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.

Analysis of coefficient quantization errors in state-space digital filters

Abstract: In this paper, we examine the sensitivity of state-space digital filters to coefficient quantization errors. A cost function using an L p norm criteria is used to measure the deviation in frequency response of the filter. The cost function is used to indicate the connection between roundoff noise and filter sensitivity to coefficient quantization errors. Then based on this cost function it is shown that low roundoff noise state-space digital filters, filters in balanced coordinates, and filters based on polynomials orthogonal on the unit circle have low sensitivity to coefficient quantization errors. Furthermore, the sensitivity of the filters is shown to depend on the second-order modes thereby exhibiting certain robustness and immunity to filter bandwidth.

Locating transformer faults through sensitivity analysis of high frequency modeling using transfer function approach

Abstract: The online condition monitoring of power transformer insulation can give early warning of electrical failure and could prevent catastrophic losses. Transfer function analysis offers the additional advantage of fault identification and location. High frequency resonance in a transformer can be modeled by analogue distributed winding concepts. Every transformer has an unique transfer function independent of the shape of the input waveform and can be evaluated through sweep and impulse tests. Results show that this transfer function changes by winding deformation, displacement, ground leakage, local breakdown and partial discharges etc. Digital simulation of impulse and variable frequency transient responses together with their fast Fourier transform spectral analysis are used in this paper to identify transformer faults and characterize their influence on transfer function. Sliding faults through the winding revealed changes in the transfer function to help locate the fault's location. This paper contributes to the development of a high frequency transformer model capable of studying faults including partial discharges, deriving condition assessment of a previously untested transformer from the varied characteristic plots to assess remaining life of a power transformer.

Self-tuning regulators for combustion oscillations

Abstract: Self–excited combustion oscillations arise from a coupling between unsteady combustion and acoustic waves, and can cause structural damage to many combustion systems. Active control provides a way of extending the system's stable operating range by interrupting the damaging thermoacoustic interaction. The active controller considered injects some fuel unsteadily into the burning region, thereby altering the heat–release rate, in response to an input signal detecting the oscillation. Although the feasibility of such a control configuration was demonstrated on laboratory–scale experiments over 15 years ago, the triple requirement for full–scale applications is to adapt the controller response to varying operating conditions and to guarantee that the controller will cause no harm, while relying as little as possible on a particular combustion model. As a first step towards meeting these requirements, a self–tuning regulator (STR) is proposed in this paper for a class of combustion systems that satisfy some fairly non–restrictive assumptions. An open–loop transfer function from the controller output voltage driving the actuator to the pressure signal detecting the oscillation is derived, and is shown to be the product of a time delay τ tot and a transfer function that satisfies certain structural properties. Using the open–loop transfer function, it is shown that the stabilizing STR structure is that of a simple phase–lead compensator if τ tot=0, and the same compensator combined with a Smith controller if τ tot=0. The adaptive rule for the adjustment of the STR parameters is derived from a Lyapunov stability analysis. Promising results are obtained on a simulation based on a nonlinear premixed flame model and on an experimental set–up which consists of a laminar flame burning in a Rijke tube.

Evaluation system for residual vibration from HDD mounting mechanism

Abstract: An evaluation system for calculating the residual vibration caused by a HDD (Hard Disk Drive) mounting system is presented. It contains both the elements for measurement and analysis. The PES (Position Error Signal) of an ideally balanced rigid rotary actuator depends on the rotational vibration of the HDD, specifically at lower frequencies. First, this evaluation technique obtains a measurement of the transfer function of the HDD rotational acceleration over actuator current. Next, using the measured power spectrum of the actuator in combination with the HDD's tracking error transfer function, the response of the entire HDD and mount system is calculated in the frequency domain. Finally the time domain system response is calculated by computation of the Inverse Fast Fourier Transform (IFFT) of the frequency response solution, assuming a random phase of the input force. Good correlation is obtained between measured and calculated system responses. Experimental result show that the dominant residual vibration is caused by the mounting mechanism response and that both the HDD and HDD mount system need to be evaluated and understood as a system, in order to achieve higher TPI (Track per inch) in the future.

Design of stable two‐dimensional analogue and digital filters with applications in image processing

Abstract: A method is proposed for the frequency domain design of linear two-dimensional analogue and digital filters with guaranteed stability. The technique used is based on the result that the numerator and the denominator of the input immittance of a two-variable network (which is passive and lossy) are strictly Hurwitz polynomials. One of these strictly Hurwitz polynomials is assigned to the denominator of a two-variable analogue transfer function and the network elements are then used as the variables of optimization thereby guaranteeing the stability of the analogue transfer function. The transfer function of the corresponding two-dimensional discrete (digital) filter is obtained from the analogue transfer function by the bilinear transformation. Examples illustrating the versatility of the technique in designing 2D digital filters of arbitrary order approximating a given magnitude and group delay response are presented. These filters are used to process a simple binary image. The results obtained demonstrate the importance of linear phase in image processing applications. The method presented here can be extended to the design of stable m-dimensional analogue and digital filters.