Automatic Control Scheme Research Articles

Multiplexed Four-Channel Rectilinear Ion Trap Mass Spectrometer

A four-channel multiplexed mass spectrometer with rectilinear ion trap (RIT) mass analyzers was designed, constructed, and characterized. The system consists of four parallel atmospheric pressure ion (API) sources, four RIT mass analyzers, four sets of ion optical elements, and four conversion dynode detectors. The complete instrument is housed in a single vacuum manifold with a common vacuum system. It has a relatively small footprint, and costs and complexity were minimized and controls simplified by sharing the electronics and control modules among different channels. Each channel of the instrument can be operated in either positive or negative ion mode with a choice of ionization methods to improve the information content from an experiment. Also, the instrument is equipped with simultaneous data acquisition capabilities from all four channels, but the use of a common RF electronics system limits the degree to which the analyzer channels can be scanned independently. The instrument was characterized over the mass/charge range of 150 to 1300 Th. Mass misassignments in different ion traps because of machining and assembly tolerances were avoided by the application of supplementary direct current signals to each mass analyzer to correct mass offsets. A multiplexed automatic gain control (AGC) scheme was developed to control the ion population in each of the traps independently. These two features allow tandem mass spectrometry to be performed with an isolation window of 1 Th so trapping identical ions in all four channels. There are two principal modes of operation. In one, the same sample is analyzed in all four channels using different ionization methods to increase the information content of the analysis. In the other mode of operation, different samples are analyzed in all four channels with the same ionization method, so providing higher throughput. These capabilities were demonstrated by examining lipids produced by Escherichia coli and complex mixtures containing drugs of abuse.

Architecture of a wireless Personal Assistant for telemedical diabetes care

Purpose Advanced information technologies joined to the increasing use of continuous medical devices for monitoring and treatment, have made possible the definition of a new telemedical diabetes care scenario based on a hand-held Personal Assistant (PA). This paper describes the architecture, functionality and implementation of the PA, which communicates different medical devices in a personal wireless network. Description of the system The PA is a mobile system for patients with diabetes connected to a telemedical center. The software design follows a modular approach to make the integration of medical devices or new functionalities independent from the rest of its components. Physicians can remotely control medical devices from the telemedicine server through the integration of the Common Object Request Broker Architecture (CORBA) and mobile GPRS communications. Data about PA modules’ usage and patients’ behavior evaluation come from a pervasive tracing system implemented into the PA. Results and discussion The PA architecture has been technically validated with commercially available medical devices during a clinical experiment for ambulatory monitoring and expert feedback through telemedicine. The clinical experiment has allowed defining patients’ patterns of usage and preferred scenarios and it has proved the Personal Assistant's feasibility. The patients showed high acceptability and interest in the system as recorded in the usability and utility questionnaires. Future work will be devoted to the validation of the system with automatic control strategies from the telemedical center as well as with closed-loop control algorithms.

AUTOMATIC GAIN CONTROL FOR UNITY FEEDBACK CONTROL SYSTEMS

In this paper, an automatic gain control scheme is proposed for analyses and designs of unity feedback control systems. It is consisted of a fast command tracking loop and a slow gain adaptive loop. The overall system is equivalent to a conventional automatic gain control loop with command tracking error input. It gives good command tracking behaviour while keeping robust characteristic of the original automatic gain control loop. It gives good robustness for coping with fast large parameter and load disturbance variations also. The stability of the controlled systems and effective of the proposed method are verified by root-loci, time responses, frequency responses, large parameter variations and fast large load disturbances testing with two numerical examples.

Extensive reduction of toxic gas emissions of firewood-fueled low power fireplaces by improved in situ gas sensorics and catalytic treatment of exhaust gas

Two different firewood-fueled high quality fireplaces for private homes were complemented with novel in situ gas sensors for residual oxygen and CO/HC flue gas analysis and with a catalytic converter for exhaust gas treatment. The sensitivity performance of the used CO/HC mixed-potential-type sensor is characterized. Based on these two gas sensor signals and on the combustion temperature a new general strategy for automatic control of the primary and secondary air streams for firewood combustion was developed. This enabled reduction of the (toxic) CO/HC-emissions to about 50% (central heater) and 15% (tiled stove), respectively, in comparison to the emissions measured when the firing process is controlled by the algorithm of the fireplace-producer. After implementation of a catalytic converter into the flue gas channel (central heater) and post-combustion chamber (tiled stove) and adaptation of the control algorithm parameters the CO/HC-emissions were further reduced to about 25% and less than 1%, respectively. Studies of the long-term stability of the catalyst material by temperature dependent gas conversion experiments indicated that the conversion kinetics is stabilized at an onset-temperature of about 155 °C.

