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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01 Dec 1981
TL;DR: Based on the experimental findings of Wu and Paul [17], two joints of an industrial robot have been redesigned and fabricated to include torque sensing capability by means of strain gauges, and the resulting control systems reduced the effective frictional torques of the joints from 1072 oz.in to 33.5oz.in this paper.
Abstract: Based on the experimental findings of Wu and Paul [17], two joints of an industrial robot have been redesigned and fabricated to include torque sensing capability by means of strain gauges. The resulting control systems reduced the effective frictional torques of the joints from 1072 oz.in to 33.5 oz.in. The stability of the closed-loop systems was analyzed by means of the describing function for limit cycles exhibited in the system, which can be removed by an insertion of phased-lead series compensating networks.
197 citations
TL;DR: In this article, the authors investigated the use of the nonlinear device known as the Clegg integrator in the design of a nonlinear feedback system, which minimizes the effect of white sensor noise on the input to the plant.
Abstract: The problem considered is the design of a feedback system containing a linear, time invariant, minimum phase plant, whose parameters are known only within given bounds, such that the time response of the system remains within specified limits. A quasi-optimal design, for given design constraints, is one which minimizes the effect of white sensor noise on the input to the plant. An investigation was conducted on the use of the non linear device known as the Clegg integrator in the design of such a system. The describing function of the Clegg integrator has the same magnitude characteristic, apart from a scale factor, as the linear integrator, but has 52 deg less phase-lag, at all frequencies, than the linear integrator; thus, when used in a feedback system, it provides a larger stability margin than the linear integrator. This property allows the nonlinear feedback system to be designed so that the sensor noise is attenuated more than in the linear design.
182 citations
TL;DR: In this paper, the authors proposed a model for constant on-time current-mode control, where the inductor, switches, and modulator are treated as a single entity and modeled based on the describing function method.
Abstract: Constant on-time current-mode control has been widely used to improve light-load efficiency, because it can reduce the switching frequency to save switching-related loss. Therefore, an accurate model for constant on-time control is indispensable to system design. However, available models for constant on-time control are unable to provide accurate physical insight or predict system response very well. This paper introduces a new modeling approach for constant on-time control. The inductor, the switches, and the pulsewidth-modulated modulator are treated as a single entity and modeled based on the describing function method. The fundamental difference between constant on-time control and constant-frequency peak-current-mode control is analyzed through the proposed model. This proposed modeling method can be easily extended to other current-mode controls, including V2 controls. A simple equivalent circuit representation is proposed for the sake of easy understanding and simulation of current-mode controls. Simulation and experimental results are used to verify the proposed model.
171 citations
TL;DR: The chattering can be caused by fast dynamics which were neglected in the ideal model, and these `unmodeled' dynamics with small time constants are usually disregarded in models of servomechanisms, sensors and data processors.
167 citations
20 Jun 2004
TL;DR: From the static and dynamic models, no-limit-cycle conditions associated with A/D, DPWM and compensator design criteria are derived and conclusions are illustrated by simulation and experimental examples.
Abstract: In digitally controlled DC-DC converters with a single voltage feedback loop, the two quantizers, namely the A/D converter and the digital pulse-width modulator (DPWM), can cause undesirable limit-cycle oscillations. In this paper, static and dynamic models that include the quantization effects are derived and used to explain the origins of limit-cycle oscillations. In the static model, existence of DC solution, which is a necessary no-limit-cycle condition, is examined using a graphical method. A concept of amplitude and offset dependent gain is introduced to extend the describing function method and derive the dynamic system model. From the static and dynamic models, no-limit-cycle conditions associated with A/D, DPWM and compensator design criteria are derived. The conclusions are illustrated by simulation and experimental examples.
156 citations