Laplace Transfer Function Research Articles

Researching low frequency vibration of automobile-robot

Automobile-robot (self-driving automobile) is being researched and developed vigorously. When the automobile-robot is moving on the road surface, the low frequency vibration excitation not only influences the ride comfort of the automobile-robot but also strongly affects the durability of the vehicle’s structures. To research the automobile-robot’s vibration in the low frequency region, a dynamic model of the vehicle is established to calculate the vibration equations in the time region. Based on the theory of the Laplace transfer function, the automobile-robot’s vibration equations in the time region are transformed and converted to the vibration equations in the frequency region. Then, the effect of the design parameters and operation parameters on the characteristic of the automobile-robot’s acceleration-frequency is simulated and analyzed to evaluate the ride comfort as well as the durability of the automobile-robot’s structures in the frequency region. The research results show that the design parameters of the stiffness, mass, and road wavelength remarkably affect the characteristic of the automobile-robot’s acceleration-frequency. To reduce the resonant amplitude of the acceleration-frequency in the vertical and pitching direction of the automobile-robot, the stiffness parameters of the automobile-robot's and tires should be reduced while the mass of the automobile-robot’s body should be increased. Additionally, the road’s roughness also needs to be decreased or the road’s quality needs to be enhanced to reduce the resonant amplitude of the automobile-robot’s acceleration-frequency.

CMOS Design of Chaotic Systems Using Biquadratic OTA-C Filters

This manuscript shows the CMOS design of Lorenz systems using operational transconductance amplifiers (OTAs). Two Lorenz systems are then synchronized in a master–slave topology and used to implement a CMOS secure communication system. The contribution is devoted to the correct design of first- and second-order OTA-C filters, using 180 nm CMOS technology, to guarantee chaotic behavior. First, Simulink is used to simulate a secure communication system using two Lorenz systems connected in a master–slave topology, which is tested using sinusoidal signals that are masked by chaotic signals. Second, the Lorenz systems are scaled to have amplitudes of the state variables below 1 Volt, to allow for CMOS design using OTA-C filters. The transconductances of the OTAs are tuned to accomplish a Laplace transfer function. In this manner, this work highlights the design of a second-order CMOS OTA-C filter, whose damping factor is tuned to generate appropriate chaotic behavior. Finally, chaotic masking is performed by designing a whole CMOS secure communication system by using OTA-C based Lorenz systems, and its SPICE simulation results show its appropriateness for hardware security applications.

Equivalence Checking of System-Level and SPICE-Level Models of Linear Circuits

Due to the increasing complexity of analog circuits and their integration into System-on-Chips (SoC), the analog design and verification industry would greatly benefit from an expansion of system-level methodologies using SystemC AMS. These can provide a speed increase of over 100,000× in comparison to SPICE-level simulations and allow interoperability with digital tools at the system-level. However, a key barrier to the expansion of system-level tools for analog circuits is the lack of confidence in system-level models implemented in SystemC AMS. Functional equivalence of single Laplace Transfer Function (LTF) system-level models to respective SPICE-level models was successfully demonstrated recently. However, this is clearly not sufficient, as the complex systems comprise multiple LTF modules. In this article, we go beyond single LTF models, i.e., we develop a novel graph-based methodology to formally check equivalence between complex system-level and SPICE-level representations of Single-Input Single-Output (SISO) linear analog circuits, such as High-Pass Filters (HPF). To achieve this, first, we introduce a canonical representation in the form of a Signal-Flow Graph (SFG), which is used to functionally map the two representations from separate modeling levels. This canonical representation consists of the input and output nodes and a single edge between them with an LTF as its weight. Second, we create an SFG representation with linear graph modeling for SPICE-level models, whereas for system-level models we extract an SFG from the behavioral description. We then transform the SFG representations into the canonical representation by utilizing three graph manipulation techniques, namely node removal, parallel edge unification, and reflexive edge elimination. This allows us to establish functional equivalence between complex system-level models and SPICE-level models. We demonstrate the applicability of the proposed methodology by successfully applying it to complex circuits.

Presentation of a New Online Method, for Time Variant and Unknown Input Time Delay Estimation, in Continuous SISO-LTI Systems

Aims: In this paper, a novel estimator is presented, for online time delay estimation, in single input-single output LTI systems, with time variant and uncertain delay in control input. Background : The main studies made on systems with time-varying delay are divided into three general categories: (1) Identification and estimation of the delay. (2) Criteria presented for stability and robust stability. (3) Control methods presented with goals like tracking. Objective: It is obvious that Laplace transfer function of a delayed system includes a time delay factor (exponential and non-rational). In this study, it is assumed that the only uncertain and time varying parameter in the system is the system’s time delay. The objective of this paper is to online estimate of this time delay. Methods: Simulations were made on a sample system with input time delay, for different types of time delay signal. Results: Finally, simulations results show rather desirable performance of the proposed estimator in dealing with time varying and uncertain delays.

