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The brake torque variation (BTV) generated due to geometric irregularities in the disc surface is generally accepted as the fundamental source of brake judder; geometric imperfections or waviness in a disc brake caliper system is often quantified as the disc thickness variation (DTV). Prior research has mainly focused on the vibration path(s) and receiver(s), though such approaches grossly simplify the source (frictional contact) dynamics and often ignore caliper dynamics. Reduction of the effective interfacial contact stiffness could theoretically reduce the friction-induced torque given a specific DTV, although this method would severely increase static compliance and fluid volume displacement. An experiment is designed to quantify the effect of disc-pad contact modifications within a floating caliper design on BTV as well as on static compliance. The major objective of this experiment is to determine if changes in the disc-pad contact geometry can also reduce BTV without limiting the static compliance of the caliper system. A conceptual half-caliper model is proposed to explain the observed effects of pad modifications. This simplified elastokinematic model uses the elastic center concept on a pad subject to spatially phased periodic displacement inputs (DTV) at the disc-pad interface. It is utilized to determine the effective variation in normal load. The model is finally employed to determine the sensitivity of key physical parameters and to identify trends that might reduce BTV.

The vibration isolation effectiveness of powertrain mount configurations is examined for electric vehicle application by considering the effect introduced by internal mount resonances. Unlike internal combustion engines where mounts are typically designed only for static support and low frequency dynamics, electric motors have higher excitation frequencies in a range where mount resonances often occur. The problem is first analytically formulated by considering a simple 3-dimensional powertrain system, and the vibration isolation effectiveness significantly deteriorates at the mount resonance(s). It is shown that by modifying the mount shape, the mount resonance(s) can be shifted while maintaining the same static rate, tuning the frequency away from any engine excitation or natural frequencies. Further, internal mount resonances are utilized to improve vibration isolation over a narrow frequency range, using non-identical mounts to split mount resonance peaks. Then a computational model for a realistic drive unit (containing electric motor, power invertor, and gearbox) is considered. The mount resonance phenomenon is replicated in the computational model, and the effect on non-identical mounts is again examined. Finally, 3 and 4-point mounting schemes are compared, and their parameters (if selected properly) exhibit better vibration isolation over a tunable frequency range of interest.

A new simplified, yet representative experiment of a floating dual-piston disk-caliper braking system is designed to isolate the rectangular seal and the piston–bore chamber from the complexities of a braking system. The physical sources of the stiffness and damping mechanisms associated with the seal during an applied pressure event are identified and quantified under harmonic excitation. A tractable analytical model of the experiment that incorporates the identified dynamic seal properties is proposed. This linear time-invariant model describes the governing equations of both the hydraulic brake system components and the mechanical caliper components and provides some insights into a seemingly nonlinear system. For a range of pressure amplitudes and brake configurations, excellent agreement between predictions and measurements is obtained for the peak-to-peak values of the piston–bore chamber pressure, the force transmitted by the pistons, and the caliper displacement. The proposed model and experiment could be utilized in brake control, vibration, and pedal feel studies.