Master of Science (M.S.), University of Dayton, 2015, Mechanical Engineering

An active, feedback vibration control strategy with the goal of abating gear whine noise in rear-wheel and all-wheel drive vehicles is developed. The control strategy was implemented using two small inertial (proof mass) actuators, mounted on the rear subframe of a luxury all-wheel drive sedan with independent rear suspension, as the active elements in this application. Acceleration information measured by accelerometers nearly-collocated with the actuators was used as the feedback signal. The effectiveness of active vibration control was successfully demonstrated by examining the extent of reduction in the shaker induced vibration of the rear subframe as well as the sound pressure inside the vehicle. The evaluation of the active control scheme was extended to rolling dynamometer tests, during which effective reduction of vibration of rear subframe and the pressure inside the vehicle were demonstrated.

Committee: Reza Kashani Ph.D. (Committee Chair); Dave Myszka Ph.D. (Committee Member); David Perkins Ph.D. (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2014, Engineering and Applied Science: Mechanical Engineering

Vibration suppression has application in many industries including aerospace for vibration suppression of flexible bodies, automobile for ride comfort though suspensions, and machining devices for precision tooling. Modal control is implemented in modal space instead of local space. As a result the different modes of a system are controlled independently using parallel controllers. The controllers using modal control being low order and simple controllers are easy to implement. The hardware implementation of the closed loop control is expensive which makes it difficult to study the control theories experimentally for academic purposes. In this thesis, the discrete modal filters are reviewed. An analytical method of modal coordinate extraction from physical response data is studied. This method is validated experimentally on an aluminum beam. A mathematical model for a velocity feedback control of a single mode for a multiple input multiple output system is developed and simulated on MATLAB platform. A low cost closed loop hardware based on Arduino microcontroller is developed for experimental implementation of the control theory. An external ADC and DAC are coupled with the Arduino. The controller is programmed based on the functions developed in C++ language.

Committee: David Thompson Ph.D. (Committee Chair); Randall Allemang Ph.D. (Committee Member); J. Kim Ph.D. (Committee Member) Subjects: Mechanics

Doctor of Philosophy, The Ohio State University, 2014, Mechanical Engineering

The topic of this scholarly research is motivated by the need for superior control of vehicle powertrain vibration, commonly accomplished using 3 or 4 passive mounts. However, emerging design trends (such as higher power density powertrains and lightweight structures) necessitate a hybrid approach utilizing active and passive methods to meet more stringent system performance targets. The chief research objective is to acquire fundamental understanding of dynamic interactions among multiple active and passive paths in a powertrain mounting system for improved control of multi-dimensional motion, in the presence of a rigid frame placed on four bushings. All hybrid paths are assumed to be an actuator in series with an elastomeric mount; and discrete linear time-invariant deterministic systems are assumed with small motions, harmonic excitations, steady state behavior, and no kinematic nonlinear effects. Also, passive elements are assumed massless while active elements possess mass. Additionally, passive torque roll axis motion decoupling concepts are explored to enhance active control capabilities given certain practical constraints. Analytical, computational, and experimental methods are utilized though no real-time control is done. First, the torque roll axis motion decoupling concept is studied in a 12 degree of freedom model of a realistic powertrain and coupled frame. Deficiency of prior literature neglecting the need for a physically realizable system is overcome by deriving improved mount compatibility conditions, implemented in new decoupling paradigms to ensure more realistic mount positions. It is mathematically shown that full decoupling is not possible for a practical system, and partial decoupling paradigms are pursued to ensure that only the powertrain roll motion is dominant. This constitutes as a major contribution. The interaction between hybrid paths is studied next as part of a resonating two path source-path-receiver system with 6 degrees of (open full item for complete abstract)

Committee: Rajendra Singh Dr. (Advisor); Jason Dreyer Dr. (Committee Member); Manoj Srinivasan Dr. (Committee Member); Vishnu Sundaresan Dr. (Committee Member); Vadim Utkin Dr. (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2010, Mechanical Engineering

