Nondisturbing extremum seeking control for multi-agent industrial systems

Industrial applications of extremum seeking control (ESC) can be a hit and miss affair. Although a gain in performance can be achieved, the dither applied to excite the system causes unwanted fluctuations in the performance of the system. The fluctuations in systems with a single extremum seeking loop are generally small. However, for systems with many extremum seeking loops, the fluctuations in each loop may add up to an intolerable amount of fluctuation in the total performance. In this article, we propose a method to cancel the dither-induced fluctuations in the overall system performance to a large extent by smartly constructing the dither signals in each extremum seeking loop using a centralized coordinator. The novelty of our method lies in the direct calculation of the dither signals that avoids the heavy computations required by other methods. Moreover, we provide a solvability analysis for the problem of cancelling dither-induced fluctuations in the total performance of the system. Furthermore, a complete stability analysis of the overall ESC scheme with dither coordination is given.publishedVersio

Gas Injection Optimization to Increase Oil Production at MRA PT. PHE ONWJ

The MRA platform is one of the offshore platforms located in the north of the Java Sea. The MRA platform has 4 production wells, namely MRA-2ST, MRA-4ST, MRA-5, and MRA-6 wells. The 4 production wells are produced using an artificial lift in the form of a gas lift. The limited gas lift at the MRA Platform at 3.1 MMSCFD makes the production of wells at the MRA Platform not optimal because the wells in the MRA Platform are experiencing insufficient gas lift. Optimization of gas lift injection is obtained by redistribution of gas lift injection for each. The results of the analysis in this study indicate that the optimum gas lift injection for the MRA-2ST well is 0.5552 MMSCFD, the MRA-6 well is 1.0445 MMSCFD, the MRA-5 well is 0.7657 MMSCFD, finally the MRA-4ST well with gas injection. lift is 0.7346 MMSCFD. The manual gas lift in the MRA-4ST is also replaced based on an economic feasibility analysis to ensure that the gas lift injection for each well can be kept constant. The redistribution of gas lift carried out by the author has increased the total production rate of the MRA Platform by 11,160 BO/year or approximately USD 781,200/year. Keywords: Gas lift; Insufficient; Optimizatio

Comparação de técnicas baseadas em modelo para otimização da produção de petróleo em sistemas multipoço

A garantia de produção de petróleo estável e em elevados patamares é o norte da indústria petrolífera. Para isso, a otimização de variáveis do processo é recorrente e a abordagem mais difundida é a alocação de gas lift, o qual é injetado para tornar os fluidos mais leves e facilitar a extração de petróleo. O típico problema de alocação de gas lift é o ponto de partida deste trabalho, dada a falta de comparativos na literatura, onde geralmente os autores abordam uma única variável de decisão – a taxa de gas lift. Metodologias para a otimização da produção de petróleo de um sistema multipoço típico de plataformas offshore aqui são confrontadas por meio de cenários de otimização que vão do caso mais difundido, que é a otimização somente da taxa de gas lift, até a otimização dinâmica. Cenários em malha aberta e em malha fechada, com PIDs lineares e não-lineares, são propostos, incluindo a abertura da válvula choke de produção como variável de decisão. Os limites operacionais da planta e as restrições causados pelo fluxo intermitente, conhecido por golfadas, são levados em conta na formulação dos problemas de otimização. A dinâmica dos poços é representada por balanços de massa fornecidos pelo FOWM (Fast Offshore Wells Model) em que foram inseridas equações de perda de carga em duas seções da tubulação – riser e tubing – para que a otimização baseada em modelo (MBO) possa ser realizada e curvas GLPC são geradas, contribuindo com o modelo ‘FOWM modificado’. Comparando as metodologias com o típico caso de otimização de gas lift, a otimização da abertura de choke em malha aberta já gera um aumento de 18% de produção, e 19% de aumento quando choke e gás são otimizados simultaneamente. Já a otimização em malha fechada, variando do ajuste mais simples de controladores até o ajuste de um PID gain scheduling, gera aumentos de produção na faixa de 26%. O maior ganho em produção é obtido com o uso do controlador não-linear, o qual compensa a perda de ganhos do processo quando altas aberturas de válvula são atingidas.Reaching stable and high production levels is a goal in oil production. In order to do so, optimizing process variables is straightforward and the most known approach is gas lift allocation, which is injected for lightening the weight column and make oil extraction easier. The typical gas lift optimization problem is the starting point for this work, given the lack of comparatives in the literature, where authors usually study only gas lift as decision variable for optimization. Methodologies for oil production optimization of a typical multiwell offshore gathering network are confronted through optimization scenarios starting from the widespread case – sole gas lift optimization – to dynamic optimization. Open-loop and closed-loop optimization scenarios, with linear and nonlinear PID control, are proposed, including choke valve opening as decision variable. Plant operational limitations and operational constraints are included in the optimization problems. The well dynamic is simulated through FOWM (Fast Offshore Wells Model) where pressure drop terms are included in the riser and tubing sections, so as to perform model-based optimization (MBO), and GLPC (Gas lift performance curves) are generated, a contribution to ‘Modified FOWM’. Comparing the proposed methodologies to the base case – sole gas lift optimization – a 18% oil production increase is verified in the choke opening optimization, whereas optimizing both gas lift and choke opening simultaneously results in 19% oil production increase. Closed-loop optimization, tuned from a simplest method to a nonlinear one (a gain scheduling PID) provided around 26% oil production increase. The greatest production increase is verified with the nonlinear PID, which compensates process gain loss when large choke valve openings are applied

