Step Response Measurements Research Articles

Time-domain identification of One Noninteger Order Plus Time Delay models from step response measurements

Practical performances of controller design methods strongly depend on relevancy of identified models. Fractional order system models promise advantage of more accurate modeling of real systems. This study presents a discussion on utilization of two fundamental numerical solution methods of fractional calculus in identification problems of One Noninteger Order Plus Time Delay with one pole (NOPTD-I) models. The identification process is carried out by estimating parameters of a NOPTD-I type transfer function template so that the step response of the NOPTD-I model can sufficiently fit experimental step response data. In the study, step responses of NOPTD-I models are numerically calculated according to two fundamental methods, which are Mittag-Leffler (ML) function and Grunwald–Letnikov (GL) definition. Particle swarm optimization (PSO) algorithm is used to perform data fitting. Illustrative examples are presented to evaluate model parameter estimation performances of these two methods for synthetically generated noisy test data. An experimental study is conducted for modeling pitch rotor of TRMS to compare experimental performances.

Frequency Response Estimation from Impulse or Step‐like Response by Virtual Experiments

AbstractThis paper considers the problem of estimating the frequency response of an unknown plant from impulse or step response measurements, possibly with non‐ideal step signals. The proposed method is direct (no model identification of the plant is needed) and it can be applied using a single set of data generated by the plant, with no need for specific experiments nor iterations. The frequency response of the plant, at a desired frequency, is estimated by a virtual experiment generating a filtered version of the data set. Numerical simulations show the effectiveness of the method.

Modal dynamics of magnetic-liquid deformable mirrors.

Magnetic-liquid deformable mirrors (MLDMs) were introduced by our group in 2004 and numerous developments have been made since then. The usefulness of this type of mirror in various applications has already been shown, but experimental data on their dynamics are still lacking. A complete theoretical modeling of MLDM dynamics is a complex task because it requires an approach based on magnetohydrodynamics. A purpose of this paper is to present and analyze new experimental data of the dynamics of these mirrors from open-loop step response measurements and show that a basic transfer function modeling is adequate to achieve closed-loop control. Also, experimental data on the eigenmodes dynamic is presented and a modal-based control approach is suggested.

Servo signal processing for flying height control in hard disk drives

A novel method of measuring the relative head-medium spacing based on a measurement in the servo sectors is developed and simulated using a read back signal model. The spacing measurement is tested experimentally on a spin stand where the flying height is varied using the resistance heater element in a thermal flying height control slider. In addition, voltage step response measurements were obtained. The data were used to perform system identification and estimate the dynamics of the thermal actuator. The model can potentially be used for thermal flying height control.

Dynamic Modeling and Control of a Piezo-Electric Dual-Stage Tape Servo Actuator

We present a data-based approach for modeling and controller design of a dual-stage tape servo actuator. Our method uses step response measurements and a generalized realization algorithm to identify a multivariable discrete-time model of the actuator. The data acquisition and modeling can be implemented in the servo firmware of a tape drive. We have designed a dual-stage controller, based on the model, using loop shaping techniques adopted for multivariable control problems. We applied the procedure to the prototype of a dual-stage actuator tape head to reduce the effect of lateral tape motion. The prototype consists of a conventional voice coil motor for coarse positioning and a micro-actuator for fine positioning. The micro-actuator, which is mounted on the voice coil motor, uses a piezo crystal to follow high-frequency lateral tape motion (up to the kilohertz regime), while the voice coil motor follows only low-frequency lateral tape motion. Compared to a single-stage design, the dual-stage servo design provides a 25% bandwidth improvement and a voice coil motor control signal that is much smaller in magnitude.

10.2: Motion Artifact Analysis on Scanning Backlight LCD

AbstractA simulation method based on temporal step response measurements is used to model motion artifacts of a scanning‐backlight LCD‐TV, including ghosts and color aberration. Simulation results are validated with perception experiments, and thus can be used to develop metrics predicting an LCD's motion performance.

PEM fuel cell model representing steady-state, small-signal and large-signal characteristics

Fuel cell applications become increasingly attractive. Therefore, comprehensive models, simulation software and analysis tools are required to characterize fuel cell behavior. This paper introduces a model capable of representing the static and dynamic (dynastatic) behavior of PEM fuel cells. The model approximates the theoretical current–voltage description with an equivalent electric circuit. The parameter values of the model are found by analyzing small-signal measurement results from electrochemical impedance spectroscopy, together with the steady-state electric characteristic and large-signal behavior from step-response measurements. Because the modeling approach is completely based on measurements on the fuel cell electric output terminals, electrochemical aspects like temperature dependency, charge double layer and adsorption effects are implicitly covered.

