Order domain analysis of speed-dependent friction-induced torque in a brake experiment

SAE Int. J. Passeng. Cars - Mech. Syst.

2015

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The transient vibration phenomenon in a vehicle powertrain system during the start-up (or shut-down) process is studied with focus on the development and experimental validation of the nonlinear powertrain models. First, a new nonlinear four-degree-of-freedom torsional powertrain model for this transient event, under instantaneous flywheel motion input, is developed and then validated with a vehicle start-up experiment. Second, the interactions between the clutch damper and the transmission transients are established via transient metrics. Third, a single-degree-of-freedom nonlinear model, focusing on the multi-staged clutch damper, is developed and its utility is then verified.

Section: Problem Formulationmentioning

confidence: 99%

Start-Up Transient Vibration Analysis of a Vehicle Powertrain System Equipped with a Nonlinear Clutch Damper

SAE Int. J. Passeng. Cars - Mech. Syst.

2015

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“…The envelope function E(t), which is the slowly varying curve describing the extremes of oscillatory response, will been utilized in this paper to evaluate the severity of the speed-dependent response and amplification of δ(t) during start-up process [6,7,8]. Hilbert transform, as introduced by Sen et al [8], is an alternative method of finding the E(t).…”

Section: Transient Envelope Analysis Using Hilbert Transformmentioning

confidence: 99%

“…Hilbert transform, as introduced by Sen et al [8], is an alternative method of finding the E(t). The transient envelop function E(t) is define as follows where Y(t) is the analytic function of δ(t), and h δ (t) is the Hilbert transform of δ(t): (7) A frequency domain technique [9] is employed to estimate Y(t), which is utilized to eventually calculate E(t) as follows, where N is the record length (in terms of discrete points) of δ(t), F is the Fourier transform of δ(t), and F −1 is the inverse Fourier transform:…”

Section: Transient Envelope Analysis Using Hilbert Transformmentioning

confidence: 99%

Analysis of Speed-Dependent Vibration Amplification in a Nonlinear Driveline System Using Hilbert Transform

SAE Int. J. Passeng. Cars - Mech. Syst.

2013

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The engine start-up process introduces speed-dependent transient vibration problems in ground vehicle drivelines as the torsional system passes through the critical speeds during the acceleration process. Accordingly, a numerical study is proposed to gain more insights about this transient vibration issue, and the focus is on nonlinear analysis. First, a new nonlinear model of a multi-staged clutch damper is developed and validated by a transient experiment. Second, a simplified nonlinear torsional oscillator model with the multi-staged clutch damper, representing the low frequency dynamics of a typical vehicle driveline, is developed. The flywheel velocity measured during the typical engine start-up process is utilized as an excitation. The envelope function of the speed-dependent response amplification is estimated via the Hilbert transform technique. Finally, the envelope function is effectively utilized to examine the effect of multi-staged clutch damper properties.

“…Geometric distortions on the rotor surface lead to time-varying interfacial normal load at the pad-rotor interface. As a consequence, a multiple order friction torque is generated since rotor surface distortion profiles are complex waveforms [1][2][3][4]. Furthermore, the frequency of this friction torque excitation is proportional to the wheel speed, which decreases during the braking (deceleration) event.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the frequency of this friction torque excitation is proportional to the wheel speed, which decreases during the braking (deceleration) event. Dynamic (resonant) amplifications occur multiple times due to a multi-order excitation and such amplifications can be felt by the driver through the brake pedal, steering wheel or seat [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Comparative signal processing analyses of a speed-dependent problem as motivated by brake judder problem

Şen¹,

Dreyer

The Journal of the Acoustical Society of America

2013

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The goal of this paper is to investigate a transient problem using several digital signal processing techniques. First, a simple linear mathematical model, where a point mass is connected to a roller through a contact interface, is developed and the dynamic interfacial force is analytically calculated as a function of the speed. In this model, the contact interface is described with a linear spring and viscous damper, and the system is excited with a base excitation, as defined by the undulations on the roller surface. Due to the time-varying speed characteristics of the roller, the resulting response is transient. Second, the dual-domain analyses of the calculated system response is carried out by using shorttime Fourier and wavelet transforms, since single-domain representation leads to a loss of information due to signal's transient characteristics. Third, the Hilbert transform is applied and the envelope curves of the interfacial force response are successfully obtained. Finally, this problem is briefly linked to brake judder phenomenon and its source regimes are briefly explained.