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This paper reports on the early findings of a study that used extremely precise and accurate measurements of shaft rotational position to detect gearbox faults. The basic operation of the magnetic field based, non-contact sensors is... more
This paper reports on the early findings of a study that used extremely precise and accurate measurements of shaft rotational position to detect gearbox faults. The basic operation of the magnetic field based, non-contact sensors is explained. The results show that small rapid variations in the rotational speed (position as a function of time) can be used to reveal gear
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This paper describes a novel design of an indirect-heating thermal actuator with integrated capacitive position sensor. The displacement of the actuator provided by the sensor enables a feedback control capability. The analytical model... more
This paper describes a novel design of an indirect-heating thermal actuator with integrated capacitive position sensor. The displacement of the actuator provided by the sensor enables a feedback control capability. The analytical model and finite element analysis (FEA) are presented to validate the design concept. The devices were fabricated using MetalMUMPs process. The experimental result shows a good agreement with the analytical analysis and the FEA. A proportional-integral (PI) feedback control application with the designed thermal actuator with integrated capacitive position sensor was conducted using the MEMS/FPGA platform and the results are documented.
The development of the hydraulic artificial knee joint controller has significantly improved the quality of life for many amputees. Even though the controller unit is very reliable, gradual deterioration inevitably takes place because the... more
The development of the hydraulic artificial knee joint controller has significantly improved the quality of life for many amputees. Even though the controller unit is very reliable, gradual deterioration inevitably takes place because the unit consists of many moving parts and is subjected to repetitive loads. This paper describes a simple method to test the reliability of hydraulic artificial knee
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The relationship between modal radiation of a short cylindrical shell and that of a corresponding infinite shell is investigated in this paper. This investigation is done in the hope that the findings can improve our understanding of... more
The relationship between modal radiation of a short cylindrical shell and that of a corresponding infinite shell is investigated in this paper. This investigation is done in the hope that the findings can improve our understanding of sound radiation from finite cylindrical shells and subsequently lead to better noise control in MRI gradient coils and other pertinent industry applications.
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ABSTRACT Design and simulation of a new type of tubular steel electro-thermal actuator capable of vertical displacement is presented. The Tubular Thermal Actuator (TTA) consists of several multiple cascaded chevron-shaped structures,... more
ABSTRACT Design and simulation of a new type of tubular steel electro-thermal actuator capable of vertical displacement is presented. The Tubular Thermal Actuator (TTA) consists of several multiple cascaded chevron-shaped structures, which are connected together by a top ring, as a platform to carry vertical displacement. The TTA is made from a 20 μm thick steel tube with an outer diameter of 1mm by laser micromachining technology. A finite element model was developed to simulate the behavior of the actuator and study the dominant heat transfer mode at this scale. The actuator could generate more than 7 μm linear motion and 2 mN forces at the top ring. In order to avoid operating the tubular actuator at its natural resonant frequencies, modal analysis has also been conducted.
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... Zili Zhou, Chris K. Mechefske, Fengfeng Xi. Abstract. ... To do so, a nonstationary model is developed using the elasto-dynamics method. First, a kinematic model is built based on rigid links and ideal joints, which is used to solve... more
... Zili Zhou, Chris K. Mechefske, Fengfeng Xi. Abstract. ... To do so, a nonstationary model is developed using the elasto-dynamics method. First, a kinematic model is built based on rigid links and ideal joints, which is used to solve the PKM nominal motion. ...
