Dynamic vacuum pressure tracking control with high-speed on-off valves

A vacuum pressure tracking system with high-speed on-off valves is a discontinuous system due to the discrete nature of high-speed on-off valves. Chamber pressure changes in the system are determined by the mass flow rates during the processes of charging and discharging. Here, a sliding mode controller with an asymmetric compensator based on average mass flow rate is designed for accurate vacuum pressure tracking. The controller output signal is converted into the duty cycles of the high-speed on-off valves via a pulse width modulation pulsing scheme. Owing to the extreme asymmetry of the processes, an asymmetric structure comprising one high-speed on-off valve in the charging unit and three high-speed on-off valves in the discharging unit is applied to weaken the impact of asymmetry. In addition, an asymmetric compensator is also designed to modify the pulse width modulation pulsing scheme to further eliminate the asymmetry. Experimental results indicate that the proposed controller achieves better performance in pressure tracking with the asymmetric compensator overcoming process asymmetry and enhancing system robustness.

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Experimental research on the influence of the pulse injector control parameters on its flow rate

Combustion Engines ◽

10.19206/ce-116852 ◽

2015 ◽

Vol 163 (4) ◽

pp. 15-20

Author(s):

Jacek CZARNIGOWSKI

Keyword(s):

Experimental Research ◽

Mass Flow ◽

Flow Rate ◽

Pulse Width ◽

Pulse Width Modulation ◽

Control Signal ◽

Control Parameters ◽

Pulse Modulation ◽

Fuel Mass ◽

The Impact

The paper presents the results of the impact of the control parameters on the fuel mass flow from the injector. The control parameters examined in the paper were: frequency and pulse width modulation of the modulated control signal (the second part of the injector control signal). The analysis covers 6 injector types of different design of the valve element and the coil. The experiments have shown that the frequency of the signal does not affect the injector performance, contrary to pulse modulation affecting the injector performance significantly.

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The Impact of Oil and Sealing Air Flow, Chamber Pressure, Rotor Speed, and Axial Load on the Power Consumption in an Aeroengine Bearing Chamber

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.1805009 ◽

2005 ◽

Vol 127 (1) ◽

pp. 182-186 ◽

Cited By ~ 9

Author(s):

Michael Flouros

Keyword(s):

Power Consumption ◽

High Speed ◽

Air Flow ◽

Flow Chamber ◽

Chamber Pressure ◽

Power Losses ◽

Rolling Element ◽

Oil Flow ◽

The Impact ◽

Circle Diameter

Trends in aircraft engines have dictated high speed rolling element bearings up to 3 million DN or more with the consequence of having high amounts of heat rejection in the bearing chambers and high oil scavenge temperatures. A parametric study on the bearing power consumption has been performed with a 124 mm pitch circle diameter (PCD) ball bearing in a bearing chamber that has been adapted from the RB199 turbofan engine DN∼2×106. The operating parameters such as oil flow, oil temperature, sealing air flow, bearing chamber pressure, and shaft speed have been varied in order to assess the impact on the power consumption. This work is the first part of a survey aiming to reduce power losses in bearing chambers. In the first part, the parameters affecting the power losses are identified and evaluated.

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A Novel Filter Extracted Equivalent Control Based Fixed Frequency Sliding Mode Approach for Power Electronic Converters

Energies ◽

10.3390/en12050853 ◽

2019 ◽

Vol 12 (5) ◽

pp. 853 ◽

Cited By ~ 2

Author(s):

Abdul Yasin ◽

Muhammad Ashraf ◽

Aamer Bhatti

Keyword(s):

Boundary Layer ◽

Pulse Width ◽

Pulse Width Modulation ◽

Sliding Mode ◽

Discontinuous Function ◽

Switching Frequency ◽

Power Electronic ◽

Power Electronic Converters ◽

Fixed Frequency ◽

Equivalent Control

The key issue in the implementation of the Sliding Mode Control (SMC) in analogue circuits and power electronic converters is its variable switching frequency. The drifting frequency causes electromagnetic compatibility issues and also adversely affect the efficiency of the converter, because the proper size of the inductor and the capacitor depends upon the switching frequency. Pulse Width Modulation based SMC (PWM-SMC) offers the solution, however, it uses either boundary layer approach or employs pulse width modulation of the ideal equivalent control signal. The first technique compromises the performance within the boundary layer, while the latter may not possess properties like robustness and order reduction due to the absence of the discontinuous function. In this research, a novel approach to fix the switching frequency in SMC is proposed, that employs a low pass filter to extract the equivalent control from the discontinuous function, such that the performance and robustness remains intact. To benchmark the experimental observations, a comparison with existing double integral type PWM-SMC is also presented. The results confirm that an improvement of 20% in the rise time and 25.3% in the settling time is obtained. The voltage sag during step change in load is reduced to 42.86%, indicating the increase in the robustness. The experiments prove the hypothesis that a discontinuous function based fixed frequency SMC performs better in terms of disturbances rejection as compared to its counterpart based solely on ideal equivalent control.

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