Calculating Open Loop Transfer Functions from Closed Loop Measurements

1958 ◽  
Vol 5 (3) ◽  
pp. 289-297 ◽  
Author(s):  
N. R. Goodman ◽  
S. Katz
Keyword(s):  
Closed Loop ◽  
Transfer Functions ◽  
Open Loop

Analysis of the Idling Start of the Moving Coil Linear Compressor

2008 ◽  
Author(s):  
Yingbai Xie ◽  
Xiuzhi Huang ◽  
Liyong Lun ◽  
Ganglei Sun
Keyword(s):  
Closed Loop ◽  
Transfer Functions ◽  
Load Condition ◽  
Open Loop ◽  
Reciprocating Compressor ◽  
Piston Motion ◽  
Linear Compressor ◽  
Simulation Results ◽  
The Stability ◽  
Stability Time

The linear compressor is driven by a linear motor. Because it has no crankcase, the piston motion and its control of the linear compressor are differing from that of the conventional reciprocating compressor. For a moving coil linear compressor, mechanical and electromagnetism system are modeled. The open loop and closed loop transfer functions of the system in no-load condition are obtained derived from these equations. The Matlab software is applied to analyze the stability, time domain and frequency domain of the system. Simulation results show that the linear compressor is stable, but the overshoot is relative high, which must be adjusted. This conclusion will be benefit for the design of the idling start of the moving coil linear compressor.

Closed-loop identification of carotid sinus baroreflex open-loop transfer characteristics in rabbits

1997 ◽  
Vol 273 (2) ◽  
pp. H1024-H1031 ◽  
Author(s):  
T. Kawada ◽  
M. Sugimachi ◽  
T. Sato ◽  
H. Miyano ◽  
T. Shishido ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Closed Loop ◽  
Transfer Functions ◽  
Carotid Sinus ◽  
Open Loop ◽  
Parametric Models ◽  
Efferent Nerve ◽  
Transfer Characteristics ◽  
Carotid Sinus Baroreflex ◽  
Closed Loop Identification

In the circulatory system, a change in blood pressure operates through the baroreflex to alter sympathetic efferent nerve activity, which in turn affects blood pressure. Existence of this closed feedback loop makes it difficult to identify the baroreflex open-loop transfer characteristics by means of conventional frequency domain approaches. Although several investigators have demonstrated the advantages of the time domain approach using parametric models such as the autoregressive moving average model, specification of the model structure critically affects their results. Thus we investigated the applicability of a nonparametric closed-loop identification technique to the carotid sinus baroreflex system by using an exogenous perturbation according to a binary white-noise sequence. To validate the identification method, we compared the transfer functions estimated by the closed-loop identification with those estimated by open-loop identification. The transfer functions determined by the two identification methods did not differ statistically in their fitted parameters. We conclude that exogenous perturbation to the baroreflex system enables us to estimate the open-loop baroreflex transfer characteristics under closed-loop conditions.

EXPERIMENTAL RESULTS FOR THE SMALL-SIGNAL STUDY OF THE PWM BOOST DC–DC CONVERTER WITH AN INTEGRAL-LEAD CONTROLLER

1995 ◽  
Vol 05 (04) ◽  
pp. 747-755 ◽  
Author(s):  
MARIAN K. KAZIMIERCZUK ◽  
ROBERT C. CRAVENS, II
Keyword(s):  
Closed Loop ◽  
Transfer Functions ◽  
Low Frequency ◽  
Input Voltage ◽  
Open Loop ◽  
Small Signal ◽  
Loop Control ◽  
Pulse Width Modulated ◽  
Bode Plots ◽  
Step Responses

An experimental verification of previously derived small-signal low-frequency open- and closed-loop characteristics and step responses of a voltage-mode-controlled pulse-width-modulated (PWM) boost DC–DC converter is presented. The Bode plots of the voltage transfer function of the control circuit, the converter and the PWM modulator, the open-loop control-to-output and input-to-output transfer functions, the loop gain, and the closed-loop control-to-output and input-to-output transfer functions are measured. The step responses to the changes in the input voltage, the duty cycle, and the reference voltage are measured. The theoretical results were in good agreement with the measured results. The small-signal model of the converter is experimentally verified.

