Patent Description:
Nipped rolls are used in a vast number of continuous process industries including, for example, papermaking, steel making, plastics calendaring and printing. In the process of papermaking, many stages are required to transform headbox stock into paper. The initial stage is the deposition of the headbox stock, commonly referred to as "white water," onto a paper machine forming fabric, commonly referred to as a "wire. " Upon deposition, a portion of the white water flows through the interstices of the forming fabric wire leaving a mixture of liquid and fiber thereon. This mixture, referred to in the industry as a "web," can be treated by equipment which further reduce the amount of moisture content of the finished product. The fabric wire continuously supports the fibrous web and transfers it to another fabric called a felt which advances it through the various dewatering equipment that effectively removes the desired amount of liquid from the web. Water from the web is pressed into the wet felt and then can be removed as the wet felt passes a suction box. Dry felts can also be used to support the fibrous web through steam dryers.

One of the stages of dewatering is effected by passing the web through a pair or more of rotating rolls which form a nip press or series thereof, during which liquid is expelled from the web via the pressure being applied by the rotating rolls. The rolls, in exerting force on the web and felt, will cause some liquid to be pressed from the fibrous web into the felt. The web can then be advanced to other presses or drying equipment which further reduce the amount of moisture in the web. The "nip region" is the contact region between two adjacent rolls through which the paper web passes.

The condition of the various wires and felts can cause variations in the amount of liquid and other materials that are removed from the web which can, in turn, alter an amount of nip pressure applied to the web in a nip region. Other components in the papermaking process such as size application stations, coating stations, doctor blades, and oscillating showers can also affect the characteristics of the web. Even nip pressure axially along the roll and stable in time is beneficial in papermaking and contributes to moisture content, caliper, sheet strength and surface appearance. For example, a lack of uniformity in the nip pressure can often result in paper of poor quality. Thus, there remains a need to monitor various components of the papermaking process and account for their potential effect on nip pressure at one or more nip regions.

<CIT> describes a system for measuring the dynamic pressure distribution between rolls in a nip roll press comprises a roll adapted to rotatably contact at least one other roll in a press nip, having one or more sensors thereon, for measuring the nip pressure at several locations along the roll length, wherein the measurements obtained by the sensors are transmitted to a computer and a display, to provide tabular, numerical and graphical representations of the pressure at one or more locations on the roll.

The present invention is defined by independent claims <NUM> and <NUM>. The dependent claims depict other embodiments of the invention.

One aspect of the present invention relates to a system associated with a sensing roll and a mating roll for collecting roll data. The sensing roll and mating roll are located relative to one another to create a nip therebetween, wherein a web of material travels through the nip from an upstream direction to a downstream direction and a continuous band, arranged to travel around in a loop pattern, contacts at least a region of the web of material at the nip or upstream from the nip. A plurality of sensors are located at axially spaced-apart locations of the sensing roll, wherein each sensor enters a region of the nip during each rotation of the sensing roll to generate a respective sensor signal. The system also includes structure for generating a periodically occurring starting reference associated with each rotation of the continuous band around the loop pattern; and a processor to receive the periodically occurring starting reference and the respective sensor signal generated by each sensor. The processor upon receiving the respective sensor signal operates to: a) determine a particular one of the plurality of sensors which generated the respective sensor signal, b) based upon a value occurring between when the respective sensor signal was generated and a most recent starting reference, identify one of a plurality of tracking segments associated with the continuous band, wherein each of the plurality of tracking segments is, respectively, associated with a different value, and c) store the respective sensor signal to associate the respective sensor signal with the identified one tracking segment.

In accordance with one related aspect of the invention, the plurality of tracking segments associated with the continuous band can be either a) a plurality of circumferential segments on the continuous band, or b) a plurality of time segments of a period of the continuous band.

In accordance with related aspects of the invention each of the respective sensor signals comprises a pressure value. In accordance with other aspects of the invention the continuous band comprises a press felt or a wire mesh. Also, in accordance with at least some aspects, the continuous band does not travel through the nip although, in different embodiments, it may travel through the nip.

