No description available.

No description available.

In this thesis, we mainly investigate the application of a nodal discontinuous Galerkin spectral element method (DGSEM) for simulating processes in column liquid chromatography. Additionally, we investigate the effectiveness of a total variation diminishing in the mean (TVDM) limiter in controlling spurious oscillations related to the Gibbs phenomenon. With an order-of-accuracy test, we demonstrated that our nodal DGSEM achieved and, in multiple instances, even exceeded theoretical convergence rates, especially with an increased number of elements, validating the use of high-order basis functions for achieving high-order accuracy. We also demonstrated how setup parameters could affect process outcomes, which suggests that numerical simulations can help guide the development of experimental methods since they can explore the solution space of an optimization problem much faster than experimental procedures by leveraging computational speed. Finally, we showed that the TVDM limiter successfully eliminated severe oscillations and negative concentrations near shock regions but introduced significant smearing of the shocks. These findings validate the nodal DGSEM as a highly accurate and reliable tool for detailed modeling of column liquid chromatography, which is essential for improving efficiency, yield, and product quality in biopharmaceutical manufacturing.

The concept of piezohydraulic actuation is to transfer the reciprocal small stroke displacement of piezoceramics into unidirectional motion by frequency rectification through a hydraulic fluid. It takes advantage of the high force capabilities that piezoelectric materials have and couples it with very stiff media such as hydraulic fluid to amplify and create this unidirectional motion. Inlet and outlet valves are connected to a pumping chamber where pressure is built by the displacement of the piezoelectric material and released by the opening of the outlet valve, thus achieving a variable flow rate that is used to push a hydraulic cylinder. Loads may be connected to this hydraulic cylinder for measuring/achieving mechanical power. As part of this research, a benchtop piezohydraulic actuator with active piezohydraulic valves has been developed and the concept of piezohydraulic actuation has been demonstrated. Displacement of a hydraulic cylinder by driving a piezoelectric stack has been achieved while the cylinder was loaded or unloaded. Lumped-parameter state-space models have been developed in order to simulate the dynamics of the active valves and entire actuator system. The model simulates the chamber pressure, displacement of the hydraulic cylinder, and power of the piezohydraulic unit. A four-stage cycle simulation was used to model the pumping operation and dynamic response of the system. Experimental results demonstrate the importance of fluid compressibility, valve timing, and fluid circuit components in the optimization of the output power of the actuation system. An array of different timing tests run on the inlet and outlet valves shows that their timing is crucial to the performance of the system. Also shown is that the optimal timing conditions change slightly while under different loads. When operating at higher frequencies (above 140 Hz), it is shown that the hydraulic fluid circuit does not respond quickly enough for the piston to fully extend against the fluid and loaded cylinder. There is not sufficient time when operating at higher frequencies to push all the fluid from the chamber into the hydraulic cylinder, operation is too fast for the dynamics of the fluid circuit. The four stage lumped-parameter model achieves good approximations of the experimental results when the load inertia was neglected while operating at frequencies below 120 Hz and under loads at or below 12.825 kg. Memory limitations caused the number of elements included in the lumped-parameter model to be limited, and are believed to be the source of the errors for the higher operation frequencies and loads. The model never converged due to the lack of elements, and the simulated system did not respond quickly enough to accurately model the fluid exiting the chamber. When operating at frequencies above the 120 Hz value, this error in modeling the fluid exiting the valves becomes very important. The simulation predicts higher values than the experiment and fails to correlate to the actual results at the higher frequencies and while under the higher loads. The errors at higher loads may also be attributed to the neglected inertia. The most recent tests on the benchtop set-up were all run with a pre-pressure value of 190 psi, a piston duty cycle of 50%, valve duty cycles of 40% for each, and a 5% outlet valve offset. Slightly better operation performance might be achieved at frequencies higher than 140 Hz by increasing the piston duty cycle and varying the valve parameters. Also, increaing the pre-pressure of the fluid may help by stiffening the system to create a faster response, however this will have an adverse effect also by creating more force against piston motion. Lastly, the hydraulic cylinder was built for high pressures and had considerable friction associated with it. Obtaining a different cylinder with less friction may also help the response time of the fluid circuit. / Master of Science

