The prediction of vibration in large electric machines

This thesis reports the development of a reliable method for the prediction of response to electromagnetically induced vibration in large electric machines. The machines of primary interest are DC ship-propulsion motors but much of the work reported has broader significance. The investigation has involved work in five principal areas. (1) The development and use of dynamic substructuring methods. (2) The development of special elements to represent individual machine components. (3) Laboratory scale investigations to establish empirical values for properties which affect machine vibration levels. (4) Experiments on machines on the factory test-bed to provide data for correlation with prediction. (5) Reasoning with regard to the effect of various design features. The limiting factor in producing good models for machines in vibration is the time required for an analysis to take place. Dynamic substructuring methods were adopted early in the project to maximise the efficiency of the analysis. A review of existing substructure- representation and composite-structure assembly methods includes comments on which are most suitable for this application. In three appendices to the main volume methods are presented which were developed by the author to accelerate analyses. Despite significant advances in this area, the limiting factor in machine analyses is still time. The representation of individual machine components was addressed as another means by which the time required for an analysis could be reduced. This has resulted in the development of special elements which are more efficient than their finite-element counterparts. The laboratory scale experiments reported were undertaken to establish empirical values for the properties of three distinct features - lamination stacks, bolted-flange joints in rings and cylinders and the shimmed pole-yoke joint. These are central to the preparation of an accurate machine model. The theoretical methods are tested numerically and correlated with tests on two machines (running and static). A system has been devised with which the general electromagnetic forcing may be split into its most fundamental components. This is used to draw some conclusions about the probable effects of various design features

3D CRANE SYSTEM

This is a research and analysis project on studying the 3D Crane System. The 3D Crane System is widely used for industrial purposes to move cargo, goods and supplies. But one of the problems is when the payload/pendulum is swinging too oscillatory. Thus, it could give the impact on the safety of personnel who controlling the crane and public servant around the crane area. The goals of this project are to analyse and study the dynamic behavior of 3D Crane System and to design and test a control strategy to improve the performance of the crane system. Through this project, the performance of the crane system is measured in terms of stability of the crane especially on the pendulum oscillation and accuracy of the crane movement to the desired position. In this project, only one control strategy had been designed, which is tuning the PID controller parameters. Thus, tuning the PID parameters expected to reduce the oscillatory of the payload and improving the performance of the crane system. Some tuning methods analysis had been used in order to obtain the tuning parameters of PID controller which are Ziegler Nichols Method and Ciancone Correlations Tuning Method. To obtain the PID tuning parameters, many experiments had been done by varying the gain to obtain the best response (constant amplitude). From the response, using the tuning method, the tuning parameters for PID controller is obtained. All the tuning parameters for each axis obtained were set into respective PID controller and combined it into 3 axis controller. The final response shows the response from actual cart position from 3 axis and response of angle payload in x and y axis. Conclude that, the objective of this project is met where the performance of the response of cart position and angle of payload is better compare before undergoing the tuning PID controller. The scopes of this project include literature review on 3D crane system and Matlab simulation by varying PID tuning parameters. The purpose of this simulation is to see the response curve based on tuning parameters obtained and compare with the response curve before the PID is tuned. Therefore, the performance of the crane system can be observed either better or not

Cuff-less continuous blood pressure monitoring system using pulse transit time techniques

This paper describes the development of a continuous cuff-less blood pressure system based on the pulse transit time (PTT) technique. In this study, PTT is defined by two different approaches denoted as PTT1 and PTT2. PTT1 is the time difference between the R-wave peak of the Electrocardiogram (ECG) and the peak of the Photoplethysmogram (PPG). PTT2 is the time difference between two peak PPG signals on same cardiac cycle at different positions on the body. The ECG is acquired on the chest using 3 lead electrodes and a reflection mode optical sensor is deployed on brachial artery and fingertip to monitor the PPGs. These data were synchronized using a National Instruments data acquisition card along with Matlab software for subsequent analysis. A wrist-type cuff-based blood pressure device was used to measure blood pressure on the right hand. Brachial blood pressure was measured on the upper left arm using oscillometric blood pressure monitor. Experiments were conducted by elevating the right hand at different position to investigate variability of PTT under the effects of hydrostatic pressure. Next the variability of PTT due to blood pressure changes during a Valsalva maneuver was investigated. The result shows that the PTT1 is inversely proportional to blood pressure in both experiments. Meanwhile, there is weak correlation between PTT2 and blood pressure measurement which suggests that by excluding the pre-ejection period (PEP) time in PTT calculation may reduce the accuracy of PTT for blood pressure measurement. In conclusion, PTT measurement between ECG and PPG signals has potential to be a reliable technique for cuff-less blood pressure measurement