In accordance with a related aspect of the present invention, the starting reference comprises a time reference; the value occurring between when the respective sensor signal was generated and a most recent starting reference is calculated from an amount of time that has elapsed between when the respective sensor signal was generated and a most recent time reference; and each of the plurality of tracking segments is, respectively, associated with a different amount of elapsed time.

In accordance with other related aspects of the invention, the continuous band can include a plurality of detectable marks along at least a portion of a surface of the continuous band, wherein at least one distinctive mark of the plurality of detectable marks is different than all of the other marks. In at least some embodiments, the plurality of marks may be evenly spaced. Additionally, the structure for generating a periodically occurring starting reference includes a detector proximate to the surface of the continuous band for detecting each of the plurality of detectable marks traveling by the detector, wherein each of the plurality of detectable marks traveling by the detector defines a respective event; and a signal generator in communication with the detector for generating the starting reference each time the one distinctive mark is detected. The detectable marks can, for example, be optically detectable, magnetically detectable, detectable using infra-red radiation, detectable using sonic waves, detectable using X-rays, or detectable based on radioactive emissions.

In another related aspect of the invention, the starting reference can be a starting count and the value occurring between when the respective sensor signal was generated and the most recent starting reference is calculated from a number of events that has occurred between when the respective sensor signal was generated and the starting count. Accordingly, each of the plurality of tracking segments can be, respectively, associated with a different number of the events. Also, generating the starting reference comprises resetting the counter to the starting count.

Another aspect of the present invention relates to a method associated with a sensing roll and a mating roll for collecting roll data that includes generating a respective sensor signal from each of a plurality of sensors located at axially spaced-apart locations of the sensing roll, wherein each respective sensor signal is generated when each sensor enters a region of a nip between the sensing roll and the mating roll during each rotation of the sensing roll; the sensing roll and mating roll located relative to one another to create the nip therebetween, wherein a web of material travels through the nip from an upstream direction to a downstream direction and a continuous band, arranged to travel around in a loop pattern, contacts at least a region of the web of material at the nip or upstream from the nip. The method also includes generating a periodically occurring starting reference associated with each rotation of the continuous band around the loop pattern and receiving the respective sensor signal generated by each sensor. Then, upon receiving the respective sensor signal, a) determining a particular one of the plurality of sensors which generated the respective sensor signal, b) based upon a value occurring between when the respective sensor signal was generated and a most recent starting reference, identifying one of a plurality of tracking segments associated with the continuous band, wherein each of the plurality of tracking segments is, respectively, associated with a different value, and c) storing the respective sensor signal to associate the respective sensor signal with the identified one tracking segment.

While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements.

The present application is related to each of the following: <CIT>; <CIT>; and <CIT>.

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, specific preferred embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention, as defined by the claims.

As illustrated in <FIG> not according to the invention, a sensing roll <NUM> and a mating roll <NUM> define a nip <NUM> receiving a fibrous web <NUM>, such as a paper web, to apply pressure to the web <NUM>. It is contemplated that, in some cases, a continuous band felt may support the web such that the felt and the web enter the nip <NUM>. The sensing roll <NUM> comprises an inner base roll <NUM> and an outer roll cover <NUM>. As shown in <FIG>, a set <NUM> of sensors <NUM> is disposed at least partially in the roll cover <NUM>. The set <NUM> of sensors <NUM> may be disposed along a line that spirals around the entire length of the roll <NUM> in a single revolution to define a helical pattern, which is a common sensor geometry arrangement for roll covers. However, the helical pattern is merely an example and any arrangement is contemplated in which at least one sensor is placed at each axial position, anywhere along the circumference, at which data is to be collected. Each sensor <NUM> can, for example, measure the pressure that is being exerted on the sensor when it enters a region of the nip <NUM> between the rolls <NUM> and <NUM>. In particular, the set <NUM> of sensors <NUM> may be positioned in the sensing roll <NUM>, for example, at different axial locations or segments along the sensing roll <NUM>, wherein the axial segments are preferably equally sized. In the illustrated embodiment, there are fourteen axial segments, labelled <NUM>-<NUM> in <FIG> not according to the invention, each having one sensor <NUM> located therein. It is also contemplated that the set <NUM> of sensors <NUM> may be linearly arranged so as to define a line of sensors, i.e., all sensors reside at the same circumferential location. One of ordinary skill will readily recognize that more than fourteen, or less than fourteen, axial segments may be provided as well along with a corresponding equal number of axially-spaced sensors located on the sensing roll. Also, in the description below, each sensor <NUM> may be referred to as a pressure sensor, for example, but other types of sensors are also contemplated such as, for example, temperature sensors.

