and implemented to quench the limit cycle and improve the rise time of the force control by more than an order of magnitude.

16 citations

Proceedings ArticleDOI
04 Dec 2001
TL;DR: The describing function method is employed in conjunction with some of the robustness tools for linear systems to develop algorithms for predicting the existence of limit cycles in uncertain systems with multiple nonlinearities connected in series.
Abstract: The describing function method can be used to analyze control systems with separable nonlinearities. Here, the method is employed in conjunction with some of the robustness tools for linear systems to develop algorithms for predicting the existence of limit cycles in uncertain systems with multiple nonlinearities connected in series. Uncertainty is assumed to exist in terms of parameter variations in both the linear and the nonlinear elements. Examples are provided to illustrate the results which are, of course, subject to the usual errors and restrictions of the describing function method.

16 citations


Network Information
Related Topics (5)
Control theory
299.6K papers, 3.1M citations
90% related
Linear system
59.5K papers, 1.4M citations
88% related
Control system
129K papers, 1.5M citations
86% related
Robustness (computer science)
94.7K papers, 1.6M citations
83% related
Electric power system
133K papers, 1.7M citations
80% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202312
202230
202142
202057
201953
201847