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 published on a yearly basis
Papers
More filters
TL;DR: In this article, the authors proposed a feedback linearized control strategy for LLC resonant converter, which can achieve better performance with elimination of the nonlinear characteristics with load feedback linearization.
Abstract: LLC resonant converter is a nonlinear system, limiting the use of typical linear control methods. This paper proposed a new nonlinear control strategy, using load feedback linearization for an LLC resonant converter. Compared with the conventional PI controllers, the proposed feedback linearized control strategy can achieve better performance with elimination of the nonlinear characteristics. The LLC resonant converter's dynamic model is built based on fundamental harmonic approximation using extended describing function. By assuming the dynamics of resonant network is much faster than the output voltage and controller, the LLC resonant converter's model is simplified from seven-order state equations to two-order ones. Then, the feedback linearized control strategy is presented. A double loop PI controller is designed to regulate the modulation voltage. The switching frequency can be calculated as a function of the load, input voltage, and modulation voltage. Finally, a 200 W laboratory prototype is built to verify the proposed control scheme. The settling time of the LLC resonant converter is reduced from 38.8 to 20.4 ms under the positive load step using the proposed controller. Experimental results prove the superiority of the proposed feedback linearized controller over the conventional PI controller.
59 citations
TL;DR: It is shown that a nonlinear microwave circuit can easily be represented by a feedback model, and this formalistic identity with nonlinear control systems suggests that methods and results can be borrowed from non linear control theory.
Abstract: It is shown that a nonlinear microwave circuit can easily be represented by a feedback model. This formalistic identity with nonlinear control systems suggests that methods and results can be borrowed from nonlinear control theory. The describing function technique, a concept that has been developed to a high degree of sophistication in control theory, is applied to the problem of phase-locking of microwave oscillators. The use of describing functions in the study of nonlinear microwave circuits may give a simple conceptual understanding of locking phenomena, for example, and thereby reduce computational efforts.
58 citations
TL;DR: In this article, a nonlinear feedback signal is sent to the controller to replace the control error itself, which used to be the deviation between the output response and the reference input of the system.
Abstract: Course keeping for ships is the core of automatic navigation in sea transportation. Much work has concentrated on developing novel control strategies for closed loop systems. We have turned our attention the other way to improve the control performance of marine autopilots in this work by “modulating” the control error using a sine function while the construction of the controller is not changed. The nonlinear feedback signal thus obtained is sent to the controller to replace the control error itself, which used to be the deviation between the output response and the reference input of the system. Such a control scheme is called “nonlinear feedback control” hereafter. Theoretical analysis by using a describing function and robust control theory shows that the same control quality is guaranteed with minor control actions for the nonlinear feedback scheme. Simulation experiments were carried out for the ship Yulong of Dalian Maritime University. It is shown that the method postulated in this paper has advantages of safety and energy saving in navigation; the maximum initial rudder angle is reduced by 31·2% with satisfactory control effect.
58 citations
TL;DR: Henon's method locates the switching point to a high degree of accuracy in one integration step while eliminating the need for a specified tolerance.
Abstract: Results show the importance of accurately locating the switching point between linear subdomains when numerically integrating a piecewise linear system of equations Henon's method locates the switching point to a high degree of accuracy in one integration step while eliminating the need for a specified tolerance
56 citations
09 Dec 2003
TL;DR: In this paper, a frequency domain analysis of the second order sliding mode algorithms, particularly of the twisting algorithm, was carried out with the use of the describing function and the locus of a perturbed relay system approach.
Abstract: A frequency domain analysis of the second order sliding mode algorithms, particularly of the twisting algorithm is carried out with the use of the describing function and the locus of a perturbed relay system approach. It is shown that in the presence of an actuator, the transient process converges to a periodic motion. Parameters of this periodic motion are analyzed. A comparison of the periodic solutions in the systems with higher order sliding mode controllers and the oscillations that occur in classical sliding mode systems with actuators is done.
54 citations