A steering system (10) and method (70) for controlling the steering
of a vehicle having a steering assembly including a steering wheel (12),
a steering column (14) connected to said steering wheel (12), and
an electric motor (20) operatively engaged with the steering assembly for
supplying torque assist. A steering angle sensor (32) is employed for sensing
an angular position c of the steering column (14). The
steering system has first and second H-infinity controllers (64A and 64B)
coupled in a feedback path (44) for generating first and second feedback
signals as a function of the driver torque and first and second characteristics
(JC and KC) of the steering system. One of the first and
second feedback signals is selected and the selected feedback signal is combined
with a feedforward signal to generate a motor control signal (U) as a function
of the estimated torque.
