Patent Description:
Vehicle electromechanical systems commonly employ rotatable shafts to adjust the position of one or more components on the vehicle. Aircrafts, for example, include flaps, slats, landing gears, etc. that are adjusted in response to rotating a shaft in a clockwise and counterclockwise direction. Not only is it desirable to measure velocity (i.e., speed and direction) of the rotating shaft to ensure the moveable component is not adjusted too quickly or whether it is moved at all, but it is also desirable to measure the position of the shaft in order to determine the current adjusted position of the moveable component, i.e., whether a given flap is open or closed. Thus, the rotational position of the shaft provides a corresponding relationship to the adjusted position of the moveable component (e.g., flat, slat, landing gear, etc.).

In other instances, some vehicles including aircraft employ dual-function dynamoelectric machine that can be utilized as both a motor and as a generator. In some situations, it is necessary to detect the position, speed and direction of the dynamoelectric machine's rotating shaft in order to sustain operation of the machine for applications operating at low speeds or at a standstill (e.g., zero speed), along with detecting a seized shaft or broken shaft. Proximity sensors are known from <CIT>, <CIT>,.

An aspect of the present invention provides a shaft monitoring system as defined by claim <NUM>.

Another aspect of the present invention provides a method of monitoring a rotatable shaft as defined by claim <NUM>.

The diagrams depicted herein are illustrative. There can be many variations to the diagram or the operations described therein without departing from the spirit of the invention. For instance, the actions can be performed in a differing order or actions can be added, deleted or modified. Also, the term "coupled", and variations thereof describes having a communications path between two elements and does not imply a direct connection between the elements with no intervening elements/connections between them. All of these variations are considered a part of the specification.

For the sake of brevity, conventional techniques related to making and using aspects of the invention may or may not be described in detail herein. In particular, various aspects of computing systems and specific computer programs to implement the various technical features described herein are well known. Accordingly, in the interest of brevity, many conventional implementation details are only mentioned briefly herein or are omitted entirely without providing the well-known system and/or process details.

A wide-variety of devices have traditionally been used to measure the rotational position of a shaft such as, for example, rotary encoders, rotary-optical encodes (sometimes simply referred to as optical encoders), resolvers that determine position based on sine and cosine output voltages, and synchro encoders that determine position based on relative voltage magnitudes between three output wires. Rotary encoders such as incremental encoders and absolute optical encoders, for example, have been traditionally employed with shafts to indicate an angular positional range of a rotated shaft. Incremental encoders generate a certain number of pulses per revolution with each pulse corresponding to a defined resolution. Every time an incremental encoder is switched on the pulse is counted from zero. In other words the position is not stored and a 'reset or reference' position must be obtained before the encoder begins counting again. Consequently, an incremental encoder can measure the change in position but not the absolute position.

An absolute optical encoder maintains position information when power is removed from the encoder. The relationship between the encoder value and the physical position of the controlled machinery is set at assembly and the system does not need to return to a calibration point to maintain position accuracy. However, absolute optical encoders require multiple code rings with various binary weightings which provide a data word representing the absolute position of the encoder within one revolution. Additional code wheels and gears must be implemented to increase the precision of the encoder, which in turn increases overall costs and weight.

Incremental encoders and absolute optical encoders both output a binary encoding signal that provides information associated with the shaft. In this case of an incremental encoder, the output binary encoding signal provides information about the motion of the shaft, but provides no information pertaining to a specific position and/or direction of the shaft. The output binary encoding signal of an absolute optical encoder may provide a general angular range of the shaft, but provides no information pertaining to a specific direction of the shaft.

Various non-limiting embodiments of the disclosure provide a shaft monitoring system that employs a proximity sensor configured to measure rotation of a proximity sensor target element (hereinafter referred to a target element) coupled to a rotating shaft. The target element includes a series of individual target sections that are sensed by the proximity sensor as the shaft rotates. The profiles and/or volumes of the individual target sections continuously change as the target element extends from the first individual target section included in the series to the last individual target section. The volume of each sensed target section with respect to the proximity sensor produces a different inductance as indicated by the proximity sensor output signal. Over a full rotation of the shaft, the proximity sensor output signal itself not only indicates a position of the shaft, but also can indicate both the rotational direction and rotational speed of the shaft.