Monitor automatic gauge control strategy with a Smith predictor for steel strip rolling

The simplified transfer function diagram block for a monitor automatic gauge control (Mon-AGC) system of strip steel rolling process was investigated. The new notion of strip sample length was given. In this way, the delay time varying with the rolling speed was evaded. After a Smith predictor was used to monitor the AGC system, the control laws were deduced for both proportional and integral regulators. The control strategies showed that by choosing the controller parameter P=∞ for both control algorithms each regulator could compensate the whole strip gage error in the first control step. The result shows that the integral algorithm is more controllable for the system regulating process and has a better steady-state precision than the proportional regulator. Compared with the traditional control strategy, the new control laws have a faster response speed and a higher steady-state precision.

Development of an automatic arc welding system using an adaptive sliding mode control

This paper develops an automatic welding control scheme for alternating current shielded metal arc welding (SMAW) system. A mathematical model of the welding control system is derived and the system parameters identified. An adaptive sliding mode controller is designed to estimate the bound of the system uncertainties and to modulate the electrode feed rate in such a way that the desired arc length and arc current are maintained as the electrode melts during the welding process. The proposed control method is suitable for any consumed electrode welding technique. The simulation and experimental results show that the automatic welding control system successfully maintains the magnitude of the arc current at the desired value and preserves the arc stability, thereby obtaining an enhanced SMAW control system performance.

F0 control in electrolarynx speech.

Over half of laryngectomy patients use an electrolarynx (EL) to communicate, but current EL devices produce a mechanical sound quality mainly due to the lack of natural F0 variation. In order to improve the sound quality of EL speech, the present study aimed to develop and evaluate an automatic F0 control scheme, where F0 in EL speech is covaried based on modulations in the rms amplitude of the EL speech signal. Declarative sentences ending with vowels produced by two male laryngectomy patients before and after the laryngectomy were used in order to develop procedures for controlling F0. The linear regression coefficients between F0 and rms amplitude in the normal speech were first determined and applied to the amplitude variation in EL speech to compute the F0 contour for the EL sentences. An analysis-by-synthesis approach was employed to modify the F0 contour of the EL speech as computed. Perceptual evaluation showed that the addition of amplitude-based F0 modulation resulted in EL speech that was judged to be more natural sounding than EL speech having constant F0, supporting the idea of using a simple linear relationship between amplitude and frequency to compute an F0 contour. [Work supported by NIH Grant No. R01DC006449.]

Development of novel control strategy for multiple circuit, roof top bus air conditioning system in hot humid countries

A novel control strategy to improve energy efficiency and to enhance passengers’ thermal comfort of a new roof top bus multiple circuit air conditioning (AC) system operating on partial load conditions is presented. A novel strategy for automatic control of the AC system was developed based on numerous experimental test runs at various operating conditions, taking into account energy saving and thermal comfort without sacrificing the proper cycling rate of the system compressor. For this task, more than 50 test runs were conducted at different set point temperatures of 21, 22 and 23 °C. Fanger’s method was used to evaluate passenger thermal comfort, and the system energy consumption was also calculated. A performance comparison between that of the conventional AC system and that of the newly developed one has been conducted. The comparison revealed that the adopted control strategy introduces significant improvements in terms of thermal comfort and energy saving on various partial load conditions. Potential energy saving of up to 31.6% could be achieved. This results in a short payback period of 17 months. It was found from the economic analysis that the new system is able to save approximately 20.0% of the life cycle cost.

WHAT TO DO WHEN THE DISINFECTION SYSTEM DOES NOT WORK: TROUBLESHOOTING CHLORINE DISINFECTION SYSTEMS

WHAT TO DO WHEN THE DISINFECTION SYSTEM DOES NOT WORK: TROUBLESHOOTING CHLORINE DISINFECTION SYSTEMSThe 180 MGD 91st Avenue Multi-Cities Wastewater Treatment Plant (WWTP), operated by the City of Phoenix, uses chloramination for disinfection. During the summer of 2007, the plant saw record low influent flows with increased reuse water demands. During the plant's diurnal low flow period, automatic control strategies became unstable which led to breakpoint chemistry problems. Unusual solids...Author(s)Jim CoughenourGary HunterDan BuhrmasterTom WalzSourceProceedings of the Water Environment FederationSubjectSession 104: Disinfection Compliance: Make It Work!Document typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2008ISSN1938-6478SICI1938-6478(20080101)2008:7L.7679;1-DOI10.2175/193864708788808852Volume / Issue2008 / 7Content sourceWEFTECFirst / last page(s)7679 - 7699Copyright2008Word count188