A Laplace Transfer-Based Citation Model and its Application in Detecting the Obsolescence Characteristics of Articles

This study describes a Laplace transfer-based citation model proposed for the actual citation process among journals. The actual citation process is a dynamic physical system which includes two continuous processes of ageing and publishing of cited articles. By deducing the Laplace transfer function for these two processes, we have established the input–output function for the actual citation process. Considering the subject of ‘automation and control systems’ as an example, time parameters associated with the ageing process were identified from the input–output function to examine the obsolescence characteristics for the subject. Experimental results show that the ageing time parameter calculated by the Laplace transferbased citation model is a good expression on the obsolescence of the field. The field shows a moderate ageing rate and a shortened obsolescence tendency on the whole. Most of the articles cited annually in this field are articles published 5–10 years ago. There is a monotonic decreasing dependence between the increment of IF and the increment of time parameter T 1 , although IF always increases regardless of whether the ageing tends to prolong or shorten.

Modelling the effect of temperature on the gel-filtration chromatographic protein separation

In this study a mechanistic model for chromatography was taken and the solution to its Laplace transfer function was obtained using the Fast Fourier Transform method. Using previously developed correlations for modelling diffusion, both in solution and intraparticle, and estimating the mass transfer coefficient, the effect of temperature in gel fittration liquid chromatography was investigated. The effect of each individual parameter on the elution curve was systematically explored allowing for reasonable estimates for the different temperature cases. In this case, a system of bovine serum albumin and phenylalanine separated by gel filtration chromatography was simulated to demonstrate how the resolution and the selectivity of the separation will change with physical parameters. Decreasing the particle size and flow rate while increasing the temperature led to higher resolution, which is consistent with experimental literature data.

Stiffness and damping real-time control algorithms for adjustable suspensions : A strategy to reduce dynamical effects on vehicles in off-road conditions

In this paper, the problem of dynamical effects of ground irregularity or stability of vehicles in off-road conditions is addressed thanks to a dynamic analysis of the vehicle. In particular, the choice of suitable real-time values for the stiffness and the damping of adjustable suspensions, in order to reduce dynamical effects, is investigated thanks to the analysis of a Laplace transfer function describing the mechanical behaviour of the vehicle. Moreover, a decoupled load transfer computation to identify the suspended masses on each suspension is used and a way to modify in real time suspension parameters by modifying the settling time value in order to drive over obstacles is proposed. This new point of view may permit to use effectively adjustable suspensions in off-road context. Previous approaches indeed only focus on the control of adjustable suspensions on road or by using an actuator in parallel of the suspension and are often dedicated to the driver comfort.

Simulation of PWM DC-DC converters using eigenvalues and eigenvectors

Abstract In this paper, a time-domain simulation of the DC-DC converters’ dynamic behavior is described. Corresponding to the state-space model for each possible operation mode of the circuit, an analytic solution is provided. Converter’s regulator is discretized using the pole-zero placement technique based on its Laplace transfer function. An algorithm results in a very accurate simulation due to the exact solution of the circuit’s equations.

Study of heat conduction through a self-heated composite cylinder by Laplace transfer functions

A study of heat conduction through a composite cylinder showing large differences in scale is presented. The system consists of a thin electrically conductive sensing layer, subjected to Joule self-heating and placed in thermal contact with an inner core and an outer concentric cylindrical sheath. The formalism of Laplace transfer functions is used to relate the operating temperature of the sensing layer to the unknown outermost temperature, to the Joule self-heating and to the thermal contact resistances. Analytical expressions for the overheating temperatures are deduced from these transfer functions. Digital filters are derived from the Laplace transfer functions by using Padé approximants and a bilinear transformation. The real-time direct and inverse heat conduction problems are solved without resorting to Laplace inversion, but rather by using the recursion relations associated with the Padé digital filters. This method allows one to easily solve the problems of heat conduction through a self-heated composite cylinder, even in the nonlinear case of a temperature dependent source term. This approach could be applied to optimize and accurately describe the operation of commonly used wire-wound resistance temperature detectors.

