Dissertations / Theses on the topic 'Hydraulic control Mathematical models'
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Casoli, Paolo, Luca Riccò, Federico Campanini, Antonio Lettini, and Cesare Dolcin. "Hydraulic Hybrid Excavator: Layout Definition, Experimental Activity, Mathematical Model Validation and Fuel Consumption Evaluation." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200473.
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Energy saving and fuel consumption reduction techniques are among the principal interests for both academic institutions and industries, in particular, system optimization and hybridization. This paper presents a new hydraulic hybrid system layout for mobile machinery implemented on a middle size excavator. The hybridization procedure took advantage of a dynamic programming (DP) algorithm, which was also utilized for the hybrid components dimensioning and control strategy definition. A dedicated experimental activity on test bench was performed on the main components of the energy recovery system (ERS). The JCMAS working cycle was considered as the reference test for a fuel consumption comparison between the standard and the hybrid excavator. A fuel saving up to 8% on the JCMAS cycle, and up to 11% during the digging cycle, has been allowed by the proposed hybrid system.
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Liang, Pei-Ji. "Mathematical models of respiratory control in humans." Thesis, University of Oxford, 1996. http://ora.ox.ac.uk/objects/uuid:567195f2-f911-4188-a1c3-96192fd7b3ee.
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This thesis is concerned with modelling the properties of human ventilation during steady-state conditions and during acute and sustained isocapnic hypoxia. Chapter 1 reviews some of the relevant studies in animals and humans. Chapter 2 describes the origins of the data studied in this thesis. In particular, it describes the experimental apparatus and the technique of dynamic end-tidal forcing used to gather the data, as well as the particular protocols employed. Chapter 3 studies the breath-to-breath variations in ventilation during steady breathing in both rest and during light exercise with the end-tidal gases controlled. The results suggest that: 1) both simple ARMA models and a simple state-space model can describe the autocorrelation present in the data; 2) variations in spectral power were present in the data which cannot be described by these models; and 3) these variations were often due to a uniform modulation and did not significantly affect the coefficients of the models. For these kinds of data, a heteroscedastic form of state-space model provides an attractive theoretical structure for the noise processes. Chapter 4 studies human ventilation during sustained isocapnic hypoxia. Two models are used. The first, developed by Painter et al. (J. Appl. Physiol. 74:2007-2015, 1993) describes hypoxic ventilatory decline (HVD) as a decline in peripheral chemoreflex sensitivity. The second is an extended model which incorporates a component of HVD that is independent of peripheral chemoreflex sensitivity. The models incorporate a parallel noise structure. It is concluded that, in some subjects but not others, there is a component of HVD which is independent of peripheral chemoreflex sensitivity. Chapter 5 studies the human ventilatory response to cyclic isocapnic hypoxia. Both a simple proportional dynamic model suggested by Clement and Robbins (Respir. Physiol. 92:253-175, 1993), and an extended model with an additional non-linear rate-sensitive component are studied. The models incorporate a parallel noise structure. The results show that, although the extended model improves the fit to the data for some subjects, both models failed to explain the data fully, especially the occasional large breaths, which were shown to occur more frequently in some parts of the hypoxic cycle than other parts.
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Rotzoll, Kolja. "Hydraulic Parameter Estimation Using Aquifer Tests, Specific Capacity, Ocean Tides, and Wave Setup for Hawai'i Aquifers." Thesis, Water Resources Research Center, University of Hawaii at Manoa, 2007. http://hdl.handle.net/10125/22265.
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The islands of Hawaii face increasing ground-water demands due to population growth in the last decades. Analytical and numerical models are essential tools for managing sustainable ground-water resources. The models require estimates of hydraulic properties, such as hydraulic conductivity and storage parameters. Four methods were evaluated to estimate hydraulic properties for basalts on the island of Maui. First, unconventional step-drawdown tests were evaluated. The results compare favorably with those from classical aquifer tests with a correlation of 0.81. Hydraulic conductivity is log-normally distributed and ranges from 1 to 2,500 m/d with a geometric mean of 276 m/d and a median of 370 m/d. The second approach developed a simplified parameter-estimation scheme through an empirical relationship between specific capacity and hydraulic parameters that utilized Hawaii's state well database. For Maui's basalts, the analysis yields a geometric-mean and median hydraulic conductivity of 423 and 493 m/d, respectively. Results from aquifer tests and specific-capacity relationships were used to generate island-wide hydraulic-conductivity maps using kriging. The maps are expected to be of great benefit in absence of site-specific field assessments. In the third approach, ocean-tide responses in the central Maui aquifer were used to estimate an effective hydraulic diffusivity of 2.3 x 10^7 m^2/d. The position of the study area necessitated refining the existing analytical solution that considers asynchronous and asymmetric tidal influence from two sides in an aquifer. Finally, measured ground-water responses to wave setup were used to estimate hydraulic parameters. Setup responses were significant as far as 5 km inland and dominated barometric-pressure effects during times of energetic swell events. The effective diffusivity estimated from setup was 2.3 x 10^7 m^2/d, matching that based on tides. Additionally, simple numerical ground-water flow models were developed to assess the accuracy of results from analytical solutions for step-drawdown tests, dual-tides and wave setup, and to evaluate sediment-damping effects on tidal propagation. The estimated mean hydraulic conductivities of the four methods range between 300 and 500 m/d for basalts in Maui. The results of different methods are consistent among each other and match previous estimates for basalts.USGS Pacific Island Water Science Center
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Ritzi, Robert William. "The use of well response to natural forces in the estimation of hydraulic parameters." Diss., The University of Arizona, 1989. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1989_119_sip1_w.pdf&type=application/pdf.
