Conventional Closed-loop System Research Articles

Chaos synchronization and communication in closed-loop semiconductor lasers subject to common chaotic phase-modulated feedback.

We propose and demonstrate a closed-loop chaos system composed of external-cavity semiconductor lasers subject to common chaotic phase-modulated optical feedback (CCPMOF). The efficient-bandwidth and time-delay signature (TDS) characteristics of the chaotic carrier, the properties of chaos synchronization, as well as the performance and security of chaos communication are systematically investigated. The numerical results demonstrate that wideband chaotic carrier with effective TDS suppression can be easily obtained, high-quality chaos synchronization with considerable mismatch robustness, frequency detuning tolerance, and phase fluctuation tolerance can be achieved in a wide operation range, and high-speed chaos communication is available. With respect to the conventional closed-loop systems, the bandwidth and complexity of chaotic carrier is greatly enhanced, and the performances of chaos synchronization and communication are obviously improved.

Analysis of Shallow Subsurface Geological Structures and Ground Effective Thermal Conductivity for the Evaluation of Ground-Source Heat Pump System Installation in the Aizu Basin, Northeast Japan

Shallow subsurface geological structure mapping combined with ground effective thermal conductivity values at the basin scale provide an appropriate method to evaluate the installation potential of ground-source heat pump systems. This study analyzed the geological structure of the Aizu Basin (Northeast Japan) using sedimentary cores and boring log and mapped the distribution of average ground effective thermal conductivity in the range from −10 m to −100 m depth calculated from cores and logs. Gravel layers dominate in alluvial fans of the northern and southern basin areas, which are found to be associated with higher average ground effective thermal conductivity values, 1.3–1.4 W/m/K, while central and western floodplain areas show lower values of 1.0–1.3 W/m/K due to the existence of thick mud layers in the shallow subsurface. The results indicate that the conventional closed-loop systems are more feasible in northern and southern basin areas than in the central and western areas. Evaluation for the installation potential of the ground-source heat pump systems using depth-based distribution maps of average ground effective thermal conductivity is the originality of this study. This approach is valuable and proper for the simple assessment of the system installation in different sedimentary plains and basins in Japan and other countries.

Reliable Output Feedback Control for Piecewise Affine Systems With Markov-Type Sensor Failure

This brief addresses the problem of robust and reliable ${\mathscr {H}_{\infty }}$ static output feedback (SOF) control for uncertain discrete-time piecewise-affine (PWA) systems with sensor failure in a descriptor system framework. The Markov chain is employed to describe the sensor failure behaviors. In particular, by utilizing a system augmentation approach, the conventional closed-loop system is initially converted into a descriptor PWA model. On the basis of a mode-dependent piecewise Lyapunov function, combined with S-procedure, a novel ${\mathscr {H}_{\infty }}$ performance analysis criterion is then presented. Furthermore, by some elegant linearization techniques, the PWA SOF controller design is proposed in terms of the feasibility of a convex optimization problem. Lastly, a numerical example illustrates the effectiveness and less conservatism of the proposed approach.

Assessment of the Installation Potential of a Ground Source Heat Pump System Based on the Groundwater Condition in the Aizu Basin, Japan

Assessment of suitable locations for a ground source heat pump (GSHP) system based on the groundwater condition of study area is important for its sustainable development. Installation potential of a GSHP system was evaluated for the Aizu Basin, Japan. Firstly, suitability assessment was done for a conventional closed-loop system by preparing a distribution map of heat exchange rates for space heating. Heat exchange rates were higher at the northern and southern areas and lower at the central area, indicating that the northern and southern areas are appropriate for the conventional system. A different type of GSHP system using an artesian well was proposed at the central area because groundwater is flowing in an upward direction and using its heat energy can increase heat exchange rates. Demonstration of this system using an artesian well for space heating resulted in higher heat exchange rates compared to the conventional system. A GSHP system using an artesian well is suitable at the central area, and the conventional one is suitable at the northern and southern areas. Assessment of the installation potential of different types of GSHP system in the same Aizu Basin based on its groundwater condition is unique to this study. It can assist in selecting suitable locations for GSHP system installation and to promote its growth in Japan.

