A study on attenuating gear teeth oscillations at low engine speeds using nonlinear vibration absorbers

© 2018 SAE International. All Rights Reserved. Gear oscillations are one of the most common sources of Noise, Vibration and Harshness (NVH) issues manifested in automotive powertrains. These oscillations are generated mainly due to impacts of the meshing gear teeth over a broad frequency range. To mitigate NVH phenomena, automotive manufacturers traditionally couple linear tuned vibration absorbers to the driveline. Common palliatives used are clutch dampers and dual mass flywheels, which generally suppress vibrations effectively only over narrow frequency bands. Nonlinear Energy Sinks (NESs) are a class of vibration absorbers with essentially nonlinear characteristics that are designed for dissipating vibration energy over broad frequency ranges (due to the employed nonlinearity). The NES does not have a preferential natural frequency; this is rather characterized by the nonlinear stiffness. An NES functions on the principle of transferring energy between the primary system (e.g. driveline) and the absorber in two ways: (i) the NES induces a unidirectional transfer of the vibration energy excess from the primary system to the absorber and (ii) the NES induces a redistribution of the vibration energy excess in the modes of the primary structure, enhancing the energy dissipation capabilities of the primary structure. This paper presents a study on the use of NESs for reducing oscillations on gear pairs operating at low engine operating speeds. Numerical simulations were performed using a gear pair model equipped with an absorber with essentially cubic nonlinear stiffness, attached to the gear wheel. The stiffness and inertia properties of the absorber were varied with the objective of obtaining the parameter combination that induces significant attenuation of the oscillatory motion of the gear wheel. The occurring motion of the system using different sets of parameters is studied and presented

Targeted energy transfer in automotive powertrains

Torsional oscillations generated by the internal combustion engine induce various NVH phenomena in the drivetrain system, one being transmission rattle. Palliatives devices such as the clutch predampers or dual mass flywheel have been used to mitigate these NVH phenomena. However, usually these devices are effective over a limited range of frequencies, and not so for broadband transient phenomenon, such as any impulsive actions. This paper considers the Targeted Energy Transfer (TET) method to mitigate torsional vibrations in automotive powertrains. TET is a concept which attempts to direct the mechanical (vibration) energy (in a nearly irreversible manner) from a source (primary system) to a strongly nonlinear attachment (Nonlinear Energy Sink – NES), where it is absorbed, redistributed and/or dissipated. In contrast to the classical powertrain palliative methods, NES should be capable of operating over a broader band of frequencies (with the additional aim of being lightweight and compact). Although the TET concept has been extensively studied for translational systems, there is a dearth of studies for rotational (torsional) ones. In the present work, preliminary parametric studies are performed on a reduced automotive powertrain model, incorporating a NES attachment. The NES parameters, including nonlinear stiffness, viscous linear damping and inertia are varied in order to determine NES effects on engine order (EO) vibration

Concept selection for clutch nonlinear absorber using PUGH matrix

Noise, vibration and harshness (NVH) refinement as well as fuel efficiency and reduced emission levels are the key objectives in modern powertrain engineering. There is an increasing plethora of NVH concerns associated with the underlying high output power-to light weight and compact concept in powertrain engineering. These phenomena contribute to a broad-band vibration response from low frequency rigid body oscillatory responses to high frequency impulsive actions. Various phenomena are briefly described and the importance of their attenuation through palliative measures emphasised. The role of non-linear oscillators as energy sinks over a broader range of responses is also described. A predictive model is presented. Predictive analysis shows effective action of non-linear energy sinks. A feasible design of a NES absorber in an automotive powertrain is constrained by multiple operating requirements such as temperature, available space, reliability and other attributes, requiring an objective analytic-subjective experiential method to arrive at an optimum solution within a series of plausible alternatives. A methodology based on the PUGH matrix approach is presented

Concept selection for clutch nonlinear absorber using PUGH matrix

Noise, vibration and harshness (NVH) refinement as well as fuel efficiency and reduced emission levels are the key objectives in modern powertrain engineering. There is an increasing plethora of NVH concerns associated with the underlying high output power-to light weight and compact concept in powertrain engineering. These phenomena contribute to a broad-band vibration response from low frequency rigid body oscillatory responses to high frequency impulsive actions. Various phenomena are briefly described and the importance of their attenuation through palliative measures emphasised. The role of non-linear oscillators as energy sinks over a broader range of responses is also described. A predictive model is presented. Predictive analysis shows effective action of non-linear energy sinks. A feasible design of a NES absorber in an automotive powertrain is constrained by multiple operating requirements such as temperature, available space, reliability and other attributes, requiring an objective analytic-subjective experiential method to arrive at an optimum solution within a series of plausible alternatives. A methodology based on the PUGH matrix approach is presented

A study on torsional vibration attenuation in automotive drivetrains using absorbers with smooth and non-smooth nonlinearities

