Patent Description:
On variable pitch propeller systems, such as those often associated to turboprop engines, it can be desirable to accurately measure the propeller blade angle, especially in the low pitch range of blade angles, often referred to as the beta (β) region. This can be done to ensure that the blade angle is controlled according to the engine power setpoint requested, such as in reverse and low pitch situations. Accurate measurement of the blade angle can also ensure that the propeller is not inadvertently commanded to transition into low or reverse beta angles.

Some variable pitch propeller systems use a measurement system which includes a sensor positioned on the stator and a feedback device which can be referred to as a ring, positioned on the rotor. The feedback ring can have position markers in the form of protrusions detected by the sensor when they come into circumferential alignment with it. Information such as blade angle can be derived from signal received from the sensor. Examples of such systems are presented in <CIT> and <CIT> for example.

While such measurement systems can be useful to a certain degree, there can be a challenge in ensuring that they achieve a required degree of accuracy in some embodiments. Indeed, while it was known to test engines on test beds for testing some systems of the engines for certification before flight, these techniques are often limited in terms of engine or propeller operating conditions which they can replicate, and may not be suitable to simulate some operating conditions which can be expected during flight. There thus remained room for improvement.

A prior art test rig for testing a blade pitch measurement system having the features of the preamble of claim <NUM> is disclosed in <CIT>.

In one aspect, there is provided a test rig for testing a blade pitch measurement system of a variable pitch propeller system, in accordance with claim <NUM>.

The mechanism may be configured for moving the second mount relative to the frame.

The test rig may further comprise a rotation sensor (or speed sensor) configured to generate a signal indicative of a rotation speed of the ring mount.

The mechanism may include an axial traverse including an axial guide, an axial motor mechanically coupled to move the second mount along the axial guide, and an axial sensor configured to generate a signal indicative of the relative displacement between the second mount and the axial guide or of relative position of the second mount along the axial guide.

The mechanism may include a radial traverse including a radial guide, a radial motor mechanically coupled to move the second mount along the radial guide, and a radial sensor configured to generate a signal indicative of the relative displacement between the second mount and the axial guide or of relative position of the second mount along the axial guide.

The controller may be further configured to perform a testing routine including controlling the rotation speed and position of the second mount trough a sequence of values associated to corresponding test conditions, and further configured to hold test data in a computer readable memory accessible to a processor of the controller, said test data associating each test condition to a corresponding rotation speed value and to a corresponding second mount position value, said testing routine being based on the test data.

The controller may be further configured to hold comparison data in a computer readable memory accessible to the processor of the controller, said comparison data including a range of permitted values for the second mount position value associated with each test condition, further configured for receiving a measured second mount position value based on a signal generated by the pitch sensor during a corresponding one of the test conditions, to compare the measured second mount position value to the range of permitted values and to generate a signal indicative of rejection if the measured second mount position value exceeds the range of permitted values.

In another aspect, there is provided a method of operating a test rig for testing a blade pitch measurement system of a variable pitch propeller system, in accordance with claim <NUM>.

The method may further comprise measuring a rotation speed of the feedback device using a rotation sensor (or speed sensor).

The method may further comprise measuring a position of the second mount along the orientation parallel to the rotation axis using an axial sensor.

The method may further comprise measuring a position of the second mount along the orientation radial to the rotation axis using a radial sensor.

The method may further comprise, using a computer, reading instructions indicating a sequence of test conditions each including a rotation speed and a position of the second mount, controlling the test rig in accordance with the sequence of test conditions, and for each test condition, receiving a corresponding signal from the pitch sensor.

The method may further comprise, for each test condition, deriving a position of the second mount from the corresponding signal received from the pitch sensor.

The method may further comprise, for each test condition, comparing the derived position of the second mount to a range of permissible values associated to the instructions, and generating a signal indicative of whether or not the derived position is within the range of permissible values.

The method may further comprise, for each test condition, deriving a rotation speed of the first mount from the corresponding signal received from the pitch sensor.

The method may further comprise, for each test condition, comparing the derived rotation speed to a range of permissible values associated to the instructions, and generating a signal indicative of whether or not the derived position is within the range of permissible values.

The method may further comprise moving the pitch sensor via the second mount from an initial radial position to a subsequent radial position along an orientation radial to the rotation axis (i.e., along a direction radial to the rotation axis) and repeating the controlling of the test rig in accordance with the sequence of test conditions in the subsequent radial position.

