Patent Description:
During aircraft operations consisting of rapid engine transitions from low to high power levels, it is desirable to reduce the response time of the engine in order to achieve a required power. For this purpose, inlet mass flow can be increased by accelerating the gas generator of the engine, thereby increasing the engine's power. This may be achieved by a variety of techniques which adjust the shape or geometry of one or more components of the engine, called variable geometry mechanisms, thereby adjusting the response of the engine.

Various control approaches for variable geometry mechanisms are known, for example based on the speed or the torque of the engine. However, reliance on these values can lead to excessive wear on the mechanical components of the variable geometry mechanisms. There is therefore a need for improved control schemes for variable geometry mechanisms.

A prior art signal processing device having the features of the preamble of claim <NUM> is disclosed in <CIT>. Further prior art signal processing devices are disclosed in <CIT>, <CIT> and <CIT>.

In accordance with an aspect of the present invention, there is provided a signal processing device for use in an aircraft engine with a variable geometry mechanism (VGM), as set forth in claim <NUM>.

In an embodiment according to the previous embodiment, wherein filtering the VGM position request signal comprises subjecting the VGM position request signal to a first-order low-pass filter having a predetermined time constant selected for filtering noise above a predetermined frequency threshold.

In an embodiment according to any of the previous embodiments, wherein filtering the VGM position request signal comprises subjecting the VGM position request signal to a rate limiter.

In an embodiment according to any of the previous embodiments, the rate limiter is configured to have a predetermined rate of change selected for filtering noise above a predetermined frequency threshold.

In an embodiment according to any of the previous embodiments, the rate limiter is configured to have a predetermined dead band selected for filtering noise above a predetermined frequency threshold.

In an embodiment according to any of the previous embodiments, the program instructions are further executable by the processing unit for at least one of reducing a noise level of the VGM position request signal and smoothing the VGM position request signal.

In an embodiment according to any of the previous embodiments, scaling the VGM position request signal by a factor associated with the predetermined range comprises reducing each of a plurality of subsequent values of the VGM position request signal by half of the value of the predetermined range.

In an embodiment according to any of the previous embodiments, the VGM position request signal is based on one of a power and a speed of the aircraft engine.

In an embodiment according to any of the previous embodiments, the program instructions are further executable by the processing unit for receiving an activation signal from an engine controller associated with the aircraft engine, wherein the filtering occurs responsive to the activation signal.

In accordance with another aspect of the present invention, there is provided a method for processing a control signal for a variable geometry mechanism (VGM) of an aircraft engine, as set forth in claim <NUM>.

In an embodiment, the method is carried out by a signal processing device, which may be for use in an aircraft engine.

In an embodiment according to any of the previous embodiments, filtering the VGM position request signal comprises subjecting the VGM position request signal to a first-order low-pass filter having a predetermined time constant selected for filtering noise above a predetermined frequency threshold.

In an embodiment according to any of the previous embodiments, filtering the VGM position request signal comprises subjecting the VGM position request signal to a rate limiter configured to have a predetermined rate of change selected for filtering noise above a predetermined frequency threshold.

In an embodiment according to any of the previous embodiments, filtering the VGM position request signal comprises subjecting the VGM position request signal to a rate limiter configured to have a predetermined dead band selected for filtering noise above a predetermined frequency threshold.

In an embodiment according to any of the previous embodiments, the method further comprises at least one of reducing a noise level of the VGM position request signal and smoothing the VGM position request signal.

In an embodiment according to any of the previous embodiments, the method further comprises receiving an activation signal from an engine controller associated with the aircraft engine, wherein the filtering occurs responsive to the activation signal.

In accordance with a still further aspect of the present invention, there is provided a control system for a variable geometry mechanism (VGM) of an engine, as set forth in claim <NUM>.

<FIG> illustrates a gas turbine engine <NUM> of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication an air inlet <NUM>, a compressor section <NUM> for pressurizing the air from the air inlet <NUM>, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, a turbine section <NUM> for extracting energy from the combustion gases, an exhaust outlet <NUM> through which the combustion gases exit the gas turbine engine <NUM>. The engine <NUM> includes a propeller <NUM> which provides thrust for flight and taxiing. The gas turbine engine <NUM> has a longitudinal center axis <NUM>.

The gas turbine engine <NUM> (sometimes referred to herein simply as "engine <NUM>") has a central core <NUM> defining a gas path through which gases flow as depicted by flow arrows in <FIG>. The illustrated engine <NUM> is a "reverse-flow" engine <NUM> because gases flow through the core <NUM> from the air inlet <NUM> at a rear portion thereof, to the exhaust outlet <NUM> at a front portion thereof. This is in contrast to "through-flow" gas turbine engines in which gases flow through the core of the engine from a front portion to a rear portion. The direction of the flow of gases through the core <NUM> of the engine <NUM> disclosed herein can be better appreciated by considering that the gases flow through the core <NUM> in the same direction D as the one along which the engine <NUM> travels during flight. Stated differently, gases flow through the engine <NUM> from a rear end thereof towards the propeller <NUM>.

