Appeal No. 96-4014
Application 08/192,939
The independent claims are directed broadly to the concept
of using a fuzzy logic controller for controlling a turboshaft
engine. In our opinion, the issue is whether it would have been
obvious to one of ordinary skill in the art to replace the mode
selector in the prior art with a fuzzy logic controller.
The prior art of figure 2 shows a schematic diagram of a
conventional turboshaft engine control system. A number of low
level controllers are connected to a mode selector. The low
level controllers are "designed to govern the engine when
specific conditions or modes are sensed" (specification, page 3,
lines 6-7). The low level controllers "examine various sensor
readings from points within the engine and produce fuel flow and
VATN angle derivatives" (specification, page 3, lines 8-10).
"These rates then drop through a chain of minimums and maximums
(min/max ladder) [in the mode selector] that selects one of those
rates." Specification, page 3, lines 11-13. Fuel flow is the
variable used to control the engine. Only one low level
controller is active at a time. As shown in figure 3b, the fuel
flow derivative can be clipped due to abrupt mode selection,
which produces less than optimal performance (specification,
page 3, line 24, to page 4, line 7).
Hisano is not the simplest reference to address because it
contains complicated hardware implementation details that tend to
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Last modified: November 3, 2007