The automotive industry is predominantly driven by legislations on stringent emissions. This has led to the introduction of downsized engines, incorporating turbocharging to maintain output power. As downsized engines have higher combustion pressures, the resulting torsional oscillations (engine order vibrations) are of broadband nature with an increasing severity, which affect noise and vibration response of drive train system. Palliative devices, such as clutch pre-dampers and dual mass flywheel have been used to mitigate the effect of transmitted engine torsional oscillations. Nevertheless, the effectiveness of these palliative measures is confined to a narrow band of response frequencies. Studying nonlinear targeted energy transfers is a promising approach to study vibration mitigation within a broader range of frequencies, using nonlinear vibration absorbers (or nonlinear energy sinks – NESs). These devices would either redistribute vibration energy within the modal space of the primary structure thus dissipating the vibrational energy more efficiently through structural damping, or passively absorb and locally dissipate a part of this energy (in a nearly irreversible manner) from the primary structure . The absence of a linear resonance frequency of an NES, enables its broadband operation (in contrast to the narrowband operation of current linear tuned mass dampers). Parametric studies are reported to determine the effectiveness of various smooth or non-smooth nonlinear stiffness characteristics of such absorbers. A reduced drivetrain model, incorporating single and multiple absorber attachments is used and comparison of the predictions to numerical integrations proves its efficacy

Damping Effects Introduced by a Nonlinear Vibration Absorber in Automotive Drivelines at Idle Engine Speeds

Legislation on vehicle emissions and the requirements for fuel efficiency are currently the key development driving factors in the automotive industry. Research activities to comply with these targets point to engine downsizing and new boosting technologies, which have adverse effects on the NVH performance, durability and component life. As a consequence of engine downsizing, substantial torsional oscillations are generated due to high combustion pressures. Meanwhile, to attenuate torsional vibrations, the manufacturers have implemented absorbers that are tuned to certain frequency ranges, including clutch dampers, Dual Mass Flywheel (DMF) and centrifugal pendulum dampers. These devices add mass/inertia to the system, potentially introducing negative effects on other vehicle attributes, such as weight, driving performance and gear shiftability. This paper provides a study of torsional damping effects of nonlinear vibration absorbers on drivetrain NVH refinement by attenuating torsional oscillations at the idling engine speeds. The nonlinear absorber concept presented operates on the principle of Targeted Energy Transfer (TET), whereby the energy excess (vibration) from a donor (primary powertrain system) is transferred to a receiver (nonlinear absorber) in a nearly irreversible manner. Thereafter, the received energy can be absorbed, dissipated, or redistributed. This potentially allows the absorber to operate over a broadband frequency range, whilst being light and compact, which is ideal for automotive powertrains. In the present work, simulations are performed using an automotive drivetrain (subsystem) model with a nonlinear absorber. The damping content of the absorber is varied to study its effect on the attenuation of torsional oscillations

A study on torsional vibration attenuation in automotive drivetrains using absorbers with smooth and non-smooth nonlinearities

The automotive industry is predominantly driven by legislations on stringent emissions. This has led to the introduction of downsized engines, incorporating turbocharging to maintain output power. As downsized engines have higher combustion pressures, the resulting torsional oscillations (engine order vibrations) are of broadband nature with an increasing severity, which affect noise and vibration response of the drive train system. Palliative devices, such as clutch pre-dampers and dual mass flywheel have been used to mitigate the effect of transmitted engine torsional oscillations. Nevertheless, the effectiveness of these palliative measures is confined to a narrow band of response frequencies. The nonlinear targeted energy transfer is a promising approach to study vibration mitigation within a broader range of frequencies, using nonlinear vibration absorbers (or nonlinear energy sinks – NESs). These devices would either redistribute vibration energy within the modal space of the primary structure, thus dissipating the vibrational energy more efficiently through structural damping, or passively absorb and locally dissipate a part of this energy (in a nearly irreversible manner) from the primary structure. The absence of a linear resonance frequency of an NES, enables its broadband operation (in contrast to the narrowband operation of current linear tuned mass dampers). Parametric studies are reported to determine the effectiveness of various smooth or non-smooth nonlinear stiffness characteristics of such absorbers. A reduced drivetrain model, incorporating single and multiple absorber attachments is used and comparison of the predictions to numerical integrations proves its efficacy

Obtaining Frequency-Domain Volterra Models From Port-Based Ordinary Differential Equations

A frequency-domain Volterra model (FVM) is a nonlinear representation obtained when the multivariable Laplace transform is applied to a sum of multidimensional convolution integrals of increasing order. Two classes of FVMs can be identified. The first class of FVM is the Volterra transfer function (VTF) which has been recognized as a useful tool for nonlinear systems modeling and simulation. The second class of FVM is the Volterra dynamic model (VDM) which has been used in the modular assembly and condensation of port-based nonlinear models. Since physical nonlinear systems are frequently modeled using ordinary differential equations (ODEs), it is of significant value to derive their equivalent FVM representations from a corresponding ODE. Even though methods to obtain VTFs for multiple-input, multiple-output (MIMO) nonlinear ODEs are available, a general procedure to obtain the two classes of FVMs does not exist. In this work, a methodology to obtain the two classes of FVMs from port-based nonlinear ODEs is explained. Two cases are shown. In the first case, the ODEs do not include cross product nonlinearities. In the second case, cross products are included. An example is presented to clarify the idea, and the time response obtained from the nonlinear ODE model is compared to its corresponding third order VTF and its linearized model

Investigación del comportamiento de fluido no newtoniano en circuito de conducción para producción de hilaza de acetato de celulosa y rediseño del circuito en caso de que sea necesario

Tesis (Ingeniero Mecánico)--Universidad Autónoma de Occidente, 1993PregradoIngeniero(a) Mecánico(a