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Qiu, Jin 1962. "Production control and capacity configuration." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28646.
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Production control and capacity configuration policies are critical to a manufacturing firm for effective inventory control. In the first part of this dissertation, a Dynamic Programming model and a solution algorithm are developed to obtain an optimal (near-optimal) production control policy. The solution algorithm is able to produce an extremely good policy under mild conditions, but is applicable only to problems with a limited number of products. For problems involving a large number of products, a heuristic algorithm based on a decomposition/aggregation scheme is then proposed. This algorithm overcomes the computational difficulty typically associated with Dynamic Programming problems with a large number of state dimensions. Computational test results are reported to show the performance of the policy generated by the heuristic algorithm. In the second part of the dissertation, the production lead time and operational cost performance of two capacity configurations are analyzed. Models are developed for each configuration to determine the amount of capacity which minimizes the total capacity acquisition and operational costs, including the inventory cost. Computational test results are presented to study the impact of problem characteristics on the superiority of each configuration.
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Jiao, Yue, and 焦月. "Mathematical models for control of probabilistic Boolean networks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41508634.
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Tan, David Kim Hong. "Mathematical models of rate control for communication networks." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624531.
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Jiao, Yue. "Mathematical models for control of probabilistic Boolean networks." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B41508634.
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Yakob, Laith. "Mathematical modelling of novel pest control strategies." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670034.
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Warren, Paul A. "Mathematical models of 3-D ocular mechanics and control." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312221.
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Kröckel, Silke. "Stochastic production-inventory systems with significant setup times." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/24367.
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Roberts, Gwendolyn Rose 1963. "A comparison of multiple univariate and multivariate geometric moving average control charts." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276779.
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This study utilizes a Monte Carlo simulation to examine the performance of multivariate geometric moving average control chart schemes for controlling the mean of a multivariate normal process. The study compares the performance of the proposed method with a multivariate Shewhart chart, a multiple univariate cumulative sum (CUSUM) control chart, a multivariate CUSUM control chart and a multiple univariate geometric moving average control chart.
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Young, Andrew J. "Active control of vibration in stiffened structures." Title page, contents and abstract only, 1995. http://hdl.handle.net/2440/37722.
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Active control of vibration in structures has been investigated by an increasing number of researchers in recent years. There has been a great deal of theoretical work and some experiment examining the use of point forces for vibration control, and more recently, the use of thin piezoelectric crystals laminated to the surfaces of structures. However, control by point forces is impractical, requiring large reaction masses, and the forces generated by laminated piezoelectric crystals are not sufficient to control vibration in large and heavy structures. The control of flexural vibrations in stiffened structures using piezoceramic stack actuators placed between stiffener flanges and the structure is examined theoretically and experimentally in this thesis. Used in this way, piezoceramic actuators are capable of developing much higher forces than laminated piezoelectric crystals, and no reaction mass is required. This thesis aims to show the feasibility of active vibration control using piezoceramic actuators and angle stiffeners in a variety of fundamental structures. The work is divided into three parts. In the first, the simple case of a single actuator used to control vibration in a beam is examined. In the second, vibration in stiffened plates is controlled using multiple actuators, and in the third, the control of vibration in a ring-stiffened cylinder is investigated. In each section, the classical equations of motion are used to develop theoretical models describing the vibration of the structures with and without active vibration control. The effects of the angle stiffener(s) are included in the analysis. The models are used to establish the quantitative effects of variation in frequency, the location of control source(s) and the location of the error sensor(s) on the achievable attenuation and the control forces required for optimal control. Comparison is also made between the results for the cases with multiple control sources driven by the same signal and with multiple independently driven control sources. Both finite and semi-finite structures are examined to enable comparison between the results for travelling waves and standing waves in each of the three structure types. This thesis attempts to provide physical explanations for all the observed variations in achievable attenuation and control force(s) with varied frequency, control source location and error sensor location. The analysis of the simpler cases aids in interpreting the results for the more complicated cases. Experimental results are given to demonstrate the accuracy of the theoretical models in each section. Trials are performed on a stiffened beam with a single control source and a single error sensor, a stiffened plate with three control sources and a line of error sensors and a ring-stiffened cylinder with six control sources and a ring of error sensors. The experimental results are compared with theory for each structure for the two cases with and without active vibration control.Thesis (Ph.D.)--Mechanical Engineering, 1995.
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陳立梅 and Lap-mui Ann Chan. "Near optimal lot-sizing policies for multi-stage production/inventory systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1990. http://hub.hku.hk/bib/B31209129.
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Mackenzie, Neil C. "The independent quadratic optimisation algorithm for the active control of noise and vibration /." Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phm15742.pdf.
