Advanced control strategy for a digital mass flow controller (original) (raw)
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Low cost MFC control unit using microcontoller
Revista Brasileira de Física Tecnológica Aplicada
In this paper we present a compact and low cost solution to set up and to monitor an electronic Mass Flow Controller (MFC) using an Arduino microcontroller. Usually, MFCs can find a great demand at materials science laboratories, mainly in techniques which requires a precise gas flow control, such as synthesis of thin films by Chemical Vapor Deposition (CVD). The control unit produced is presented in details by using schematic diagrams of the circuit and a detailed configuration for connect the controller to the MFC are presented. The control unit is also capable to work with two Mass Flow Controllers (MFCs) simultaneously at manual and remote (via computer software) regime. The source code is quite simple and allows the user easily modify parameters as type of gas and flux capacity of the controllers. Although the low resolution of ADC (Analog-to-Digital Converter) (10 bits) and DAC (Digital-to-Analog Converter) (using PWM - “Pulse Width Modulation”, 8 bits), the flux can be adjus...
Long-Term Drift Measurements in MEMS-Based Mass Flow Controllers
Reliability, Testing, and Characterization of MEMS/MOEMS II, 2003
Micro-electromechanical systems (MEMS) components find increasing use in devices which measure and control gas flow, for medical and industrial use. Little or no information on the reliability of these devices has been published. This work reports the results of long-term performance studies of pressure-based mass flow controllers (MFCs) comprised of MEMS microvalves, pressure sensors, and critical flow orifices. Specifically, the details of long-term drift in the silicon pressure sensors (which comprise the flow sensor) are presented. Generally, pressure-based MFCs using MEMS components retain a flow accuracy of better than 1% of full scale over a 20:1 dynamic range, with response time under 0.5 sec, after more than three million operation cycles. The primary cause of inaccuracy within this dynamic range, and of inaccuracy larger than 1% of full scale beyond this range, is attributable to uncompensated zero-offset drift in the silicon pressure sensors, whose behavior is intrinsic to the flow sensor. Data is presented which details this characteristic, across many MFCs. Mechanical, thermal, fluidic, pneumatic and electronic mechanisms possibly responsible for the drift are also presented. Means to overcome this long-term drift phenomenon in silicon pressure sensors will complete the discussion.
A highly automated testing facility for calibration and performance testing of mass flow controllers
Proceedings of International Symposium on Semiconductor Manufacturing
A highly automated testing laboratory has been developed at the Oak Ridge National Laboratory towards the goal of improving the mass flow controller (MFC) and its impact on the semiconductor community. Developed initially for SEMATECH, this facility has validated and implemented many of the SEMATECH Semaspec test methods for mass flow controllers, which are now becoming SEMI standards. The facility features several testbeds for the evaluation of MFC reliability, accuracy, surrogate gas factors, and process gas calibrations, in addition to many other aspects of mass flow controllers and other low flow devices. The facility is highly automated, with many test methods being performed in a virtually "hands-off' mode. Integral in this facility is the gravimetric calibrator, a true mass flow device which allows the rapid calibration of flow devices against hazardous and corrosive process gases to the level of approximately 0.3% of reading. The capabilities of this facility have been demonstrated through baseline MFC performance for the SEMI-SEMATECH member companies. The facility is now being opened as a Department of Energy National User Facility, enabling MFC manufacturers, equipment suppliers, and end users access to all facility capabilities for development and evaluation work of the MFC.
Directly Digital Flow Controller
Analytical Chemistry, 2005
An improved directly digital flow controller is evaluated for its ability to modulate gas flow rates. As in the older device, the "GasDAC" (named for its similarity to a weighted-resistor digital-to-analog converter) is capable of controlling gas flow in a linear and reproducible manner with the advantage of having an adjustable range of flow rates. The new design incorporates venting to prevent "puffing" when the individual flow channels are opened. The temporal characteristics of the GasDAC are also examined; modulation frequencies of 10 Hz with various types of waveforms are possible with the new device.
Reliability of MEMS-based mass-flow controllers for semiconductor processing
2003 IEEE International Reliability Physics Symposium Proceedings, 2003. 41st Annual.
Microfabricated components are finding increasing application in semiconductor processing. In this work, we report the results of detailed reliability and MTTF studies on mass-flow controllers (MFCs) created from silicon pressure sensors, microfabricated orifices for use in the flow sensor, and microvalves. Attributes studied include accuracy, response time, inboard leak rate, and particle generation, all monitored versus number of cycles. From these measurements, MTTF is calculated to be greater than 3M cycles. Failure modes are also discussed in detail.
Metrological performances of mass flow controllers for dynamic gas dilution
Accreditation and Quality Assurance, 2013
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Multivariable control design for the water gas shift reactor in a fuel processor
2004
The water gas shift (WGS) reactor is an essential component of the fuel processor in fuel cell power plants. The WGS reactor combines CO and H 2 O in the reformate stream to produce H 2 and CO 2 in a mildly exothermic, equilibrium limited reaction. Proper regulation of the steam-to-carbon ratio and the operating temperature is critical to achieving adequate CO conversion during transients. We consider the control problem for the high temperature shift reactor of a catalytic partial oxidation (CPO) based natural gas fuel processor in a PEM fuel cell power plant. The manipulated variable is the water injection rate and the measurements available are the inlet and exit temperatures of the reactor and the reformate flow from the CPO reactor and the objective is to maintain proper water content in the inlet and CO conversion in the reactor. A linear state space model is obtained by linearizing a nonlinear dynamic model of the system around an operating point of interest. A multivariable controller is designed using the LQR method. We compare various control architectures by selectively dropping the terms in the multivariable controller. It is shown that the reactor exit temperature measurement improves the observability of the system but has negligible influence on the control performance. Such multivariable control analysis provides a systematic framework for the evaluation of alternative control architectures and the impact of sensors.
control system has been applied to 7-stages printing machine existed in Cellopack Company for Packing Industries, 6th of October City. The approach utilizes an experimental databased modeling in discrete-time basis which suitable for PIP control system design. Here, the full state variable feedback control can be implemented directly from the measured input and output signals of the controlled process, without resort to the design and implementation of a deterministic state reconstruction or stochastic Kalman filter. All requirements are comfortably met for several operating conditions by using a straightforward to implement, fixed gain, linear PIP algorithm.
International Journal of Electrochemical Science, 2015
Environmental pollution, depletion of fossil fuel reserves and energy needs of a growing world population, are among the important issues concerning the future of energy. In this context, fuel cells are considered as alternative energy sources. In this study, one cell direct methanol fuel cell system, consisting of various sensors and control elements and controlling system are built. Experimental temperature control is conducted with fuzzy control technique over the systems. Then, useful and simple mathematical model that can adequately represent the system is established and the parameters of this model are determined by particle swarm optimization (PSO) method using experimental data. In addition, ANFIS model of the system with the 4-input and 1 output is established through the polarization curves. Also, membership function types and numbers of input variables having an impact on the ANFIS modeling are investigated. Beside to the experimental PID concentration control with sensor, ANFIS is tested for the sensor-less concentration control over the mathematical model in the simulation studies.