Turning now to <FIG>, a shaft monitoring system <NUM> is illustrated. This example is outside the scope of the claims. The shaft monitoring system <NUM> includes a proximity sensor <NUM> configured to monitor a target element <NUM> coupled to a shaft <NUM>, and a signal processing system <NUM> configured to process the output signal generated by the proximity sensor <NUM>.

The signal processing system <NUM> includes an inductance-to-voltage converter (IVC) <NUM>, an analog-to-digital converter (ADC) <NUM> and a controller <NUM>. The IVC <NUM> receives a proximity sensor output signal indicative of a measured inductance between the proximity sensor and the target element <NUM>, and converts the measured inductance into an analog voltage signal. The ADC <NUM> receives the analog voltage signal and converts it into a digital signal indicative of the measured inductance. The controller <NUM> processes the digital signal to determine the angular position of the shaft (e.g., degree of rotation), the speed of the shaft (e.g., rotations per minute (RPM)), and rotational direction of the shaft (e.g., clockwise rotation or counter clockwise rotation). The speed of the shaft and rotational direction of the shaft together can define a velocity of the shaft. Accordingly, the proximity sensor output signal itself can provide the angular position of the shaft, the speed of the shaft, and the rotational direction of the shaft without requiring additional sensors and/or software algorithms to determine shaft speed and shaft direction.

The proximity sensor <NUM> can be positioned near the shaft <NUM>, which includes the proximity sensor target element <NUM> (hereinafter referred to a target element <NUM>) coupled thereto. The proximity sensor <NUM> includes an inductive sensing element <NUM>, while the target element <NUM> is formed from various materials including, but not limited to, metal and ferrous materials. Energizing the inductive sensing element <NUM> (e.g., using an alternating current (AC) signal) induces a magnetic field, which can interact with the target element <NUM>. For example, a change in distance between the proximity sensor <NUM> and the target element <NUM> varies the strength of the magnetic field, and in turn varies the inductance of the sensing element <NUM>.

With this in mind, the target element <NUM> can be coupled to the shaft <NUM> in a manner that allows the distance between the proximity sensor <NUM> and the target element <NUM> to change as the shaft <NUM> rotates. Such an arrangement causes the inductance of the sensing element <NUM> to also change as the shaft <NUM> rotates, thereby producing a relationship between the measured inductance indicated by the proximity sensor output signal and the rotational position of the shaft <NUM>. In this manner, the proximity sensor output signal alone can be processed by the signal processing system <NUM> to determine the shaft position, shaft speed and shaft direction.

Turning to <FIG>, operating concepts of the proximity sensor <NUM> and a target element <NUM> are illustrated according to non-limiting embodiments of the present disclosure. In the examples described with respect to the various embodiments of the application, the target element <NUM> comprises a ferromagnetic material and is illustrated as being coupled to an outer surface of the shaft <NUM>. The target element <NUM> also extends <NUM> degrees about a shaft axis from one target element end (e.g., a first target section) to an opposite target element end (e.g., a last target section) to define circumferential profile. It should be appreciated, however, that the inventive concept is not limited to the aforementioned arrangement and that other arrangements of the target element <NUM> and shaft <NUM> can be implemented without departing from the scope of the invention.

The proximity sensor <NUM> includes a housing <NUM> that contains an inductive coil <NUM> (sometimes referred to as a "winding") that is wound around a core <NUM>. The inductive coil <NUM> can be formed from various materials including, but not limited to metal. The core <NUM> extends along a center axis <NUM> to define a core length (L), and can be formed from various materials including, but not limited to metal, ferrite, and ferromagnetic material. Although the inductive coil is illustrated as having three turns, the proximity sensor <NUM> is not limited thereto and more or less turns can be implemented without departing from the scope of the invention.