<FIG> illustrates a gas turbine engine <NUM>, of a type typically provided for use in subsonic flight, comprising an inlet <NUM>, through which ambient air is propelled, a compressor section <NUM> for pressurizing the air, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section <NUM> for extracting energy from the combustion gases. The turbine section <NUM> illustratively comprises a compressor turbine <NUM>, which drives the compressor assembly and accessories, and at least one power or free turbine <NUM>, which is independent from the compressor turbine <NUM> and rotatingly drives a rotor shaft <NUM> about a propeller shaft axis A through a reduction gearbox <NUM>. Hot gases may then be evacuated through exhaust stubs <NUM>. A rotor <NUM>, in the form of a propeller through which ambient air is propelled, is hosted in a propeller hub <NUM>. Rotor <NUM> may, for example, correspond to a propeller of a fixed-wing aircraft or a main (or tail) rotor of a rotary-wing aircraft such as a helicopter. The rotor <NUM> may comprise a plurality of circumferentially-arranged blades <NUM> connected to the hub <NUM> by any suitable means and extending radially therefrom. Turboshaft engines can have some similarities in operation to turboprop engines.

As depicted in <FIG>, the plurality of circumferentially interspaced blades <NUM> are each rotatable about a radially-extending axis R through a range of adjustable blade angles, the blade angle being the angle between the chord line (i.e. a line drawn between the leading and trailing edges of the blade) of the propeller blade section and a plane perpendicular to the axis of propeller rotation. A horizontally extending blade has a low pitch if its chord is oriented close to vertical, and high pitch if its chord is oriented close to horizontal (also known as the "feathered" position). A measurement system <NUM> provides blade pitch (or beta) angle position feedback during rotation of the propeller <NUM>.

Generally, the measurement system <NUM> includes a feedback device in the formof a ring <NUM> having a plurality of position markers that rotate with the ring <NUM> about axis A. The measurement system <NUM> also includes a pitch sensor <NUM> designed to detect the position markers of the ring. The measurement system <NUM> can also include any suitable electronics to receive and process the signal, and may be associated to a computer which acts in actively controlling the pitch of the blades based on various inputs such as user inputs and algorithms. The electronics and any associated circuitry can be referred to asa controller <NUM>. The controller <NUM> can form part of a broader aircraft computer or be a standalone device designed to communicate with the aircraft computer, for instance. During operation of the propeller <NUM>, the sensor <NUM> can be held on the engine casing, and the propeller <NUM> and the ring <NUM> can thus rotate relative to the sensor <NUM>. This can be practical in some embodiments due to the fact that it can help avoid having to mount any sensitive equipment on the propeller and avoid means of communication which would be required to communicate from a rotating sensor to non-rotating controller <NUM>. The sensor <NUM> can be received on an engine sensor mount forming part or otherwise secured to the engine casing, whereas the ring can be received on an engine ring mount forming part or otherwise mounted in a manner to rotate with the propeller. The feedback device mount can alternately be referred to as the first mount, and the sensor mount can alternatively be referred to as the second mount for convenience.

In an embodiment such as presented in <CIT> and <CIT> for example, the markers can be provided in the form of protrusions in the ring. The sensor <NUM> may be a variable reluctance sensor, a capacitive sensor, a hall effect sensor, and the like, and detect passage of the position markers and generates a sensor signal indicative of the passage of the position markers. While being mounted in a manner to rotate together with the propeller, the ring <NUM> can be configured for axial displacement relative to the other components of the components, and this axial displacement can occur based on a change in the pitch angle of the blades when the blades are in the beta region, for instance. The position markers can include two position markers having different slopes relative to the axial orientation in a corresponding circumferential plane, and the axial position of the ring can be derived from the distance measured between the two position markers using the sensor <NUM> and controller <NUM>.

While <FIG> shows a configuration with the sensor <NUM> being radially external tothe ring <NUM>, alternate embodiments can have a sensor which is radially internal to the ring and oriented radially outwardly, for example.

In some embodiments, there may be some significant tolerance in the ultimate radial or axial spacing between the ring <NUM> and the sensor <NUM> on the engine, based on the manufacturing tolerances of the respective mounts, and of any other component therebetween due to tolerance stacking. Accordingly, in addition to compliance with their own individual manufacturing tolerances, the certification process may additionally require that the ring and/or the sensor operate suitably independently of whether they are installed on an engine having a zero, or a perfect relative position between the sensor mount and the ring mount, or on an engine having one or two "worst case scenarios" corresponding to the greatest possible deviations from the perfect position which could be allowed within manufacturing tolerances. In some cases, the sensor and/or ring can be designed to accommodate a radial and/or axial deviation by trimming upon installation on the engine, but this may not be possible for every case, and any possible deviation not accommodated by trimming on assembly may need to be taken into account in the simulations performed in the context of the certification process.

Accordingly, while such measurement systems can be useful to a certain degree, there can be a challenge in ensuring that they achieve a required degree of accuracy in some embodiments, before approving their use for flight. Indeed, while one avenue is to test engines on test beds for testing some systems of the engines, this may not feasibly allow to replicate the conditions associated with the entire engine operating envelope to be tested.