Although illustrated as a turboprop engine, the gas turbine engine <NUM> may alternatively be another type of engine, for example a turbofan engine, also generally comprising in serial flow communication a compressor section, a combustor, and a turbine section, and a fan through which ambient air is propelled. A turboshaft engine may also apply. Similarly, although illustrated as a reverse-flow engine, the techniques described herein can also be applied to through-flow engines. In addition, although the engine <NUM> is described herein for flight applications, it should be understood that other uses, such as industrial or the like, may apply.

Still referring to <FIG>, the engine <NUM> has multiple spools which perform compression to pressurize the air received through the air inlet <NUM>, and which extract energy from the combustion gases before they exit the core <NUM> via the exhaust outlet <NUM>. According to the illustrated example, the engine <NUM> is provided in the form of a multi-spool engine having a low pressure (LP) spool <NUM> and a high pressure (HP) spool <NUM> independently rotatable about axis <NUM>. However, it is understood that a multi-spool engine could have more than two spools. It should also be noted that the embodiments described herein also consider the use of single-spool engines.

The LP spool <NUM> includes at least one component to compress the air that is part of the compressor section <NUM>, and at least one component to extract energy from the combustion gases that is part of the turbine section <NUM>. More particularly, the LP spool <NUM> has a low pressure turbine <NUM> which extracts energy from the combustion gases, and which is drivingly engaged to an LP compressor <NUM> for pressurizing the air. The LP turbine <NUM> (also referred to as the power turbine) drives the LP compressor <NUM>, thereby causing the LP compressor <NUM> to pressurize the air. Both the LP turbine <NUM> and the LP compressor <NUM> are disposed along the axis <NUM>. In the depicted embodiment, both the LP turbine <NUM> and the LP compressor <NUM> are axial rotatable components having an axis of rotation that is coaxial with the center axis <NUM>. They can include one or more stages, depending upon the desired engine thermodynamic cycle, for example.

In the depicted embodiment, the LP spool <NUM> has a power shaft <NUM> which mechanically couples the LP turbine <NUM> and the LP compressor <NUM>, and extends axially between them. The shaft <NUM> is coaxial with the central axis <NUM> of the engine <NUM>. The shaft <NUM> allows the LP turbine <NUM> to drive the LP compressor <NUM> during operation of the engine <NUM>. The shaft <NUM> is not limited to the configuration depicted in <FIG>, and can also mechanically couple the LP turbine <NUM> and the LP compressor <NUM> in any other suitable way provided that it transmits a rotational drive from the LP turbine <NUM> to the LP compressor <NUM>. For example, the shaft <NUM> can be combined with a geared LP compressor <NUM> to allow the LP compressor <NUM> to run at a different rotational speed from the LP turbine <NUM>. This can provide more flexibility in the selection of design points for the LP compressor.

Still referring to <FIG>, the engine <NUM> includes an output drive shaft <NUM>. The drive shaft <NUM> extends forwardly from the LP turbine <NUM> and is drivingly engaged thereto. In the illustrated example, the drive shaft <NUM> is distinct from the power shaft <NUM> and mechanically coupled thereto to be driven by the LP turbine <NUM>. In the depicted embodiment, the drive shaft <NUM> and the power shaft <NUM> are coaxial and interconnected. <FIG> shows that the power and drive shafts <NUM>, <NUM> are interconnected with a spline <NUM>. The spline <NUM>, which can include ridges or teeth on the drive shaft <NUM> that mesh with grooves in the power shaft <NUM> (or vice versa), allows for the transfer of torque between the drive shaft <NUM> and the power shaft <NUM>. In the depicted embodiment, the power shaft <NUM> lies at least partially within the drive shaft <NUM>, such that the spline <NUM> transfers the rotational drive or torque generated by the LP turbine <NUM> from the drive shaft <NUM> to the power shaft <NUM>. The spline <NUM> can operate so that the power shaft <NUM> and the drive shaft <NUM> rotate at the same rotational speed. Other mechanical techniques can also be used to interconnect the power and drive shafts <NUM>, <NUM>. For example, the power and drive shafts <NUM>, <NUM> can be interconnected by curvic coupling, pins, and interference fits. Other configurations of the drive shaft <NUM> and the power shaft <NUM> are also possible. For example, the drive shaft <NUM> and the power shaft <NUM> can be a single shaft driven by the LP turbine <NUM>. The drive shaft <NUM> therefore transfers the rotational output of the LP turbine <NUM> in a forward direction to drive another component.