The inductive coil <NUM> includes opposing first and second ends <NUM> and <NUM> that are electrically connected to an alternating current (AC) source <NUM>. Accordingly, the AC source <NUM> delivers AC current through the inductive coil <NUM> so as to induce an electromagnetic field. The first and second ends <NUM> and <NUM> are also electrically connected to the signal processing system <NUM> via terminals <NUM> and <NUM>. The inductance of the coil <NUM> is applied to terminals <NUM> and <NUM> in the form of a proximity sensor output signal, and delivered to the signal processing system <NUM>. In this manner, the proximity sensor output signal can be processed by the signal processing system <NUM> to determine the shaft position, shaft speed and shaft direction as described herein.

<FIG> illustrate an example of the target element <NUM> in greater detail. The target element <NUM> is formed on an outer surface of the shaft <NUM>, which extends along the rotational center axis <NUM> to define a shaft length (Ls). The target element <NUM> has a varying volume, which can be sensed by the proximity sensor <NUM> as the shaft <NUM> rotates.

According to the invention, a series of target sections that can be sensed by the proximity sensor <NUM>. Although sixteen target sections <NUM> are illustrated (labeled <NUM> through <NUM>), it should be appreciated that the target element <NUM> can include more or fewer target sections <NUM> without departing from the scope of the invention. Distinct target sections <NUM> are shown for ease of illustration.

The profiles (e.g., height, width and/or volume) of the individual target sections <NUM> continuously change as the target element <NUM> extends from the first individual target section <NUM> (e.g., section <NUM>) located at one end of the target element <NUM> to the last individual target section <NUM> (e.g., section <NUM>) located at the opposite end of the target element <NUM>. In a non-limiting embodiment, the first target element <NUM> can be formed to have a minimum volume of the target element <NUM> while the last target element <NUM> can be formed to have a maximum volume of the target element <NUM>. Accordingly, the target element <NUM> will present an ambiguous position once per <NUM> degrees, which is when the first target element <NUM> or the last target element <NUM> is aligned beneath the proximity sensor <NUM>.

The profile of each sensed target section <NUM> with respect to the proximity sensor <NUM> produces a different measured inductance, which is reflected by the proximity sensor output signal delivered to the signal processing system <NUM>. In a non-limiting embodiment, the target element <NUM> is also shown as having an inclined or ramp profile. It should be appreciated, however, that the target element <NUM> can have a different profile. For example, the target element <NUM> can have a step-like profile that include a series of steps that change in volume from the first section (e.g., section <NUM>) to the last section (e.g., section <NUM>).

In one or more non-limiting embodiments, a dummy target element <NUM> can be coupled to the outer surface of the shaft <NUM> and adjacent to the target element <NUM> as shown in <FIG>. The dummy target element <NUM> can have a mirror image profile with respect to the target element <NUM>. In this manner, the dummy target element <NUM> can serve as a counterweight to the target element <NUM> and improve the balance of the rotating shaft <NUM>.

Referring collectively to <FIG>, <FIG>, the proximity sensor <NUM> is illustrated measuring the target element <NUM> while the shaft <NUM> is in a first position. According to a non-limiting embodiment, the proximity sensor <NUM> is positioned such that the sensor axis <NUM> is perpendicular with respect to the rotational center axis <NUM> of the shaft <NUM> and a first target section <NUM> (e.g., target section <NUM>) is aligned with the axis <NUM> of the proximity sensor <NUM>. In this example, target section <NUM> has a profile of being the lowest-volume target section <NUM> or the target section <NUM> with the lowest height (H) (and the largest distance from the sensor <NUM> when located in proximity of the sensor <NUM>) extending from the surface of the shaft <NUM> and perpendicular to the rotational center axis <NUM>. Accordingly, a maximum distance is defined between the proximity sensor <NUM> and the target element <NUM> such that the coil <NUM> realizes a minimum inductance.