A broadband bistable piezoelectric cantilever-based vibration energy harvester with nonlinear high power extraction

This work presents a nonlinear vibration energy harvester, which combines a nonlinear bistable broadband piezoelectric cantilever used to transduce ambient vibration energy, with synchronized capture for efficient harvesting over broadband sources. An accurate model of the bistable transducer, that augments the Butterworth van Dyke piezoelectric model to capture the external magnetic force added as a bias to the external vibrations, is presented. Its validity has been demonstrated through physical implementation and experimental validation against simulation of the mathematical model. For efficient extraction of the transduced energy, nonlinear extraction circuits, namely synchronous charge extraction (SCE) and parallel synchronized switch harvesting on inductor (SSHI), are employed. The switching in these circuits is implemented using a fully self-propelled, low-power electronic breaker circuit, capable of detecting extrema in the waveform to perform switching. Both simulated and experimental power outputs from the bistable harvester have been presented, with the SCE and parallel-SSHI providing average outputs with more than one-hundred (100) fold increase over the harvested power reported in literature for the same input, and further, even more significant gains are observed for broadband excitations. For the above mentioned harvester, bistability is introduced through the use of two repelling magnets, one mounted on the cantilever tip and the other at a fixed location opposite it. Excitations that can overcome the repulsive magnetic force cause the cantilever to snap between its two equilibrium states, increasing amplitude and velocity of vibration, resulting in higher power outputs. This improved performance is observed whenever the cantilever operates in the bistable mode. Lower-amplitude excitations are unable to overcome the repulsive force, causing the cantilever to vibrate around one of its equilibrium states, and with smaller amplitudes in the presence of the opposing repulsion. To circumvent this issue, the second part of the work presents a completely mechanical way of increasing the range of excitation amplitudes over which the system remains bistable, by spring-loading the previously fixed-positioned magnet, and restricting its motion in the horizontal direction, towards and away from the cantilever. Then, whenever the cantilever moves towards the spring-loaded magnet, the latter is pushed away due to the repulsive force, increasing the distance between the magnets, thereby reducing the repulsive force required to be overcome for bistable operation. The opposite occurs when the cantilever moves away. Thus, the role of spring-loading is to introduce a type of negative feedback, through the self-adjustment of the distance between the magnets, favoring bistable operation over a larger range of excitations, and this is accomplished without an added energy cost. A 90% gain in power output levels over the fixed magnet system was observed