26.3: Characterizing LCD Motion Color Artifacts Using Simulation Methods

AbstractA method to characterize motion color artifacts from temporal step response measurements of the primary colors is proposed. The apparent image is calculated from the Motion Picture Response Curves, which are the result of the convolution of the step responses with a one‐frame wide shift function. The model predictions are validated with a perception experiment.

Robust Servo Control of a High Friction Industrial Turbine Gas Valve by Indirectly Using the Standard$mu$-Synthesis Tools

The current mu-synthesis tools are not directly suitable for industrial turbine fuel and water control because they lead to high-order controllers with physically meaningless states. The production valve example here is the Woodward GS6 Turbine Gas Metering Valve that has a single-phase permanent magnet motor coupled by a shaft to an inertia disc and a gas metering shoe with a high level of dry (nonlinear) friction and flow forces. The embedded TI-DSP-2407 processor that runs the position controller in the 1 ms loop rate practically limits the maximum controller order to seven. This paper describes how an industrial seventh-order 2-degrees of freedom (DOF) controller was designed by indirectly using the standard tools available in the mu-Toolbox. Step, limit cycle, and frequency response measurements show that the new design compares favorably well with the standard production controller. However, the key advantages were that the first design downloaded into the controller did not require retuning, the design process was higher level, and the measure of "robustness" was in terms of the physical description of plant uncertainties

In Situ Transient FTIR and XANES Studies of the Evolution of Surface Species in CO Oxidation on Au/TiO2

The adsorption of CO and its reaction with oxygen were investigated using a combination of in situ Fourier transform infrared spectroscopy, step response measurements in a microreactor, (18)O isotopic labeling, and X-ray absorption near edge structure spectroscopy. An as-prepared sample in which Au is present as a surface oxyhydroxy complex does not adsorb CO. On an activated sample in which only metallic Au is detected, 0.18 +/- 0.03 mol CO/(mol Au) are adsorbed on Au at -60 degrees C, which shows an IR band at 2090 cm(-1). When oxygen is present in the gas phase, this species reacts with a turnover rate of 1.4 +/- 0.2 mol CO(mol Au min)(-1), which is close to the steady-state turnover rate. In contrast, there is a very small quantity of adsorbed oxygen on Au. A small IR peak at 1242 cm(-1) appears when an activated sample is exposed to CO. It reacts rapidly with oxygen and is shifted to 1236 cm(-1) if (18)O is used. It is assigned to the possible intermediate hydroxycarbonyl.

Demonstration of all-photonic spectral label-switching for optical MPLS networks

All-photonic label-switching of weight four spectral packet labels (concurrent quadruple wavelength conversion) is demonstrated for optical multiprotocol label-switching networks. The experimental setup is based on cross-gain modulation in a fiber ring laser using a semiconductor optical amplifier gain medium and uses commercially available components. Static transfer functions and step response measurements for various input-output label-switching combinations show that a noisy input label with small extinction ratio can be switched to a clean, amplified, output label

APPROXIMATE REALIZATION OF VALVE DYNAMICS WITH TIME DELAY

This paper describes the model identification of control valve dynamics with a time delay. An experimental set-up is used to perform both frequency response and step response measurements on the control valve. An approximate realization algorithm and a new time delay estimation method are applied on the experimental data. The results illustrate that the suggested approach provides a good time delay estimate and a reasonable state space description for the valve dynamics.

RF performance evaluation of ferroelectric varactor shunt switches

This paper addresses experimental RF performance evaluation, and electrical-parameter extraction of different-size ferroelectric varactor shunt switches. Ferroelectric varactor shunt-switch operation is based on the nonlinear dielectric tunability of a Ba0.6Sr0.4TiO3 (BST) thin film sandwiched between two metal layers in a parallel-plate configuration. Coplanar-waveguide implementation of the varactor shunt switch results in a high-speed RF switch, through a simple two-metal layer Si MMIC compatible process on high-resistivity Si substrates. The experimental RF performance of the switches shows low insertion loss for smaller-area devices, with good isolation for larger-area devices. To optimize the device design, the rf performances of multiple devices are tested, and the electrical parameters are extracted. The capacitance of the varactor shunt switches tested are tunable by more than 4:1 for bias voltages below 12 V. The switching speed of the devices tested is approximately 43 ns, based on the step-response measurements. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 370–374, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21172

Adaptive Linear Dynamic Matrix Control applied to an integrating process

Dynamic Matrix Control (DMC) has proven to be a powerful tool for optimal regulation of chemical processes under constrained conditions. It is based on a linear convolution model derived from step-response measurements. A model predictive control algorithm optimises closed-loop performance for a nominal operating point. However, as the process moves away from this point, control usually becomes sub-optimal due to process non-linearity. As seen in this work, the DMC algorithm can be made adaptive, to establish a new local model, by recursive estimation of the local step response parameters from normal plant variations. However, when used for control of plants containing integrating process units, steady-state offsets occur for sustained changes. Thus, a novel Adaptive Linear Dynamic Matrix Control (ALDMC) algorithm has been developed and used to control a 2-input/2-output system with an integrating behaviour. Comparisons of model control and plant control with and without these features demonstrated the importance of integral compensation for integrating processes, and model adaptation in the case of plant/model mismatch. Some cross-compensation of integration by the adaptive feature was also noted. An holistic technique is demonstrated which simultaneously recognises residual integration disturbances and matrix parameter variations, whereas previous techniques which recognise only one of these will fail in the presence of the other.

