Topic
Describing function
About: Describing function is a research topic. Over the lifetime, 1742 publications have been published within this topic receiving 26702 citations.
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TL;DR: In this article, the steady-state temperature responses of parallel-flow and counterflow heat exchangers subject to sinusoidal flow rate changes of large amplitude were derived based on the assumption that the fluids pass through a series of lumped heat exchanger with lumped capacitances and that the steady state responses are to be expressed by Fourier series.
Abstract: A computational method is presented for obtaining the steady-state temperature responses of parallel-flow and counterflow heat exchangers subject to sinusoidal flow rate changes of large amplitude. The method is based on the assumptions that the fluids pass through a series of lumped heat exchangers with lumped capacitances and that the steady-state responses are to be expressed by Fourier series, and it enables us to reduce the computation time remarkably. The frequency-and amplitude-dependent describing functions between the input sinusoidal flow rate changes and the fundamental component of the steady-state response of the outlet temperature of tube-side or shell-side fluid are also derived. Numerical examples are given to show the effects of the amplitude of the flow rate changes on the describing function plots. Finally the nonlinear behavior of the steady-state periodic responses computed by this method is confirmed by means of digital simulations.
1 citations
TL;DR: In this article, it was shown that the amplitude of stable oscillation depends both on the nonlinearity and the linear part and is determined from the intersection point, whereas the frequency is independent of the non-linearity.
Abstract: It is shown that for non-linearities with real describing functions incorporated in a feedback system, the limit cycle stability of the system can be ascertained from the negative slope of the describing function plot at its intersection point with a describing function, independent plot of the system. It is also shown that amplitude of stable oscillation depends both on the non-linearity and the linear part and is determined from the intersection point, whereas the frequency is independent of the non-linearity and can be determined from the associated linear part parameters alone. The analysis is confined to second order systems with appropriate constraints.
1 citations
TL;DR: In this article, a drive system design for controlling the position and rate of solar power arrays on orbiting spacecraft is presented, in which the signal processing and logic functions are performed by digital and linear integrated circuits.
Abstract: This paper summarizes a drive system design for controlling the position and rate of solar power arrays on orbiting spacecraft. There are no gears or sliding contact elements used anywhere in the system and only low-speed bearings are needed. Such mechanization is particularly well suited to solid lubrication techniques, and wear rates are very low, so that the drive system can operate directly in the space environment for long periods of time. Three major components were developed for implementation of this design concept. They are: 1) a brushless dc torque motor; 2) a rotary power transformer; and 3) an offset-tooth shaft position and rate sensor. These components are combined in a hybrid system configuration in which the signal processing and logic functions are performed by digital and linear integrated circuits. A root contour and describing function analysis, confirmed by experimentation, shows that several modes of limit cycle generation can occur in the vicinity of null. Compensation circuits are given that inhibit or suppress limit cycling and provide controlled electronic damping of the system. The system offers relatively high stiffness and can be operated at indefinitely low angular rates with minimum power consumption.
1 citations
02 Jul 2007
TL;DR: In this paper, a self-tuning adaptive lead-lag controller for nonlinear mechatronic systems has been proposed, which takes into account nonlinear terms of the plant, and this approach reduces the manufacturing cost of high performance and precision.
Abstract: A new procedure for design of self-tuning adaptive lead-lag controllers for use with highly nonlinear systems is developed. The application of this approach to a nonlinear mechatronic system that a conventional linear control has not been successful is also demonstrated. The self-tuning block determines the parameters of the lead-lag controller by solving a set of linear algebraic equations. This control procedure takes into account nonlinear terms of the plant, and this approach reduces the manufacturing cost of mechatronic systems that are required to have high performance and precision.
1 citations
23 May 2000
TL;DR: In this paper, a CNN model for a semilinear hyperbolic equation with hysteresis operator is proposed and the dynamic behavior of the CNN model is studied using a describing function method.
Abstract: A semilinear hyperbolic equation with hysteresis operator is considered. A CNN model for an such equation is made. Dynamic behavior of the CNN model is studied using a describing function method. Traveling wave solutions are proved for the CNN model.
1 citations