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This paper documents progress on a project whose objective is to improve the performance of a machine vision based parts inspection system through the development and testing of robust neuro-fuzzy based algorithms. An inspection problem... more
This paper documents progress on a project whose objective is to improve the performance of a machine vision based parts inspection system through the development and testing of robust neuro-fuzzy based algorithms. An inspection problem faced by a Canadian automotive parts manufacturer is being used as a case study. The problem involves a vision system that is being used to
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This paper describes a novel design for polysilicon micro ring thermal actuators (RTA) fabricated using the multi-user-MEMS-process (MUMPs). A RTA is comprised of a ring supported by 12 thin spokes. The spokes are 2×2μm in cross section... more
This paper describes a novel design for polysilicon micro ring thermal actuators (RTA) fabricated using the multi-user-MEMS-process (MUMPs). A RTA is comprised of a ring supported by 12 thin spokes. The spokes are 2×2μm in cross section and 155μm long. The inner diameter of the ring is 390μm, and its outer diameter is 440μm. The spokes are placed almost radially
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Ongoing development of magnetic resonance imaging (MRI) technology leads to high magnetic field strength (up to 7-9 T) and high-speed switching current in gradient coils for the purpose of improving MRI image quality. These two factors... more
Ongoing development of magnetic resonance imaging (MRI) technology leads to high magnetic field strength (up to 7-9 T) and high-speed switching current in gradient coils for the purpose of improving MRI image quality. These two factors among others contribute largely to the high levels of structure-borne noise that surrounds current MRI scanners. In this paper, the forcing function and distribution acting on gradient coils are described (gradient coils x, y and z). Single point forces and vibration responses of harmonic, transient and impulsive excitations are investigated. Modal expansion method is used to predict the whole cylinder vibration of a thin-walled model under these excitations. Experimental testing of a thin-walled model and a single-layered gradient coil is done by using National Instruments PXI. The measured whole- body radial vibration modes show an agreement with the analytical results. This agreement indicates that modal expansion method could be used to predict th...
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A new method, called Kinetostatic Modelling Method is proposed for analysis of parallel kinematic machines (PKMs) in the paper. First, system modelling includes mobility study, kinematic model and inverse kinematic is conducted. Then,... more
A new method, called Kinetostatic Modelling Method is proposed for analysis of parallel kinematic machines (PKMs) in the paper. First, system modelling includes mobility study, kinematic model and inverse kinematic is conducted. Then, kinetostatic modelling is presented. It includes ...
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Abstract In this paper, the optimum design of parallel kinematic toolheads is implemented using genetic algorithms with the consideration of the global stiffness and workspace volume of the toolheads. First, a complete kinetostatic model... more
Abstract In this paper, the optimum design of parallel kinematic toolheads is implemented using genetic algorithms with the consideration of the global stiffness and workspace volume of the toolheads. First, a complete kinetostatic model is developed which includes ...
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... model order selection technique based on goodness-of-fit tests for robust condition detection ... A sufficient and justifiable evaluation can be obtained by examining these three properties. ... was constructed to provide data on a... more
... model order selection technique based on goodness-of-fit tests for robust condition detection ... A sufficient and justifiable evaluation can be obtained by examining these three properties. ... was constructed to provide data on a commercial transmission as its health progresses from ...
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Research Interests: Mechanical Engineering, Civil Engineering, Signal Processing, Time Series, Modeling, and 18 moreSynchronization, Vibration, Signal Analysis, Time-Frequency Analysis, Measurement, Fault diagnosis, Regression Analysis, Time Frequency Analysis, Experimental Study, Transfer Function, Sensorimotor synchronisation, Moving average, Interdisciplinary Engineering, ARMA model, Transient Response, Adaptive Algorithm, Time Series Model, and Autoregressive model
... Japkowicz [6] used an autoencoder neural network to detect faults in gearboxes. ... Several types of neural networks have been proposed for novelty detection including Autoassociators [6 ... A control system was created using a... more
... Japkowicz [6] used an autoencoder neural network to detect faults in gearboxes. ... Several types of neural networks have been proposed for novelty detection including Autoassociators [6 ... A control system was created using a National Instruments PXI chassis and analogue input ...
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A comprehensive experimental study has been conducted to investigate the possibilities of using micro-perforated panel (MPP) acoustic absorbers in magnetic resonance imaging (MRI) scanners. The experimental acoustic measurements include... more
A comprehensive experimental study has been conducted to investigate the possibilities of using micro-perforated panel (MPP) acoustic absorbers in magnetic resonance imaging (MRI) scanners. The experimental acoustic measurements include measurements in an impedance tube, measurements in an MRI scanner bore mock-up, and in situ measurements in an actual MRI scanner. The experimental results are in good agreement with theoretical calculations. This study confirms that MPP acoustic absorbers have multiple absorption frequency bands and wider frequency bands at higher frequency ranges when they are used in cylindrically shaped ducts such as MRI scanner bores. It has also been found that the acoustic noise level in the scanner bore is significantly increased when the air gap depth behind the MPP is too large. This study shows that an MPP absorber, when properly designed, is effective in reducing the acoustic noise in MRI scanners. And, when designing an MPP absorber for MRI scanners, the air gap depth should be carefully considered.