Smart structures are currently utilized in many applications from precision positioning control of large space structures to active vibration control of machine components. Despite their relative easiness in controlling, positioning accuracy and longevity can be compromised by the hysteresis. In addition, current active control algorithms are limited predominantly to the control of a single or multiple sinusoidal waves and these are incapable of addressing more complicated multi-spectral signals such as modulated signatures. This dissertation introduces model-based and nonlinear control techniques aimed at the reduction of hysteretic effect and for their application to active motion control. A nonlinear energy-based hysteresis model is developed for a piezoelectric stack actuator and model predictive sliding mode control is applied to force the system state to reach a sliding surface in an optimal manner and to accurately track the reference signal. This method is employed on pre-stressed curved unimorph actuators (modeled by a second order differential equation) with an additional time delay term to describe the hysteretic effect. Simulations and experiments are conducted to validate this approach, and the results highlight significantly improved hysteresis reduction in the displacement control mode. Also, it has been verified that the performance of the novel control methods is not much affected by the accuracy of actuator model. Next, enhanced adaptive filtering algorithms are developed with application to active vibration control. A feedback loop with the model predictive sliding mode control is introduced in the adaptive filtering system. The goal of this study is to manage multi-spectral signals while achieving smooth and effective convergence, self-adaptability, and stability. The performance for new adaptive filtering algorithms is validated numerically and experimentally for different signals and other prevailing characteristics. The proposed algorithms are (open full item for complete abstract)

Committee: Gregory Washington PhD (Advisor); Rajendra Singh PhD (Advisor); Vadim Utkin PhD (Committee Member); Marcelo Dapino PhD (Committee Member) Subjects: Engineering

Master of Science (MS), Ohio University, 2012, Civil Engineering (Engineering and Technology)

Many variable stiffness and damping devices have been proposed in an attempt to mitigate the effects of unwanted vibrations in civil engineering structures. This work proposes a novel variable stiffness or damping device called the Continuously Variable Amplification Device (CVAD) that improves upon past limitations. It consists of a sphere and rollers in series with a spring or damper, and is able to produce a large, continuous, and rapidly varying range of stiffness or damping values. A series of relationships and equations are derived and validated to describe the amplification of the device. A numerical simulation is developed that pairs the CVAD with SSASD and RSASD devices and places it in a seismically excited eight story structure in a supplemental damping role. In addition, centralized control laws are created and applied to the CVAD devices. The results demonstrate the device and its centralized control laws are a marked improvement over the state-of-the-art.

Committee: Kenneth Walsh Ph.D (Advisor); Eric Steinberg Ph.D (Committee Member); Deboriah McAvoy Ph.D (Committee Member); Douglas Green Ph.D (Committee Member) Subjects: Civil Engineering

Doctor of Engineering, Cleveland State University, 2008, Fenn College of Engineering

Flywheel energy storage has distinct advantages over conventional energy storagemethods such as electrochemical batteries. Because the energy density of a flywheel rotor increases quadratically with its speed, the foremost goal in flywheel design is to achieve sustainable high speeds of the rotor. Many issues exist with the flywheel rotor operation at high and varying speeds. A prominent problem is synchronous rotor vibration, which can drastically limit the sustainable rotor speed. In a set of projects, the novel Active Disturbance Rejection Control (ADRC) is applied to various problems of flywheel rotor operation. These applications include rotor levitation, steady state rotation at high speeds and accelerating operation. Several models such as the lumped mass model and distributed three-mass models have been analyzed. In each of these applications, the ADRC has been extended to cope with disturbance, noise, and control effort optimization; it also has been compared to various industry-standard controllers such as PID and PD/observer, and is proven to be superior. The control v performance of the PID controller and the PD/observer currently used at NASA Glenn has been improved by as much as an order of magnitude. Due to the universality of the second order system, the results obtained in the rotor vibration problem can be straightforwardly extended to other vibrational systems, particularly, the MEMS gyroscope. Potential uses of a new nonlinear controller, which inherits the ease of use of the traditional PID, are also discussed.

