COMMISSIONER'S DECISION
Section 2, Disclaimed Subject Matter: GAS TURBINE ENGINE CONTROL
Applicant's system for controlling a gas turbine by a model generated signal in
the event of an erroneous signal from a sensor being in excess of a tolerance
value, is considered subject matter within the Act. No disclaimer is made
in the disclosure, nor an file. Rejection withdrawn.
************
This decision deals with Applicant's request for review by the Commissioner of
Patents of the Final Action of application 292,813, class 341-112, assigned to
the General Electric Company. The invention is entitled METHOD AND APPARATUS
FOR FAILURE DETECTION AND CORRECTION IN GAS TURBINE ENGINE CONTROL SYSTEM. The
inventors are Henry A. Spang and Robert P. Wanger. The Examiner refused the
application for being directed to non-statutory subject matter.
The application relates to failure correction of a control system 10 in a gas
turbine engine as shown in Figure 1 below. Such engines include electrical
sensors 12, 13 which measure engine control parameters, typically temperatures
and pressures, and also engine controlled parameters, typically fuel flow.
The sensor signals are used to control the position of actuators 14 which vary
engine controlled parameters. A computer 18 uses the sensed values of the
control and controlled parameters and the known engine behaviour characteristics
which are calculated according to a mathematical model to compute output signals
modifying the controlled parameters for maintaining a desired level of engine
performance. The improvement resides in the replacement of an erroneous input
signal generated from the mathematical model. The erroneous input signal is
modified or replaced when the difference between the sensed signal and the
computed estimate of the signal exceeds a certain tolerance value.
(See figure I)
In the Final Action the Examiner rejected the application for lack of pat-
entable subject matter since it defined a computer program, and for being
directed to matter consisting of disclaimed commonly known apparatus.
He stated (in part):
...
Gas turbine engines having "electrical sensors" connected to
"computational units" which may be "digital" belong to conven-
tional engine control systems i.e. are prior art, as acknow-
ledged and effectively disclaimed by the applicant (see page 1,
lines 5-25).
...
The improvement is said to reside in the fact that in case of
the loss of a sensor, the computer will continue to provide
output signals to control the engine, because the computer is
programmed to do so.
...
In response to the Final Action Applicant argued that the known elements of
the combination are not disclaimed, as follows (in part):
...
It is respectfully requested therefore that the Commissioner
disregard the Examiner's remarks in respect of disclaimer, it
being understood that a combination claim, while it may implic-
itly disclaim the individual elements of the combination so
defined, is none the less directed to the combination which it-
self is the invention defined by such a claim. Only combination
claims are at issue in the present case and the discussion of
patentable merits should be restricted to such combination claims.
...
The issue before the Board is whether or not the subject matter of the applic-
ation is directed to statutory subject matter, and whether or not the subject
matter is disclaimed by Applicant. Claim 1 reads:
An improved gas turbine engine control system of the type which
comprises means for measuring and transmitting the values of
engine control parameters, means for measuring and transmitting
the values of engine controlled parameters, actuator means for
setting values of engine controlled parameters and control
computational means for receiving the control parameter values
and the controlled parameter values and generating signals in
response thereto to position the actuator means and to modify
the controlled parameter values in order to maintain a desired
level of engine performance wherein the improvement comprises:
computer means disposed between the control parameter measuring
and transmitting means and the control computational means
which receives both the control parameter values and the control-
led parameter values and calculates signals representing estimates
of the engine control parameter values and transmits said signals
to the control computational means.
Dealing first with the issue of disclaimed subject matter in the application,
we note that the application refers to various elements to illustrate that
suitable structure is known to carry out Applicant's conception of operation.
We see no mention in the disclosure that they are disclaimed. We note also in
Applicant's response that he says he has not filed any disclaimers under
Section 52 of the Act. Applicant also urges that only combination claims are
present in the disclosure, and no claims are directed to known elements per se.
We are in agreement, for we find that the apparatus of failure detection and
correction viewed as a whole is directed to a combination of elements. We
dismiss therefore the rejection based on disclaimed subject matter.
We now deal with the rejection that the subject matter is a computer program
and is not patentable subject matter. We are here guided by the decision of
the Federal Court of Appeal in Schlumberger Canada Ltd. v. Commissioner of
Patents (1981) .56 CPR 204, in which Pratte, J. commented as follows:
In order to determine whether the application discloses
a patentable invention, it is first necessary to determine
what, according to the application, has been discovered.
and
I am of opinion that the fact that a computer is or should
be used to implement discovery does not change the nature
of that discovery.
What is new here is the discovery that a model generated signal can replace
an erroneous input signal from a faulty sensor in the feedback control loop of
a gas turbine. The control is performed by means of a computer which continu-
ously compares each control parameter sensor input signal with the model estimate
of the signal. In the event of the signal difference exceeding an arbitrary
tolerance value, the faulty control sensor is inhibited and prevented from
updating the engine model and the engine controlled parameter. The sole
practical application of the engine model is in connection with the operation
of the engine. The model gives the interrelationship between signal para-
meters to provide information for controlling any single parameter by means
of the other parameters to provide a desired engine performance.
In summary, the calculated numbers, i.e. the control parameters, in this
application are not the product or end result of the operation but rather are
parameters to be used within a system of controlling an engine. In comparison,
in Schlumberger the measured data were recomputated and plotted for interpreta-
tion by an operator. Applicant's system however produces an end result which
is more than a mere calculation. It produces a control system for an engine.
We find that the combination performs a function for which the patent laws
were designed to protect, i.e. a system for controlling an engine, and thus
the subject matter falls into the statutory subject matter category of Section
2 of the Patent Act.
We recommend that the rejection of the application for lack of patentable
subject matter and for being disclaimed matter be withdrawn, and the applica-
tion be returned to the Examiner.
A. McDonough M.G. Brown S.D. Kot
Chairman Assistant Chairman Member
Patent Appeal Board
I have reviewed the prosecution of this application and concur with the
reasoning and findings of the Board. Accordingly, I am returning the
application to the Examiner.
Agent for Applicant
J.H.A. Gari‚py
Commissioner of Patents Swabey, Mitchell, Houle, Marcoud & Sher
1001 boul. de Maisonneuve ouest,
Suite 800,
Montreal, Quebec,
H3A 3C8
Dated at Hull, Quebec
this 29th. day of August, 1984