It was found that this challenge can be satisfactorily addressed at least in some embodiments by using a test rig to validate the accuracy of the measurement system. There are, however, several challenges which may need to be addressed to be able to achieve this. For example, an embodiment of a measurement system such as presented in <CIT> can measure blade pitch based on the relative axial position between the ring and the probe, the relative axial position changing based on blade pitch in the beta region. Accordingly, for testing such a measurement system, to be able to simulate changes in blade pitch, one needs the test rig to allow for changes in relative axial position between the ring and the probe in addition to allowing an adjustable rotation speed of the ring, both of which may need to be achievable within a relatively high degree of accuracy. For instance, the required degree of precision/accuracy in the determination of the relative axial position to allow determining the blade pitch with a sufficient degree of precision, can be very high, such as in the order of <NUM>" (<NUM>), and there can be some challenges in achieving an arrangement which allows to reach the required degree of precision while also allowing for the required relative movements between the components.

Moreover, in an embodiment wherein there can exist a significant tolerance in the relative radial positions between the ring mount and the sensor mount on the engine, the test rig may further be required to allow testing for different possible values of relative radial positions between the ring and the sensor within this tolerance, in addition for allowing the relative axial movement and the rotation of the ring.

It was found that such challenges could be overcome at least in some embodiments using a test rig <NUM> such as presented in <FIG>. Indeed, it was found that such a test rig could be used to determine whether a sensor <NUM>, <NUM>, a ring <NUM>, <NUM>, or one or more other components of the measuring system <NUM> could be certified for flight, and/or otherwise certified to be within acceptable manufacturing tolerances. Suchtests can be performed separately from the engine <NUM>, and the propeller <NUM> onto which the components are to be ultimately assembled. As such, the components used for testing are the sensor <NUM>, <NUM>, the ring <NUM>, <NUM>, and a testing system <NUM>. The testingsystem can incorporate additional components of the measuring system <NUM> such as oneor more parts of the controller <NUM>, for instance. With reference to <FIG>, the sensor 306and ring <NUM> are mounted to corresponding mounts <NUM>, <NUM>. The testing system <NUM> is operatively coupled to allow receiving and processing the sensor's signal, and comparing values derived from the sensor's signal to expected values based on calibration, for one or more test conditions. The test conditions can include various ring <NUM> rotation speeds in one or more relative radial positions between the sensor <NUM> and the ring <NUM>, and/or in one or more various relative axial positions between the sensor <NUM> and the ring <NUM>, to name some examples. Various features can be included into the test rig in order to allow conveniently achieving such test conditions, for instance.

For instance, the ring mount <NUM> can be precisely mechanically connected to a shaft <NUM> associated to a rotation motor <NUM>, and the sensor mount <NUM> can be precisely mechanically connected to the housing or other non-rotating part of the motor <NUM>. The degree of precision implied will depend on the ultimate application and can be achieved by the person skilled in the art. The motor <NUM> provides for the rotation of the ring <NUM>,via the ring mount <NUM> and shaft <NUM>, relative to the sensor <NUM>. In some embodiments, it can be useful to use some form of speed sensor to provide relatively precise rotation speed information to the testing system. The speed sensor <NUM> can form part of the motor itself, or be incorporated into the motor controller for instance, and the motor controller can be included as part of or separately from the testing system <NUM>. The speed sensor <NUM> can provide an signal which is to be acquired by the testing system and converted into data for performing the comparisons, for instance. The testing system can have other data in the form of expected flight values and tolerance data, for instance, to which it compares the data obtained from the testing in the test rig to validate or reject one or more measurement system component. Rotation speed data can be included as part of the expected flight values and tolerance data, for instance, to form a basis for the comparisons.

The test rig <NUM> has an axial traverse <NUM>. The axial traverse <NUM> is part of, or the entirety of, a mechanism used to move the sensor <NUM> axially relative to the ring <NUM>, or perhaps more accurately to move the sensor mount <NUM> axially relative to the ring mount <NUM>. The axial traverse <NUM> can include an axial motor <NUM>. Preferably, the axial traverse <NUM> can further include an axial sensor <NUM> which can be used to provide precise information about the relative axial position or displacement in or between the various testing conditions. The position sensor <NUM> can form part of the motor itself, or be incorporated into the motor controller for instance, and the motor controller can be included as part of or separately from the testing system. The axial sensor <NUM> can provide a signal which is to be acquired by the testing system <NUM> and converted into data for performing the comparisons, for instance. Corresponding axial position data can be included as part of the expected flight values and tolerance data, for instance, to form a basis for the comparisons.

