AE Seminar
"Slip Dynamics of Longitudinal Ground Vehicle Braking: Using the Tools of Nonlinear Analysis to Visualize Stability and Lockup"
featuring
Brian J. Olson
Chief Scientist and Principal Engineer |The Johns Hopkins University Applied Physics Laboratory
Tuesday, April 28
3:30 - 4:30 p.m.
Guggenheim 442
About the Seminar:
The longitudinal braking dynamics of rubber-tired ground vehicles are investigated with an emphasis on visualizing complex behavior using simple geometric constructions and linking the underlying mathematics to familiar driving experiences. Planar single- and two-wheel models are developed with empirically derived tire-road friction characteristics, capturing the coupled motion of the vehicle body and independently braked wheels through the slip dynamics of each tire. By recasting the governing equations motion in terms of vehicle speed and wheel slip, rather than wheel angular rates, the full system collapses to a relatively simple phase-plane problem governed by slip-dependent equilibrium functions. The corresponding phase-plane trajectories and slip-torque bifurcation diagrams provide intuitive pictures of how increasing brake torque (“pushing harder on the brakes”) moves the system from stable braking, to the possibility of lockup in one or both wheels, to guaranteed lockup in both wheels. These diagrams reveal regions with multiple possible steady-braking outcomes and hysteresis, making clear why a driver may sometimes feel either smooth deceleration or sudden skidding under ostensibly similar conditions. The analysis identifies a critical slip values and associated brake torques at which finite-slip equilibria lose stability via saddle-node bifurcations, refining the standard textbook assumption that lockup onset coincides with peak tire friction and highlighting the role of vehicle-to-wheel inertia ratio. Application to a U.S. automaker driveline durability/reliability assessment is briefly discussed.
About the Speaker:
Dr. Brian J. Olson is a Fellow of the American Society of Mechanical Engineers, a Principal Engineer at the Johns Hopkins University Applied Physics Laboratory (JHU/APL), and Chief Scientist of the JHU/APL Aerospace and Mechanical Engineering group within the Air and Missile Defense Sector. He received his B.S. (1999), M.S. (2001) and Ph.D. (2006) degrees in Mechanical Engineering from Michigan State University with additional study at the University of Surrey and research at the Budapest University of Technology and Economics. Dr. Olson has nearly 20 years of applied research experience in dynamics and vibration of linear and nonlinear mechanical systems including modeling and simulation (M&S), test and evaluation, engineering measurements, and digital signal processing. He specializes in analytical, semi-analytical, and multi-body dynamics M&S for multi-fidelity workflow. His fundamental research encompasses several areas including vibration reduction in cyclic vibratory systems, circulant and group-theoretic decomposition of symmetric systems, nonlinear dynamics of ground vehicle traction, and stereoscopic methods for velocimetry in fluid diagnostics.