Abstract
In a standard vehicle, the driver controls the trajectory of the vehicle using steering, acceleration and braking inputs. Vehicle response is strongly influenced by the chassis sub-system, which mediates the forces delivered to the vehicle via the tires. A measure of vehicle chassis system performance is developed, based on comparing a given passive chassis system to an ideal active chassis. The ideal chassis optimally distributes tire forces and uses active torque vectoring (traction or braking at each wheel) plus independent four-wheel-steering, so as to make the very best use of available friction. To conduct the analysis, optimal force allocation is applied to a specified maneuver using a conventional vehicle. The capability of the vehicle to follow the original path is evaluated as surface friction is reduced; thus the capability of the active chassis to improve this performance is used as a metric for baseline chassis performance. In this way, tire friction utilization, together with optimal force allocation and active chassis control is used as an evaluation tool, whether or not active controls are part of the vehicle design. This is a novel use of advanced vehicle control techniques; it provides a fundamental metric for chassis performance in specified maneuvers, and has applications in vehicle development and refinement. While the present study uses simulation only, it is possible in the future to conduct evaluation using an experimental test; however a validated model would still be needed to perform the analysis.
KEYWORDS – Active Chassis Systems, Tire Force Optimization, Force Allocation, Inverse Tire Model, Vehicle Development