A rotatable load, which in the embodiment shown includes the propeller <NUM>, is mountable to the engine <NUM>, and when mounted, is drivingly engaged to the LP turbine <NUM>, and is located forward of the LP turbine <NUM>. In such a configuration, during operation of the engine <NUM>, the LP turbine <NUM> drives the rotatable load such that a rotational drive produced by the LP turbine <NUM> is transferred to the rotatable load. The rotatable load can therefore be any suitable component, or any combination of suitable components, that is capable of receiving the rotational drive from the LP turbine <NUM>, as now described.

In the embodiment shown, a reduction gearbox <NUM> (sometimes referred to herein simply as "RGB <NUM>") is mechanically coupled to a front end of the drive shaft <NUM>, which extends between the RGB <NUM> and the LP turbine <NUM>. The RGB <NUM> processes and outputs the rotational drive transferred thereto from the LP turbine <NUM> via the drive shaft <NUM> through known gear reduction techniques. The RGB <NUM> allows for the propeller <NUM> to be driven at its optimal rotational speed, which is different from the rotational speed of the LP turbine <NUM>.

Still referring to <FIG>, the HP spool <NUM> with at least one component to compress the air that is part of the compressor section <NUM>, and at least one component to extract energy from the combustion gases that is part of the turbine section <NUM>. The HP spool <NUM> is also disposed along the axis <NUM> and includes an HP turbine <NUM> drivingly engaged (e.g. directly connected) to a high pressure compressor <NUM> by an HP shaft <NUM> rotating independently of the power shaft <NUM>. Similarly to the LP turbine <NUM> and the LP compressor <NUM>, the HP turbine <NUM> and the HP compressor <NUM> can include various stages of axial rotary components. In the depicted embodiment, the HP compressor <NUM> includes a centrifugal compressor 42A or impeller and an axial compressor 42B, both of which are driven by the HP turbine <NUM>. During operation of the engine <NUM>, the HP turbine <NUM> drives the HP compressor <NUM>.

It can thus be appreciated that the presence of the above-described LP and HP spools <NUM>, <NUM> provides the engine <NUM> with a "split compressor" arrangement. More particularly, some of the work required to compress the incoming air is transferred from the HP compressor <NUM> to the LP compressor <NUM>. In other words, some of the compression work is transferred from the HP turbine <NUM> to the more efficient LP turbine <NUM>. This transfer of work may contribute to higher pressure ratios while maintaining a relatively small number of rotors. In a particular embodiment, higher pressure ratios allow for higher power density, better engine specific fuel consumption (SFC), and a lower turbine inlet temperature (sometimes referred to as "T4") for a given power. These factors can contribute to a lower overall weight for the engine <NUM>. The transfer of compression work from the HP compressor <NUM> to the LP compressor <NUM> contrasts with some conventional reverse-flow engines, in which the high pressure compressor (and thus the high pressure turbine) perform all of the compression work.

In light of the preceding, it can be appreciated that the LP turbine <NUM> is the "low-speed" and "low pressure" turbine when compared to the HP turbine <NUM>. The LP turbine <NUM> is sometimes referred to as a "power turbine". The turbine rotors of the HP turbine <NUM> spin at a higher rotational speed than the turbine rotors of the LP turbine <NUM> given the closer proximity of the HP turbine <NUM> to the outlet of the combustor <NUM>. Consequently, the compressor rotors of the HP compressor <NUM> may rotate at a higher rotational speed than the compressor rotors of the LP compressor <NUM>. The engine <NUM> shown in <FIG> is thus a "two-spool" engine <NUM>.

The HP turbine <NUM> and the HP compressor <NUM> can have any suitable mechanical arrangement to achieve the above-described split compressor functionality. For example, and as shown in <FIG>, the HP spool <NUM> includes a high pressure shaft <NUM> extending between the HP compressor <NUM> and the HP turbine section <NUM>. The high pressure shaft <NUM> is coaxial with the power shaft <NUM> and rotatable relative thereto. The relative rotation between the high pressure shaft <NUM> and the power shaft <NUM> allow the shafts <NUM>, <NUM> to rotate at different rotational speeds, thereby allowing the HP compressor <NUM> and the LP compressor <NUM> to rotate at different rotational speeds. The HP shaft <NUM> can be mechanically supported by the power shaft <NUM> using bearings or the like. In the depicted embodiment, the power shaft <NUM> is at least partially disposed within the HP shaft <NUM>.