Active control of spray combustion

Effect of a forced dilution air jet on air-fuel spray mixing and emissions has been investigated. Temperature measurements have been made at a number of forcing frequencies in the range of 100-1100 Hz and blowing ratios between 6-15. Open-loop flame response to forcing has also been acquired by recording pressure and heat release spectra. The results show that the mean temperature field inside the flame can be altered due to jet modulation. Significant effects are observed by forcing at locations close to the dump plane. Enhancements in temperature of the order of 100–200 ˚C, and reduction in pattern factor of the order of 40% were observed. Substantial reductions in nitric oxide emissions can be obtained over a range of flow conditions. More rigorous burning can be obtained due to enhanced fuel air mixing. A multi-resolution technique is utilized to analyze temperature fields to decompose the response of different hierarchical scales to forcing. Forcing is found to have most impact on large-scale structures that are in the order of characteristic jet length scale. Bulk mixing is not the only factor that determines pollutant emissions level. Consequently, there exist select frequencies, which affect both emissions and mixing positively. An artificial intelligence based extremum-seeking algorithm is introduced to optimize the combustor behavior. The second part of this dissertation deals with syngas combustion. Stability of a pre-mixed gas turbine combustor is quite sensitive to fuel composition. Behavior of a premixed confined hydrogen enriched methane flame is studied with regard to thermo-acoustic instability induced flashback, emissions, flammability limits and acoustics over a range of conditions. Hydrogen addition extends the flammability limits and enables lower emissions levels to be achieved. Contrarily, increased RMS pressure fluctuation levels, and higher susceptibility to flashback is observed with increasing hydrogen volume fraction inside the fuel mixture. In addition, a semi-analytical model has been utilized to capture the flame holding and flashback dynamics utilizing G-equation. A limit cycle behavior in the flame front movement is observed due to a non-linearity in the feedback term. Experiments including phase locked radical imaging and PLIF measurements have been performed at varying fuel composition

Modeling and Control of Hydraulic Linear and Free-Piston Engines.

The EPA has developed a free-piston engine (FPE) and a hydraulic linear engine (HLE) for application as hydraulic power plants in a hydraulic hybrid vehicle. Both engines extract power from the piston motion using a linear hydraulic pump. This dissertation's objective is to compare HLE and FPE performance trends through modeling while developing the control tools necessary to enable reliable engine operation. A physics-based engine model combines dynamics, thermodynamics, and hydraulics correlations to evaluate performance trends and assist with control development. Preliminary simulations show that asymmetric piston behavior causes variations in cylinder-to-cylinder HLE efficiency that necessitate cylinder balancing. An adaptive control scheme estimates and adjusts for HLE cylinder performance discrepancies. A control-oriented model captures HLE behavior using an estimate of rotational kinetic energy sampled at the turnaround points. State feedback control ensures that the HLE tracks a set point and a recursive least squares algorithm estimates periodic differences in HLE response. An extremum seeking algorithm exploits the adaptive scheme to optimize injection timing of each cylinder individually. Precise control of piston turnaround location is paramount to reliable FPE operation. Combining an energy balance and the Otto cycle, a control-oriented model implicitly describes FPE clearance height evolution. A linearization of the control-oriented model suggests open-loop unstable operating conditions at high load. State feedback using dynamic inversion stabilizes the FPE system. In order to constrain piston motion, a reference governor manages load changes. When implemented on the physics-based model with the feedback control law, the reference governor successfully enforces a position constraint of 0.5 mm. Using the proposed control and modeling methods, a series of physics-based simulations explore HLE, FPE, and conventional engine performance. The primary difference in engine behavior is friction. While the FPE exhibits low frictional losses and the highest relative hydraulic conversion efficiency, it also suffers from a restricted power range compared to the HLE and the conventional engine due to engine speed limitations. The HLE has lower friction than the conventional engine at most operating conditions. However, inertial forces resulting from a large piston assembly mass increase HLE bearing loads and friction at high speeds.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/102345/1/kzaseck_1.pd

Screening of reservoir types for decision-making on the application of intelligent wells

Abstract unavailable please refer to PD