Динамическая модель отопительных приборов и систем

In order to develop previously performed work we consider the problem of constructing a dynamic mathematical model of heating devices and systems. The heating system at the same time seems to be equivalent heater. The output value of the model in this case is the power (heat capacity). Decision is executed by the "gray box", that is the structure of the model is determined by analyzing the physics of the processes occurring in heating devices and systems, and the numerical values of its parameters are found from the experimental data by parametric identification. The resulting differential equation is linear with respect to the unknown quantity-power heater(heating), input the same size-water inlet temperature of the heating system and the temperature of the indoor air are included in this equation in a linear fashion, and the flow is in non-linear manner. It is shown that a constant flow of coolant model can be represented by the transfer functions in the iso-mapping Laplace transfer function of the channel "coolant temperature at the inlet to the heater(heating system) – thermal capacity of the heater(heating)" is a inertia component of the first order, and the channel "indoor air temperature-heat capacity of the heater(heating)" - inertia-forcing component with a negative coefficient of transmission. The qualitative features of the model parameters, in particular, their dependence on the coolant flow are analyzed. Algorithmic block diagram of the control object, which includes the heating system and the thermal regime of the building itself is provided. The results of the parametric model identification from experimental data is described. The model can be used in the development of intelligent control systems heating buildings.

Real-time heat conduction in a self-heated composite slab by Padé filters

A study of the heat conduction through a miniature composite slab showing large differences in scale is presented. The system consists of a highly conductive thin sensing film, subjected to self-heating and encapsulated by insulating layers. The formalism of the Laplace transfer functions is used to relate the operating temperature of the coated sensing film to the unknown outermost temperatures and to self-heating. The use of Padé approximants provides approximations of these transfer functions by rational functions that are much more accurate than most of the concurrent approaches. Then the real-time evolution of the operating temperature of the sensing film is established without resorting to the Laplace inversion, but using recursive digital filters constructed from the Padé approximants. Finally, the inverse analysis that is proposed allows to regain the evolution of the outermost temperatures from the knowledge of the operating temperature, even in the presence of a significant self-heating and a nonlinear regime. The present systemic approach could be applied to optimize and accurately describe the real-time operation of many miniature resistive sensors used for example in biomedical instrumentation.

Dynamic load modelling of a paper mill for small signal stability studies

This paper considers a power system where about half the demand comprises industrial loads and some include large rotating machines. Therefore, the behaviour of these loads during system disturbances has to be considered for system stability studies. This paper describes a practical approach to the development of a Laplace transfer function (TF) model of a (paper) mill load connected to this power system. A PSCAD/EMTDCTM simulation model of the mill (the detailed model) was built from available information on the types of load within the mill. This detailed model was verified in a piece-wise manner, e.g. against individual motor starts. Instead of using the available generic load models, system identification theory is applied to evaluate the transfer function load model from simulated small signal disturbance responses. The model is developed for both voltage and frequency changes, and considers the actual frequency range of inter-area oscillations within the power system. In this paper the focus of the work is to accurately represent the mill load behaviour for small signal disturbances. It is recognised that the large signal requirements of a load model for transient stability studies are also important but the inevitable non-linearity of such a model would tend to saturate the loads’ behaviour during lesser disturbances. The performance of the developed small signal load model is tested using some practical disturbance profiles from this power system. This modelling approach allows development work to commence before real-life disturbance measurements are available since such data is currently scant. However, modern high bandwidth monitoring has recently come on-line for the mill and the TF load model will be fully verified over time as disturbance data builds up.

Development and Comparison of Laplace Domain and State-Space Models of a Half-Car With Flexible Body (ESDA2010–24518)

Math models of wheeled ground vehicle dynamics, including flexible body effects, have been the subject of research and development for many years. These models are typically based on a finite system of simultaneous ordinary differential equations (e.g., state-space models). Higher order models that include flexible body effects offer improved accuracy over a wider frequency range than lower order rigid body models; however, higher order models are typically more sensitive to uncertainties in the model parameters and have increased computational requirements. Lower order models with the desired accuracy may be achieved by model reduction of higher order models. A new more general infinite dimensional Laplace transfer function is derived for beam bending governed by a fourth order wave equation. The resulting infinite dimensional transfer functions for beam bending are then used to develop a transfer function model of a “half-car” with a flexible body. The infinite dimensional transfer function of the half-car model is then used to assess the accuracy of the state-space models. Differences between the models due to model reduction are compared to theoretical upper bounds.