Because having even nip pressure is beneficial during paper manufacturing, correctly calculating and displaying the nip pressure profile are also beneficial since any corrections or adjustments to be made to the rotating rolls based on an inaccurate calculated nip pressure profile could certainly exacerbate any operational problems. There are three primary measurements of variability. The nip pressure profile has variability that can be termed cross-directional variability as it is the variability of average pressure per cross-direction position across the nip. Another type of variability represents the variability of the high speed measurements at each position in the single line of sensors. This variability represents the variability of other equipment in the paper making process such as, for example, wires and felts and also including the rotational variability of the mating roll, i.e., the roll nipped to the sensing roll. The third variability in the nip profile includes the variability of multiple sensors, discussed below, at each cross-directional position of the roll. This variability represents the "rotational variability" of the sensing roll as it rotates through its plurality of sensing positions and can only be seen by having a plurality of sensors in the same position.

One benefit of embedding a single set of sensors in covered rolls is to measure the real-time pressure profile and adjust loading pressures and roll crowns or roll curvature (using, for example, internal hydraulic cylinders) to achieve a flat pressure profile. As an alternative to a single set of sensors, two pluralities or arrays of sensors can be included on a sensing roll as described more fully in the earlier referenced <CIT>. The sensing roll can, for example, be separated into <NUM> axial segments. First and second pluralities of sensors, respectfully, are disposed at least partially in the roll cover. Each of the first plurality of sensors is located in one of the <NUM> axial segments of the sensing roll. Likewise, each of the second plurality of sensors is located in one of the <NUM> axial segments of the sensing roll. Each sensor of the first plurality has a corresponding sensor from the second plurality located in a same axial segment of the sensing roll. The first plurality of sensors can be disposed along a line that spirals around the entire length of the roll in a single revolution to define a helical pattern. In a similar manner, the second plurality of sensors can be disposed along a line that spirals around the entire length of the roll in a single revolution to define a helical pattern. The first and second pluralities of sensors can be separated from one another by <NUM> degrees. Each sensor measures the pressure that is being exerted on the sensor when it enters a region of a nip. It is contemplated that the first and second pluralities of sensors may be linearly arranged so as to define first and second lines of sensors, which are spaced approximately <NUM> degrees apart. Various alternative configurations of a plurality of sensors are also contemplated. For example, a plurality of sensors could be helically arranged in a line that spirals, in two revolutions, around the entire length of roll.

Typically, the sensing roll <NUM> and the mating roll <NUM> are sized differently, i.e., they have a different size radially and circumferentially. Each roll may have variations in its size circumferentially across the axial dimension. Further, as the roll rotates, the distance from the central axis (radial dimension) to the outer surface may vary for each axial position at the same angle of rotation even were the circumferential dimensions to be the same for each axial position.

For example, rolls are periodically ground which results is small arbitrary changes in diameter from the manufacture's specification. There may also be slippage with one or more of the rolls resulting in the sensing roll surface traveling at a speed that is different than the mating roll surface. Consequently, it is rare that two rolls would have exactly the same period of rotation or have periods that are exact harmonics.

Thus, as the sensing roll <NUM> and mating roll <NUM> travel through multiple rotations relative to one another, a particular sensor <NUM> may not always enter the region of the nip <NUM> with the same circumferential portion of the mating roll <NUM> as it did in a previous rotation. This behavior can be utilized to create data maps corresponding to the surface of the mating roll <NUM>. Different average pressure matrices, each collected and built during different periods of time can be compared with one another to investigate how they vary from one another. Variability between the different data maps can indicate possible problems with the mating roll <NUM>, such as roll surface irregularities, bearing wear, and roll flexing. Variability analysis of the sensor data may also indicate possible problems with upstream or downstream processing equipment, e.g., upstream rolls, an upstream forming wire, an upstream felt or downstream rolls.