Hybrid automatic voltage control strategy and its application to Northeast China 500 kV power grid

AbstractThis paper introduces an integrated control strategy based on hybrid control theory for the control of voltage and reactive power in power system substations. The strategy adopts a hierarchical, multilayer structure to achieve a multi‐objective optimization of voltage and reactive power control and improves the traditional “nine‐area diagram” control method. The new hybrid control strategy not only solves the problem of oscillatory responses caused by the changes of the on‐load tap changer (OLTC) taps and switching the shunt capacitors, but also responds to the global optimal control commands of voltage and reactive power from the master station with good steady‐state responses. The hybrid automatic voltage control (HAVC) strategy is tested via simulation of the Northeast China 500 kV grid and the results demonstrate the effectiveness of the strategy. Copyright © 2007 John Wiley & Sons, Ltd.

Convective–dispersive gangue transport in flotation froth

The transport of gangue through flotation froth has been described by solving the convection–diffusion equation. Gangue recovery is predicted to be proportional to liquid recovery, which is consistent with experimental observation. In addition, it is seen that the dependency of gangue recovery upon particle size is due to processes within the pulp phase rather than the froth, insofar as the transport of particles in a given froth is approximately independent of size. The importance of maintenance of positive bias in column flotation, previously stressed by other workers, is reinforced. This model utilises a simplified representation of the froth and, as a consequence, it does not necessarily give accurate gangue recovery estimates for practical flotation processes. However, the convective–diffusive model does illuminate the physical processes behind gangue recovery in the concentrate which will aid the development of automatic control strategies.

Two-dimensional boundary element analysis of creep continuum damage problems with plastic effects

In this paper, a quadratic boundary element formulation for elasto-plastic creep damage problems in which strains and deformations are mainly creep dominant is presented. In order to cover both plastic and creep deformations, the initial strain formulation is employed. The Euler method with automatic time-step control scheme is implemented for time integrations. Creep rupture life is predicted using a continuum damage mechanics approach. The proposed formulation is applied to the uniaxial, perforated plate and rotating disk.

Persistence of improvements in postural strategies following motor control training in people with recurrent low back pain

This study investigated long-term effects of training on postural control using the model of deficits in activation of transversus abdominis (TrA) in people with recurrent low back pain (LBP). Nine volunteers with LBP attended four sessions for assessment and/or training (initial, two weeks, four weeks and six months). Training of repeated isolated voluntary TrA contractions were performed at the initial and two-week session with feedback from real-time ultrasound imaging. Home program involved training twice daily for four weeks. Electromyographic activity (EMG) of trunk and deltoid muscles was recorded with surface and fine-wire electrodes. Rapid arm movement and walking were performed at each session, and immediately after training on the first two sessions. Onset of trunk muscle activation relative to prime mover deltoid during arm movements, and the coefficient of variation (CV) of EMG during averaged gait cycle were calculated. Over four weeks of training, onset of TrA EMG was earlier during arm movements and CV of TrA EMG was reduced (consistent with more sustained EMG activity). Changes were retained at six months follow-up ( p < 0.05). These results show persistence of motor control changes following training and demonstrate that this training approach leads to motor learning of automatic postural control strategies.

Analog AGC Circuitry for a CMOS WLAN Receiver

The IEEE 802.11a standard uses orthogonal frequency division multiplexing (OFDM) to allow high data rates in multipath WLAN environments. The high peak-to-average power ratio (PAPR) of OFDM signals, along with stringent settling-time constraints, make conventional closed-loop automatic gain control (AGC) schemes impractical for WLAN receivers. In a direct conversion receiver, AGC and channel-select filtering are performed by analog baseband circuitry. A baseband signal processor using a new open-loop analog gain-control algorithm for OFDM is described. The new AGC algorithm uses switched coarse gain-setting steps followed by an analog open-loop fine gain-setting step to set the final gain of variable gain amplifiers (VGAs). The AGC was implemented in a 0.18-mum CMOS process using newly designed circuits including linear VGAs, RMS detectors, and current-mode computation circuitry. Simulation and measurement results verify that the new AGC circuit converges with gain error less than 1dB to the desired level within 5.6 mus

Process-Based Quality for Thermal Spray Via Feedback Control

Quality control of a thermal spray system manufacturing process is difficult due to the many input variables that need to be controlled. Great care must be taken to ensure that the process remains constant to obtain a consistent quality of the parts. Control is greatly complicated by the fact that measurement of particle velocities and temperatures is a noisy stochastic process. This article illustrates the application of quality control concepts to a wire flame spray process. A central feature of the real-time control system is an automatic feedback control scheme that provides fine adjustments to ensure that uncontrolled variations are accommodated. It is shown how the control vectors can be constructed from simple process maps to independently control particle velocity and temperature. This control scheme is shown to perform well in a real production environment. We also demonstrate that slight variations in the feed wire curvature can greatly influence the process. Finally, the geometry of the spray system and sensor must remain constant for the best reproducibility.