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Yan, Li, and 顏理. "On the traffic flow control system." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39431174.
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Leung, Ho-yin, and 梁浩賢. "Stochastic models for optimal control problems with applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841781.
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Chang, Min-Yung. "Active vibration control of composite structures." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-09162005-115021/.
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Kadiri, Mostafa. "Shape οptimizatiοn and applicatiοns tο hydraulic structures : mathematical analysis and numerical apprοximatiοn." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC214/document.
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Nous nous intéressons à l’étude théorique et numérique de plusieurs modèles d’écoulement (Saint-Venant, multicouches, milieux poreux stationnaires et non stationnaires) et de leurs applications à l’optimisation de formes de certains ouvrages hydrauliques. Nous explorons le caractère bien posé des systèmes, nous dérivons un système adjoint lié à chaque modèle.Une méthode de pénalisation est utilisée pour relaxer la contrainte d’incompressibilité de la vitesse.Nous exprimons le gradient de forme en fonction de la vitesse u comme variable d’état, des variables adjointes, et le vecteur unité normal au bord du domaine.Nous adoptons une méthode d’éléments finis discrète pour approcher la solution du problème pénalisé et établissons des estimations à priori afin de prouver la convergence de la solution approchée vers la solution du système non perturbé.Le problème d’optimisation est implémenté en utilisant la méthode adjointe continue et la méthode d’éléments finisWe are interested in the theoretical and numerical study of different flow models (shallow water system, multilayer, stationary and non stationary porous media) and their applications to the shape optimization of some hydraulic structures.We explore the well-posedness of the models and derive the adjoint equations related to each system.A penalty method is used to relax the incompressibility constraint for the velocity. We express the shape gradient of the cost function in terms of the velocity value as a state variable, the adjoint variables and the unit normal vector to the boundary of the domain.We propose a discrete finite element method to approximate the solution for the penalizedproblem and establish a priori estimates to prove the convergence of the approximate solution to the solution of the non perturbed problem. Error estimates for the velocity and the pressure are established.The optimization procedure is implemented using the continuous adjoint method and the finite element method
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Cao, Min, and 曹敏. "Models for delivery and price equilibrium and statistical quality control in supply chains." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38576090.
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Sun, Daning. "Structured policies for complex production and inventory models." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/31002.
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For inventory models minimizing the long-run average cost over an infinite horizon, the existence of optimal policies was an open question for a long time. Consider a deterministic, continuous time inventory system satisfies the following conditions: the production network is acyclic, the joint setup cost function is monotone, the holding cost and the backlogging cost rates are nonnegative, the demand rates are constant over time, the production rates are infinite or finite non-increasing, and backlogging may be allowed or not. For this very general extension of the Wilson-Harris EOQ model, we prove the existence of optimal policies. Very few properties of optimal policies have been discovered since the 1950's. Restricting the above inventory model to infinite production rates, we present some new properties of optimal policies, such as the Latest Ordering Property, and explicit expressions for echelon inventories and order quantities in terms of ordering instants.
An assembly production system with n facilities has a constant external demand occurring at the end facility. Production rates at each facility are finite and non-increasing along any path in the assembly network. Associated with each facility are a set-up cost and positive echelon holding cost rate. The formulation of the lot-sizing problem is developed in terms of integer-ratio lot size policies. This formulation provides a unification of the integer-split policies formulation of Schwarz and Schrage [34] (1975) and the integer-multiple policies formulation of Moily [20] (1986), allowing either assumption to be operative at any point in the system. A relaxed solution to this unified formulation provides a lower bound to the cost of any feasible policy. The derivation of this Lower Bound Theorem is novel and relies on the notion of path holding costs, a generalization of echelon holding costs. An optimal power-of-two lot size policy is found by an 0(n³ log n) algorithm and its cost is within 2% of the optimum in the worst case.
Mitchell [18] (1987) extended Roundy's 98%-effectiveness results for one-warehouse multi-retailer inventory systems with backlogging. We extend this 98%-effectiveness result
for series inventory systems with backlogging. The nearly-integer-ratio policies still work. The continuous relaxation provides a lower bound on the long-run average cost of any feasible policy. The backlogging model is also reduced in 0{n) time to an equivalent model without backlogging. Roundy's results [27] (1983) are then applied for finding a 98%-effective backlogging policy in O(nlogn) time.
In an EOQ model with n products, joint setup costs provide incentives for joint replenishment. These joint setup costs may be modelled as a positive, nondecreasing, submodular set function. A grouping heuristic partitions the n products into groups, and all products in the same group are always jointly replenished. Each group is then considered as a single "aggregate product" being replenished independently of the other groups, and therefore according to the EOQ formula. As a result, possible savings when several groups are simultaneously replenished are simply ignored. Our main result is that the cost of the best such grouping solution cannot be worse than 44.8% above the optimum cost. Known examples show that it can be as bad as 22.4% above the optimum cost. These results contrast with earlier results for power-of-two policies, the best of which never being worse than about 2% above the optimum cost.Business, Sauder School of
Graduate
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Terciyanli, Erman. "Alternative Mathematical Models For Revenue Management Problems." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610711/index.pdf.