The sensing and mating rolls <NUM> and <NUM> may be each separated into <NUM> axial segments. All of the axial segments on the sensing roll <NUM> may or may not be of the same length, and all of the axial segments on the mating roll <NUM> also may or may not be of the same length. In the illustrated embodiment, it is presumed that all of the axial segments on the sensing roll <NUM> are of the same length and all of the axial segments on the mating roll <NUM> are of the same length. The axial segments on the sensing roll <NUM> may be aligned with the axial segments on the mating roll <NUM>. Furthermore, the mating roll <NUM> may be separated into individual circumferential segments such as, for example, <NUM> circumferential segments, all of substantially the same dimension.

<FIG> not according to the invention illustrates how rotation of the sensing roll <NUM> and the mating roll <NUM> can change a circumferential segment of the mating roll <NUM> that enters a nip region coincidentally with a sensor on each rotation of the sensing roll <NUM>. <FIG> is presented as series of position snapshots from <NUM> to <NUM> of the rotating sensing roll <NUM> which also correspond to <NUM> rotations of the sensing roll <NUM> and <NUM> rotations of the mating roll <NUM>. The left-most portion of <FIG> shows a starting position (i.e., where a first sensor reading is collected) and the right-most position of the two rolls <NUM> and <NUM> after <NUM> rotations of the sensing roll <NUM> after the first sensor reading was collected. At the starting position, circumferential segment #<NUM> of the mating roll <NUM> is positioned in the region of the nip <NUM> along with the sensor 26A. The mating roll <NUM>, in this example, is rotating slightly faster than the sensing roll <NUM> such that at a second position snapshot following a complete rotation from the starting position, the sensor 26A is once again positioned in the region of the nip <NUM> but the mating roll <NUM> has rotated so that circumferential segment #<NUM> is in the region of the nip <NUM>. The values of <FIG> are selected just as examples to illustrate with concrete numbers operating principles of the present invention. In accordance with the example values of <FIG>, when the sensing roll had completed <NUM> rotations, the mating roll <NUM> has completed <NUM> rotations. Thus, after <NUM> rotations from the starting position (indicated by position #<NUM> in <FIG>), the sensor 26A of the sensing roll <NUM> has been able to collect <NUM> sensor readings, presuming it collected a reading at the starting position, and has "seen" all portions of the circumference of the mating roll <NUM>. Therefore, <NUM> circumferential segments can be selected as an example number of circumferential segments. One of ordinary skill will recognize that the mating roll <NUM> could be broken into more circumferential segments but that it would take more than <NUM> rotations of the sensing roll <NUM> to collect data from sensor 26A that corresponds to each of the different circumferential segments.

It would be rare that the period of the mating roll would be an integer ratio of the period of the sensing roll. Hence it is very unlikely that a stationary pattern would be maintained between these rolls and this would tend to even out the sampling of tracking segments, discussed below.

Because the one sensor 26A enters the region of the nip <NUM> concurrently with different circumferential segments of the mating roll <NUM> in the illustrated embodiment, the nip pressure measured by the one sensor 26A may vary during sequential roll rotations due to the change in pressure caused by the mating roll <NUM>. Aspects of the present invention contemplates mapping readings, or signals, from each sensor <NUM> of the set <NUM> over time to see how the pressure readings, or signals, vary for each sensor due to each sensor entering the region of the nip <NUM> concurrently with different circumferential segments of the mating roll <NUM>. As noted above, the mapped data may be used to determine possible problems with the mating roll <NUM> and, as more fully described below, data collection can be performed involving possible problems related to upstream or downstream processing equipment other than the sensing roll <NUM> and the mating roll <NUM>.

Hence, the present invention contemplates using sensors <NUM> to measure for rotational variability that is generated by the high speed rotation of the mating roll <NUM> when pressure signals, or readings, from the sensors <NUM> are time synchronized to the mating roll position. In order to measure for rotational variability, the mating roll <NUM> must have some impact on the pressure in the nip <NUM> to be measured. The dominant impact on the sensed nip pressure will likely be that of the mating roll <NUM> which directly presses against the sensing roll <NUM>. However, it may be possible to synchronize sensor measurements with upstream rolls (not shown) which form another nip and impact the water content and thickness of the web which affect the nip pressure seen by the sensing roll <NUM>. Furthermore, as rolls (not shown) in a downstream nip may pull the web and cause changes in web tension, it may be possible to also synchronize sensor measurements with these rolls. The sensing and mating rolls <NUM> and <NUM> will be used to illustrate the principles of this invention; however all principles are applicable to upstream and downstream processing equipment, such as upstream and downstream rolls, an upstream forming wire or an upstream felt.

