Tag: nonlinear dynamics
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Multibody simulation of medieval mechanical clock
Background and MotivationThe verge-and-foliot escapement is among the earliest mechanical regulation mechanisms, yet its motion and timekeeping performance remain challenging to predict quantitatively because the device operates through intermittent contact between the crown wheel teeth and the pallets mounted on the verge. From an engineering standpoint, this makes the system highly sensitive to geometry, inertia
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Non-linear analysis of powertrain torsional vibration accounting for backlash
This thesis investigates the non-linear torsional vibration behavior of automotive powertrains, explicitly accounting for backlash effects in transmission components. A lumped-parameter dynamic model is developed to represent dead-zone non-linearities, intermittent contact, and impact phenomena. Time- and frequency-domain analyses are performed to study the influence of operating conditions, torque excitation, and system parameters on the dynamic
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Mechanical nonlinearities (Geometric or Contact) in inertial MEMS sensors
Mechanical nonlinearities play an important role in inertial MEMS sensors and cannot be avoided. The trend to push the performance to the limits caused second-order nonlinear effects to become a critical phenomenon that must be considered: these effects are already visible and characterized on mass production devices. External shocks and vibrations could also induce other
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Experimental characterization of nonlinear motion of MEMS resonators
Mechanical nonlinearities play an important role in inertial MEMS sensors, in particular due to geometrical and process constraints. The trend to push the performance to the limits caused second-order nonlinear effects to become a critical phenomenon that must be taken into account: these effects are already visible and characterized on mass production devices. Several methods
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SSM-enhanced Control-Based Continuation (CBC)
In this project we aim to experimentally determine the backbone and the frequency response of a system using Control Based Continuation. CBC consists, loosely speaking, in creating a phase controller (PLL, Phase-Locked Loop) to lock a system at resonance (90°) and then extract the backbone by increasing the forcing with continuation algorithms, typical of numerical
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Contact dynamics in inertial MEMS sensors
Nowadays, mechanical robustness is a key spec for inertial MEMS sensors. The contacts occurring in silicon structures are a relevant problem that may generate dangerous particles or even cause the breakage of the MEMS sensor. Despite these critical phenomena impacting the sensor’s manufacturing and lifetime functionality, the modeling approaches currently adopted are too simplified. The
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Substructuring techniques and pROMs for the optimization of a MEMS voice recognition device
This thesis aims to develop strategies to alleviate the computational burden of optimising a novel, purely mechanical voice recognition device. The device is composed of many repeated cells, each slightly varied through parametric optimisation of a high-fidelity finite element model with millions of degrees of freedom. Direct simulation of such models is computationally prohibitive, making
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Optimization of systems with Internal Resonances
MEMS design is usually done following linear vibration theory, however, their real behavior often turns out to be nonlinear. To address this issue, our group developed optimization algorithms to target backbone curves, which are striclty connected to the nonlinearity of the vibration modes. As of now, the backbone computation can target only a single mode.
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Topology Optimization in nonlinear dynamics
Topology optimization techniques for the design of MEMS devices in a linear dynamics framework have already been studied in several works in the literature. However, since there is no control of the degree of nonlinearity of the structure during the optimization process, the outcome of these routines often departs significantly from linearity. The consequence is
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ROM for large rotations in a MEMS micromirror
MEMS micromirrors are micro components used to deflect light rays in many applications, such as to build projectors. Mainly due to their large rotations, these devices exhibit a nonlinear behavior that challenges the construction of traditional nonlinear Reduced Order Models. In this thesis, the candidate will investigate the subject of large rotations (moving on from