Reliable Control of Discrete-Time Piecewise-Affine Time-Delay Systems via Output Feedback

This paper addresses the problem of delay-dependent robust and reliable $\mathscr {H}_{\infty }$ static output feedback (SOF) control for uncertain discrete-time piecewise-affine (PWA) systems with time-delay and actuator failure in a singular system setup. The Markov chain is applied to describe the actuator faults behaviors. In particular, by utilizing a system augmentation approach, the conventional closed-loop system is converted into a singular PWA system. By constructing a mode-dependent piecewise Lyapunov–Krasovskii functional, a new $\mathscr {H}_{\infty }$ performance analysis criterion is then presented, where a novel summation inequality and S-procedure are succeedingly employed. Subsequently, thanks to the special structure of the singular system formulation, the PWA SOF controller design is proposed via a convex program. Illustrative examples are finally given to show the efficacy and less conservatism of the presented approach.

A Piecewise-Markovian Lyapunov Approach to Reliable Output Feedback Control for Fuzzy-Affine Systems With Time-Delays and Actuator Faults

This paper addresses the problem of delay-dependent robust and reliable $\mathscr {H}_{\infty }$ static output feedback (SOF) control for a class of uncertain discrete-time Takagi-Sugeno fuzzy-affine (FA) systems with time-varying delay and actuator faults in a singular system framework. The Markov chain is employed to describe the actuator faults behaviors. In particular, by utilizing a system augmentation approach, the conventional closed-loop system is converted into a singular FA system. By constructing a piecewise-Markovian Lyapunov-Krasovskii functional, a new $\mathscr {H}_{\infty }$ performance analysis criterion is then presented, where a novel summation inequality and S-procedure are succeedingly employed. Subsequently, thanks to the special structure of the singular system formulation, the piecewise-affine SOF controller design is proposed via a convex program. Lastly, illustrative examples are given to show the efficacy and less conservatism of the presented approach.

Standing column wells—Modeling the potential for applications in geothermal heating and cooling

Standing column wells (SCWs) have the potential to deliver much higher rates of heat transfer to geothermal heating and cooling systems in buildings via heat pumps than can conventional vertical borehole heat exchange arrays. The development of a numerical model for clusters of standing column wells is described in this article. The model is three-dimensional, dynamic, and solves the governing equations using a finite-volume discretization scheme with a fully implicit algorithm. The slower-acting field equations are solved using a wider time interval than that used for the faster-acting well equations, and the two sets of equations are coupled through the field equation source terms. A groundwater bleed feature is incorporated. The model has been verified thermally and hydraulically using existing field data. Two test cases have been applied to reveal the advantages of using SCWs in U.K. conditions, competing with the conventional closed-loop system of vertical borehole heat exchangers. Results of the applications suggest that SCWs can deliver substantially higher rates of heat transfer than conventional closed loop borehole heat exchanger arrays, especially when groundwater bleed is operational. With appropriate earth conditions in the United Kingdom, SCWs can deliver space heating and direct cooling, for example, chilled beam or chilled ceiling, successfully to offer a substantial saving on carbon emissions. Another important practical consequence of this is that far less geotechnical drilling is needed when using standing column wells than is the case with closed-loop arrays.

ACTIVE VIBRATION CONTROL OF SEISMICALLY EXCITED STRUCTURES BY ATMDS: STABILITY AND PERFORMANCE ROBUSTNESS PERSPECTIVE

This paper demonstrates the trade-off between nominal performance and robustness in intelligent and conventional structural vibration control schemes; and, proposes a systematic treatment of stability robustness and performance robustness against uncertainty due to structural damage. The adopted control strategies include an intelligent genetic fuzzy logic controller (GFLC) and reduced-order observer-based (ROOB) controllers based on pole-placement and linear quadratic regulator (LQR) conventional schemes. These control strategies are applied to a seismically excited truss bridge structure through an active tuned mass damper (ATMD). Response of the bridge-ATMD control system to earthquake excitation records under nominal and uncertain conditions is analyzed via simulation tests. Based on these results, advantages of exploiting heuristic intelligence in seismic vibration control, as well as some complexities arising in realistic conventional control are highlighted. It has been shown that the coupled effect of spill-over (due to reduction and observation) and mismatch between the mathematical model and the actual plant (due to uncertainty and modeling errors) can destabilize the conventional closed-loop system even if each is alone tolerated. Accordingly, the GFLC proves itself to be the dominant design in terms of the compromise between performance and robustness.