The test rig <NUM> further has a radial traverse <NUM>. The radial traverse <NUM> is a mechanism used to move the sensor <NUM> radially relative to the ring <NUM>, or perhaps more accurately to move the sensor mount <NUM> radially relative to the ring mount <NUM>. The radial traverse <NUM> can include a radial motor <NUM>. Preferably, the radial traverse <NUM> can further include a radial sensor <NUM> which can be used to provide precise information about the relative radial position or displacement in or between the various testing conditions. The position sensor can form part of the motor itself, or be incorporated into the motor controller for instance, and the motor controller can be included as part of or separately from the testing system. The sensor <NUM> can provide a signal which is to be acquired by the testing system <NUM> and converted into data for performing the comparisons, for instance. Corresponding radial position data can be included as part of the expected flight values and tolerance data, for instance, to form a basis for the comparisons.

The testing system <NUM> the testing system can include a software package configured for controlling the operation of the test rig. The test rig controlling elements can include software stored in a computer readable medium and executable by the computer to control the motors, in a manner which can be based on the feedback provided by corresponding sensors, to simulate various testing conditions. The testing conditions can include different rotation speeds, different relative axial positions, and/or different relative radial positions, for instance. Accordingly, the testing system can incorporate a controller is configured to perform a testing routine including controlling the rotation speed and position of the second mount trough a sequence of values associated to corresponding test conditions, and to hold test data in a computer readable memory accessible to a processor of the controller. The test data can associate each test condition to a corresponding rotation speed value and to a corresponding second mount position value. The testing routine can be based on the test data. The testing system can, using a computer, read instructions indicating a sequence of test conditions each including a rotation speed and a position of the second mount, control the test rig in accordance with the sequence of test conditions, and for each test condition, receive a corresponding signal from the pitch sensor. Data pertaining to the testing conditions can be associated to the data derived from the sensor signal.

Indeed, the testing system can further include a software package identical or comparable to the software package which will form part of the engine's measurement system <NUM>, in association with the functionality of reading and processing the sensor's signal, and deriving therefrom a rotation speed of the ring and/or an axial position of the sensor relative the ring. This latter software package can be included in the form of computer readable instructions stored in a non-transitory computer readable medium accessible to a processor forming part of the testing system, for instance. Accordingly, for each test condition of the sequence, a position of the second mount can be derived from the corresponding signal received from the pitch sensor.

The testing system can further include a software package configured for making comparisons between the data derived from the sensor in corresponding testing conditions and a range of values considered acceptable in those testing conditions. This latter software package can be included in the form of computer readable instructions stored in a non-transitory computer readable medium accessible to a processor forming part of the testing system, for instance. In an alternate embodiment, the data obtained from the testing system can be transferred to another computer which has the latter software package and which is configured to perform such comparisons, for instance, or the comparison can be made by a human inspector using an user interface. For instance, a speed as provided by the speed sensor in a given test condition can have a first value, and the speed derived from the sensor signal can have a second value. A tolerance can be associated to the first value, in a manner that if the second value is within the tolerance, the sensor is accepted, whereas if the second value exceeds the tolerance, the sensor can be rejected. Similarly, a first value of relative axial position can be established from an initial calibration, and/or from precisely known displacement from the initial calibration such as may be achieved via sensor <NUM>. A second value of relative axial position can be derived from the sensor signal in given test conditions. A tolerance can be associated to the first value, in a manner that if the second value is within the tolerance, the sensor is accepted, whereas if the second value exceeds the tolerance, the sensor can be rejected. Different testing conditions can be simulated by adjusting one or more of the rotation speed, the relative axial position, and the relative radial position, for instance. For each test condition, a rotation speed of the first mount can be derived from the corresponding signal received from the pitch sensor.

Indeed, the controller can further be configured to hold comparison data in a computer readable memory accessible to the processor of the controller. The comparison data can include a range of permitted values for the second mount position value associated with each test condition. It can be configured for receiving a measured second mount position value based on a signal generated by the pitch sensor during a corresponding one of the test conditions, to compare the measured second mount position value to the range of permitted values and to generate a signal indicative of rejection if the measured second mount position value exceeds the range of permitted values. For each test condition, the controller can comparing the derived position of the second mount to a range of permissible values associated to the instructions, and generating a signal indicative of whether or not the derived position is within the range of permissible values. For each test condition, the controller can compare the derived rotation speed to a range of permissible values associated to the instructions, and generating a signal indicative of whether or not the derived position is within the range of permissible values.

The sensor can be moved via the second mount from an initial radial position to a subsequent radial position along an orientation radial to the rotation axis, and the controlling of the test rig in accordance with the sequence of test conditions can be repeated in the subsequent radial position, potentially for a plurality of radial positions.

