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Dynamics and Vibrations
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Sensors based on nonlinear dynamics and active interrogation
Several current micro-sensing technologies are based on vibratory responses, such as bio-chemical detectors (which use mass measurements) and tapping-mode atomic force microscopy. In those technologies, highly nonlinear systems can provide increased sensitivity and selectivity. In that context, we are creating a comprehensive and radically novel sensing paradigm which provides ultra high sensitivity, robustness, as well as multi-functional sensing capabilities (e.g. sensor self-calibration).
MEMS inertial sensor applications and sports training devices
Miniature and wireless MEMS inertial measurement systems to analyze and to teach the fine motor skills required in sports and other applications. For instance, when attached to or embedded in sports equipment, our patented designs enable detailed analysis of athletic performance. To date, developed designs for sports include those for fly fishing, golf (illustration above right), baseball, hockey, bowling, crew and curling. In addition, we are actively extending our concept to support portable gait measurement, knee injury detection and surgical training.
Inverse problems and system identification: modeling and identification of mistuning in bladed disks
Bladed disks such as those found in jet engines are cyclically symmetric structures. However, slight deviations from this symmetry caused by manufacturing, wear, etc. can result in a highly non-symmetric distribution of stresses during the vibration of such systems. Such a phenomenon is also known as vibration localization and leads to extremely high stresses, causing high cycle fatigue and premature failure of the structure. These deviations, known as mistuning, can be identified using reduced-order modeling techniques along with experimental response data. With the mistuning known, more accurate models can be constructed to predict the dynamics of the system (e.g. stresses and aeroelastic responses).
High-sensitivity damage detection in nonlinear systems
Current vibration-based damage detection methods have significant limitations and exhibit low performance when applied to nonlinear and high-dimensional systems. We take a radically different approach, and overcome these existing limitations through the development of robust and highly sensitive nonlinear techniques for identifying the location and level of multiple, simultaneous damages. One of the enabling key advancements is our novel approach for modeling nonlinear systems using augmented linear system models.
Driver behavior has significant effects on emerging multi-vehicle patterns. Analyzing car-following models that incorporate driver reaction time, it can be shown that a single driver can bring vehicular traffic to a halt. When a driver brakes harder than a critical threshold predicted by the theory, he/she creates a ripple that gets amplified as it propagates backward on the chain of vehicles leading to a stop-and-go wave. This nonlinear string instability is responsible for a large fraction of traffic congestion occurring on highways. (Gabor Orosz)
Researchers at the U-M focus on dynamics and vibrations as an integral part of understanding many physical systems and technologies, ranging from MEMS sensors and devices to air and space structures to the development of novel materials. One of the key common elements of all these is the crucial time dependence of the processes governing these systems. For example, the complex dynamics of DNA supercoiling can only be described by accurate dynamic modes which take onto account their dynamic behavior, the identification of mistuning and vibration localization in turbomachinery can only be accomplished through advanced computational dynamics techniques combined with physical measurements, the understanding of the causes for the high sensitivity and resolution of sound detection in the human ear can only be discovered through novel complex and high-fidelity dynamic models.Furthermore, U-M researchers develop novel solutions for a broad range of inverse problems in dynamics (e.g. system identification, sensing and damage detection, acoustic signal processing) which are used in technologies spanning turbomachinery, bio-engineering, naval communications and sonar detection, microphones and MEMS devices. These novel solutions depend on dynamic models and the exploitation of dynamic phenomena. Both applied and fundamental problems in linear and nonlinear dynamics are tackled.
Acoustics, time reversed acoustic processing, vibration
Biological and epidemiological systems, aerospace and automotive structures, and turbomachinery. Research blends novel methods and theory with fundamental experiments in linear and nonlinear dynamics from macro to nano-scale.
Structural acoustics, cochlear mechanics, electroacoustic transducers
Accurate finite element methods for dynamics, phononic material design
Topology optimization for vibration
Topology optimization for vibration characteristics, negative Poisson ration material design
Sustainable manufacturing, vibration control, mechatronics
nonlinear dynamics of complex systems, time-delay systems, connected vehicles, neural networks, gene-regulatory networks
Nonlinear and computational dynamics, dynamics of DNA and DNA-protein interactions, wireless sensors for athlete training and human motion analysis, structural dynamics
Linear and nonlinear vibrations, wave propagation in anisotropic materials
Structural dynamics and vibrations, adaptive material-based systems, structural control and health monitoring