Correlating low energy impact damage with changes in modal parameters: a preliminary study on composite beams

This paper is an experimental study of the effects of multi-site damage on the vibration response of a composite beam damaged by low energy impact. The variation of the modal parameters with different levels of impact energy and density of impact is studied. Specimens are impacted symmetrically in order to induce a global rate of damage. A damage detection tool Damage Index is introduced in order to verify the estimation of damping ratios. Design of Experiments is used to establish the sensitivity of both energy of impact and density of damage. The DOE analysis results (using natural frequency only) indicate that impact energy for 2nd, 3rd and 4th bending modes is the most significant factor contributing to the changes in the modal parameters for this kind of symmetrical dynamic test

Dynamic Behaviour of Flat Post-Tensioned Floor Plates

Vibration is a serviceability limit state for the design of suspended floor systems in buildings that is not well understood by many structural engineers. Dynamic behaviour is an important design consideration for slender, two-way floors, particularly for those of post-tensioned concrete construction. At present, there are no reliable design guidelines that deal with this problem. This paper describes a research program on the dynamic behaviour of posttensioned concrete floors that is presently underway at Queensland University of Technology in Brisbane, Australia. Results from this research will enable the development of much needed design guidance on the dynamic behaviour post-tensioned concrete floors in buildings. A full-scale, post-tensioned slab specimen has been constructed in the university’s structural laboratory. Purpose-designed support brackets have been fabricated which have enabled an investigation on the effects of various support conditions at the corners of the specimen. A series of static and dynamic tests are being performed in the laboratory to obtain basic material properties and behavior of the specimen. Data collected from these experiments will be used to tune finite element models for computational, parametric studies. Preliminary finite element analyses of both composite and homogeneous material cross-sections have been calibrated against results from initial laboratory experiments. Further field instrumentation and testing of floors in existing buildings will be conducted to validate computational studies. These computational studies will be expanded to generate predictive guidelines for the free vibration and response of two-way, post-tensioned concrete floors

Piezoelectric vibration energy harvesting from airflow in HVAC (Heating Ventilation and Air Conditioning) systems

This study focuses on the design and wind tunnel testing of a high efficiency Energy Harvesting device, based on piezoelectric materials, with possible applications for the sustainability of smart buildings, structures and infrastructures. The development of the device was supported by ESA (the European Space Agency) under a program for the space technology transfer in the period 2014-2016. The EH device harvests the airflow inside Heating, Ventilation and Air Conditioning (HVAC) systems, using a piezoelectric component and an appropriate customizable aerodynamic appendix or fin that takes advantage of specific airflow phenomena (vortex shedding and galloping), and can be implemented for optimizing the energy consumption inside buildings. Focus is given on several relevant aspects of wind tunnel testing: different configurations for the piezoelectric bender (rectangular, cylindrical and T-shaped) are tested and compared, and the effective energy harvesting potential of a working prototype device is assessed

Significance of low energy impact damage on modal parameters of composite beams by design of experiments

This paper presents an experimental study on the effects of multi-site damage on the vibration response of composite beams damaged by low energy impacts around the barely visible impact damage limit (BVID). The variation of the modal parameters with different levels of impact energy and density of damage is studied. Vibration tests have been carried out with both burst random and classical sine dwell excitations in order to compare that which of the methods among Polymax and Half Bandwidth Method is more suitable for damping estimation in the presence of damage. Design of experiments (DOE) performed on the experimental data show that natural frequency is a more sensitive parameter for damage detection than the damping ratio. It also highlighted energy of impact as the factor having a more significant effect on the modal parameters. Half Bandwidth Method is found to be unsuitable for damping estimation in the presence of damage

Experimental studies of the resultant contact forces in drillbit-rock interaction

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