The split compressor arrangement also allows bleed air to be drawn from between the HP compressor <NUM> and the LP compressor <NUM>. More particularly, in the embodiment of <FIG>, the engine <NUM> includes an inter-stage bleed <NUM> port or valve that is aft of the HP compressor <NUM> and forward of the LP compressor <NUM>, which may provide for increased flexibility in the available bleed pressures. In a particular embodiment, the bleed pressure design point of the inter-stage bleed <NUM> is selected based on the pressure ratio of the LP compressor <NUM>, which runs independently from the HP compressor <NUM>. For operability, variable inlet guide vanes (VIGV) <NUM> and variable guide vanes (VGV) <NUM> can be used on the LP compressor <NUM> and at the entry of the HP compressor <NUM>, together with the inter-stage bleed <NUM>.

It should be noted that the engine of <FIG> represents only one example engine, and that the embodiments described herein can be applied to any other suitable manner of engine.

The engine <NUM> includes one or more variable geometry mechanisms (VGMs) which may assist in achieving optimized engine transient response. In some embodiments, the VGMs consists of one or more VGVs, for instance the VIGV <NUM> and the VGV <NUM>, which may be one of inlet compressor guide vanes for directing air into the compressor section <NUM>, outlet guide vanes for directing air out of the compressor section <NUM>, variable stator vanes for directing incoming air into rotor blades of the engine <NUM>, and/or one or more variable nozzles, variable bleed-off valves, for instance the inter-stage bleed <NUM>, and the like. It should be understood that one or more of the above-mentioned VGMs may be adjusted for the purpose of decreasing the response time of the engine <NUM> during rapid engine transitions, e.g. from low to high power levels, or vice-versa. Indeed, adjustment of the position (e.g. the angle) of the VGMs can impact the inlet mass flow to the engine <NUM>, and in turn allow the engine <NUM> to operate at a required power.

In some embodiments, as illustrated in <FIG>, the engine <NUM> has a dual compression system with a low-spool compression system (LPC), including the LP spool <NUM>, and a high-spool compression system (HPC), including the HP spool <NUM>, which are separate from one-another. The VGMs include the VIGV <NUM> at the air inlet <NUM> near the LPC and the VGVs <NUM> upstream of the HPC. It should be noted that other VGMs may also be included for both the LPC and the HPC. In other embodiments, the engine <NUM> includes only one compression system, and includes fewer or more VGMs.

With reference to <FIG>, an embodiment of an engine control system <NUM> for the engine <NUM> is illustrated. The engine control system <NUM> includes one or more sensors <NUM>, an engine controller <NUM>, and a VGM controller <NUM>. The sensors <NUM> are coupled to the engine controller <NUM>, which in turn is coupled to the VGM controller <NUM>. In some embodiments, some of the sensors <NUM> are also coupled to the VGM controller <NUM>. The engine controller <NUM>, and optionally the VGM controller <NUM>, are configured for obtaining various inputs from the sensors <NUM>.

The engine controller <NUM> can be communicatively coupled to any number of systems for effecting control of the engine <NUM>. For instance, the engine controller can be coupled to fuel flow valves, gear actuators, and the like. The VGM controller <NUM> is communicatively coupled to the VGMs <NUM>, <NUM>, and any other VGMs of the engine <NUM>, for issuing commands thereto, for instance to control positions of the VGMs <NUM>, <NUM>. Although the engine control system <NUM> in <FIG> is illustrated as including only the sensors <NUM>, the engine controller <NUM>, and the VGM controller <NUM>, it should be noted that practical applications of the engine control system <NUM> may include any number of other suitable components and controllers.

The sensors <NUM> are configured for acquiring various data about the engine <NUM> and the aircraft in which the engine <NUM> operates. The sensors <NUM> can be disposed throughout the engine <NUM> and/or the aircraft, and can be configured for measuring any suitable information about the operation of the engine <NUM> and/or the aircraft. The sensors <NUM> can include pressure sensors, temperature sensors, rotation sensors, speed sensors, accelerometers, gyrosensors, and the like. In some embodiments, the sensors <NUM> include one or more virtual sensors, which use other measurements to derive a desired value, for example in software.