Continuing the example of <FIG>, the mating roll <NUM> may have rotational characteristics that generate, for example, a sinusoidal pressure pattern which is <NUM> N/m<NUM> (<NUM> pounds per square inch (psi) peak-to-peak). In the illustrated example of <FIG> and <FIG> not according to the invention, to start, the pressure pattern is "<NUM>" when circumferential segment #<NUM> of the mating roll <NUM> is in the region of the nip <NUM>. <FIG> and <FIG> are a table of how collecting <NUM> sensor readings from sensor 26A would be associated with the different circumferential segments of the mating roll <NUM>. The left column <NUM> is the sequential number assigned to the sensor reading and the middle column <NUM> represents a pressure reading value from sensor 26A according to the sinusoidal pattern described above and right column <NUM> is the circumferential segment of the mating roll <NUM> in the region of the nip when a corresponding pressuring reading is taken from the sensor 26A. Each pressure reading value is time-synchronized with the period of rotation of the mating roll <NUM> by associating that value with one of the circumferential segments of the mating roll <NUM> that was in the region of the nip <NUM> when the pressure reading was sensed.

One convenient way to characterize the difference in periodicity is using units-of-measure that measure that difference in terms of time segments, e.g., <NUM> time segments in the illustrated embodiment. The length of each time segment is the mating roll period divided by the number of predefined time segments. As discussed below, the predefined number of time segments may correspond to a predefined number of mating roll circumferential segments. A period of the sensing roll <NUM> can be described as being x time segments smaller/larger than a period of the mating roll <NUM>. For example, according to <FIG>, the sensing roll <NUM> may have a period that is <NUM> mating roll time segment more than the period of the mating roll <NUM> (equivalently, the mating roll <NUM> can have a period that is <NUM> mating roll time segment smaller than the period of the sensing roll). In such an example, as the sensing roll <NUM> makes one complete revolution, the mating roll <NUM> will make more than a complete revolution by an amount equal to <NUM> mating roll time segment due to it having a smaller period than the sensing roll <NUM>.

As noted above, the <NUM> time segments of the mating roll period can correspond to <NUM> circumferential segments around the mating roll <NUM>. Thus, even though, at a conceptual level, it is the period of the mating roll <NUM> that is being separated into a plurality of time segments, that concept can correspond to a physical circumference of the mating roll <NUM>, wherein each individual time segment of the mating roll period also corresponds to a circumferential segment around the mating roll <NUM>. Accordingly, differences in rotational periods between the sensing roll <NUM> and the mating roll <NUM> measured in units of "time segments" can just as easily be considered in units of "circumferential segments. " In the description of at least some embodiments of the present invention below, reference to "circumferential segments" is provided as an aid in understanding aspects of an example embodiment of the present invention. However, one of ordinary skill will recognize that "time segments" and mating roll periodicity could be utilized as well without departing from the scope of the present invention. The "circumferential segments" and "time segments" can also be referred to generically as "tracking segments"; this latter term encompassing both types of segments associated with the mating roll <NUM> and other periodic components as described below.

As mentioned above, data similar to that of <FIG> and <FIG> is captured for each sensor <NUM> of the set <NUM>. Thus, as each sensor <NUM> arrives at the region of the nip <NUM> and senses a pressure reading, a particular mating roll outer surface portion at an axial location corresponding to that sensor and at one of the <NUM> circumferential segments of the mating roll <NUM> will also be in the nip <NUM>. Determining the mating roll segment that is in the nip <NUM> can be accomplished in a variety of different ways. One way involves indexing a particular one of the <NUM> mating roll segments with a trigger signal that is fired each time the mating roll <NUM> completes one revolution; a time period since the last trigger signal can be used to determine which of the <NUM> segments (measured relative to the indexed segment) is in the nip <NUM>. For example, if the time between each firing of the trigger signal is <NUM>, then each time segment is <NUM>, which corresponds to one of the <NUM> mating roll circumferential segments. A pressure signal generated by a sensor <NUM> in the nip region occurring at <NUM> after the trigger signal would be assigned to time segment <NUM> as three <NUM> segments will have passed, e.g., the nip region, from when the trigger signal is made to when the pressure signal is generated.