The failure of oil well drillstrings due to torsional and longitudinal stresses caused by stick-slip phenomena during the drilling operation causes great expense to industry. Due to the complicated and harsh drilling environment, modelling of the drillstring becomes an essential requirement in studies. Currently, this is achieved by modelling the drillstring as a torsional lumped model (which ignores the length of the drillstring) for real-time measurement and control. In this thesis, a distributed-lumped model including the effects of drillstring length was developed to represent the drillstring, and was used to simulate stick-slip vibration. The model was developed with increasing levels of detail and the resultant models were validated against typical measured signals from the published literature. The stick-slip model describes the friction model that exists between the cutting tool and the rock. Based on theoretical analysis and mathematical formulation an efficient and adaptable model was created which was then used in the application of a method of species conserving genetic algorithm (SCGA) to optimise the drilling parameters. In conclusion, it was shown that the distributed-lumped model showed improved detail in predicting the transient response and demonstrated the importance of including the drillstring length. Predicting the response of different parameters along the drillstring is now possible and this showed the significant effect of modelling the drillcollar. The model was shown to better represent real system and was therefore far more suited to use with real time measurements. / Iraqi Government, Ministry of Higher Education and Scientific Research.

This work reports the experimental and numerical study of the thermal management of Li-ion battery packs under the context of electric vehicle (EV) or hybrid EV (HEV) applications. Li-ion batteries have been extensively demonstrated as an important power source for EVs or HEVs. However, thermal management is a critical challenge for their widespread deployment, due to their highly dynamic operation and the wide range of environments under which they operate. To address these challenges, this work developed several experimental platforms to study adaptive thermal management strategies. Parallel to the experimental effort, multi-disciplinary models integrating heat transfer, fluid mechanics, and electro-thermal dynamics have been developed and validated, including detailed CFD models and lumped parameter models. The major contributions are twofold. First, this work developed actively controlled strategies and experimentally demonstrated their effectiveness on a practical sized battery pack and dynamic thermal loads. The results show that these strategies effectively reduced both the parasitic energy consumption and the temperature non-uniformity while maintaining the maximum temperature rise in the pack. Second, this work established a new two dimensional lumped parameter thermal model to overcome the limitations of existing thermal models and extend their applicable range. This new model provides accurate surface and core temperatures simulations comparable to detailed CFD models with a fraction of the computational cost. / Ph. D. / Li-ion batteries have been widely used today as power source of electric vehicles (EV) or hybrid electric vehicles (HEV). Thermal management represents an important issue for the safe and efficiency of Li-ion batteries in EVs and HEVs. Thermal issues can lead to decreased energy efficiency, reduced battery lifetime, and even catastrophic failures. However, effective thermal management of Li-ion batteries is challenging due to several reasons, including the highly dynamic operation of the batteries and the wide range of ambient conditions under with the vehicles operate. To address these challenges, this work studied the thermal management problem through both experimental and numerical methods. Experimentally, actively controlled strategies have been designed and tested on our customized experimental platforms, and the results demonstrated the effectiveness such strategies. Numerically, multidisciplinary models have been developed and validated to provide comprehensive information of battery operation, and furthermore to simulate operation under extreme conditions that are difficult study experimentally. This dissertation reports both the experimental and numerical results, with a detailed analysis of their implications and applications.

Due to the mathematical complexity of current musculoskeletal spine models, there is a need for computationally-efficient models of the intervertebral disc (IVD). The aim of this study is to develop a mathematical model that will adequately describe the motion of the IVD under axial cyclic loading and three-dimensional quasi-static loading as well as maintain computational efficiency for use in future musculoskeletal spine models. A viscoelastic standard nonlinear solid (SNS) model is introduced within this study. It was developed to predict the axial response of the human lumbar IVD subjected to low-frequency vibration. Nonlinear axial behavior of the SNS model was simulated by a strain-dependent elastic modulus on the standard linear solid (SLS) model. The SNS model was able to predict the dynamic modulus of the IVD for frequencies of 0.01, 0.1, and 1 Hz. Furthermore, the model was able to quantitatively predict the load relaxation at a frequency of 0.01 Hz. However, model performance was unsatisfactory when predicting load relaxation and hysteresis at higher frequencies (0.1 Hz and 1 Hz). Results suggest that the standard solid model may require strain-dependent elastic and viscous behavior to represent the dynamic response to compressive strain. The SNS model was expanded to a three-dimensional elastic model by adding a matrix of spring elements in parallel with the SNS model. The geometry and orientation of the added elements represent the regional variations in stiffness and physiologic fiber angle. Results suggest that lordotic posture may be advantageous when modeling the intervertebral joint (IVJ) behavior. / Master of Science