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The objective of this paper is to find the relatively low-frequency (200-2,000 Hz) mode shapes of a single-winding gradient coil cylinder with intermediate wall thickness. The dynamic behavior of a gradient coil cylinder plays a crucial... more
The objective of this paper is to find the relatively low-frequency (200-2,000 Hz) mode shapes of a single-winding gradient coil cylinder with intermediate wall thickness. The dynamic behavior of a gradient coil cylinder plays a crucial role in determining and controlling the vibroacoustic performance of magnetic resonance imaging (MRI) scanners. Modal analyses of the gradient coil cylinder were carried out under different boundary conditions to obtain the various mode shapes. Theoretical modes, predicted by using modified Love's governing equations, and numerical modes simulated using a finite element method show close agreement with experimental modal results and reveal the mode shapes for both free-end and fixed-end boundary conditions. These results were further compared to in situ measurements of the mode shapes of the gradient coil cylinder insert during scanning in a 4 Tesla MRI. The general agreement among the analytical, numerical, and experimental mode shapes indicates that a linear combination of basic beam vibration and ring vibration patterns occupy the dynamic vibration modes in the low frequency range. The in situ vibration measurements show that the forcing function developed by the distributed Lorentz forces on the surface of the single-winding gradient coil results in predominantly beam-type bending mode patterns in the low frequency range.
Research Interests: Computer Aided Design, Magnetic Resonance Imaging, Finite element method, Multidisciplinary, Low Frequency, and 12 moreTransducers, Dynamic Analysis, Experimental Modal Analysis, Theoretical Models, Analytical Model, Numerical Model, Reproducibility of Results, Lorentz Force, Boundary Condition, Sensitivity and Specificity, Equipment Design, and Equipment Failure Analysis
Both the acoustic and magnetic fluctuation frequency response functions for a Siemens AS25 body gradient coil inside a 4 Tesla whole-body MR system were measured and analyzed in this study. In an attempt to correlate the acoustic noise... more
Both the acoustic and magnetic fluctuation frequency response functions for a Siemens AS25 body gradient coil inside a 4 Tesla whole-body MR system were measured and analyzed in this study. In an attempt to correlate the acoustic noise inside the gradient coil with magnetic field oscillations, triangular and trapezoidal gradient impulses of varying amplitudes and widths were used to excite the gradient coil. The acoustic and magnetic responses to these inputs were measured. The results show the existence of discrete resonances in both acoustic and uniform magnetic field fluctuation spectra, while gradient magnetic field fluctuation spectra show no such resonances. In addition, the dominant amplitude peaks in spectra fluctuate similarly with respect to trapezoidal gradient impulse flat-top widths. This implies that these phenomena are correlated, and that the trapezoidal impulse flat-top width may be used as a way to suppress both acoustic noise and uniform magnetic field oscillations.
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Research Interests: Engineering, Biomechanics, Modeling, Modal Analysis, Low Frequency, and 13 moreImage Quality, Structural Analysis, Whole Body Vibration, VIBRATION ANALYSIS, Physical sciences, Sound and Vibration, Structural Acoustics, High Speed, Experimental Tests, Transient Response, Nuclear Magnetic Resonance Imaging, Coil, and Whole Body
ABSTRACT Viscoelastic damping material attached on the surface of a structure is widely used to suppress the resonance vibration in aerospace, automobiles, and various other applications. A full treatment of damping material is not an... more
ABSTRACT Viscoelastic damping material attached on the surface of a structure is widely used to suppress the resonance vibration in aerospace, automobiles, and various other applications. A full treatment of damping material is not an effective method because the damping effect is not significantly increased compared to that obtained by an effective partial damping treatment. In addition, the weight of the structure is increased significantly, which can cause poor system performance. Topology optimization is recently implemented in order to find an effective optimal damping treatment. The objective function is maximization of the damping effect (i.e. the modal loss factor) and the constraint is a maximum allowable volume of damping material. In this paper we compare the modal loss factors obtained by topology optimization to the ones obtained by other approaches, in order to determine which approach provides a better damping treatment (i.e. higher value of the modal loss factor). As a result, topology optimization provides about up to 61.14 per cent higher modal loss factor, as confirmed by numerical example. The numerical model for finite element analysis and topology optimization is also experimentally validated by comparing the numerical results to the experimental modal loss factors.
