Browsing by Author "Verulkar, Adwait"
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- Computation of Direct Sensitivities of Spatial Multibody Systems with Joint FrictionVerulkar, Adwait; Sandu, Corina; Dopico, Daniel; Sandu, Adrian (ASME, 2022-07)Friction exists in most mechanical systems and may have a major influence on the dynamic performance of the system. The incorporation of friction in dynamic systems has been a subject of active research for several years owing to its high nonlinearity and its dependence on several parameters. Consequently, optimization of dynamic systems with friction becomes a challenging task. Gradient-based optimization of dynamical systems is a prominent technique for optimal design and requires the computation of model sensitivities with respect to the design parameters. The novel contribution of this paper is the derivation of the analytical methodology for the computation of direct sensitivities for smooth multibody systems with joint friction using the Lagrangian index-1 formulation. System dynamics have been computed using two different friction models; the Brown and McPhee, and the Gonthier et al. model. The methodology proposed to obtain model sensitivities has also been validated using the complex finite difference method. A case study has been conducted on a spatial multibody system to observe the effect of friction on the dynamics and model sensitivities, compare sensitivities with respect to different parameters and demonstrate the numerical and validation aspects. Since design parameters can have very different magnitudes and units, the sensitivities have been scaled with the parameters for comparison. Finally, a discussion has been presented on the interpretation of the case study results. Due to the incorporation of joint friction, ‘jumps’ or discontinuities are observed in the model sensitivities akin to those observed for hybrid dynamical systems.
- Tread rubber compound effect in winter tires: An experimental studyShenvi, Mohit Nitin; Verulkar, Adwait; Sandu, Corina; Mousavi, Hoda (Elsevier, 2022-02)This paper presents an indoor experimental study focused on analyzing the effect of various tread rubber compounds on the tire performance on ice. A set of sixteen tires (two per rubber compound) with identical dimensions, construction, and tread pattern, but of different tread rubber compounds, was investigated using the Terramechanics Rig which measures all forces and moments acting on a tire that is rolling (free or with slip) on ice. All operational parameters (normal load, inflation pressure, ice static coefficient of friction, ice temperature) were kept constant. Testing the tires under free rolling provided insights into the effect of the tread rubber compound on the resistive forces. The investigation led to conclusive evidence that the tread rubber compound affects drawbar pull coefficient significantly (double for best than for the worst tire). It was found that the effect of the tread rubber compound in the lower slip region is most prominent, which is also where vehicles operate most of the time. The decrease in the stiffness is generally considered a positive sign for improvement in available friction but this cannot be a generalized conclusion when analyzing the tire as a whole, which is one of the major findings of this study.