Use of inductive compensation for improving bandwidth and noise performance of high frequency optical receiver preamplifiers

In the standard bipolar receiver amplifier configuration of a cascode stage followed by an emitter follower, inclusion of an inductor in series with the collector resistor is shown to give an improvement in the noise and bandwidth performance over that of the unmodified circuit. The bandwidth improvement is of the order of a factor of two. The predictions are confirmed by step response measurements.

Accurate RF voltage measurements using a sampling voltage tracker

The RF voltage measurement capability of an equivalent-time sampling system has been investigated over the frequency range of 1-100 MHz. The system is easily calibrated from step response measurements, independent of thermal transfer standards. Comparison measurements made with NBS-calibrated thermal converters show agreement generally within the stated uncertainties presently provided by NBS for such calibrations. The system offers several advantages over conventional thermal transfer techniques: AC/DC transfers are not required, loading and transmission line problems are reduced, and direct measurement of voltages from 2 V to as low as 10 mV are possible. In addition, other waveform characteristics are readily obtained, e.g. average and peak values, harmonic distortion, etc. >

CO 2 step-response experiments during alkali catalyzed carbon gasification; evaluation of the so-called CO overshoot

The so-called CO overshoot during alkali carbonate catalyzed carbon gasification has been studied in detail. It is concluded that the CO overshoot, observed during inert gas to CO 2 step-response measurements over a reduced potassium carbonate carbon sample, is caused by a combination of several effects: 1. 1) Initial oxidation of the potassium carbon sample with formation of CO and an oxidized potassium carbon sample. 2. 2) Increased gasification due to a temperature increase because the initial oxidation is highly exothermic. 3. 3) Adsorption of CO 2 by the potassium carbon system. By using 13CO 2/inert gas mixtures these three effects can be detected separately. Temperature measurements during the CO overshoot reveal a large temperature rise (up to 70 K, depending on the CO 2 flow rate) whereas calculations indicate even a higher temperature increase. After carbothermic reduction of K C = 0.019 potassium carbonate/Norit activated carbon samples at 1073 K in He, no potassium is lost up to 3600 s. An O K ratio of the catalyst lower than K 2O is calculated, while apparent contradictions in literature concerning the O K ratio are explained.

Inverse Nyquist array technique in the design of a multivariable controller for a solid-fuel boiler

Abstract This paper presents an application of the inverse Nyquist array (INA) technique to the design of a multivariable controller for a boiler subsystem. The boiler is a 1.6 MVV water boiler using solid fuel. The subsystem studied consists of the boiler underpressure and the flue-gas oxygen content. First a simple transfer function model based on step response measurements is constructed. The subsystem model is analysed and the interactions are decreased with a constant compensator using Rosenbroek's INA method. Finally, scalar PI controllers are tuned for the approximately decoupled system. A brief description of the microcomputer control system is given. The control system and the designed multivariable controller have worked well since their installation in February 1983.

Determination of BWR incore power feedback effects by radial coherence measurements

Measurements have been performed on the coherence of the signals of BWR incore neutron detectors at different radial positions. It appears that the coherence decreases with increasing detector distance and with decreasing frequency. These space-dependent effects can be explained by the distributed noise source formed by the boiling process in the core and incore power feedback effects that limit the range over which it influences the neutron detector signals. Using the measured coherences and applying a theory based on detector adjoint functions, estimates for the at-power reactivity transfer function can be made. The estimates can be improved by reduction of the influence of other noise sources using an autoregressive model of the noise signals. The results are compared with the results of step response measurements of the reactor transfer function.

Experimental Determination of the Transient Frequency and Voltage Dependency of Load Networks

For the investigation of the control behaviour of large power systems the static and dynamic dependency of load networks is required. Up to now nearly no load parameters describing the transient frequency and voltage dependency of the real and reactiv power are available. This is caused by identification difficulties such like generating of suitable test signals, large load disturbances and the security requirements for power systems. In spite of these difficulties extensive step response measurements were carried out in different power systems.After smoothing the strongly disturbed input/output signals by ensemble averaging the static and dynamic load parameters were estimated by the method of least square error adaption. The results show that the transfer behaviour of load networks has an essential non negligible influence on the control behaviour of large power systems.