Robust vehicle steering control design based on the disturbance observer

Abstract

A robust steering controller is introduced for improving the yaw dynamics of a passenger car. A specific two degree of freedom control architecture known as the disturbance observer is adapted to the vehicle yaw dynamics control problem and shown to robustly improve performance. The relevant design specifications are formulated in terms of eigenvalues (Γ-stability) and in frequency domain as bounds on weighted sensitivity and complementary sensitivity functions (β-stability). The parameter space method is used to map the specifications for controller design. A Popov criterion based nonlinear stability analysis is also carried out to prove robust absolute stability (Φ-stability) in the presence of actuator rate limitation. Simulations are used to demonstrate the effectiveness of the final design.