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In this study, the seat inventory control problem is considered for airline networks from the
perspective of a risk-averse decision maker. In the revenue management literature, it is generally
assumed that the decision makers are risk-neutral. Therefore, the expected revenue is
maximized without taking the variability or any other risk factor into account. On the other
hand, risk-sensitive approach provides us with more information about the behavior of the
revenue. The risk measure we consider in this study is the probability that revenue is less
than a predetermined threshold level. In the risk-neutral cases, while the expected revenue
is maximized, the probability of revenue being less than such a predetermined level might
be high. We propose three mathematical models to incorporate the risk measure under consideration.
The optimal allocations obtained by these models are numerically evaluated in
simulation studies for example problems. Expected revenue, coefficient of variation, load factor
and probability of the poor performance are the performance measures in the simulation
studies. According to the results of these simulations, it shown that the proposed models can
decrease the variability of the revenue considerably. In other words, the probability of revenue
being less than the threshold level is decreased. Moreover, expected revenue can be increased
in some scenarios by using the proposed models. The approach considered in this thesis is especially proposed for small scale airlines because risk of obtaining revenue less than the
threshold level is more for this type of airlines as compared to large scale airlines.
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Iyogun, Paul Omolewa. "Lower bounds for production/inventory problems by cost allocation." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27323.
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This thesis presents a cost allocation method for deriving lower bounds on costs of feasible policies for a class of production/inventory problems. Consider the joint replenishment problem where a group of items is replenished together or individually. A sequence of reorders for any particular item will incur holding, backorder and set-up costs specific to the item, in addition whenever any item is replenished a joint cost is incurred. What is required of the total problem is the minimization of a cost function of the replenishment sequence or policy.
The cost allocation method consists of decomposing the total problem into sub-problems, one for each item, by allocating the joint cost amongst the items in such a way that every item in the group receives a positive allocation or none. The result is that, for an arbitrary feasible cost allocation, the sum of the minimum costs for the subproblems is a lower bound on the cost of any feasible policy to the total problem. The results for the joint replenishment problem follows:
For the constant and continuous demand case we reproduce the lower bound of Jackson, Maxwell and Muckstadt more easily than they did. For the multi-item dynamic
lot-size problem, we generalize Silver-Meal and part-period balancing heuristics, and derive a cost allocation bound with little extra work. For the 'can-order' system, we use periodic policies derived from the cost allocation method and show that they are superior to the more complex (s,c,S) policies. The cost allocation method is easily
generalized to pure distribution problems where joint replenishment decisions are taken at several facilities. For example, for the one-warehouse multi-retailer problem, we reproduce Roundy's bound more easily than he did. For the multi-facility joint replenishment problem (a pure distribution system with an arbitrary number of warehouses),
we give a lower bound algorithm whose complexity is dr log r where d is the maximum number of facilities which replenish a particular item and r is the number of items.Business, Sauder School of
Graduate
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Ozcaldiran, Kadri. "Control of descriptor systems." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/13531.
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Smerlas, Alex. "Robust multivariable control of helicopters : from mathematical models to flight tests." Thesis, University of Leicester, 1999. http://hdl.handle.net/2381/30174.
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This thesis describes the design and flight testing of advanced robust multivariable control laws for high performance fly-by-wire helicopters. The control laws are synthesised using H optimisation, which provides robust stability against a wide class of systems with unmodelled dynamics and parametric uncertainty. This is the first time that an H-based control system has been designed and successfully tested in both ground-based simulators and in real flight, on a fly-by-wire, variable stability helicopter.;The helicopter is a multivariable and highly nonlinear system. The dynamics vary significantly with the aircraft's orientation in the three-dimensional inertial space, the magnitude and direction of the velocity and different loading configurations. This implies a high pilot workload during operational tasks. The developed control laws provide the pilot with a means to fly the aircraft safely and effectively throughout its flight envelope.;Special attention is paid to the effects of high order rotor dynamics on the control law robustness and performance, to controller implementation issues and to the effects of aircraft configurations to the perceived handling qualities of the helicopter.;For systems that undergo large parameter variations, a novel gain scheduled methodology is proposed, which not only stabilises the linearised plants within the scheduling variable region, but also achieves H performance control objectives. This method exploits the attractive observer-based structure of the H loop shaping feedback compensators.
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Hodge, Steven Eric. "Discrete-time closed-loop control of a hinged wavemaker." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26704.
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The waves produced by a flap-type wavemaker, hinged in the middle, are modelled using first-order linear wavemaker theory. A simplified closed-loop, discrete-time system is proposed. This includes a proportional
plus integral plus derivative (PID) controller, and the wavemaker in order to compare the actual wave spectral density with the desired wave spectral density at a single frequency. Conventional discrete-time control theory is used with the major difference being the use of a relatively long timestep duration between changes in waveboard motion.
The system response is calculated for many controller gain combinations
by the computer simulation program CBGANES. System stability is analyzed for the gain combinations by using two different methods. One method is an extension of the Routh criterion to discrete-time and the other is a state-space eigenvalue approach. The computer simulation and the stability analysis provide a means for selecting possible controller gains for use at a specific frequency in an actual wave tank experiment.