The engine controller <NUM> is configured for controlling operation of the engine <NUM>. This can include modulating a fuel flow to the engine, adjusting various operational parameters of the engine, for instance a gearing of the RGB <NUM>, and the like. In some embodiments, the engine controller <NUM> is configured for altering the operation of one or more VGMs, for example the VIGV <NUM> and the VGV <NUM>, via the VGM controller <NUM>. For example, the engine controller <NUM> can send instructions to the VGM controller <NUM> indicative of desired changes in engine operating conditions: for instance, the engine controller <NUM> can request changes relating to temperature, pressure, and the like. The VGM controller <NUM> is configured for interpreting the instructions from the engine controller <NUM> and causing suitable changes to the position and/or orientation of the VGMs <NUM>, <NUM> to enact the requested changes to the engine operating conditions. In other embodiments, the VGM controller <NUM> obtains various inputs from the sensors <NUM> indicating changes in the operating conditions of the engine <NUM>, and determines based thereon corresponding changes to the operating conditions of the VGMs <NUM>, <NUM>, to be implemented.

The VGM controller <NUM> is configured for issuing commands to the VGMs <NUM>, <NUM> in order to effect changes in the position, orientation, and the like, of the VGMs <NUM>, <NUM>. In some embodiments, the VGM controller <NUM> issues the commands to motors, actuators, or similar active elements of the VGMs <NUM>, <NUM>, to cause movement in the VGMs <NUM>, <NUM>, in line with the instructions received by the VGM controller <NUM> from the engine controller <NUM>. For example, a position of the VIGV <NUM> and/or the VGV <NUM>, an orientation of the VIGV <NUM> and/or the VGV <NUM>, a degree of openness of an aperture formed by the VIGV <NUM> and/or the VGV <NUM>, and/or any other suitable aspects of the VIGV <NUM> and/or the VGV <NUM> can be adjusted. In another example, the position and/or a degree of openness of a variable bleed-off valve can be adjusted. Still other embodiments, involving one of inlet compressor guide vanes for directing air into the compressor section <NUM>, outlet guide vanes for directing air out of the compressor section <NUM>, variable stator vanes for directing incoming air into rotor blades of the engine <NUM>, and/or one or more variable nozzles, variable bleed-off valves, for instance the inter-stage bleed <NUM>, and the like, are also considered.

With reference to <FIG>, an embodiment of the VGM controller <NUM> is illustrated. The VGM controller <NUM> is composed of a VGM steady-state (VGMSS) unit <NUM>, a VGM bias (VGMB) unit <NUM>, a signal adder <NUM>, a signal processing device <NUM>, and a VGM control loop (VGMCL) <NUM>. The VGM controller <NUM> is configured for transmitting, via the VGMCL <NUM>, signals to the actuators in the VGMs <NUM>, <NUM>, to effect a change in their position and/or orientation. In some embodiments, different VGM controllers <NUM> can be provided for each of the VGMs in the engine <NUM> in other embodiments, a single VGM controller <NUM> can control operation of multiple VGMs, for instance the VGMs <NUM>, <NUM>. Although the foregoing discussion focuses only on a single VGM <NUM>, is should be understood that the same notions could be applied to a multi-VGM system.

The VGMSS unit <NUM> and the VGMB unit <NUM> are configured for providing different portions of a control signal, which are combined via the signal adder <NUM>. The VGMSS unit <NUM> is configured for producing a first signal which is indicative of a requested setting for the VGM <NUM> based on a current steady-state operation condition for the engine <NUM>, and the VGMB unit <NUM> is configured for producing a second signal which is indicative of a requested change for the setting of the VGM <NUM>. In some embodiments, the second signal is produced in response to a transition between operating conditions for the engine <NUM>, for example acceleration, deceleration, changes in altitude, and the like.

The first and second signals are then combined by the adder <NUM> to form a VGM position request signal. The VGM position request signal is then transmitted, via the signal processing device <NUM>, to the VGM control loop <NUM>, for controlling the VGM <NUM>. For example, the signal sent to the VGM <NUM> by the VGM controller <NUM> can be a voltage-encoded signal, in which the desired setting for the VGM <NUM> is set based on the voltage level of the signal. In one particular control scheme, a higher voltage level can indicate that the requested setting for the VGM <NUM> is more open, and a lower voltage level can indicate that the requested setting for the VGM <NUM> is more closed. Other approaches are also considered.

The VGMSS unit <NUM> produces the first signal having a voltage which substantially corresponds to the current setting for the VGM. By adding the second signal produced by the VGMB unit <NUM>, via the adder <NUM>, to the first signal produced by the VGMSS unit <NUM>, the resultant combined signal (i.e. the VGM position request signal) indicates a new desired setting for the VGM <NUM>. For instance, if the second signal produced by the VGMB unit <NUM> is negative, the resulting VGM position request signal will be lower than a previous value of the VGM position request signal, indicating that the engine controller <NUM> provided instructions which should result in a closing of the VGM <NUM>. Conversely, if the second signal produced by the VGMB unit <NUM> is positive, the resulting VGM position request signal will be higher than a previous value of the VGM position request signal, indicating that the engine controller <NUM> provided instructions which should result in an opening of the VGM. Of course, other control schemes, for instance using signals on carrier waves, using digital signals, or other approaches, are also considered.