Due to the detrimental effects of ride vibrations on occupants and increasing safety concerns, improvement in vehicle dynamic characteristics has become a key focus of researchers. Typically, ride and handling problems have been dealt with independently. There is a dearth of vehicle models capable of capturing occupant biodynamics and its implication on vehicle ride and handling. Also in general, the objective of conventional control systems has been to attenuate vertical dynamic response of the sprung mass of a vehicle. Feedback control based algorithms are predominantly used in active/semi-active suspensions that ignore the biodynamics of occupants. In the current work, a new 50 degree-of-freedom (DOF) combined nonlinear multi-occupant vehicle model is developed using the lumped parameter modelling (LPM) approach. The current model provides a platform for performing a combined study of ride, handling and occupant biodynamics. The model is capable of simulating the combined effect of sitting occupancies, road inputs and driving maneuvers on biodynamic responses. It is analyzed using MATLAB/SIMULINK functionalities and validated by independently correlating the computed responses with existing experimental results. A study is performed on ride behavior of a vehicle-occupant system under two different transient road inputs. In addition, the effect of road roughness on vehicle ride is also studied. Random road profiles are generated from road roughness spectrum given in the ISO 8608:1995 manual. Insights are developed into the ride dynamics of a vehicle traversing over roads of classes A, B, C and D at given test velocities. The effect of sitting occupancies and vehicle velocities on lateral dynamics is also studied. Results underscore the need for considering sitting occupancies while analyzing vehicle dynamics and also highlight the potential of the current model. Furthermore, a Moore-Penrose Pseudoinverse based feed-forward controller is developed and implemented in an independently acting semi-active seat suspension system. Feasibility of feed-forward control in primary suspensions is also investigated. Finally, issues of stability, performance and limitation of the controller are discussed.