In <FIG> not according to the invention, a processor <NUM> can be present that can generate a real-time nip profile. In addition, the processor <NUM> can also receive a trigger signal <NUM> related to the rotation of the mating roll <NUM>. As just described, some circumferential segment or position <NUM> of the mating roll <NUM> can be indexed or encoded such that a signal generator <NUM> detects the encoded segment <NUM> and generates the trigger signal <NUM> each time the signal generator <NUM> determines that the segment <NUM> of the mating roll <NUM> completes another full rotation. When the mating roll <NUM> is rotated such that the circumferential position or segment <NUM> is aligned with a detector portion of the signal generator <NUM>, then the one of the <NUM> circumferential segments that happens to be positioned in the nip region can arbitrarily be labeled as the first circumferential segment such that the other circumferential segments can be numbered relative to this first segment. This particular rotational position of the mating roll <NUM> can be considered a reference position. As the mating roll <NUM> rotates, its rotational position will vary relative to that reference position and the amount of this variance determines which of the <NUM> circumferential segments will be positioned in the nip region. Accordingly, based on the rotational position of the mating roll <NUM> relative to that reference position a determination can be made as to which of the <NUM> circumferential segments is in the nip region when a particular sensor <NUM> generates a pressure signal. <FIG> illustrates the overall architecture of one particular system for monitoring paper production product quality. The system of <FIG> includes the processor <NUM>, noted above, which defines a measurement and control system that evaluates and analyzes operation of the roll <NUM>. The processor <NUM> comprises any device which receives input data, processes that data through computer instructions, and generates output data. Such a processor can be a hand-held device, laptop or notebook computer, desktop computer, microcomputer, digital signal processor (DSP), mainframe, server, other programmable computer devices, or any combination thereof. The processor <NUM> may also be implemented using programmable logic devices such as field programmable gate arrays (FPGAs) or, alternatively, realized as application specific integrated circuits (ASICs) or similar devices. The processor <NUM> may calculate and display the real-time average pressure profile calculated at the end of the prior collection session. For example, the pressure measurements from the sensors <NUM> can be sent to a wireless receiver <NUM> from transmitter(s) <NUM> located on the sensing roll <NUM>. The signals can then be communicated to the processor <NUM>. It is contemplated that the processor <NUM>, in addition to calculating a real-time average pressure profile, may use the real-time average pressure profile to automatically adjust crown and loading mechanisms to achieve a flat pressure profile. Crown and loading mechanisms may also be adjusted manually by an operator using information provided by the real-time average pressure profile.

There are other ways to determine the position of the mating roll <NUM>. One way is to use a high precision tachometer that divides the rotation of the roll <NUM> into a number of divisions, perhaps <NUM>. In this example, each time segment would be <NUM> positions on the high precision tachometer. All methods of determining the position of the mating roll are included in this invention.

