Adaptive Rear-Wheel Steering Control of a Four-Wheel Vehicle Over Uncertain Terrain

Hybrid electric vehicles offer many advantages over a traditional internal combustion engine powertrain in the area of ride handling and vehicle stability. An electric powertrain improves control system flexibility due an increased availably of measurement sensing and hardware actuation. It also avoids the limits imposed on vehicle handling by mechanical linkage connections alone. The purpose of the current research is to develop a rear-wheel steer assist control algorithm for vehicle stability under unsafe conditions. It is important that the driver is still part of the control, but is treated as a measurable disturbance. The rear-wheel stability control is an adaptive pole-placement approach utilizing an on-line recursive least squares algorithm with a variable forgetting factor to account for long drive times when vehicle stability is not in question.