The ring <NUM> can be rotated at a known speed using motor <NUM>. In some embodiments, the motor <NUM> is a servo motor, which can be an AC or DC servo motor. The motor <NUM> should be capable of performing the maximum propeller acceleration/deceleration rates recorded on an actual engine, such as engine <NUM>. A speed command may be provided to the motor <NUM> from the testing system <NUM> or from a separate device for controlling speed of the ring <NUM>. A motor speed sensor <NUM> may be mechanically coupled to motor <NUM> and communicatively coupled to the testing system <NUM>. The sensor used for the motor speed sensor <NUM> may be a rotary encoder (magnetic or optical), resolver, variable reluctance probe, etc..

In some embodiments, the motor <NUM>, <NUM> of the axial traverse and/or of the radial traverse can be a stepper motor or a servo motor, and can be controlled by the testing system <NUM>. A step rate or velocity command and direction can be sent from the testing system <NUM> to the motors <NUM>, <NUM> in order to position the sensor <NUM> at a desired location. Corresponding position sensors <NUM>, <NUM> may be mechanically coupled to the motor <NUM>, <NUM> or between holder <NUM> and frame portion <NUM>, and communicatively coupled to the testing system <NUM>. The axial traverse and/or radial traverse sensor <NUM>, <NUM>, can be of a rotary type if coupled to the motor <NUM>, <NUM> itself, and may be a rotary encoder (magnetic or optical), resolver, variable reluctance probe, and the like. The axial traverse and/or radial traverse sensor <NUM>, <NUM>, can be of a linear type if coupled between the holder <NUM> and the frame portion <NUM> and may be a magnetic or optical linear encoder, a Linear Variable Differential Transformer (LVDT), a laser displacement probe, a mechanical micrometer or depth gauge, and the like.

The position of the sensor holder relative to the ring holder can be precisely determined using calibration. The sensor and the ring can then be precisely set into the corresponding holders. The sensor reading can then provide its own indication of the axial position of the ring relative to the sensor. If the sensor reading deviates from the calibration in excess of a certain threshold value, the sensor can be rejected. If the sensor reading deviates from the calibration by a value which remains within a tolerance, the sensor can be approved, or further testing can be conducted, for instance. An offset corresponding to the deviation can then be applied to the sensor reading in order to correct the sensor reading to the calibrated value for all further tests to be conducted, for instance. The axial traverse can then be used to change the axial position of the sensor relative to the ring and the readings from the sensor can be compared to expected values based on the axial traverse position information obtained from the test rig, in various simulated flight scenarios, to determine whether the readings taken at the other axial positions are correct (within allowed tolerances) or not.

In some embodiments, there may be some tolerance in the ultimate radial or axial position between the ring and the sensor on the engine. This tolerance can extend from zero, or a perfect relative position between the sensor and the ring, to one or two "worst case scenarios" corresponding to the greatest possible deviations from the perfect position which could be allowed within manufacturing tolerances. The testing performed using the test rig may be specifically intended to simulate the best and worst case scenarios. To this end, the radial traverse of the test rig can be used to change the relative radial position between the sensor and the ring between a simulated perfect radial position (or perfect air gap), and a simulated worst case position (e.g. a maximum possible air gap), for instance. Similarly, and if relevant, the axial traverse can be used to perform similar testing for simulating possible variations in the axial position due to an eventual axial manufacturing tolerance on the engine.

In some embodiments, it can be preferred for the speed of the motor used to rotate the ring mount to be controllable to within an accuracy of within +/- <NUM> RPM, preferably within +/- <NUM> RPM, and to reach acceleration speeds of at least <NUM> RPM/sec,and max speeds of at least <NUM> RPM, for instance. Alternately, it can be considered suitable in some embodiments for the measurement of the rotation speed achieved by the rotation speed sensor to be of within +/- <NUM> RPM, preferably within +/- <NUM> RPM, for instance. In some embodiments, it can be preferred for the axial traverse motor to be configured for achieving a satisfactory slew rate representive of engine operation, such as of a slew rate of <NUM> in/sec (<NUM>/s) in velocity for an acceleration of <NUM> in/sec<NUM> (<NUM>/s<NUM>) for instance, andit can be preferred for the axial traverse position sensor to have an accuracy indetermining the axial displacement from an initial position better than <NUM>" (<NUM>), preferably better than <NUM>" (<NUM>), for instance.

In one embodiment, each one of the axial traverse <NUM> and the radial traverse 352can include a corresponding guide or rail <NUM>, <NUM>, a motor <NUM>, <NUM> generating a movement of the sensor mount <NUM> relative to the corresponding guide or rail <NUM>, <NUM>, and a position sensor <NUM>, <NUM> providing a signal indicative of the movement or position of the sensor mount <NUM> relative to or along the guide or rail <NUM>, <NUM>. In one embodiment, the axial guide <NUM> is fixed relative to the frame <NUM>, and the radial guide <NUM> is moved by the axial motor <NUM> along the axial guide <NUM>. In embodiments without a radial traverse, the axial traverse forms a mechanism configured to move the sensor mount relative to the ring mount along an orientation parallel to the rotation axis A. In embodiments with aradial traverse, the axial traverse forms a mechanism configured to move the sensor mount relative to the ring mount along an orientation parallel to the rotation axis A, and the mechanism is further configured to move the sensor mount radially relative to the rotation axis. Other mechanisms than an axial traverse can be used to provide comparable movability, such as industrial robots, in other embodiments. In alternate embodiments, the axial traverse can be configured to be moved radially by the radial traverse and the radial guide can be fixed relative to the frame.