The computer simulation performance response and the two stability analyses predict the same results for varying controller gains. It is evident that integral control is essential in order to achieve a desired response for this long duration timestep application. The variation in discrete timestep duration and in desired spectral density (an indirect indication of frequency variation) provide variation in the constraints on controller gain selection. The controller gain combinations yielding the fastest stable response at a single frequency are for large proportional gain and small integral and derivative gains.Applied Science, Faculty of
Mechanical Engineering, Department of
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Agi, Egemen. "Mathematical Modeling Of Gate Control Theory." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611468/index.pdf.
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The purpose of this thesis work is to model the gate control theory, which explains the modulation of pain signals, with a motivation of finding new possible targets for pain treatment and to find novel control algorithms that can be used in engineering practice. The difference of the current study from the previous modeling trials is that morphologies of neurons that constitute gate control system are also included in the model by which structure-function relationship can be observed. Model of an excitable neuron is constructed and the response of the model for different perturbations are investigated. The simulation results of the excitable cell model is obtained and when compared with the experimental findings obtained by using crayfish, it is found that they are in good agreement. Model encodes stimulation intensity information as firing frequency and also it can add sub-threshold inputs and fire action potentials as real neurons. Moreover, model is able to predict depolarization block. Absolute refractory period of the single cell model is found as 3.7 ms. The developed model, produces no action potentials when the sodium channels are blocked by tetrodotoxin. Also, frequency and amplitudes of generated action potentials increase when the reversal potential of Na is increased. In addition, propagation of signals along myelinated and unmyelinated fibers is simulated and input current intensity-frequency relationships for both type of fibers are constructed. Myelinated fiber starts to conduct when current input is about 400 pA whereas this minimum threshold value for unmyelinated fiber is around 1100 pA. Propagation velocity in the 1 cm long unmyelinated fiber is found as 0.43 m/s whereas velocity along myelinated fiber with the same length is found to be 64.35 m/s. Developed synapse model exhibits the summation and tetanization properties of real synapses while simulating the time dependency of neurotransmitter concentration in the synaptic cleft. Morphometric analysis of neurons that constitute gate control system are done in order to find electrophysiological properties according to dimensions of the neurons. All of the individual parts of the gate control system are connected and the whole system is simulated. For different connection configurations, results of the simulations predict the observed phenomena for the suppression of pain. If the myelinated fiber is dissected, the projection neuron generates action potentials that would convey to brain and elicit pain. However, if the unmyelinated fiber is dissected, projection neuron remains silent. In this study all of the simulations are preformed using Simulink.
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Miller, Andrew J. "Polyhedral approaches to capacitated lot-sizing problems." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/24284.
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Bhatnagar, Rohit. "A model for multi-plant coordination : implications for production planning." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28421.
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Firms in several discrete parts manufacturing industries, e.g., electronics equipment, computers, telecommunications equipment etc. operate in a multi-plant environment where products are processed successively at several plants. Prior studies have ignored the interaction between different plants in a multi-plant scenario. The objective of this dissertation is to study the impact of coordination on the cost performance of a two-plant firm.We propose a model that jointly determines production and inventory decisions so that the total cost of holding inventory and overtime, at the two plants is minimized. Our model captures the interaction between the two plants and is preferable to the uncoordinated or the sequential approach which ignores this interaction. We consider the case with limited capacity and explicitly model setup times. Strategies based on Lagrangian relaxation and Lagrangian decomposition methodologies are proposed to solve the model.
Two main findings emerge from this research. First, our results indicate that coordination could lead to improved cost performance and enhanced profits for firms. Two parameters, the setup time to processing time ratio and the capacity utilization at the two plants played a significant role in determining the cost improvements. Managerial implications relating to implementation of the coordinated model are discussed. The second important finding of this research is that Lagrangian decomposition consistently outperforms Lagrangian relaxation in terms of achieving better deviation from the optimal solution, for this problem. A Linear Programming based technique for further enhancing the convergence between the upper and lower bounds is presented.
In the quest for improved performance, multi-plant coordination represents an important strategy for firms. The contribution of the current research is in modelling some of the salient issues of this problem and exploring promising methodological directions.
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Cooper, William L. "Revenue management, auctions, and perishable inventories." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/25805.
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Bleninger, Tobias. "Coupled 3D hydrodynamic models for submarine outfalls environmental hydraulic design and control of multiport diffusers." Karlsruhe Univ.-Verl. Karlsruhe, 2006. http://www.uvka.de/univerlag/volltexte/2007/238/.
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Bleninger, Tobias. "Coupled 3D hydrodynamic models for submarine outfalls environmental hydraulic design and control of multiport diffusers /." Karlsruhe : Universitätsverlag, 2007. http://www.uvka.de/univerlag/volltexte/2007/238/.
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Orzechowska, J. E. "A mathematically reduced approach to predictive control of perishable inventory systems." Thesis, Coventry University, 2014. http://curve.coventry.ac.uk/open/items/df30d207-00e9-4fae-a86d-9fc2871f0539/1.