Turning to <FIG>, the proximity sensor <NUM> is illustrated measuring the target element <NUM> while the shaft <NUM> is rotated counter-clockwise (in almost a full rotation) into a second position from the first position shown in <FIG>. While in the second position, a second target section <NUM> (e.g., target section <NUM>) is aligned with the axis <NUM> of the proximity sensor <NUM>. In this example, target section <NUM> has a profile of being the largest-volume target section <NUM> or the target section <NUM> with the greatest height extending from the surface of the shaft <NUM>. Accordingly, a minimum distance is defined between the proximity sensor <NUM> and the target element <NUM> such that the coil <NUM> realizes a maximum inductance.

<FIG> illustrates the proximity sensor output signal <NUM> generated by the proximity sensor <NUM> in response to measuring the counter-clockwise rotation of the target element <NUM> from <NUM> degrees (<NUM>°) to <NUM> degrees (<NUM>°) as described above with respect to <FIG> and <FIG>. At <NUM>°, the lowest volume target section <NUM> (e.g., section <NUM>) of the target element <NUM> is aligned with the axis <NUM> such that the distance between the proximity sensor <NUM> and the target element <NUM> is at its maximum. As a result, the inductance of the coil <NUM> is at its minimum (Min). As the shaft <NUM> rotates counter-clockwise, the target sections <NUM> increase in volume (e.g., height). Accordingly, the inductance of the coil <NUM> gradually increases until the largest volume target section <NUM> (e.g., section <NUM>) of the target element <NUM> is aligned with the axis <NUM>. As a result, the inductance of the coil <NUM> is at its maximum (Max), thereby defining a proximity sensor output signal <NUM> having a positive slope.

It should be appreciated that the proximity sensor output signal <NUM> illustrated in <FIG> is generated using a target element <NUM> comprising a ferro-magnetic material and a coil <NUM> of the proximity sensor <NUM> excited at a low-frequency (e.g.,: frequency where the effects of magnetic permeability is greater than the effects of eddy current). In another non-limiting embodiment, a target element <NUM> comprising a non-magnetic metallic material and a coil <NUM> excited at a low-frequency (e.g.,: frequency where the effects of magnetic permeability is greater than the effects of eddy current) can result in a measured inductance that decreases as the shaft <NUM> rotates counter-clockwise. As a result, the output signal <NUM> will have a negative slope.

In another embodiment, the target element <NUM> can comprise a ferro-magnetic material and the coil <NUM> of the proximity sensor <NUM> can be excited at a highfrequency (e.g., frequency where the effects of magnetic permeability is less than the effects of eddy current). Accordingly, the measured inductance may decreases as the shaft <NUM> rotates counter-clockwise. As a result, the output signal <NUM> will have a negative slope.

<FIG> illustrates a proximity sensor output signal <NUM> generated by the proximity sensor <NUM> in response to measuring a clockwise rotation of the target element <NUM> from <NUM>° to <NUM>° as described above with respect to <FIG> and <FIG>. At <NUM>°, the largest volume target section <NUM> (e.g., section <NUM>) of the target element <NUM> is aligned with the axis <NUM> such that the distance between the proximity sensor <NUM> and the target element <NUM> is at its minimum. As a result, the inductance of the coil <NUM> is at its maximum (Max). As the shaft <NUM> rotates clockwise, the target sections <NUM> decrease in volume (e.g., height). Accordingly, the inductance of the coil <NUM> gradually decreases u the lowest volume target section <NUM> (e.g., section <NUM>) of the target element <NUM> is aligned with the axis <NUM>. As a result, the inductance of the coil <NUM> is at its minimum (Min), thereby defining a proximity sensor output signal <NUM> having a negative slope.

As described herein, the proximity sensor output signal <NUM> alone can be utilized to determine position, speed and direction of the shaft <NUM>. For instance, the proximity sensor output signal <NUM> can be converted into a digital signal using the ADC <NUM> (see <FIG>), which is then processed by the controller <NUM>. The controller <NUM> can compute the rotational position of the shaft <NUM> based on the amplitude of the proximity sensor output signal <NUM>. For example, each rotational angle of the shaft can be associated with a inductance or inductance range. In at least one non-limiting embodiment, a unique inductance is associated with each angle, notwithstanding the ambiguity that may be present at the interface between minimum volume portion of the target element and the maximum volume portion of the target element <NUM>. This ambiguity can be resolved using a software algorithm programmed in the controller <NUM>.