Regulation of Hydrogen Peroxide Dosage in a Heterogeneous Photo-Fenton Process

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2167
Author(s):  
Karla Estefanía Saldaña-Flores ◽  
René Alejandro Flores-Estrella ◽  
Victor Alcaraz-Gonzalez ◽  
Elvis Carissimi ◽  
Bruna Gonçalves de Souza ◽  
...  
Keyword(s):  
Gallic Acid ◽  
Organic Compounds ◽  
Closed Loop ◽  
Transfer Functions ◽  
Direct Synthesis ◽  
Synthesis Method ◽  
Open Loop ◽  
Fenton Process ◽  
Control Approach ◽  
Curve Method

In this work, a classical linear control approach for the peroxide (H2O2) dosage in a photo-Fenton process is presented as a suitable solution for improving the efficiency in the treatment of recalcitrant organic compounds that cannot be degraded by classical wastewater treatment processes like anaerobic digestion. Experiments were carried out to degrade Lignin, Melanoidin, and Gallic acid, which are typical recalcitrant organic compounds present in some kinds of effluents such as vinasses from the Tequila and Cachaça industries. Experiments were carried in Open-Loop mode for obtaining the degradation model for the three compounds in the form of a Transfer Function, and in Closed-Loop mode for controlling the concentration of each compound. First-order Transfer Functions were obtained using the reaction curve method, and then, based on these models, the parameters of Proportional Integral controllers were calculated using the direct synthesis method. In the Closed-Loop experiments, the Total Organic Carbon removal was 39% for lignin, 7% for melanoidin, and 29% for Gallic acid, which were greater than those obtained in the Open-Loop experiments.

Remarks on the Modelling of Active Structures With Colocated Piezoelectric Actuators and Sensors

1995 ◽  
Author(s):  
N. Loix ◽  
A. Preumont
Keyword(s):  
High Frequency ◽  
Closed Loop ◽  
Transfer Functions ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop System ◽  
Local Effects ◽  
Open Loop System ◽  
Active Structures ◽  
Modelling Techniques

Abstract This paper aims to attract the attention of the designers of active structures on the importance of evaluating properly the feedthrough component of the open-loop transfer functions. It is shown that overlooking the feedthrough component can change significantly the location of the zeros of the open-loop system and, as a result, alter drastically the performance of the closed-loop system. The feedthrough term may result from the quasi-static contribution of the high frequency modes or from local effects that are neglected by over-simplified modelling techniques (e.g. plate or beam instead of shell). The problem is illustrated with a cantilever beam provided with strain actuators.

Identification of open-loop transfer functions in closed-loop baroreflex system using random breathing in humans

2003 ◽  
Author(s):  
T. Yingthawomsuk ◽  
T. Kawada ◽  
T. Sato ◽  
M. Inagaki ◽  
K. Sunagawa ◽  
...  
Keyword(s):  
Closed Loop ◽  
Transfer Functions ◽  
Open Loop

OPEN- AND CLOSED-LOOP DC AND SMALL-SIGNAL CHARACTERISTICS OF PWM BUCK-BOOST CONVERTER FOR CCM

1995 ◽  
Vol 05 (03) ◽  
pp. 261-303 ◽  
Author(s):  
MARIAN K. KAZIMIERCZUK ◽  
ROBERT CRAVENS
Keyword(s):  
Transfer Function ◽  
Closed Loop ◽  
Transfer Functions ◽  
Voltage Divider ◽  
Boost Converter ◽  
Open Loop ◽  
Equivalent Series Resistance ◽  
Small Signal ◽  
Offset Voltage ◽  
Parasitic Components

DC and small-signal circuit models of the PWM buck-boost converter for the continuous conduction mode (CCM) are derived. The models take into account parasitic components, such as the equivalent series resistance (ESR) of the filter capacitor, the ESR of the inductor, the transistor on-resistance, and the diode forward resistance and offset voltage. The component values and the parasitics were measured for a prototype converter. The dc voltage transfer function and the efficiency of the converter are derived from the dc model. Small-signal open-loop transfer functions are derived from the small-signal model. The derivation of the transfer function for an integral-lead controller with the loading effect of the voltage divider network in the feedback loop is given. Small-signal closed-loop transfer functions are derived. Bode plots are given for various transfer functions of the converter.