Evaluation of variable speed limits to improve traffic safety

This paper examines automated control strategies of variable speed limits that aim at reducing crash potential on instrumented freeways. A real-time crash prediction model was developed to estimate crash potential based on short-term variation of traffic flow characteristics. A microscopic traffic simulation model was used to realistically simulate changes in traffic conditions as an effect of variable speed limits and combined with the crash prediction model for the evaluation of control logics. Within this integrated evaluation framework, the study investigated the effect of strategy control factors on the crash potential reduction and total travel time. The study results indicated that variable speed limits could reduce crash potential by 5–17%, by temporarily reducing speed limits during risky traffic conditions when crash potential exceeded the pre-specified threshold.

Multivariate Image Analysis of Flames for Product Quality and Combustion Control in Rotary Kilns

Rotary kilns are widely used in industry to achieve effective gas−solid heat transfer at high temperatures by direct contact with hot flue gases obtained by combustion. However, various disturbances related to nonpremixed combustion often used in practice introduces undesired variability in product quality and forces overheating, especially when obtaining the desired quality is dependent upon reaching a minimal solids discharge temperature. This paper investigates the use of digital RGB flame images and multivariate image analysis (MIA) techniques to quantify these combustion-related variations and to predict the future behavior of product quality. Very good solids discharge temperature forecasts were obtained over a time window running from current time t to about the mean residence time within the kiln using only a single flame image collected at time t. This information will be used to develop innovative automatic flame image-based control schemes to improve quality control and reduce fuel consumption.

An Automatic Bi-Directional Bus Repeater Control Scheme Using Dynamic Collaborative Driving Techniques

This paper describes a newly developed automatic direction control scheme for bi-directional bus repeaters that uses dynamic collaborative driving techniques. Repeater directions are rapidly determined by detecting the direction of control signal propagation through an additional control signal line that is driven by dynamic collaborative drivers. Application to an on-chip peripheral bus reduces control circuit transistor counts by about 75% and the number of control signal lines by about 50% without loss of speed. Experimental results for a 0.18-μm CMOS implementation indicate that the proposed scheme is four times faster than a conventional scheme with no bi-directional bus reneaters.

A Regulated Charge Pump With Small Ripple Voltage and Fast Start-Up

A regulated charge pump circuit is realized in a 3.3-V 0.13-/spl mu/m CMOS technology. The charge pump exploits an automatic pumping control scheme to provide small ripple output voltage and fast start-up by decoupling output ripple and start-up time. The automatic pumping control scheme is composed of two schemes, an automatic pumping current control scheme and an automatic pumping frequency control scheme. The former automatically adjusts the size of pumping driver to reduce ripple voltage according to output voltage. The latter changes the pumping period by controlling a voltage-controlled oscillator (VCO). The output frequency of the VCO varies from 400 kHz to 600 kHz by controlling the input bias voltage of the VCO. The prototype chip delivers regulated 4.5-V output voltage from a supply voltage of 3.3 V with a flying capacitor of 330 nF, while providing 30 mA of load current. The area is 0.25 mm/sup 2/ and the measured output ripple voltage is less than 33.8 mV with a 2-/spl mu/F load capacitor. The power efficiency is greater than 70% at the range of load current from 1 to 30 mA. An analytical model for ripple voltage and recovery time is proposed demonstrating a reasonable agreement with SPICE simulation results.

A Decentralized Automatic Generation Control Scheme for Competitive Electricity Markets

This paper presents the design of a decentralized automatic generation control (AGC) scheme for interconnected multiarea power system. The proposed controller incorporates various types of transactions taking place in a competitive electricity market. The controller has been designed by appropriately assigning the eigenstructure of each isolated subsystem via state feedback, satisfying the sufficient conditions for stability. The functioning of the proposed decentralized controller has been demonstrated on a 39-bus New England system and a 75-bus Indian power system, and the results have been compared with those obtained by using a centralized control scheme. Compliance with the North American Electric Reliability Council standards for AGC has also been established.