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The design and optimisation of inventory replenishment systems has already been exhaustively studied by the operational research community. Many classical mathematical methods and simulation techniques have been developed and introduced in the literature. However, what can be observed is the fact that in a real case scenario the lead-time, deterioration of goods and demand for product are likely to be time-varying and uncertain, which traditionally have not necessarily been reflected in the model formulations. Therefore, in response to the dynamical nature of inventory systems, the potential of algorithms based on control theory to reduce the undesirable influences of system uncertainties on inventory level stability, have been investigated /proposed. Consequently, the mapping of the inventory problem into the control theory domain, for cost-benefit inventory trade-off achievement has been realised. Although, the application of control theory in inventory optimisation appears to be beneficial, there are certain reasons why the approach has gained yet little attention among the operational research community. One reason is that it cannot be adopted easily by researchers who are unfamiliar with control theory and another is due to a communication gap which exists between the control theory and operational research communities. Prompted by these observations, the thesis presents a novel, systematic mathematical approach for finding the optimal order quantities. The proposed approach has been mathematically demonstrated to be equivalent in study-sate to model-based predictive control, which is one of the more well-established productive control techniques with industrial application today. The mathematically reduced approach attempts to bridge the identified gap to fulfil the lacking dual perceptions of both communities. It enables the straightforward benefits afforded by predictive control without the necessity to become familiarised with principles of control theory. The method is shown to be applicable for both perishable and non-perishable inventory. Although the novel technique was inspired by MPC and noticing the MPC patterns in the mathematical description, the resulting proposal is no longer MPC. It is in fact a minimum variance approach, or dear beat controller, with an incorporated Smith predictor. Therefore using the adjective ‘predictive’ in the title of the thesis refers to both, the inspiration of MPC and the predictive nature of the minimum variance controller to accommodate lead time, being incorporated within an inherent Smith predictor. The developed approach is considered to be transferable to other applications, where similar model formulations may be applicable.
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吳景濤 and King-to Ng. "A novel bit allocation buffer control algorithm for low bit-rate videocompression." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31221518.
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朱國基 and Kwok-kei Chu. "Design and control of a six-legged mobile robot." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31225895.
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Razavi, H. Ali. "Identification and control of grinding processes for intermetalic [sic] compunds [sic]." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/18917.
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Oleś, Katarzyna A. "Searching for the optimal control strategy of epidemics spreading on different types of networks." Thesis, University of Stirling, 2014. http://hdl.handle.net/1893/21199.
Full textAbstract:
The main goal of my studies has been to search for the optimal control strategy of controlling epidemics when taking into account both economical and social costs of the disease. Three control scenarios emerge with treating the whole population (global strategy, GS), treating a small number of individuals in a well-defined neighbourhood of a detected case (local strategy, LS) and allowing the disease to spread unchecked (null strategy, NS). The choice of the optimal strategy is governed mainly by a relative cost of palliative and preventive treatments. Although the properties of the pathogen might not be known in advance for emerging diseases, the prediction of the optimal strategy can be made based on economic analysis only. The details of the local strategy and in particular the size of the optimal treatment neighbourhood weakly depends on disease infectivity but strongly depends on other epidemiological factors (rate of occurring the symptoms, spontaneously recovery). The required extent of prevention is proportional to the size of the infection neighbourhood, but this relationship depends on time till detection and time till treatment in a non-nonlinear (power) law. The spontaneous recovery also affects the choice of the control strategy. I have extended my results to two contrasting and yet complementary models, in which individuals that have been through the disease can either be treated or not. Whether the removed individuals (i.e., those who have been through the disease but then spontaneously recover or die) are part of the treatment plan depends on the type of the disease agent. The key factor in choosing the right model is whether it is possible - and desirable - to distinguish such individuals from those who are susceptible. If the removed class is identified with dead individuals, the distinction is very clear. However, if the removal means recovery and immunity, it might not be possible to identify those who are immune. The models are similar in their epidemiological part, but differ in how the removed/recovered individuals are treated. The differences in models affect choice of the strategy only for very cheap treatment and slow spreading disease. However for the combinations of parameters that are important from the epidemiological perspective (high infectiousness and expensive treatment) the models give similar results. Moreover, even where the choice of the strategy is different, the total cost spent on controlling the epidemic is very similar for both models. Although regular and small-world networks capture some aspects of the structure of real networks of contacts between people, animals or plants, they do not include the effect of clustering noted in many real-life applications. The use of random clustered networks in epidemiological modelling takes an impor- tant step towards application of the modelling framework to realistic systems. Network topology and in particular clustering also affects the applicability of the control strategy.
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Tchikanda, Serge William. "Modeling for high-speed high-strength precision optical fiber drawing." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/20051.
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林志立 and Chi-lap Lam. "Analysis of inventory systems with demands met either from inventory or by special deliveries." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1988. http://hub.hku.hk/bib/B3120868X.
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黎錦強 and Kam-keung Lai. "Optimal (s,S) policies for inventory systems with a maximum issue quantity restriction." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B42574481.
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Tai, Hoi-lun Allen, and 戴凱倫. "Quantitative analysis in monitoring and improvement of industrial systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B4394193X.