Z변환을 이용한 시간영역에서의 승차감 평가

철도차량의 승차감은 승객이 느끼는 감정이므로 물리적인 진동의 크기뿐만 아니라 인간의 감응도(느낌)도 고려하여야 하며, 이러한 진동에 대한 인간의 감응도를 나타낸 것이 주파수 보정곡선이다. 주파수 보정곡선은 라플라스 변환형태의 전달함수이기 때문에 이 전달함수를 직접 사용하여 시간 영역에서의 승차감의 평가가 불가능하다. 이를 해결하기 위해서 본 논문에서는 라플라스 변환형태의 전달함수를 시간 영역에서 사용할 수 있는 전달함수로 변환하는 방법을 제시하고 다양한 예제를 통해 이 방법에 대한 타당성을 입증하였다. In evaluating the ride comfort of railway vehicles, relationship between passenger's feeling and vibration characteristics is very important because human feeling is dependent on frequency spectrum of vibration. Therefore, the weighing curves in frequency domain are used to evaluate the ride comfort of railway vehicles. These curves have been defined in the Laplace transfer functions. It is necessary to convert the Laplace weighing function to the z weighing function in order to obtain the rms value in the time domain. In the present paper, we have applied Tustin's approximation to transform the Laplace weighing function to the z weighing and validated this method by reviewing the various cases.

Modelling and Simulation of the Pyroelectric Detector Using MATLAB/Simulink

An attempt was made to obtain a simple Laplace transfer function model of a pyroelectric detector which would make an excellent basis for the analysis of its dynamic behaviour. Knowledge of the transfer function model of the pyroelectric detector is necessary for its simulation studies in MATLAB/Simulink environment. A simple model of the pyroelectric detector was implemented in MATLAB/Simulink and some exemplary results of investigation of its voltage response to incident radiation and frequency characteristics were presented.

Continuous Modeling of a Multi‐Link Flexible Transmission

The problem of dynamic, infinite dimension, modeling of a transmission is considered. An accurate Laplace transfer function matrix of the system that consists of flexible shafts connected by gears that are either rigid or flexible is found. The first step is deriving a set of single input, infinite dimension, transfer functions for a single uniform link. The building blocks of those transfer functions are time delays, representing the wave motion, and low order rational expressions, representing the boundary phenomena. The next step is combining these individual transfer functions into an overall model of the transmission, by means of the link reaction approach that makes use of the geometric relationships and reaction moments between neighboring links. The outcome is a generalized dynamic model with the moments in the gear pairs as the generalized state vector. The explicit and highly structured form of the transfer functions allows physical insight into the system, exact calculation of natural frequencies and the construction of exact simulation schemes built from standard blocks that are available in multi‐purpose simulation software.

Estimation of the responses of axisymmetric bodies in spread irregular waves

A method is presented of estimating the responses of axisymmetric bodies floating in spread irregular seas, using a Laplace transfer-function formulation of a floating body time-domain model. A general-case spread-wave model is formulated, using separate wave excitation transfer functions, and a simplification of this approach is proposed, reducing both model complexity and computation time. Responses are computed using both approaches and a comparison made to assess the circumstances in which the simplified approach may be used effectively. The results are also interpreted to highlight the implications of using an equivalent unidirectional wave as an approximation to a spread wave.

Transfer function modeling of multi-link flexible structures

The paper considers the problem of deriving the accurate, infinite dimension, Laplace transfer function matrix of a system consisting of links that are individually governed by a one-dimensional wave equation. The first step is deriving some single input transfer functions, for a single uniform link. The building blocks of those transfer functions are time delays, representing the wave motion, and low-order rational expressions, representing the boundary phenomena. The transfer function approach enables simple yet accurate simulation schemes, exact frequency response for the entire frequency range, finite time analytical solutions, and a good starting point for dedicated control laws. The transfer function provides also an alternative way of obtaining many of the well-known properties of flexible structures. Three methods of modeling multi-link systems are presented. Two of them provide systematic and easy to use approaches for deriving models for systems of any order.

Self Tuning from Noisy Response for Temperature Controller

This paper presents a self tuning strategy from noisy response data for a temperature controller. A general pre-filtering procedure in modeling and identification from noisy response data is not required in the proposed method for a general purpose controller. A two-step procedure for the regulator design is proposed. Laplace transfer function model from noisy step response data is built based on the Laguerre functions and thier orthonomal proparties. Then a regulator is directly computed based on the dominant parameters of estimated transfer function. The sequential self tuning is quite simple. An experiment shows that the proposed method could be successfully and also be easily applied in practice.

Dynamics of the wet-end section in paper mills

A model representing the wet-end section of a paper mill has been developed to characterize its dynamic behavior during the grade change. The model is based on the mass balance relationships written for the simplified wet- end white water network. From the linearization of the dynamic model, higher-order Laplace transfer functions were obtained followed by the reduction procedure to give simple lower-order models in the form of 1 st -order or 2 nd -order plus dead times. The dynamic response of the wet-end is influenced both by the white water volume and by the level of wire retention. Effects of key manipulated variables such as the thick stock flow rate, the ash flow rate and the retention aid flow rate on the major controlled variables were analyzed by numerical simulations. The simple dynamic model developed in the present study can be effectively used in the operation and control.