A Critical Assessment of Open-Loop Active Gate Drivers Under Variable Operating Conditions

ABSTRACT The use of studded tires has been a subject of controversy from the time they came into market. While studded tires contribute to traffic safety under severe winter conditions by increasing tire friction on icy roads, they also cause damage to the road surface when running on bare roads. Consequently, one of the main challenges in studded tire development is to reduce road wear while still ensuring a good grip on ice. Therefore, a research project was initiated to gain understanding about the mechanisms and influencing parameters involved in road wear by studded tires. A test method using the institute's internal drum test bench was developed. Furthermore, mechanisms causing road wear by studded tires were derived from basic analytical models. These mechanisms were used to identify the main parameters influencing road wear by studded tires. Using experimental results obtained with the test method developed, the expected influences were verified. Vehicle driving speed and stud mass were found to be major factors influencing road wear. This can be explained by the stud impact as a dominant mechanism. By means of the test method presented, quantified and comparable data for road wear caused by studded tires under controllable conditions can be obtained. The mechanisms allow predicting the influence of tire construction and variable operating conditions on road wear.

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Treatment system response to transient AOX (adsorbable organic halogen) loadings

Water Science & Technology ◽

10.2166/wst.1997.0489 ◽

1997 ◽

Vol 35 (2-3) ◽

pp. 85-91

Author(s):

D. A. Barton ◽

J. D. Woodruff ◽

T. M. Bousquet ◽

A. M. Parrish

Keyword(s):

Paper Industry ◽

Model Development ◽

Operating Conditions ◽

System Response ◽

Additional Information ◽

Organic Halogen ◽

Aox Removal ◽

Variable Operating Conditions ◽

Plant Shutdown

If promulgated as proposed, effluent guidelines for the U.S. pulp and paper industry will impose average monthly and maximum daily numerical limits of discharged AOX (adsorbable organic halogen). At this time, it is unclear whether the maximum-day variability factor used to establish the proposed effluent guidelines will provide sufficient margin for mills to achieve compliance during periods of normal but variable operating conditions within the pulping and bleaching processes. Consequently, additional information is needed to relate transient AOX loadings with final AOX discharges. This paper presents a simplistic dynamic model of AOX decay during treatment. The model consists of hydraulic characterization of an activated sludge process and a first-order decay coefficient for AOX removal. Data for model development were acquired by frequent collection of influent and effluent samples at a bleach kraft mill during a bleach plant shutdown and startup sequence.

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Performance evaluation and boron rejection in a SWRO system under variable operating conditions

Computers & Chemical Engineering ◽

10.1016/j.compchemeng.2021.107441 ◽

2021 ◽

pp. 107441

Author(s):

A. Ruiz-García ◽

I. Nuez

Keyword(s):

Performance Evaluation ◽

Operating Conditions ◽

Variable Operating Conditions

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Open-Loop Class-BD Audio Amplifiers with Balanced Common-Mode Output

Electronics ◽

10.3390/electronics10121381 ◽

2021 ◽

Vol 10 (12) ◽

pp. 1381

Author(s):

Wojciech Kołodziejski ◽

Stanisław Kuta ◽

Jacek Jasielski

Keyword(s):

Experimental Studies ◽

Open Loop ◽

Modulation Scheme ◽

Output Stage ◽

Radiation Emission ◽

Common Mode ◽

Audio Amplifiers ◽

Gate Control ◽

Output Filter ◽

Gate Drivers

This paper presents new architectures and implementations of original open-loop Class-BD audio amplifiers with balanced Common-Mode output. The output stage of each proposed amplifier includes the typical H-bridge with four MOSFETs and four additional MOSFET switches that balance and keep the Common-Mode output constant. The presented amplifiers employ the extended NBDD PWM or PSC PWM modulation scheme. When the output stage is built only on NMOSFET transistors, gate drivers require a floating power supply, using a self-boost charge pump with capacitive isolation of the control signal. The use of complementary MOSFETs in the output stage greatly simplifies gate control systems. The proposed amplifiers were compared to the typical Class-BD configuration, using the optimal NBDD modulation with respect to audio performance of the Differential-Mode (DM) and Common-Mode (CM) outputs. Basic SPICE simulations and experimental studies have shown that the proposed Class-BD amplifiers have similar audio performance to the prototype with the optimal NBDD modulation scheme, while at the same time having a balanced constant voltage CM output, thus eliminating the main contributor to radiation emission. As a result, the filtering of the DM output signals can be greatly simplified, while the filtering of the CM output signals can be theoretically eliminated. Practically, due to the timing errors added by the gate drivers, spikes are generated at the CM output, which are very easy to filter out by the reduced LC output filter, even at very low L.

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A Multiple Harmonic Open-Loop Controller for Hydro/Aerodynamic Force Measurements in Rotating Machinery Using Magnetic Bearings

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.1473159 ◽

2002 ◽

Vol 124 (4) ◽

pp. 827-834 ◽

Cited By ~ 3

Author(s):

D. O. Baun ◽

E. H. Maslen ◽

C. R. Knospe ◽

R. D. Flack

Keyword(s):

Frequency Domain ◽

Time Domain ◽

Open Loop ◽

Rotating Machinery ◽

Operating Conditions ◽

Rotor Vibration ◽

Aerodynamic Forces ◽

Analog Input ◽

Input And Output ◽

The Time Domain

Inherent in the construction of many experimental apparatus designed to measure the hydro/aerodynamic forces of rotating machinery are features that contribute undesirable parasitic forces to the measured or test forces. Typically, these parasitic forces are due to seals, drive couplings, and hydraulic and/or inertial unbalance. To obtain accurate and sensitive measurement of the hydro/aerodynamic forces in these situations, it is necessary to subtract the parasitic forces from the test forces. In general, both the test forces and the parasitic forces will be dependent on the system operating conditions including the specific motion of the rotor. Therefore, to properly remove the parasitic forces the vibration orbits and operating conditions must be the same in tests for determining the hydro/aerodynamic forces and tests for determining the parasitic forces. This, in turn, necessitates a means by which the test rotor’s motion can be accurately controlled to an arbitrarily defined trajectory. Here in, an interrupt-driven multiple harmonic open-loop controller was developed and implemented on a laboratory centrifugal pump rotor supported in magnetic bearings (active load cells) for this purpose. This allowed the simultaneous control of subharmonic, synchronous, and superharmonic rotor vibration frequencies with each frequency independently forced to some user defined orbital path. The open-loop controller was implemented on a standard PC using commercially available analog input and output cards. All analog input and output functions, transformation of the position signals from the time domain to the frequency domain, and transformation of the open-loop control signals from the frequency domain to the time domain were performed in an interrupt service routine. Rotor vibration was attenuated to the noise floor, vibration amplitude ≈0.2 μm, or forced to a user specified orbital trajectory. Between the whirl frequencies of 14 and 2 times running speed, the orbit semi-major and semi-minor axis magnitudes were controlled to within 0.5% of the requested axis magnitudes. The ellipse angles and amplitude phase angles of the imposed orbits were within 0.3 deg and 1.0 deg, respectively, of their requested counterparts.

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