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Zhang, Xiaohong. "Optimal feedback control for nonlinear discrete systems and applications to optimal control of nonlinear periodic ordinary differential equations." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40185.
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Zhang, Yi. "Numerical modeling of shock wave propagation and contaminant fate and transport in open channel networks." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/20159.
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Sood, Gaurav. "Simulation and control of a hip actuated robotic model for the study of human standing posture." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99794.
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Human stance in quiet mode, relies on feedback from eyes, skin, muscles and the inner ear and the control produced is a combination of strategies which enable a person to stay standing. This thesis presents the simulation and control of a hip actuated robotic model of human standing posture.The first part of the thesis is devoted to recalling basic elements of the human balance system and to describe the balance strategies it uses to maintain an upright stance. Of the strategies presented, we consider the hip strategy which motivated the formulation of a hip actuated robot. An investigation into the control of nonlinear underactuated robots by linear controllers is done to verify the range and efficiency of the controlled system.
The second part of the thesis includes the investigation of two simplified models of the robot. Results using linear state feedback control are presented. The two models used are compared to clarify the use of one over the other.
We found that for linear controls, the size of the region of convergence decreased underactuated systems of increasing complexity. For our four degrees of freedom robot, the region of convergence is of 2.3 degrees for the actuated joints and of 1 degree for the unactuated joints. Our system is Lyapunov stable when the fully simplified model is assumed.
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Thompson, Christopher David. "An analytical and experimental investigation of respiratory dynamics using P/D control and carbon dioxide feedback." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43059.
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This thesis addresses the problem of defining the control law for human respiration.
Seven different drivers have been identified as possibly having an input to the
respiratory controller. These seven represent a combination of feedforward and feedback
inputs arising from neural and humoral mechanisms.
Using the assumption that carbon dioxide concentrations in the arterial blood have the
strongest effect, a control equation with proportional and derivative components based on
this driver was evaluated. The methodology for the evaluation was to create a model of
the respiratory system incorporating the P/D controller, obtain experimental data of one
test subject's respiratory response to exercise, then compare model generated output with
experimental data, and adjust the parameters in the control equation to yield optimal
model performance.
The usual practice of testing controller performance has been to apply single step loads
to a model and evaluate its response. A multi-step protocol was used here to provide a
better, more generalized test of controller performance. This thesis may represent the
first documented use of an approach of this type for evaluating respiratory controller
performance.
Application of a multi-step protocol revealed a non-linear controller was needed to keep
pace with system changes. Respiratory system operation was effectively managed using
a controller of the form:
VENTILATION = F(dCO2/dT,Q) + F(CO2,Q) + CONSTANT.Master of Science
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Vaezi, Masoud. "Modeling and control of hydraulic wind power transfer systems." Thesis, 2014. http://hdl.handle.net/1805/6172.
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Indiana University-Purdue University Indianapolis (IUPUI)Hydraulic wind power transfer systems deliver the captured energy by the blades to the generators differently. In the conventional systems this task is carried out by a gearbox or an intermediate medium. New generation of wind power systems transfer the captured energy by means of high-pressure hydraulic fluids. A hydraulic pump is connected to the blades shaft at a high distance from the ground, in nacelle, to pressurize a hydraulic flow down to ground level equipment through hoses. Multiple wind turbines can also pressurize a flow sending to a single hose toward the generator. The pressurized flow carries a large amount of energy which will be transferred to the mechanical energy by a hydraulic motor. Finally, a generator is connected to the hydraulic motor to generate electrical power. This hydraulic system runs under two main disturbances, wind speed fluctuations and load variations. Intermittent nature of the wind applies a fluctuating torque on the hydraulic pump shaft. Also, variations of the consumed electrical power by the grid cause a considerable load disturbance on the system. This thesis studies the hydraulic wind power transfer systems. To get a better understanding, a mathematical model of the system is developed and studied utilizing the governing equations for every single hydraulic component in the system. The mathematical model embodies nonlinearities which are inherited from the hydraulic components such as check valves, proportional valves, pressure relief valves, etc. An experimental prototype of the hydraulic wind power transfer systems is designed and implemented to study the dynamic behavior and operation of the system. The provided nonlinear mathematical model is then validated by experimental result from the prototype. Moreover, this thesis develops a control system for the hydraulic wind power transfer systems. To maintain a fixed frequency electrical voltage by the system, the generator should remain at a constant rotational speed. The fluctuating wind speed from the upstream, and the load variations from the downstream apply considerable disturbances on the system. A controller is designed and implemented to regulate the flow in the proportional valve and as a consequence the generator maintains its constant speed compensating for load and wind turbine disturbances. The control system is applied to the mathematical model as well as the experimental prototype by utilizing MATLAB/Simulink and dSPACE 1104 fast prototyping hardware and the results are compared.
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Fair, Kerry. "Developing a real time hydraulic model and a decision support tool for the operation of the Orange River." Thesis, 2002. http://hdl.handle.net/10413/4674.