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A new planar micro electrothermal actuator capable of bidirectional rotation is presented. The ring thermal actuator has a wheel-like geometry with eight arms connecting an outer ring to a central hub. Thermal expansion of the arms... more
A new planar micro electrothermal actuator capable of bidirectional rotation is presented. The ring thermal actuator has a wheel-like geometry with eight arms connecting an outer ring to a central hub. Thermal expansion of the arms results in a rotation of the outer ring about its center. An analytical model is developed for the electrothermal and thermal-mechanical aspects of the
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... The above analysis indicates that the clearance control of the joints in design and manufacturing is important. ... A vibration analysis model and the modeling method are presented for a fully flexible 3PRS manipulatora sliding-leg... more
... The above analysis indicates that the clearance control of the joints in design and manufacturing is important. ... A vibration analysis model and the modeling method are presented for a fully flexible 3PRS manipulatora sliding-leg tripod with flexible links and joints. ... J. Robot. ...
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In this paper, a new method for optimal calibration of parallel kinematic machines (PKMs) is presented. The basis of the methodology is to exploit the least error sensitive regions in the workspace to yield optimal calibration. To do so,... more
In this paper, a new method for optimal calibration of parallel kinematic machines (PKMs) is presented. The basis of the methodology is to exploit the least error sensitive regions in the workspace to yield optimal calibration. To do so, an error model is devel- oped that takes into consideration all the geometric errors due to imprecision in manu- facturing and
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High-field, high-speed Magnetic Resonance Imaging (MRI) generates high sound levels within and nearby the scanner. The mechanism and process that produces the gradient magnetic field (a cylindrical electro-magnet, called the gradient coil... more
High-field, high-speed Magnetic Resonance Imaging (MRI) generates high sound levels within and nearby the scanner. The mechanism and process that produces the gradient magnetic field (a cylindrical electro-magnet, called the gradient coil cylinder, which produces a spatially and temporally varying magnetic field inside a static background magnetic field) is the primary source of this noise. This noise can cause difficulties in verbal communication in and around the scanner, heightened patient anxiety, temporary hearing loss and possible permanent hearing impairment for health care workers and patients. In order to effectively suppress the sound radiation from the gradient coil cylinder the sound field within and nearby the gradient coil needs to be characterized This characterization may be made using an analytical solution of the sound pressure field, computational simulation, measurement analysis or some combination of these three methods. This paper presents the computational simulation and measurement results of a study of the sound radiation from a head and neck gradient coil cylinder within a 4 Tesla MRI whole body scanner. The measurement results for the sound pressure level distribution along the centerline of the gradient coil cylinder are presented. The sound pressure distributions predicted from Finite Element Analysis of the gradient coil movement during operation and subsequent Boundary Element Analysis of the sound field generated are also presented. A comparison of the measured results and the predicted results shows close agreement. Because of the extremely complex nature of the analytical solution for the gradient coil cylinder, a treatment of the analytical solution and comparison to the computational results for a simple cylinder vibrating in a purely radial direction are also presented and also show close agreement between the two methods thus validating the computational approach used with the more complex gradient coil cylinder.
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ABSTRACT In this paper, we describe a condition classification technique designed to detect fault occurrence in an automotive light assembly during endurance testing. Inputs to the classifier are features extracted from vibration... more
ABSTRACT In this paper, we describe a condition classification technique designed to detect fault occurrence in an automotive light assembly during endurance testing. Inputs to the classifier are features extracted from vibration measurement data. They contain time domain parameters and frequency band energy parameters calculated using wavelet packet transforms. A support vector machine with Gaussian radial basis function kernel is designed for multiclass classification. A multiplex parameter estimation is achieved by searching for a minimum bound of the support vector count to achieve structural risk minimization. Through experiments, we show that the combination of effective feature extraction and classification with good generalization capability allows the proposed condition-monitoring system to be accurate and reliable. Additionally, acoustic signals known to have low signal to noise ratio are used as tests. We show that with the proposed methodology, acoustic signals can be used with increased sensitivity and accuracy for condition-monitoring purposes.