Committee: Paul Lin (Committee Chair) Subjects: Engineering

Doctor of Philosophy, University of Akron, 2005, Engineering

Smart materials are increasingly used in structural control of vibration and wave propagation. Most of existing studies have focused on the vibration control using smart materials in the form of patches or films, and ring-type has seldom been used. There is not much research on control of cylindrical shells using tunable materials. To meet this need, the present study develops theoretical models for adaptively–passive and active control of vibration and wave propagation in cylindrical shells using smart materials. One unique characteristic of shape memory alloy (SMA), i.e., the controllable elastic modulus with respect to temperature, is adopted in adaptively–passive control of vibration; with the capability of providing line circumferential distributed control forces due to their property of piezoelectricity in piezoelectric ceramic materials (e.g., PZT), the ring-type actuators are proposed to actively control the forced vibration response. The cylindrical shells both in vacuo and filled with fluid are investigated, and two different problems are considered: one is the wave propagation and transmission, and the other is the forced vibration response from external excitation. With the controllable elastic modulus of SMA, SMA wall joint has the capability of controlling the vibration source with wide-band frequencies or with a time-varying frequency. With the solution of the characteristics of the free wave propagation from the dispersive equation, the vibration response and characteristics of reflection/transmission from incident wave are investigated by using the wave approach and the method of residues. Numerical simulation indicates that the SMA wall joint has the potential to solve the problem of pass-band, and the transmission loss is more than 20dB for all frequency ranges providing a proper temperature. This SMA wall joint is also adopted to adaptively control the forced vibration response from external excitation. Parametric study demonstrates that the SMA (open full item for complete abstract)

Committee: Pizhong Qiao (Advisor) Subjects: Engineering, Mechanical

Doctor of Philosophy, The Ohio State University, 2017, Civil Engineering

The protection of large infrastructure is a critical and complex issue facing civil engineers. Earthquakes are especially unpredictable and pose a great threat to critical infrastructure that directly affect people's lives. To tackle this problem, the latest innovation is the development of intelligent structures. Intelligent structures have technology installed to dampen the movement caused by forces of nature. The goal is to develop a new generation of smart structures equipped with sensors and control devices that can react in real-time during an earthquake. Structural control methods have been the subject of significant research in the past 20 years but still face limitations. This investigation consists of four parts. In Part I, four ideas are introduced for vibration control of smart structures: decentralized control, agent-based modeling, replicator dynamics from evolutionary game theory, and energy minimization. Two new control algorithms are presented: 1) a single-agent Centralized Replicator Controller (CRC) and a decentralized Multi-Agent Replicator Controller (MARC) for real-time vibration control of smart structures. The use of agents and a decentralized approach enhances the robustness of the entire vibration control system. The proposed control methodologies are applied to vibration control of a 3-story steel frame and a 20-story steel benchmark structure subjected to two sets of seismic loadings: historic earthquake and artificial accelerograms and compared with the corresponding centralized and decentralized conventional control algorithms. In Part II, the aforementioned control algorithms are integrated with a multi-objective optimization algorithm in order to find Pareto optimal values for replicator dynamics parameters with the goal of achieving maximum structural performance with minimum energy consumption. The patented neural dynamic model of Adeli and Park is used to solve the multi-objective optimization problem. Vibration control of irre (open full item for complete abstract)

Committee: Hojjat Adeli (Advisor); Ethan Kubatko (Committee Member); Kevin Passino (Committee Member); Daniel Pradel (Committee Member) Subjects: Civil Engineering

Doctor of Philosophy, The Ohio State University, 2016, Mechanical Engineering

The topic of this scholarly research is the creation of semi-analytical models to predict vibro-acoustic modal characteristics of plate and shell structures with combined active and passive damping treatments. While several damping mechanisms have been historically studied, this research considers only piezoelectric active patches along with constrained layer passive damping patches or a distributed passive damping (cardboard) liner. In particular, this work extends prior literature and presents some novel treatment configurations, in addition to studying interactions between the active and passive mechanisms. The main focus is on the development of a linear time-invariant mathematical framework for steady-state frequency-domain analysis of plates and shells with concurrent active/passive treatments; distinct plate and shell modes (under classical boundaries) are considered while incorporating frequency-dependent material properties. First, a Rayleigh-Ritz model is proposed for concurrent active and passive patches on a thin rectangular plate, where compact passive patches are included as multiple layers and active patches are assumed to provide a control input. Complex eigensolutions are computed for a damped plate structure (using an iterative scheme for spectrally-varying properties) to determine the natural frequencies and modal loss factors. Experimental validation is carried out for the sinusoidal response of the structure given disturbance and control input, after which the effect of the passive damping on active control is assessed. This model is then utilized to analyze a practical transmission casing cover (with bolted edges), to calculate acoustic radiation using the Rayleigh-integral formulation, and to examine a reduced-order Euler beam model for comparative studies at selected modes. Next, the semi-analytical thin plate model is extended to a thin cylindrical shell. In the new theory, a distributed passive damping liner is included and sliding in (open full item for complete abstract)

