Broadband excitation in the system identification of active magnetic bearing rotor systems

One of the targets of the climate and energy package of the European Union is to increase the energy efficiency in order to achieve a 20 percent reduction in primary energy use compared with the projected level by 2020. The energy efficiency can be improved for example by increasing the rotational speed of large electrical drives, because this enables the elimination of gearboxes leading to a compact design with lower losses. The rotational speeds of traditional bearings, such as roller bearings, are limited by mechanical friction. Active magnetic bearings (AMBs), on the other hand, allow very high rotational speeds. Consequently, their use in large medium- and high-speed machines has rapidly increased. An active magnetic bearing rotor system is an inherently unstable, nonlinear multiple-input, multiple-output system. Model-based controller design of AMBs requires an accurate system model. Finite element modeling (FEM) together with the experimental modal analysis provides a very accurate model for the rotor, and a linearized model of the magneticactuators has proven to work well in normal conditions. However, the overall system may suffer from unmodeled dynamics, such as dynamics of foundation or shrink fits. This dynamics can be modeled by system identification. System identification can also be used for on-line diagnostics. In this study, broadband excitation signals are adopted to the identification of an active magnetic bearing rotor system. The broadband excitation enables faster frequency response function measurements when compared with the widely used stepped sine and swept sine excitations. Different broadband excitations are reviewed, and the random phase multisine excitation is chosen for further study. The measurement times using the multisine excitation and the stepped sine excitation are compared. An excitation signal design with an analysis of the harmonics produced by the nonlinear system is presented. The suitability of different frequency response function estimators for an AMB rotor system are also compared. Additionally, analytical modeling of an AMB rotor system, obtaining a parametric model from the nonparametric frequency response functions, and model updating are discussed in brief, as they are key elements in the modeling for a control design. Theoretical methods are tested with a laboratory test rig. The results conclude that an appropriately designed random phase multisine excitation is suitable for the identification of AMB rotor systems.

Efficiency of water use in sunflower grown in hydroponic system under saline stress

In order to identify alternatives for the use of saline water in agricultural production, the effects of the use of brackish water in the preparation of the nutrient solution for the cultivation of sunflower (cv. EMBRAPA 122-V2000) were studied in hydroponic system on consumption and efficiency of water use for the production of achenes and biomass. A completely randomized design was used, analyzed in a 5x2 factorial scheme with three replications. The factors studied were five levels of salinity of nutrient solution (1.7 - control; 4.3; 6.0; 9.0; and 11.5dS m-1) and two plant densities - one or two plants per vessel. It was concluded that the water consumption of sunflower is a variable sensitive to the salinity of the nutrient solution, especially after the fourth week of crop, and that the efficiency of water use in the production of achenes and biomass of sunflower is greater when the plant density increases from one to two plants per vessel, even under saline stress.

Pipework data in design system integration

This thesis work describes the creation of a pipework data structure for design system integration. Work is completed in pulp and paper plant delivery company with global engineering network operations in mind. User case of process design to 3D pipework design is introduced with influence of subcontracting engineering offices. Company data element list is gathered by using key person interviews and results are processed into a pipework data element list. Inter-company co-operation is completed in standardization association and common standard for pipework data elements is found. As result inter-company created pipework data element list is introduced. Further list usage, development and relations to design software vendors are evaluated.

Variable speed drive in fan system monitoring

Fan systems are responsible for approximately 10% of the electricity consumption in industrial and municipal sectors, and it has been found that there is energy-saving potential in these systems. To this end, variable speed drives (VSDs) are used to enhance the efficiency of fan systems. Usually, fan system operation is optimized based on measurements of the system, but there are seldom readily installed meters in the system that can be used for the purpose. Thus, sensorless methods are needed for the optimization of fan system operation. In this thesis, methods for the fan operating point estimation with a variable speed drive are studied and discussed. These methods can be used for the energy efficient control of the fan system without additional measurements. The operation of these methods is validated by laboratory measurements and data from an industrial fan system. In addition to their energy consumption, condition monitoring of fan systems is a key issue as fans are an integral part of various production processes. Fan system condition monitoring is usually carried out with vibration measurements, which again increase the system complexity. However, variable speed drives can already be used for pumping system condition monitoring. Therefore, it would add to the usability of a variablespeed- driven fan system if the variable speed drive could be used as a condition monitoring device. In this thesis, sensorless detection methods for three lifetime-reducing phenomena are suggested: these are detection of the fan contamination build-up, the correct rotational direction, and the fan surge. The methods use the variable speed drive monitoring and control options for the detection along with simple signal processing methods, such as power spectrum density estimates. The methods have been validated by laboratory measurements. The key finding of this doctoral thesis is that a variable speed drive can be used on its own as a monitoring and control device for the fan system energy efficiency, and it can also be used in the detection of certain lifetime-reducing phenomena.