Syfte – Syftet för denna studie var att utveckla en sensorlös modell som beräknar en estimeradtemperatur i en BLDC-motors statorlindningar, detta för att undersöka hur väl det går attskydda handhållna produkter mot oaktsam användning och för att kunna motverka körningunder höga temperaturer, vilket skulle kunna förlänga livslängden för handhållna produkter. Metod – Denna studie har använt forskningsmetoden Design Science Research för att utvecklaen artefakt som sensorlöst estimerar temperatur i en BLDC-motors statorlindningar.Artefaktens prestanda för den estimerade temperaturen var noggrannhet, precision ochkonvergeringstid, vilket utvärderats genom analys av kvantitativa data som samlats in underolika experiment. Resultat – Den utvecklade artefakten i studien baserades på en kombination av CurrentInjection och Lumped Parameter Thermal Network samt ett Kalman Filter, artefaktensprestanda uppfyllde inte Husqvarna AB:s krav. Artefaktens precision och noggrannhet för att estimera temperatur i en BLDCmotorsstatorlindningar blev 7,2 °C ± 23,8 °C och dess konvergeringstid blev 7,3 sför dess medelvärde och 18,4 s för dess precision. Implikationer – Denna studie och dess resultat kan användas som en hänvisning på hur välen kombination av Current Injection, Lumped Parameter Thermal Network och Kalman Filterkan estimera temperaturen i statorlindningar för BLDC-motorer med en resistans på 20 mΩ,induktans på 10 uH, nominell hastighet på ~20 000 RPM med terminering av typen Delta ochsom är icke salient. Begränsningar – Studiens begränsningar listas nedan. Utvecklingstiden för artefakten utfördes under begränsad tid. Vilket bidragit till mindre optimering av artefakterna. Vilket bidragit till färre iterationer av artefakter. Artefakten utvärderas endast på VESC hårdvara och dess mjukvara som grund.Artefaktens prestanda påverkas av noggrannheten samt precisionen vidmätning av ström och spänning. Experimenten som utfördes var begränsade. Hade intervallen som experimenten utfördes gällande temperatur, hastighetoch dynamisk last varit större skulle artefaktens prestanda kunna bli undersökti mer verkliga förhållanden. En bättre bromsbänk och en klimatkammareskulle använts. Endast en BLDC motor utvärderades. Utvärdering av fler motorer skulle kunna visa på skillnader i prestanda förartefakten mellan olika mindre motorer, det vill säga visa på dess generellatillämpbarhet. Analys av artefaktens prestanda vid enbart konvergerande tillstånd utfördes inte. Vilket skulle kunna visa på om artefaktens prestanda vid enbart konvergeradetillstånd hade uppfyllt Husqvarna AB:s krav. Nyckelord – Estimera Temperatur, BLDC-motor, Statorlindningar, Current Injection,Lumped Parameter Thermal Network, Kalman Filter, VESC / Purpose – The purpose of this study was to develop a sensorless model that calculates anestimated temperature in a stator winding of a BLDC motor, to investigate how well it is possibleto protect handheld products from inadvertent use and to be able to counteract operation underhigh temperatures, which could prolong service life of the handheld products. Method – This study has used the research method Design Science Research to develop anartifact that sensorlessly estimates temperature in a BLDC motor's stator windings. Theperformance of the artifact for the estimated temperature is accuracy, precision, andconvergence time, which was evaluated by analysing quantitative data collected during differentexperiments. Findings – The artifact developed in the study is based on a combination of Current Injectionand Lumped Parameter Thermal Network and a Kalman Filter, the performance of the artifactdid not meet Husqvarna AB's requirements. The precision and accuracy of the artifact for estimating temperature in a statorwinding of a BLDC motor was 7,2 °C ± 23,8 °C and its convergence time was 7,3 sfor its mean and 18,4 s for its precision. Implications – This study and its results can be used as a reference regarding how well acombination of Current Injection, Lumped Parameter Thermal Network and Kalman Filter canestimate the temperature in stator windings for non-salient BLDC motors with a resistance of20 mΩ, inductance of 10 uH, nominal speed of ~20 000 RPM with termination of the Deltatype. Limitations – The limitations of the study are listed below. The development time for the artifact was performed for a limited time. Which has contributed to less optimization of the artifacts. Which has contributed to fewer iterations of artifacts. The artifact is evaluated only on VESC hardware and its software as a basis.The performance of the artifact is affected by the accuracy and precision inmeasuring current and voltage. The experiments performed were limited. Had the intervals at which the experiments were performed regardingtemperature, speed and dynamic load been greater, the performance of theartifact could have been examined in more real conditions. A better brakebench and a climate chamber would be used. Only one BLDC motor was evaluated. Evaluation of more motors could show differences in the performance of theartifact between different smaller motors, that is, show its general applicability. Analysis of the performance of the artifact in convergent states alone was notperformed. Which could show if the performance of the artifact could fulfill HusqvarnaAB's requirements if the analysis were only performed in convergingconditions. Keywords – Estimate Temperature, BLDC Motor, Stator Windings, Current Injection,Lumped Parameter Thermal Network, Kalman Filter, VESC

In this report the problem of constructing a bus depot with electrical buses despite the lack of grid capacity, was analyzed. A potential solution is investigated, namely smart control of heat pumps in industries. The possibility of allocating grid capacity to the bus depot by reducing power consumption in heat pumps during peak hours, is taken into consideration. The maximum amount of released capacity in an industrial area is calculated through the controlling of heat pumps. This investigation was made through simulations with a simplified building energy model (lumped capacity model) which was applied to a reference building. After mapping the area Boländerna and the geothermal wells located there, IKEA Uppsala was chosen as the reference building, since a third of the total number of wells were found in that area. To take the whole capacity of Boländerna into account, the model was scaled up to estimate the total, possible reduction of power. The bus depot requires 6 MW nighttime and 4 MW daytime, the total amount of electrical power that could be withdrawn, if all heat pumps were on maximum heat, in the chosen area were 0.75 MW and by controlling the heat pumps during an optimized level, the amount of 142 kW could be made available to the electric grid. 142 kW is not enough cover the need for the bus depot but it could supply the need for a slow charger to one of the buses and is therefore a possible sub-solution to the larger problem.