Control and steering feel issues in the design of an electric power steering system

We address control and steering feel issues in the development of electric power assist steering (EPAS) systems. The steering system performance requirements impose natural constraints on the compensator gain, phase lag over a frequency range of driver inputs, and pole and zero locations. We develop a novel method based on a nonlinear constrained optimization procedure for fixed-structure optimal controller synthesis for EPAS. The control law obtained minimizes an objective function (H/sub 2/-norm) for a given controller structure, while accounting for requirements of steering torque amplification, steering response and steering feel.