Appeal No. 96-4156
Application 08/218,135
the torque applied to the steering wheel by the operator. The
primary steering system, which is used under normal, no-fault
conditions, has two main feedback loops, i.e., an inner loop
and an outer loop. The inner loop forms a position controller
in which the position of the steered wheels SDW is repeated by
angularly positioning the repeater shaft RS, which is
connected to a torsional spring TLS. The outer loop forms a
torque demand steering controller which uses a torque sensor
TQS attached to the steering wheel SGW through steering shaft
SS to control a multiplied torque for the steered wheels SDW.
In the event of loss of electrical power, the primary torque
demand steering system automatically defaults to an open-loop
secondary steering system. In secondary system operation, the
motor DCM serves as a generator to control the servo valve SV
to manage the hydraulic flow to the piston HP to control the
steered wheels SDW.
The Examiner finds (EA4): "O'Neil, on the other hand,
discloses a power steering system comprising means for
coupling a reaction torque from a mechanical position means to
the steering wheel so as to oppose torque applied by a driver
to [the] steering wheel when an error or failure in the
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Last modified: November 3, 2007