Pezhman A. Hassanpour

Design and Implementation of a General Control System Platform

In this study, the design and implementation of a general control system platform for educational purposes was performed. This project has been designed to facilitate the understanding of control systems in mechanical engineering by creating a foundational system to position-control the rotation of a DC motor, and then employing it as a teaching tool in the undergraduate Control Systems course at Loyola Marymount University (LMU). The objective of this effort was to lay the groundwork for a more “hands-on” control systems education at LMU by designing the general mechanical platform and a pilot on-off controller to illustrate its functionality and feasibility in the classroom. With the foundational stages complete, students in future classes will be able to design and build different controllers for this same device in order to investigate and apply their newly-acquired knowledge of control systems.Copyright

Analysis of the Quality Factor and Response Time of Resonant Biosensor

The relationship between the overall damping and response time of resonant biosensors is investigated in this paper. The governing equation of motion is derived using a single degree-of-freedom model of the resonator considering the dynamic effect of adsorption of the measured parameter. It is shown that the adsorption leads to a damping force on the resonant sensor. If not taken into account, this damping force results in misinter-pretation of the sensor readings.Copyright

Reducing Stress Concentration in RF MEMS Switch by Optimizing Serpentine Spring Design

In this paper we present a method of reducing stress concentrations in serpentine beam structures to improve the fatigue life of RF MEMS switches. It was found that slight design modifications to the turning corners of serpentine springs can greatly improve the uniformity of stresses through the structure with minimal negative impact on the original spring constant. Before RF MEMS switches are widely adopted, they must achieve a low actuating voltage and working lives of greater than 10 billion cycles. The sharp turning corners of serpentine springs results in stress concentration creating an area prone to fatigue failure. In this paper, fillets of increasing radius were added to the inner and outer edges of a serpentine spring and the structure analyzed to determine their effect on global maximum stress and effective spring constant of the structure. It was found that adding fillets reduces maximum stress in the structure while redistributing the stress throughout the length of the meander. This results in a more uniform structure without significantly increasing the overall spring constant of the structure.Copyright

Experimental Determination of the Mass Moment of Inertia of a Flywheel Using Dynamics and Statistical Methods

This paper presents the analysis of the mass moment of inertia (MMI) of a flywheel using experiment data. This analysis includes developing two models for determining the MMI of the flywheel. The first model considers the effect of mass moment of inertia only, while the second model takes the effect of friction in the ball bearings into consideration. The experiment results have been used along with both models to estimate the MMI of the flywheel. It has been demonstrated that while the model with no friction can be used for estimating the MMI to some extent, the model with friction produces the most accurate result. On the other hand, an effective application of the model with friction requires several experimental measurements using different standard masses. This translates into more expensive method in terms of experiment time and equipment cost.Copyright

Low Cost Experimental Vibration Analysis of a Cantilever Beam Under Base Excitation

This paper presents the investigation of operational deflection shapes of vibration of a cantilever beam using a low-cost digital video camera, and by application of image processing techniques. The beam is uniform and under base excitation. The analytical model of the system is developed using dimensionless formulation. The analytical ODS’s are derived, and then compared with those found from experiment. The significance of this research is that it provides the researchers an inexpensive alternative tool for investigating the behavior of systems with low-frequency dynamics.Copyright

Nonlinear Forced Vibration of a Beam-Type Resonator With Attached Eccentric Mass

In this paper, the nonlinear model of an asymmetric micro-bridge resonator with an attached eccentric mass is investigated. The resonator is treated using the Euler-Bernoulli beam theory. The attached mass represents the electrostatic comb-drive actuator in micro-electromechanical applications. The center of mass of the actuator is assumed to be off the neutral axis of the beam. The governing equations of motion are derived assuming that a concentrated harmonic force is applied to the attached mass. The nonlinear forced vibration of the system is studied using the method of multiple scales. It has been demonstrated that the eccentricity of the mass may lead to different types of nonlinear resonance, e.g., superharmonic and internal resonance. The end application of the structure under investigation is in resonant sensing and energy harvesting applications.Copyright

Nonlinear Free Vibration of a Beam With Off-Axis Attached Mass

A model of a clamped-clamped beam with an attached lumped mass is presented in this paper. The system is modeled using the Euler-Bernoulli beam theory. In the models presented in literature, it is assumed that the center of mass of the attached mass is located on the neutral axis of the beam. In this paper, this assumption is relaxed. The governing equations of motion are derived. It has been shown that the off-axis center of mass of the attached mass generates an amplitude-dependent transverse force in the beam, which introduces a quadratic nonlinearity. The nonlinear governing equations of motion are solved using the Multiple Scales method. The nonlinear free vibration frequencies are determined.Copyright

Dynamic Analysis of a Beam-Type Resonator With Off-Axis Attached Mass

In this paper, the model of a micro-machined beam-type resonator is presented. The resonator is a micro-bridge which is modeled using Euler-Bernoulli beam theory. A comb-drive electrostatic actuator is attached to the micro-bridge for the excitation/detection of vibrations. In the models presented in the literature, it is assumed that the center of mass of the comb-drive is located on the neutral axis of the beam. In this paper, it is demonstrated that this assumption can not be applied for asymmetric-shaped comb-drives. Furthermore, the governing equations of motion are derived by relaxing the above assumption. It has been shown that the off-axis center of mass of the comb-drive generates an amplitude-dependent transverse force in the beam, which is essentially a nonlinear effect. The governing equations of motion are solved using a hybrid analytical-numerical approach. The end application of the structure under investigation is in resonant sensing and energy harvesting applications.Copyright