In some embodiments, the VGMB unit <NUM> receives, as part of the instructions provided by the engine controller <NUM>, a speed signal, which can be used as a basis for the first signal produced by the VGMSS unit <NUM>, and the second signal produced by the VGMB unit <NUM>. In some embodiments, the VGMSS unit <NUM> and/or the VGMB unit <NUM> is provided with one or more lookup tables, maps, algorithms, and/or other types of mathematical relationships which allow the VGMSS unit <NUM> and/or the VGMB unit <NUM> to produce the first and/or the second signal based on the speed signal received from the engine controller <NUM>. Although the present discussion focuses primarily on the use of a speed signal, it should be noted that other signals, for instance a power signal, a torque signal, a pressure signal and/or any other suitable signal, are also considered.

However, the speed signal (or power, torque, etc. signal) received from the engine controller <NUM>, or from the sensors <NUM>, can, in certain instances, exhibit noise of various types, including white, Brownian, etc., jitter, and the like. In addition, small but expected variations in the speed signal are possible, despite not being indicative of actual changes in the requested speed for the engine <NUM>. This can lead to the VGMSS unit <NUM> and/or the VGMB unit <NUM> continually producing slightly varying signals, despite the engine <NUM> operating substantially at steady-state, and no actual change in the VGM <NUM> position having been requested. Put differently, the VGMSS unit <NUM> and/or the VGMB unit <NUM> can interpret the noise in the speed signal received from the engine controller <NUM> as instructions to effect changes in the position of the VGM <NUM>, and therefore produce varying first or second signals indicative of these perceived changes. Due to the random nature of signal noise, this can result in increased wear on the actuators which move the VGM <NUM>, and the VGM <NUM> itself, due to repeated and continuous changes in position.

To address this issue, the combined signal provided by the adder <NUM> is then sent to the signal processing device <NUM>. It should be noted that in some embodiments, the adder <NUM> and the signal processing device <NUM> can be embodied as a single device. The signal processing device <NUM> is configured for processing the combined signal to mitigate the risk of continually adjusting the position, orientation, and the like, of the VGM <NUM>, by removing, reducing, or mitigating the noise, dithering, and minor variations present in the combined signal, thereby producing a filtered signal. The signal processing device <NUM> then transmits the filtered signal to the VGM control loop <NUM>, which is configured for operating the actuators of the VGM <NUM>, as discussed hereinabove. In some embodiments, the signal processing device <NUM> is configured for filtering the combined signal to remove portions of the signal which are considered noise.

The signal processing device <NUM> evaluates the combined signal against a signal range for the combined signal: when variations over time in the combined signal are within the signal range, the variations are attributed to noise, and the signal processing device <NUM> performs one or more signal processing techniques to reject the variations. This is so that the movements effects produced by the VGMCL <NUM> based on the processed signal are smoother and more gradual, which can assist in reducing wear on the VGMs <NUM>, <NUM>. The signal range can be any suitable range, and can be centered at a current setting for the VGM <NUM>, for instance based on the first signal produced by the VGMSS unit <NUM>. For example, if the VGMSS unit <NUM> and the VGMB unit <NUM> use a speed signal (expressed as revolutions-per-minute, or RPM) as a basis for controlling operation of the VGM <NUM>, the signal range can be <NUM> RPM centered at the current speed of the engine <NUM>, based on the first signal. If the current speed of the engine is <NUM> RPM, any change in the speed of the engine between <NUM> and <NUM> RPM would fall within the signal range of <NUM> RPM, and would be rejected or processed by the signal processing device <NUM>. Other examples, signal ranges, and the like, are also considered.

When changes in the combined signal from one sampling time to a subsequent sampling time fall within the signal range, the changes can be considered noise and/or minor variations. In response, the signal processing device <NUM> performs processing of the combined signal to remove the noise of the combined signal. In some embodiments, the noise in the combined signal consists of high-frequency signal components: for instance, any signal portion having a frequency above <NUM>, <NUM>, or <NUM>, or any other suitable value, can be considered noise.

The signal processing device <NUM> can be configured for processing the combined signal provided by the adder <NUM> in any suitable fashion in order to mitigate the noise present in the combined signal due to the speed signal obtained at the VGMSS unit <NUM> and/or the VGMB unit <NUM>, from the engine controller <NUM> and/or the sensors <NUM>. In some embodiments, the signal processing device <NUM> includes, or is substantially composed of, an electronic filter, which may be implemented using hardware or software. For example, the filter can be embodied as a resistor-capacitor (RC) filter, a resistor-inductor (RL) filter, a resistor-inductor-capacitor (RLC) filter, a T filter, a π filter, and the like. In another example, the signal processing device <NUM> is configured for obtaining a digital representation of the combined signal, for instance via an analog-to-digital converter (ADC), for filtering the digital representation in software, and for producing the filtered signal as an analog signal, for instance via a digital-to-analog converter (DAC). Still other filtering approaches are considered.