An initial relative axial position between the ring mount and the sensor mount can be achieved within a very high degree of accuracy using a calibration procedure. In one example, the calibration procedure can use a precise measurement instrument, such as a <NUM>" (<NUM>) dial indicator gauge <NUM> securely held in a fixture <NUM> having one nor more reference surfaces <NUM>. A first step represented in <FIG> can include zeroing the dial indicator gauge <NUM> to a known distance between a reference surface <NUM> and a sensing tip of the dial indicator. This can be achieved by separating the reference surface <NUM> from a granite table or precision cast iron plate <NUM> by a known distance using gauge blocks <NUM>. The fixture <NUM> can have a locating feature <NUM> such as a reference pin slot spaced from the reference surface <NUM> by a precisely known distance <NUM>. The locatingfeature <NUM> can then be known to be precisely spaced from the zero position of the dial indicator gauge <NUM> by distance <NUM>, precisely known to be the sum of distance <NUM> andthe height of the gauge block stack <NUM>.

In a second step, the fixture <NUM> can be precisely positioned in the sensor mount320 using the locating feature <NUM>. It can then be moved along the axial guide <NUM> until reaching the zero of the dial indicator gauge <NUM> in reference to a desired reference feature such as a receiving surface of the ring mount, or an axial edge of the ring <NUM>, for instance, at which point the axial traverse position sensor <NUM> can be zeroed, and the fixture <NUM> can be replaced by the sensor <NUM> using the same locating feature of the mount <NUM> for precision. If present, the radial traverse can be zeroed using a similar technique.

The testing system <NUM> can be configured for testing the sensor in accordance with a method <NUM> as illustrated in <FIG>. At step <NUM>, a sensor signal is received from the sensor <NUM> while the sensor <NUM> is positioned relative to the ring <NUM> at a known position, and the ring <NUM> is rotating at a known speed. In some embodiments, the testing system <NUM> sends control signals to one or more motors, such as motors <NUM>, <NUM>, <NUM> to cause the ring <NUM> to rotate at the known speed and to cause the sensor <NUM> to be placed at the known position. Alternatively, these settings are provided independently from the testing system <NUM>.

The sensor <NUM> may be a variable reluctance sensor that detects the change in presence or proximity of the position markers <NUM> and outputs a semi-sinusoidal signal in response. The amplitude of the signal is highest when the position markers <NUM> are closest to the sensor <NUM> and lowest when the position markers <NUM> are furthest from the sensor <NUM>. The sensor may be a passive sensor or an active sensor. For a passive sensor, the semi-sinusoidal signal is processed by the testing system <NUM> in order to get a waveform that can be more readily counted and timed. For example, a zero-crossing detector circuit may be used to generate a square pulse train from the semi-sinusoidal signal. Any design for a zero-crossing detector may be used.

At step <NUM>, a measured position and a measured speed are determined from the received sensor signal. The measured position may be an axial position, a radial (air gap) position, or a combination thereof. For example, the time period between edge transitions of the square pulse train may be measured and used to calculate the relative position (parallel to axis A in <FIG>) between the ring <NUM> and the sensor <NUM> and to determine the rotational speed of the ring <NUM>. These calculated values become the measured position and measured speed, respectively. It will be understood that through step <NUM>, the testing system <NUM> emulates the detection unit <NUM> used to determine the position and speed of the ring <NUM> as the propeller <NUM> rotates while in operation. In some embodiments, the measured position and measured speed are determined from the sensor signal as per the teachings of <CIT>. Alternatively, other methods for determining the measured position and measured speed may be used.

At step <NUM>, the measured position and speed are compared to the known position and speed to determine sensor accuracy, and may also be used to evaluate the accuracy of the position markers <NUM> or the detection unit <NUM> for investigation purposes. The differences between measured and known values may be compared to thresholds corresponding to acceptable accuracy deviations. At step <NUM>, the sensor <NUM> is accepted or rejected based on the sensor accuracy. In other words, if the difference between the measured and known values exceeds the threshold, the sensor is rejected. If the difference between the measured and known values does not exceeded the threshold, the sensor is accepted. Different thresholds may be used for position and speed, in accordance with the specifications of the application. In some embodiments, a sensor <NUM> having only one out of two acceptable accuracies is rejected. More than two test points may also be used.