Accordingly, a given amplitude proximity sensor output signal <NUM> can indicate a particular rotational angle, i.e., position of the shaft <NUM>. The controller <NUM> can compute the speed of the shaft <NUM> based on the period of the proximity sensor output signal <NUM>. That is, the change in position of the change in time indicates the rotational speed of the shaft <NUM>. Lastly, the controller <NUM> can compute the direction of the shaft <NUM> based on the slope of the proximity sensor output signal <NUM>. For example, a proximity sensor output signal <NUM> having a positive slope (see <FIG>) indicates the shaft <NUM> is rotating in a counter-clockwise direction. On the other hand, proximity sensor output signal <NUM> having a negative slop (see <FIG>) indicates the shaft <NUM> is rotating in a clockwise direction.

Referring now to <FIG>, an arrangement of a proximity sensor <NUM> and a target element <NUM> coupled to a shaft <NUM> is illustrated according to another non-limiting embodiment. The target element <NUM> is formed on an outer surface of the shaft <NUM>, which extends along a rotational center axis <NUM> to define a shaft length (Ls). The target element <NUM> includes a series of individual target sections <NUM> that can be individually sensed by the proximity sensor <NUM> as the shaft <NUM> rotates. Although sixteen target sections <NUM> are illustrated (labeled <NUM> through <NUM>), it should be appreciated that the target element <NUM> can include more or fewer target sections <NUM> without departing from the scope of the invention. As described herein, distinct sections <NUM> are shown for ease of illustration.

The profiles of the individual target sections <NUM> continuously change as the target element <NUM> extends from the first individual target section (e.g., section <NUM>) to the last individual target section (e.g., section <NUM>). In this example, the changing profiles include varying widths (w) of the individual target sections <NUM>. Although the first target section <NUM> (section <NUM>) is shown as having the smallest width (w) while the last target section <NUM> (section <NUM>) is shown as having the largest width (w), it should be appreciated that the first target section <NUM> (section <NUM>) can have the largest width (w) while the last target section <NUM> (section <NUM>) can have the smallest with without departing from the scope of the invention.

The widths of the individual target sections <NUM> extend parallel to the rotational center axis <NUM> of the shaft <NUM>. As the shaft <NUM> rotates, target sections <NUM> of varying widths (and thus varying volumes) are aligned with the center axis <NUM>. Accordingly, each sensed target section <NUM> produces a different measured inductance, which is reflected by the proximity sensor output signal delivered to the signal processing system <NUM>. As described herein, a unique inductance is associated with each angle, notwithstanding the ambiguity that may be present at the interface between minimum volume portion of the target element and the maximum volume portion of the target element <NUM>. This ambiguity can be resolved using a software algorithm programmed in the controller <NUM>.

<FIG> illustrates the proximity sensor output signal <NUM> generated by the proximity sensor <NUM> in response to measuring the clockwise rotation of the target element <NUM> from <NUM>° to <NUM>° as described above with respect to <FIG>. At <NUM>°, the lowest volume target section <NUM> (e.g., section <NUM>) of the target element <NUM> is aligned with the center axis <NUM>. As a result, the inductance of the coil <NUM> is at its minimum (Min). As the shaft <NUM> rotates clockwise, the target sections <NUM> increase in width and volume. Accordingly, the inductance of the coil <NUM> gradually increases until the largest volume target section <NUM> (e.g., section <NUM>) of the target element <NUM> is aligned with the center axis <NUM>. As a result, the inductance of the coil <NUM> is at its maximum (Max), thereby defining a proximity sensor output signal <NUM> having a positive slope. Although the proximity sensor output signal <NUM> is described in terms of a clockwise rotation of the target element <NUM>, the target element <NUM> can be rotated counter-clockwise to generate a proximity sensor output signal <NUM> having a negative slope without departing from the scope of the invention.