Whether implemented in hardware or software, the filter may be any suitable type of filter, such as a first-order low-pass filter. For example, the first-order low-pass filter can be designed to have a time constant selected for filtering the combined signal to remove noise, for example based on the frequency threshold associated with noise, as discussed hereinabove. In some embodiments, the signal processing device <NUM> can additionally perform signal smoothing, noise reduction, signal modulation and/or demodulation, and the like. Alternatively, separate signal smoothing, noise reducing, or other devices can be incorporated into the VGM controller <NUM> and placed between the adder <NUM> and the signal processing device <NUM> to perform one or more signal pretreatment operations, prior to the signal processing device <NUM> receiving the combined signal.

In other embodiments, the signal processing device <NUM> includes, or is substantially composed of, a rate limiter circuit, or a device which implements rate-limiting functionality in software. The rate limiter circuit can be designed to have a characteristic rate-of-change and/or a dead-band selected for filtering the combined signal to remove noise. A software-based rate-limiter can have a similarly-selected characteristic rate-of-change and/or dead-band.

When the signal processing device <NUM> evaluates the combined signal against the signal range and determines that variations in the combined signal are not due to noise and/or minor variations in the signals from the sensors <NUM> and/or the engine controller <NUM>, the signal processing device is configured for producing the processed signal and for providing the processed signal to the VGMCL <NUM>, which is configured for interpreting the processed signal and for commanding operation of the VGM <NUM>, for instance via actuators thereof. The VGMCL <NUM> can be a substantially analog device, which performs analog-domain signal processing to transform the processed signal into commands for the VGM <NUM>. Alternatively, the VGMCL <NUM> can be implemented in software, for example as part of a full-authority digital engine controls (FADEC), and can produce via software the necessary commands for the VGM <NUM>.

The processed signal produced by the signal processing device <NUM> is a scaled version of the combined signal. The combined signal can be reduced based on the signal range such that the movements effects by the VGMCL <NUM> based on the processed signal are smoother when transitioning beyond a suitable range and more rapid albeit less accurate, which can assist in rapid tracking on the VGMs <NUM>, <NUM>. In an example in which the combined signal is a speed-based signal measured in RPM, the range can be expressed as <NUM> RPM. In the case of a transition from <NUM> RPM to <NUM> RPM, the processed signal can track the transition over subsequent sampling times by reducing the value of each subsequent RPM value by half the value of the signal range. For instance, if the combined signal is sampled at <NUM> RPM, this can be reduced by <NUM> (half the signal range of <NUM> RPM) to <NUM> RPM. In this fashion, the actual transition in the VGMs <NUM>, <NUM> commanded by the VGMCL <NUM> is offset, when compared to the combined signal, and the movement commanded in the VGMs <NUM>, <NUM> is more rapid beyond the suitable range, thereby produced in the VGMs <NUM>, <NUM> is smoother when transitioning back within the suitable range.

It should be noted that other approaches for producing the processed signal as a scaled version of the combined signal are considered. For example, the processed signal can be a time-delayed version of the combined signal. In another example, the processed signal can be a time-dilated version of the combined signal. In a further example, the processing device <NUM> can perform one or more signal processing techniques when producing the processed signal, for instance interpolation or similar techniques.

In some embodiments, the signal processing device <NUM> is configured for being activated or deactivated based on one or more events. For example, the signal processing device <NUM> can be active during certain portions of a flight mission of the aircraft. In another example, the signal processing device <NUM> can be activated in response to an activation signal, for instance as commanded by the engine controller <NUM>, and can be deactivated in similar fashion. Still other events are considered.

As such, the VGM controller <NUM> is configured for controlling operation of the VGMs <NUM>, <NUM>, while substantially ignoring unrequested changes to the position and/or orientation of the VGMs <NUM>, <NUM>, induced by noisy power, torque, or other signals used during the production of the control signals for the VGMs <NUM>, <NUM>. It should be noted that the terms "position" and "orientation", as used herein, can be used interchangeably, and the use of one does not exclude the use of the other.