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This thesis describes the development of a decision support tool to be used in the operation of Vanderkloof Dam on the Orange River so that the supply of water to the lower Orange River can be optimised. The decision support tool is based on a hydrodynamic model that was customised to incorporate real time data recorded at several points on the river. By incorporating these data into the model the simulated flows are corrected to the actual flow conditions recorded on the river, thereby generating a best estimate of flow conditions at any given time. This information is then used as the initial conditions for forecast simulations to assess whether the discharge volumes and schedules from the dam satisfy the water demands of downstream users, some of which are 1400km or up to 8 weeks away. The various components of the decision support system, their functionality and their interaction are described. The details regarding the development of these components include: • The hydraulic model of the Orange River downstream of Vanderkloof Dam. The population and calibration of the model are described. • The modification of the code of the hydrodynamic engine so that real time recorded stage and flow data can be incorporated into the model • The development of a graphical user interface to facilitate the exchange of data between the real time network of flow gauging stations on the Orange River and the hydraulic model • The investigation into the effect of including the real time data on the simulated flows • Testing the effectiveness of the decision support system.Thesis (M.Sc.)-University of Natal, Durban, 2002.
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Betts, Curt M. "Numerical techniques for coupled neutronic/thermal hydraulic nuclear reactor calculations." Thesis, 1994. http://hdl.handle.net/1957/36090.
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The solution of coupled neutronic/thermal hydraulic nuclear reactor calculations
requires the treatment of the nonlinear feedback induced by the thermal hydraulic
dependence of the neutron cross sections. As a result of these nonlinearities, current
solution techniques often diverge during the iteration process. These instabilities arise
due to the low level of coupling achieved by these methods between the neutronic and
thermal hydraulic components. In this work, this solution method is labeled the
Decoupled Iteration (DI) method, and this technique is examined in an effort to
improve its efficiency and stability. An examination of the DI method also serves to
provide insight into the development of more highly coupled iteration methods. After
the examination of several possible iteration procedures, two techniques are developed
which achieve both a higher degree of coupling and stability.
One such procedure is the Outer Iteration Coupling (OIC) method, which
combines the outer iteration of the multigroup diffusion calculation with the controlling
iteration of the thermal hydraulic calculations. The OIC method appears to be stable for
all cases, while maintaining a high level of efficiency. Another iteration procedure
developed is the Modified Axial Coupling (MAC) procedure, which couples the
neutronic and thermal hydraulic components at the level of the axial position within the
coolant channel. While the MAC method does achieve the highest level of coupling
and stability, the efficiency of this technique is less than that of the other methods
examined.
Several characteristics of these coupled calculation methods are examined during
the investigation. All methods are shown to be relatively insensitive to thermal
hydraulic operating conditions, while the dependence upon convergence criteria is quite
significant. It is demonstrated that the DI method does not converge for arbitrarily
small convergence criteria, which is a result of a non-asymptotic solution
approximation by the DI method. This asymptotic quality is achieved in the coupled
methods. Thus, not only do the OIC and MAC techniques converge for small values of
the relevant convergence criteria, but the computational expense of these methods is a
predictable function of these criteria. The degree of stability of the iterative techniques
is enhanced by a higher level of coupling, but the efficiency of these methods tends to
decrease as a higher degree of coupling is achieved. This is apparent in the diminished
efficiency of the MAC procedure. Seeking an optimum balance of efficiency and
stability, the OIC technique is demonstrated to be the optimum method for coupled
neutronic/thermal hydraulic reactor calculations.Graduation date: 1994
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Paião, Ana Pedro Lemos. "Optimal control and mathematical models in epidemiology." Doctoral thesis, 2019. http://hdl.handle.net/10773/29401.
Full textAbstract:
In this PhD thesis, we prove sufficient optimality conditions for delayed optimal
control problems, by transforming them into equivalent non-delayed problems.
Such transformation is done by considering a technique proposed by Guinn in
1976 and later promoted by Maurer and his collaborators. In this way, we are
able to use well-known sufficient optimality conditions for non-delayed optimal
control problems and to return to the delayed ones. We propose and study
several models that can translate the spread of cholera and that consider different
types of treatment or prevention measures. Corresponding optimal control
problems are formulated and studied. Such theoretical analysis are then
applied to real cholera outbreaks that occured in Haiti and Yemen.Nesta tese de doutoramento, provamos condições suficientes de otimalidade para problemas de controlo ótimo com tempos de atraso, transformando-os em problemas equivalentes sem tempos de atraso. Tal transformação é feita considerando uma técnica proposta por Guinn em 1976 e mais tarde promovida por Maurer e seus colaboradores. Deste modo, somos capazes de usar condições suficientes de otimalidade conhecidas para problemas de controlo ótimo sem tempos de atraso e voltar aos que consideram tempos de atraso. Propomos e estudamos vários modelos que traduzem a propagação da cólera e que consideram diferentes tipos de tratamento ou de medidas de prevenção. Problemas de controlo ótimo correspondentes são formulados e estudados. Tais análises teóricas são depois aplicadas a epidemias de cólera reais que ocorreram no Haiti e no Iémen.
Programa Doutoral em Matemática Aplicada
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Kanchanasaratool, Narongsak. "Control of flexible structure." Phd thesis, 2003. http://hdl.handle.net/1885/148681.
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