Turning now to <FIG>, an arrangement of a proximity sensor <NUM> and a target element <NUM> coupled to a shaft <NUM> is illustrated according to another non-limiting embodiment. The target element <NUM> is formed on an end of the shaft <NUM> and is aligned with the shaft center axis <NUM>. Accordingly, both the shaft <NUM> and the target element <NUM> rotate about the center axis <NUM>.

The target element <NUM> includes a series of individual target sections <NUM> that can be individually sensed by the proximity sensor <NUM> as the shaft <NUM> rotates. Although <NUM> target sections <NUM> are illustrated (labeled <NUM> through <NUM>), it should be appreciated that the target element <NUM> can include more or fewer target sections <NUM> without departing from the scope of the invention. As described herein, distinct sections <NUM> are shown for ease of illustration.

In at least one non-limiting embodiment shown in <FIG>, the proximity sensor <NUM> is positioned such that the sensor axis <NUM> is parallel with respect to the rotational center axis <NUM> of the shaft <NUM>. However, the proximity sensor <NUM> is offset with respect to the rotational center axis <NUM> such that it is substantially aligned with a target center line <NUM> that extends along the centers of the target sections <NUM>. In this example, a first target section <NUM> (e.g., target section <NUM>) is aligned with the axis <NUM> of the proximity sensor <NUM> and has a profile of being the largest-volume target section <NUM> or the target section <NUM> with the greatest width (w) extending from the surface of the shaft <NUM> and parallel with the rotational center axis <NUM>. Accordingly, a minimum distance is defined between the proximity sensor <NUM> and the target element <NUM> (e.g., target section <NUM>) such that the coil <NUM> realizes a maximum inductance.

<FIG> illustrates the proximity sensor output signal <NUM> generated by the proximity sensor <NUM> in response to measuring the counter-clockwise rotation of the target element <NUM> from <NUM>° to <NUM>° as described above with respect to <FIG>. At <NUM>°, the lowest volume target section <NUM> (e.g., section <NUM>) of the target element <NUM> is aligned with the center axis <NUM> of the proximity sensor <NUM>. As a result, the inductance of the coil <NUM> is at its minimum (Min). As the shaft <NUM> rotates clockwise, the target sections <NUM> increase in volume. Accordingly, the inductance of the coil <NUM> gradually increases until the largest volume target section <NUM> (e.g., section <NUM>) of the target element <NUM> is aligned with the center axis <NUM>. As a result, the inductance of the coil <NUM> is at its maximum (Max), thereby defining a proximity sensor output signal <NUM> having a positive slope. Although the proximity sensor output signal <NUM> is described in terms of a clockwise rotation of the target element <NUM>, the target element <NUM> can be rotated counter-clockwise to generate a proximity sensor output signal <NUM> having a negative slope without departing from the scope of the invention.

It should be appreciated that the proximity sensor output signal <NUM> illustrated in <FIG> is generated using a target element <NUM> comprising a ferro-magnetic material and a coil <NUM> of the proximity sensor <NUM> excited at a low-frequency (e.g.,: frequency where the effects of magnetic permeability is greater than the effects of eddy current). In another non-limiting embodiment, a target element <NUM> comprising a non-magnetic metallic material and a coil <NUM> excited at a low-frequency (e.g., frequency where the effects of magnetic permeability is greater than the effects of eddy current) can result in a measured inductance that decreases as the shaft <NUM> rotates clockwise. As a result, the output signal <NUM> will have a negative slope.

In another embodiment, the target element <NUM> can comprise a ferro-magnetic material and the coil <NUM> of the proximity sensor <NUM> can be excited at a highfrequency (e.g., frequency where the effects of magnetic permeability is less than the effects of eddy current). Accordingly, the measured inductance may decreases as the shaft <NUM> rotates clockwise. As a result, the output signal <NUM> will have a negative slope.