With reference to <FIG>, there is provided a method <NUM> for controlling operation of the VGMs <NUM>, <NUM>. At step <NUM>, a VGM position request signal is obtained. The VGM position request signal is indicative of a requested position change for a VGM, for instance one of the VGMs <NUM>, <NUM>. The VGM position request signal can be obtained, for instance, from the adder <NUM>, which combines the first and second signals to produce the VGM position request signal based on instructions obtained from the engine controller <NUM>.

Optionally, at step <NUM>, a noise level of the VGM position request signal is reduced and/or the VGM position request signal is smoothed, for instance via the signal processing device <NUM>. The noise level reduction and/or smoothing can be implemented using any suitable techniques.

At decision step <NUM>, a determination is made regarding whether a variation of the VGM position signal is within a predetermined range. The predetermined range can be, as described hereinabove, a range centered at a current value for the VGM position signal. When the variation of the VGM position signal is within the predetermined range, the method moves to step <NUM>. When the variation of the VGM position signal is not within the predetermined range, the method moves to step <NUM>.

At step <NUM>, the VGM position request signal is filtered to reduce a level of noise in the VGM position request signal, thereby producing a filtered signal. For example, the filtering can be performed by the signal processing device <NUM>, and can comprise removing, reducing, or mitigating the noise and/or minor variations to produce the filtered signal.

At step <NUM>, the filtered VGM position request signal is transmitted to a controller of the VGM, for example the VGMCL <NUM>. The filtered VGM position request signal can be transmitted using any suitable protocol, and in any suitable format.

When the determination performed at step <NUM> indicates that the variation of the VGM position request signal is outside the predetermined range, the method <NUM> moves to step <NUM>. At step <NUM>, a processed signal, based on the VGM position request signal, is transmitted to a controller of the VGM, for example the VGMCL <NUM>. Transmitting the processed signal comprises processing the signal to scale the signal based on the signal range. The processed signal can be a noise-reduced and/or smoothed version of the VGM position request signal, or a delayed, time-dilated, interpolated, or other signal which has been processed to produce a smoother and/or more gradual movement in the VGMs <NUM>, <NUM>.

With reference to <FIG>, the method <NUM> may be implemented by a computing device <NUM>, comprising a processing unit <NUM> and a memory <NUM> which has stored therein computer-executable instructions <NUM>.

It should be noted that the engine controller <NUM>, the VGM controller <NUM>, and any other suitable elements of the engine control system <NUM>, may be implemented as part of a full-authority digital engine controls (FADEC) or other similar device, including electronic engine control (EEC), engine control unit (EUC), various actuators, and the like.

The methods and systems for controlling operation of a VGM of an aircraft engine described herein may be implemented in a high level procedural or object oriented programming or scripting language, or a combination thereof, to communicate with or assist in the operation of a computer system, for example the computing device <NUM>. Alternatively, the methods and systems described herein may be implemented in assembly or machine language. The language may be a compiled or interpreted language. Program code for implementing the methods and systems described herein may be stored on a storage media or a device, for example a ROM, a magnetic disk, an optical disc, a flash drive, or any other suitable storage media or device. The program code may be readable by a general or special-purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. Embodiments of the methods and systems described herein may also be considered to be implemented by way of a non-transitory computer-readable storage medium having a computer program stored thereon. The computer program may comprise computer-readable instructions which cause a computer, or more specifically the processing unit <NUM> of the computing device <NUM>, to operate in a specific and predefined manner to perform the functions described herein, for example those described in the method <NUM>.

Claim 1:
A signal processing device (<NUM>) for use in an aircraft engine (<NUM>) with a variable geometry mechanism (VGM) (<NUM>, <NUM>), the device (<NUM>) comprising:
a processing unit (<NUM>); and;
a non-transitory computer-readable memory (<NUM>) communicatively coupled to the processing unit (<NUM>) and having stored thereon computer-readable program instructions (<NUM>) executable by the processing unit (<NUM>) for:
obtaining a VGM position request signal via an input interface, the VGM position request signal indicative of a requested position change for the VGM (<NUM>, <NUM>);
determining whether a variation of the VGM position request signal is within a predetermined range; and
when the variation of the VGM position request signal is not within the predetermined range, producing a processed signal by scaling the VGM position request signal by a factor associated with the predetermined range, and transmitting the processed signal, based on the VGM position request signal, to a controller (<NUM>) of the VGM (<NUM>, <NUM>) to adjust the position of the VGM (<NUM>, <NUM>) on the basis of the processed signal,
characterised in that:
the program instructions (<NUM>) are further executable by the processing unit (<NUM>) for, when the variation of the VGM position request signal is within the predetermined range:
filtering the VGM position request signal to reduce a level of noise in the VGM position request signal; and
transmitting the filtered VGM position request signal to the controller (<NUM>) of the VGM (<NUM>, <NUM>), via an output interface.