In some embodiments, the method <NUM> is repeated at a plurality of rotational speeds and relative positions between the sensor <NUM> and the ring <NUM>. An example method <NUM> is illustrated in <FIG>. At step <NUM>, a change in speed and/or position is effected by changing the settings of the test mount <NUM>, for example through control of the motors <NUM>, <NUM>.

In some embodiments, the measured position of the sensor <NUM> relative to the ring <NUM> may include an offset that takes into account a tolerance of a pole piece of the sensor <NUM> and/or tolerance stack up of the testing system <NUM>. Indeed, if the tolerance of the pole piece of the sensor is greater than the system level accuracy requirements, an offset is added to each measured position by the test system <NUM> to remove (or reduce) the effect caused by the discrepancy in tolerances. The offset may be input directly into the testing system <NUM> through a user interface. Alternatively, the testing system <NUM> may determine the offset. In some embodiments, the method <NUM> includes a step of determining the sensor offset, as shown in the example of <FIG>. The offset is determined at step <NUM> at the outset of method <NUM>. In some embodiments, the offset is determined by positioning the sensor <NUM> at an offset determining position and setting the ring speed to an offset determining speed. The axial center of the ring <NUM> may be used as the offset determining position, due to the typically smaller magnetically induced axial position error at that point, but other positions may also be used. The offset determining speed is selected as a low speed at which a speed induced error may be eliminated. The offset is calculated by finding a difference between a measured position of the sensor <NUM> relative to the ring <NUM> and the offset determining position. This value may be added to all subsequent measured values, as found at step <NUM>.

In some embodiments, the offset is also used to accept/reject the sensor <NUM>, through a comparison with an offset threshold. If the offset is greater than the offset threshold, the sensor <NUM> is rejected at step <NUM>. If the offset is within the bounds of the offset threshold, then the sensor <NUM> is accepted and the method <NUM> continues onto subsequent steps to determine sensor accuracy.

In some embodiments, one or more additional tests are run concurrently with the sensor accuracy test. An example is illustrated in <FIG>, where a peak voltage output detection test is performed at step <NUM> of method <NUM> concurrently with the sensor accuracy test. The peak detection test measures the minimum and maximum voltage magnitudes of the sensor <NUM> for each of the position markers <NUM>, when the ring <NUM> is rotating at minimum and maximum speeds. This test may be triggered upon receipt of a sensor signal at step <NUM>, when the known speed is the maximum or minimum speed. Alternatively, the test may be triggered from the measured speed, as determined at step <NUM>.

Generally, the peak detection test selects and records the smallest positive and negative magnitudes of voltage over a complete ring revolution when the ring <NUM> is rotating at the minimum speed, and selects and records the largest magnitudes of voltage over a complete ring revolution when the ring <NUM> is rotating at the maximum speed. These values may be compared to minimum and maximum thresholds to ensure that the sensor <NUM> outputs a minimum voltage for all position markers <NUM> and that the maximum voltage does not exceed a maximum output voltage for optimal system accuracy. In the example illustrated, the outcome of the peak detection test is used to accept/reject the sensor at step <NUM> jointly with the sensor accuracy as determined at step <NUM>. Alternatively, separate steps of accepting/rejecting the sensor are used, one based only on sensor accuracy and one based only on peak detection.

In another example of a test performed concurrently to the sensor accuracy test, a shorted coil test may be performed. When the sensor <NUM> is a dual coil design (each wound concentrically around the same pole piece), if one coil is shorted it will affect the axial positional reading accuracy of the other coil. The shorted coil test consecutively shorts each of the coils and simultaneously measures the positional reading accuracy of the un-shorted coil to ensure the accuracy shift is not beyond an acceptable value.

Although the methods <NUM>, <NUM>, <NUM> each show different features of method <NUM> independently, it will be understood that various combinations may be used, such that two or more of the features shown in methods <NUM>, <NUM>, <NUM> may be performed concurrently in a single embodiment.

In some embodiments, the testing system <NUM> is configured to perform the various tests on the sensor in a fully automated manner, for example through the use of automated test scripts. The testing system <NUM> may comprise a user interface through which an Acceptance Test Procedure (ATP) may be configured, whereby tests, speeds, positions, and other system settings are selected by an operator. Once the ATP is configured and started, the testing system <NUM> can control the position of the sensor <NUM> through the motor <NUM>, the rotation of the ring <NUM> through the motor <NUM>, and read the input sensor signal to perform the various tests.