Ventilatory stability to transient CO2 disturbances in hyperoxia and normoxia in awake humans

1997 ◽  
Vol 83 (2) ◽  
pp. 466-476 ◽  
Author(s):  
Jie Lai ◽  
Eugene N. Bruce
Keyword(s):  
Closed Loop ◽  
Transfer Functions ◽  
Response Duration ◽  
Periodic Breathing ◽  
Open Loop ◽  
Phase Delay ◽  
Ventilatory Responses ◽  
Loop Transfer Function ◽  
Random Disturbances ◽  
Peak Value

Lai, Jie, and Eugene N. Bruce. Ventilatory stability to transient CO2 disturbances in hyperoxia and normoxia in awake humans. J. Appl. Physiol. 83(2): 466–476, 1997.—Modarreszadeh and Bruce ( J. Appl. Physiol. 76: 2765–2775, 1994) proposed that continuous random disturbances in arterial [Formula: see text] are more likely to elicit ventilatory oscillation patterns that mimic periodic breathing in normoxia than in hyperoxia. To test this hypothesis experimentally, in nine awake humans we applied pseudorandom binary inspired CO2 fraction stimulation in normoxia and hyperoxia to derive the closed-loop and open-loop ventilatory responses to a brief CO2 disturbance in terms of impulse responses and transfer functions. The closed-loop impulse response has a significantly higher peak value [0.143 ± 0.071 vs. 0.079 ± 0.034 (SD) l ⋅ min−1 ⋅ 0.01 l CO2 −1, P = 0.014] and a significantly shorter 50% response duration (42.7 ± 13.3 vs. 72.3 ± 27.6 s, P = 0.020) in normoxia than in hyperoxia. Therefore, the ventilatory responses to transient CO2 disturbances are less damped (but generally not oscillatory) in normoxia than in hyperoxia. For the closed-loop transfer function, the gain in normoxia increased significantly ( P < 0.0005), while phase delay decreased significantly ( P< 0.0005). The gain increased by 108.5, 186.0, and 240.6%, while phase delay decreased by 26.0, 18.1, and 17.3%, at 0.01, 0.03, and 0.05 Hz, respectively. Changes in the same direction were found for the open-loop system. Generally, an oscillatory ventilatory response to a small transient CO2 disturbance is unlikely during wakefulness. However, changes in parameters that lead to additional increases in chemoreflex loop gain are more likely to initiate oscillations in normoxia than in hyperoxia.

scholarly journals Closed-loop control of an open cavity flow using reduced-order models

2009 ◽  
Vol 641 ◽  
pp. 1-50 ◽  
Author(s):  
ALEXANDRE BARBAGALLO ◽  
DENIS SIPP ◽  
PETER J. SCHMID
Keyword(s):  
Degrees Of Freedom ◽  
Closed Loop ◽  
Transfer Functions ◽  
Reynolds Numbers ◽  
Open Loop ◽  
Reduced Order Models ◽  
Loop Control ◽  
Reduced Order ◽  
Global Modes ◽  
Proper Orthogonal

The control of separated fluid flow by reduced-order models is studied using the two-dimensional incompressible flow over an open square cavity at Reynolds numbers where instabilities are present. Actuation and measurement locations are taken on the upstream and downstream edge of the cavity. A bi-orthogonal projection is introduced to arrive at reduced-order models for the compensated problem. Global modes, proper orthogonal decomposition (POD) modes and balanced modes are used as expansion bases for the model reduction. The open-loop behaviour of the full and the reduced systems is analysed by comparing the respective transfer functions. This analysis shows that global modes are inadequate to sufficiently represent the input–output behaviour whereas POD and balanced modes are capable of properly approximating the exact transfer function. Balanced modes are far more efficient in this process, but POD modes show superior robustness. The performance of the closed-loop system corroborates this finding: while reduced-order models based on POD are able to render the compensated system stable, balanced modes accomplish the same with far fewer degrees of freedom.

On closed-loop equilibrium strategies for mean-field stochastic linear quadratic problems

2020 ◽  
Vol 26 ◽  
pp. 41
Author(s):  
Tianxiao Wang
Keyword(s):  
Optimal Control ◽  
Closed Loop ◽  
Optimal Control Problems ◽  
Mean Field ◽  
Open Loop ◽  
Time Inconsistency ◽  
Control Problems ◽  
Linear Quadratic ◽  
Linear Quadratic Optimal Control ◽  
Equilibrium Strategies

This article is concerned with linear quadratic optimal control problems of mean-field stochastic differential equations (MF-SDE) with deterministic coefficients. To treat the time inconsistency of the optimal control problems, linear closed-loop equilibrium strategies are introduced and characterized by variational approach. Our developed methodology drops the delicate convergence procedures in Yong [Trans. Amer. Math. Soc. 369 (2017) 5467–5523]. When the MF-SDE reduces to SDE, our Riccati system coincides with the analogue in Yong [Trans. Amer. Math. Soc. 369 (2017) 5467–5523]. However, these two systems are in general different from each other due to the conditional mean-field terms in the MF-SDE. Eventually, the comparisons with pre-committed optimal strategies, open-loop equilibrium strategies are given in details.

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