Committee: Rajendra Singh (Advisor); Daniel Mendelsohn (Committee Member); Chia-Hsiang Menq (Committee Member); Manoj Srinivasan (Committee Member); Jason Dreyer (Committee Member) Subjects: Mechanical Engineering

PhD, University of Cincinnati, 2005, Engineering : Mechanical Engineering

The gear whine problem that widely occurs in power transmission systems is typically characterized by one or more high amplitude tonal acoustic signals. The whine response originates from the vibration of the gear pair system caused by transmission error excitation that arises from tooth profile errors, misalignment and tooth deflections. In very severe cases, the gear vibrations can also reduce life and performance of the power transmission systems. The fundamental gear whine problem has been of interest to many researchers for a very long time. However, most of the work have focused on shaping the gear tooth profiles, adding vibration isolation to the gearbox, and other passive control methods. Effort involving active gearbox vibration control is still quite limited. In fact, other than those papers on the active control of the vibration transmitted through support struts of gearboxes, only a few isolated studies that directly deal with control of gearbox internal components have been seen. Therefore, addressing this research gap is the primary aim of this dissertation study. In this research, a dynamic finite element model is first developed for a power re-circulating gear train system for use to examine the feasibility of applying an active shaft transverse vibration control system near the gear pair in the effort to tackle the gear excitation problem more directly. For this particular actuator setup and gearbox system, a complete set of controller which is based on the FXLMS algorithm combined with improved frequency estimation technique is designed. A series of computational studies are performed to refine the algorithm design and to determine the most suitable parameters. Finally, a series of experimental studies are performed on an actual power re-circulating gearbox system that is equipped with the designed active control system. In some cases, up to 14 dB of reduction in the vibration response can be achieved. Also, the controller is capable of handling up (open full item for complete abstract)

Committee: Dr. Teik Lim (Advisor) Subjects: Engineering, Mechanical

Doctor of Philosophy (Ph.D.), University of Dayton, 2012, Mechanical Engineering

Extensive studies have been carried out, in recent years, to find methods to mitigate the unwanted structure vibration caused by human excitation, machinery, and winds. Modern structures such as floors and bridges using high strength materials, and extending across long spans are very flexible with negligible damping. Vibration control devices and strategies are constantly being developed to eliminate/dissipate the unwanted vibration and to increase the serviceability level of such structures. One such method for abating the vibration is tuned mass damping. In this dissertation, semi-active control of air-suspended tuned mass dampers with pendulum configuration was explored. A novel semi-active Air Sprung PTMD was designed, built, and evaluated, analytically and experimentally. The dynamics and control of such PTMD were evaluated, and its effectiveness was compared with that of the conventional passive PTMD. The main reason for introducing semi-active control to a TMD is to enable the TMD to adapt itself, robustly, to the primary structure's parameters (mainly mass and stiffness) changes and maintain its tuning. Following extensive analytical work, simulation, and experimentation it was found that the velocity feedback can modify the stiffness of the semi-active air-suspended tuned mass damper. Positive velocity feedback increases the stiffness while negative velocity feedback decreases it. Moreover, pressure and the acceleration feedback adjust the damping of the semi-active TMD. The air spring used in this work is of convoluted type. This type of air springs, because of their particular geometry, experiences a rather severe change in their cross-sectional area, as they contract and expand. It was found that to properly account for the impact of this important parameter on the inner-working of the air spring, one needs to consider two areas for the air spring, namely, the effective area and the geometric area. The effective area of the air spring is the area us (open full item for complete abstract)

Committee: Reza Kashani PhD (Committee Chair); Raul Ordonez PhD (Committee Member); Steven Donaldson PhD (Committee Member); Muhammad Usman PhD (Committee Member) Subjects: Mechanical Engineering