With reference to <FIG>, there is illustrated an embodiment of a computing device <NUM> for implementing part or all of the testing system <NUM> described above. The computing device <NUM> can be used to perform part or all of the functions of the test system <NUM>. In some embodiments, the testing system <NUM> is composed only of the computing device <NUM>. In some embodiments, the computing device <NUM> emulates the detection unit308, as found in an engine controller of an engine <NUM> and forms a subset of the testingsystem <NUM>. Although only one computing device <NUM> is illustrated, more than one computing device <NUM> may be used to implement the features of the testing system <NUM>.

The processing unit <NUM> may comprise any suitable devices configured to implement the methods <NUM>, <NUM>, <NUM>, <NUM> such that instructions <NUM>, when executed by the computing device <NUM> or other programmable apparatus, may cause the functions/acts/steps performed as part of the methods <NUM>, <NUM>, <NUM>, <NUM> as described herein to be executed.

The memory <NUM> may include a suitable combination of any type of computer memory that is located either internally or externally to device, for example random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like.

The methods and systems for testing a sensor of a propeller blade angle position feedback system 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 for testing a sensor of a propeller blade angle position feedback system 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 for testing a sensor of a propeller blade angle position feedback system 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 for testing a sensor of a propeller blade angle position feedback system 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 methods <NUM>, <NUM>, <NUM>, <NUM>.

<FIG> presents another example embodiment of a test rig <NUM>. In this embodiment, the test rig <NUM> has a ring mount <NUM> secured to a shaft <NUM> of the rotation motor <NUM>. The rotation motor <NUM> having a housing secured to a frame plate <NUM>. In this embodiment, the ring <NUM> is designed to be secured to the propeller system using a plurality of bolts <NUM>, and the ring mount <NUM> is designed to receive the ring <NUM> using the same bolts <NUM>. Accordingly, the ring <NUM> can be secured to the ring mount <NUM> using the bolts <NUM>. A cover box <NUM> is used to form a partition the rotating components from the environment during operation, for protection to any surrounding operator. The sensor mount and the sensor mount movement mechanism are on the left hand side of the figure.

In this embodiment, the sensor and ring <NUM> interact on the basis of variations in a magnetic field. In this context, it was preferred to use non-ferromagnetic materials in the rig for any component located adjacent to the magnetic field between the sensor and ring, especially if such components are non-symmetric relative to this field, to avoid or mitigate any undesired effects on the magnetic field on the operation. Accordingly, the ring mount <NUM>, including the bolts <NUM> for instance, and sensor mount can be made of non-ferromagnetic materials such as aluminum or <NUM> series steel (which have less than <NUM>% the amount of ferromagnetism than ferromagnetic steels can have, for instance). It can be convenient, for instance, for the mounts to be machined of aluminum and for the bolts to be made of <NUM> series steel. In this embodiment, the cover <NUM> was found to be relatively symmetrical to the magnetic field relative to an axially extending slot formed in one of its side, and across which the sensor magnetically interacts with the ring. Due to the symmetricity of the cover relative to the magnetic field in the region where the magnetic field has a significant strength, it was found that using a ferromagnetic material for the cover did not cause any significant interference with the operation of the system based on comparisons which were made with and without the cover.

It was also found convenient in this embodiment to provide a mount which allowed to adjust the runout of the ring <NUM> relative to the rotation axis. In this example, this was achieved by using bolts <NUM> which have a smaller diameter than the diameters of the bores formed axially across the mount <NUM> and through which they extend. In this manner, the bolts can be released, and the ring moved in its radial plane relative to the mount to a certain extent to adjust the its concentricity relative to the rotation axis, before the bolts are re-tightened. Selecting a motor which has a shaft that rotates with a high degree of concentricity with its rotation axis can also be helpful in achieving a satisfactory accuracy.

Claim 1:
A test rig (<NUM>) for testing a blade pitch measurement system (<NUM>) of a variable pitch propeller system, the blade pitch measurement system (<NUM>) including a feedback device (<NUM>; <NUM>) configured to move relative to a pitch sensor (<NUM>; <NUM>) in a propeller axis orientation when the pitch varies, the test rig (<NUM>) comprising:
a frame (<NUM>),
a first mount (<NUM>) rotatably mounted to the frame (<NUM>) and configured to receive the feedback device (<NUM>; <NUM>),
a rotation motor (<NUM>) drivingly coupled to the first mount (<NUM>) to rotate the first mount (<NUM>) relative to the frame (<NUM>) around a rotation axis (A),
a second mount (<NUM>) configured to receive the pitch sensor (<NUM>; <NUM>),
a mechanism configured for moving the second mount (<NUM>) along an orientation parallel to the rotation axis (A), and
a controller (<NUM>) configured to control the rotation of the rotation motor (<NUM>) to a variable rotation speed, and for controlling the movement of the second mount (<NUM>) to variable positions via the mechanism,
characterized in that:
the mechanism is further configured for moving the second mount (<NUM>) radially relative to the rotation axis (A).