Transfer function

About: Transfer function is a research topic. Over the lifetime, 14362 publications have been published within this topic receiving 214983 citations. The topic is also known as: system function & network function.

Vector Control of Single-Phase Voltage-Source Converters Based on Fictive-Axis Emulation

Abstract: This paper presents an alternative way for the current regulation of single-phase voltage-source dc-ac converters in direct-quadrature (dq) synchronous reference frames. In a dq reference frame, ac (time varying) quantities appear as dc (time invariant) ones, allowing the controller to be designed the same as dc-dc converters, presenting infinite control gain at the steady-state operating point to achieve zero steady-state error. The common approach is to create a set of imaginary quantities orthogonal to those of the real single-phase system so as to obtain dc quantities by means of a stationary-frame to rotating-frame transformation. The orthogonal imaginary quantities in common approaches are obtained by phase shifting the real components by a quarter of the fundamental period. The introduction of such delay in the system deteriorates the dynamic response, which becomes slower and oscillatory. In the proposed approach of this paper, the orthogonal quantities are generated by an imaginary system called fictive axis, which runs concurrently with the real one. The proposed approach, which is referred to as fictive-axis emulation, effectively improves the poor dynamics of the conventional approaches while not adding excessive complexity to the controller structure.

Filtering in the time and frequency domains

Abstract: Long regarded as a classic of filter theory and design, this book stands as the most comprehensive treatment of filtering techniques, devices and concepts as well as pertinent mathematical relationships. Analysis and theory are supplemented by detailed design curves, fully explained examples and problem and answer sections. Discussed are the derivation of filtering functions, Fourier, Laplace, Hilbert and z transforms, lowpass responses, the transformation of lowpass into other filter types, the all-pass function, the effect of losses on theoretical responses, matched filtering, methods of time-domain synthesis, and digital filtering. This book is invaluable for engineers other than those who are filter design specialists who need to know about the possibilities and limits of the filtering process in order to use filters competently and confidently in their system designs.

Synthesis of a non-linear feedback system with significant plant-ignorance for prescribed system tolerances†

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.

Optical Transfer of the Three-Dimensional Object*†

Abstract: A transfer theory is developed that determines the image space, and three-dimensional image spectrum, of a 3–D object. For both incoherent and coherent illumination, the image is found to obey convolution, transfer, and sampling theorems that resemble the familiar results of ordinary 2-D theory. A 3-D transfer function is related to the pupil function of the image-forming optical system. One result of the theory is that with incoherent illumination, the object image space contains no more than 1/(λ3f/no.4) degrees of freedom/unit volume, where λ is the wavelength of light. The transfer theory is based on the existence of volumes of stationarity, termed “isotomes;” into which the object must be partitioned. Isotomicity is shown to be approximated, over sufficiently small volumes, in the diffraction-limited case.