With reference now to <FIG>, a method of determining position of a shaft is illustrated according to a non-limiting embodiment of the present disclosure. The method begins at operation <NUM> and at operation <NUM> a proximity sensor is positioned near a target element coupled to a shaft. At operation <NUM>, the proximity sensor measures the inductance corresponding to a given target section that is aligned with the proximity sensor. At operation <NUM>, the proximity sensor generates a proximity sensor output signal based a measured inductance corresponding to a given target section included in target element that is coupled to the shaft. At operation <NUM>, the shaft position is determined based on the proximity sensor output signal, and the method ends at operation <NUM>.

Turning to <FIG>, a method of determining position, speed and direction of a rotating shaft is illustrated according to a non-limiting embodiment of the present disclosure. The method begins at operation <NUM> and at operation <NUM> a proximity sensor is positioned near a target element coupled to a shaft. At operation <NUM>, the shaft is rotated (i.e., in a clockwise direction or counter-clockwise). At operation <NUM>, the proximity sensor measures the inductance corresponding to a given target section that is aligned with the proximity sensor. At operation <NUM>, the proximity sensor generates a proximity sensor output signal based on a sequence of measured inductances corresponding to rotated target sections rotating along with the shaft. At operation <NUM>, the shaft position, the shaft direction and/or the shaft speed is determined based on the proximity sensor output signal, and the method returns to operation <NUM> to rotate the shaft. At operation <NUM>, the shaft position, the shaft direction and/or the shaft speed is reported, e.g., to a display screen or a graphic user interface (GUI). As the shaft continues rotation (e.g., clockwise or counter-clockwise), the changed shaft position, shaft direction and/or the shaft speed can be actively reported in real-time.

As described herein, various non-limiting embodiments of the disclosure provide a shaft monitoring system that employs a proximity sensor configured to measure rotation of a proximity sensor target element (hereinafter referred to a target element) coupled to a rotating shaft. The target element includes a series of individual target sections that are sensed by the proximity sensor as the shaft rotates. The profiles and/or volumes of the individual target sections and/or distance between the target sections and the proximity sensor continuously change as the target element extends from the first individual target section included in the series to the last individual target section. The volume of each sensed target section with respect to the proximity sensor and/or the distance between each target section and the proximity sensor produces a different inductance as indicated by the proximity sensor output signal. Over a full rotation of the shaft, the proximity sensor output signal itself not only indicates a position of the shaft, but also can indicate both the rotational direction and rotational speed of the shaft.

Various embodiments of the invention are described herein with reference to the related drawings. Alternative embodiments of the invention can be devised without departing from the scope of this invention. Various connections and positional relationships (e.g., over, below, adjacent, etc.) are set forth between elements in the following description and in the drawings. These connections and/or positional relationships, unless specified otherwise, can be direct or indirect, and the present invention is not intended to be limiting in this respect. Accordingly, a coupling of entities can refer to either a direct or an indirect coupling, and a positional relationship between entities can be a direct or indirect positional relationship. Moreover, the various tasks and process steps described herein can be incorporated into a more comprehensive procedure or process having additional steps or functionality not described in detail herein.

Additionally, the term "exemplary" is used herein to mean "serving as an example, instance or illustration. " Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms "at least one" and "one or more" may be understood to include any integer number greater than or equal to one, i.e. one, two, three, four, etc. The terms "a plurality" may be understood to include any integer number greater than or equal to two, i.e. two, three, four, five, etc. The term "connection" may include both an indirect "connection" and a direct "connection.

Claim 1:
A shaft monitoring system comprising:
a rotatable shaft (<NUM>) including a target element (<NUM>) coupled thereto that rotates along with the shaft, the target element including a series of distinct individual target sections arranged sequentially and contiguously one after another around a full turn in the direction of rotation of the shaft;
a proximity sensor (<NUM>) located adjacent to the target element, the proximity sensor configured to measure an inductance of the target element based on one or both of a volume of the target element indicated by the individual target section sensed by the proximity sensor and a distance between the individual target section of the target element and the proximity sensor, and to generate a proximity sensor output signal based on the measured inductance; and
a signal processing system (<NUM>) in signal communication with the proximity sensor, the signal processing system configured to determine at least one of a position of the shaft, a rotational speed of the shaft, and a rotational direction of the shaft based on the proximity sensor output signal.