Large-scale rotating bending fatigue tests for offshore pipe connections

A testing apparatus featuring rotating bending fatigue techniques was designed and constructed to investigate the fatigue behavior of full-sized threaded connections used to couple offshore piping and structures. Rotating bending tests were performed where flexural loads are applied to the pipe with a hydraulic loading system while simultaneously rotating the pipe by belt drive attached to an electric motor. While rotating bending fatigue testing is not a new concept, the relatively large scale of the tests presented special problems that make the apparatus distinctive. This rotating bending apparatus allows more rapid testing than conventional closed-loop systems. Additionally, conventional closed-loop axial fatigue tests would have required a testing frame with fatigue load capacity exceeding 4455 kN (1,000,000 lbs). Several specially manufactured devices are featured that require large service loads combined with exacting machine tolerances. Currently, a fatigue frequency of 2.0 Hz has been achieved with an equivalent deformation range of 25.4 mm (1.0 in.). Faster speeds are believed possible.

Impact of Dewatering Technology on the Cost of Drilling-Waste Disposal

Summary The use of mobile, chemically enhanced centrifugation dewatering systems toprocess liquid waste from two deep exploratory wells in Kern County, CA, saved $136,900 in waste-disposal costs. Liquid waste in the wells was reduced by 45%. This paper tracks daily costs and chemical usage for each well to isolate keycost factors. Introduction The use of different types of dewatering technology to process effluent fromvarious industries has been well documented. others have reported on the use ofa centralized facility to process drilling waste transported from a number ofdrilling sites to the facility, hut the application of the technology at anactive drilling location has been limited by the complexity of dewatering. Theuse of the technology as an on-line addition to the rig's solids controlequipment has been suggested, but the results of such on-line processing havenot been extensively reported in the literature. This paper reviews the use ofone such dewatering paper reviews the use of one such dewatering technique, chemically enhanced centrifugation, at two active drilling locations. Chemically enhanced centrifugation uses chemical coagulants and flocculants toachieve fine-particle flocculation. The flocculated solids are then separatedfrom the waste stream with a high-speed centrifuge. This solids-separationtechnique differs from conventional "closed-loop" mud systems in oneimportant way: conventional closedloop systems rely on additionalsolidsprocessing equipment, such as "microclones" (small-diameterhydrocyclones), and traditional centrifuges to separate water and solids fromthe waste stream. Processing in this manner generally fails because theadditional solids-processing equipment cannot remove extremely fine particlesfrom the waste stream. When the particles from the waste stream. When therecovered water is returned to the mud system, fine solids are ala returned tothe mud. Continued reuse of the recovered water eventually results in afine-particle accumulation in the mud system that can be corrected only throughmassive dilution. Thus, the objective of waste-volume reduction is defeated or, at least, severely compromised. Chemically enhanced centrifugation, however, removes fine solids by treatment with chemical coagulants and flocculants. In July 1988, Arco Oil and Gas Co.'s Western Dist. began field testing of twodewatering units that used chemically enhanced centrifugation to process liquiddrilling waste. Both units were mobile in the sense that the component partscould be loaded onto two trailer trucks and transported to the drillinglocation for assembly. Both units were comparable in design and operation andwere furnished by the same service company. Before the units were selected, alist of checkpoints that were considered key to the successful operation ofsuch a unit was prepared (see Table 1). Available units were prepared (see Table 1). Available units were compared on the basis of a physical examinationfollowing this list. The unit with the best score was selected for the tests. Operational considerations limited the size of the reserve pit at bothfield-trial locations. The dewatering units were used to create aminimum-discharge (closed-loop) solids-control system. Because the cost ofliquid-waste disposal was $10.85/bbl, the plan was to send all the effluents tothe dewatering unit for processing. The recovered water would be returned asneeded to the mud system, and the solids separated by the centrifuge would bedischarged to the reserve pit. Because this recovered water was to be pit. Because this recovered water was to be reused in the mud system, asuspended-solids content of less than 500 mg/L and a residual-polymer contentof less than 0.1 lbm/bbl in the recovered water were dewatering goals. Thepurpose of these field trials was to assess the ability of the dewatering unitto achieve water-clarity goals for less than $10.85/bbl. This assessment wouldprovide one means of evaluating the economic viability of thisminimum-discharge solids-control system. Well Background Data The Mettler No. 1 was drilled in the Tejon (North) field, Kern County, CA. The dewatering test began July 26 and was completed Oct. 24. The dewateringunit was on location 96 days. Fig. 1 is a schematic of the well's hole size andcasing programs. The Arco-Texaco No. 801 was drilled in the Midway Sunsetfield, Kern County. The dewatering test began Aug. 18 and was completed Dec.20. Difficulty in setting cement plugs for directional control caused the timeplugs for directional control caused the time on location to be significantlylonger than planned (125 days). Fig. 2 is a schematic planned (125 days). Fig.2 is a schematic of the well's hole size and casing programs. JPT P. 730