Eucalyptus growth in silvopastoral system under different crown dia meters

The aim of this study was to evaluate the effect of different crown diameters on the early growth of eucalyptus intercropped with Brachiaria decumbens in a silvopastoral system. The experiment was conducted in a B. decumbens established pasture, where hybrid eucalyptus urograndis (clone GG100) was planted, spaced 8 x 3 m. A randomized block design was used, with six replicates. Treatments consisted of five crown diameters (0.0, 1.0, 1.5, 2.0, and 3.0 m) surrounding the eucalyptus plants. Five weeding hoes were performed throughout the experiment, according to the different crown diameters, aiming to maintain the eucalyptus plants free from B. decumbens interference. At 90, 180, 270, and 360 DAP, the height and the diameter of the eucalyptus plants were evaluated, and at 360 DAP, surface biomass and leaf area were evaluated. At 90 DAP, it was verified that the non-weeded plants had lower growth, compared to those submitted to crowns. Crown diameters of 2.51 and 2.64 m allowed greater growth in height and diameter at ground level of eucalyptus plants, respectively, in all periods evaluated. Biomass production and leaf area per plant at 360 DAP were also influenced by the different crown diameters. It was concluded that crown diameter around 2 meters provided favorable conditions for early growth of eucalyptus and less involvement in the area occupied by forage.

Study of the application of the high performance liquid chromatography-particle beam interface-mass spectrometry technique on some pesiticides and the reduction phenomena in the system

This work includes two major parts. The first part of the work concentrated on the studies of the application of the highperfonnance liquid chromatography-particle beam interface-mass spectrometry system of some pesticides. Factors that have effects on the detection sensitivity were studied. The linearity ranges and detection limits of ten pesticides are also given in this work. The second part of the work concentrated on the studies of the reduction phenomena of nitro compounds in the HPLC-PB-MS system. Direct probe mass spectrometry and gas chromatography-mass spectrometry techniques were also used in the work. Factors that have effects on the reduction of the nitro compounds were studied, and the possible explanation is proposed. The final part of this work included the studies of reduction behavior of some other compounds in the HPLC-PB-MS system, included in them are: quinones, sulfoxides, and sulfones.

Development of Bioreactors for Nitrifying Water In Closed System Hatcheries Of Penaeid And Non-Penaeid Prawns

In the present study the development of bioreactors for nitrifying water in closed system hatcheries of penaeid and non-penaeid prawns. This work is an attempt in this direction to cater to the needs of aquaculture industry for treatment and remediation of ammonia and nitrate in penaeid and non-penaeid hatcheries, by developing nitrifying bacteria allochthonous to the particular environment under consideration, and immobilizing them on an appropriately designed support materials configured as reactors. Ammonia toxicity is the major limiting factors in penaeid and non-penaeid hatchery systems causing lethal and sublethal effects on larvae depending on the pH values. Pressing need of the aquaculture industry to have a user friendly and economically viable technology for the removal of ammonia, which can be easily integrated to the existing hatchery designs without any major changes or modifications. Only option available now is to have biological filters through which water can be circulated for the oxidation of ammonia to nitrate through nitrite by a group of chemolithotrophs known as nitrifying bacteria. Two types of bioreactors have been designed and developed. The first category named as in situ stringed bed suspended bioreactor(SBSBR) was designed for use in the larval rearing tanks to remove ammonia and nitrite during larval rearing on a continuous basis, and the other to be used for nitrifying freshly collected seawater and spent water named as ex situ packed bed bioreactior(PBBR). On employing the two reactors together , both penaeid and non-penaeid larval rearing systems can be made a closed recirculating system at least for a season. A survey of literature revealed that the in situ stringed bed suspended reactor developed here is unique in its design, fabrication and mode of application.

Hysteresis in a system driven by either generalized force or displacement variables: martensitic phase transition in single-crystalline Cu-Zn-Al

We report on experiments aimed at comparing the hysteretic response of a Cu-Zn-Al single crystal undergoing a martensitic transition under strain-driven and stress-driven conditions. Strain-driven experiments were performed using a conventional tensile machine while a special device was designed to perform stress-driven experiments. Significant differences in the hysteresis loops were found. The strain-driven curves show reentrant behavior yield point which is not observed in the stress-driven case. The dissipated energy in the stress-driven curves is larger than in the strain-driven ones. Results from recently proposed models qualitatively agree with experiments.

Studies in molecular mechanics using spectroscopic data exact force field and bond in homogeneity

This thesis deals with some studies in molecular mechanic using spectroscopic data. It includes an improvement in the parameter technique for the evaluation of exact force fields, the introduction of a new and simple algebraic method for the force field calculation and a study of asymmetric variation of bonding forces along a bond.

Studies in molecular spectroscopy

This thesis is divided into two parts. The first part deals with some studies in molecular mechanics Using spectroscopic data and has four chapters in it. Certain approximation methods for the evaluation of molecular force fields are herein developed The second part, which consists of the last two chaptcrs, deals with infrared spectral studies of ternary liquid systems and a polymer film prepared by glow discharge method.