In an example environment in which there are <NUM> axially arranged sensors <NUM>, each of which can be uniquely referred to using an axial segment index value that ranges from "<NUM>" to "<NUM>", and there are <NUM> circumferential segments on the mating roll <NUM> (or time segments), each of which can be uniquely referred to using a tracking segment index value ranging from "<NUM>" to "<NUM>", there are <NUM> (i.e., <NUM> x <NUM> = <NUM>) unique permutations of pairs consisting of a sensor number and a circumferential segment number (or time segment number), wherein each permutation is identifiable by a two-element set comprising a respective axial segment index value and a respective tracking segment index value. In the illustrated embodiment, the sensor numbers also correspond to the mating roll axial segments. Therefore the data collected can be considered a <NUM> x <NUM> matrix as depicted in <FIG> not according to the invention. Each row of <FIG> represents one of the <NUM> mating roll circumferential segments (or time segments) and each column represents one of the <NUM> axially arranged sensors <NUM> and, thus, each cell represents one of the possible <NUM> permutations. Each column also corresponds to a mating roll outer surface portion at an axial location aligned with and corresponding to the sensor <NUM> assigned that column. Each cell represents a combination of a sensor number (or axial segment number) and a particular mating roll circumferential segment (or time segment). For example, cell <NUM> represents a value that will relate to a pressure reading that occurred when sensor number <NUM> (number <NUM> of the <NUM>-<NUM> sensors defining the set <NUM>) entered the region of the nip <NUM> concurrently with a mating roll outer surface portion at an axial location corresponding to sensor number <NUM> and mating roll circumferential segment number <NUM> (or time segment number <NUM>). Thus, each cell of the matrix represents a unique permutation from among all the possible permutations of different axial segment numbers (e.g., <NUM>-<NUM>) and circumferential segment numbers (e.g., <NUM>-<NUM>) (or time segments <NUM>-<NUM>). A value stored in a particular matrix element is thereby associated with one particular permutation of possible axial segment numbers and circumferential segment numbers (or time segments).

The matrix of <FIG> can, for example, be a "counts" matrix wherein each cell represents the number of times a particular sensor and a particular mating roll outer surface portion at an axial location corresponding to that sensor and a particular mating roll circumferential segment were concurrently in the region of the nip <NUM> to acquire a pressure reading value. <FIG> illustrates a similarly sized matrix (i.e., <NUM> x <NUM>) but the values within the matrix cells are different from those of <FIG>. The cell <NUM> still represents a value that is related to sensor number <NUM> (or axial segment <NUM>, out of <NUM>-<NUM> axial segments, of the mating roll <NUM>) and circumferential segment <NUM> but, in this example, the value is a cumulative total of pressure readings, e.g., in N/m<NUM> (pounds/inch<NUM>), acquired by the sensor for that circumferential segment during a plurality of rotations of the sensing roll <NUM>. Thus, each time sensor number <NUM> happens to enter the region of the nip <NUM> along with the mating roll circumferential segment number <NUM>, the acquired pressure reading value is summed with the contents already in the cell <NUM>. Each of the <NUM> cells in this matrix of <FIG> not according to the invention is calculated in an analogous manner for their respective, associated sensors and segments.

From the matrices of <FIG> and <FIG>, an average pressure matrix depicted in <FIG> can be calculated. For example, cell <NUM> includes the number of pressure readings associated with sensor number <NUM> (or axial segment <NUM> of the mating roll <NUM>) and circumferential segment number <NUM> while cell <NUM> includes the total or summation of all those pressure readings. Thus, dividing cell <NUM> by cell <NUM> provides an average pressure value for that particular permutation of sensor number and mating roll circumferential segment number which entered the region of the nip <NUM> concurrently.

As a result, the matrix of <FIG> not according to the invention represents an average pressure value that is sensed for each particular sensor number and mating roll circumferential segment number. The length of time such data is collected determines how many different pressure readings are used in such calculations.

The raw pressure readings, or pressure signals, from the sensors <NUM> can be affected by a variety of components in the system that move the web of material. In particular, the average values in the average pressure matrix of <FIG> are related to variability synchronized to the mating roll <NUM>. However, there may be other variability components that are not synchronized with the mating roll <NUM> such as variability in a cross direction (CD), shown in <FIG>. One measure of this CD variability is captured by calculating an average for each column of the average pressure matrix. Thus, the average pressure matrix of <FIG> can also include a row <NUM> that represents a column average value. Each of the <NUM> columns may have <NUM> cells that can be averaged together to calculate an average value for that column. For example, cell <NUM> would be the average value in the <NUM> cells of the second column of the average pressure matrix.

Individual collection sessions of pressure readings to fill the matrices of <FIG>, <FIG>, and <FIG> may be too short to build robust and complete matrices due to data buffer and battery life limitations of data acquisition systems in communication with the sensing roll <NUM>. In such cases, consecutive collection sessions can be combined by not zeroing the matrices (i.e., counts and summation matrices) upon starting a new collection session or combining the separate matrices collected in a post hoc fashion. Consequently, collections may be stopped and restarted without loss of data fidelity as long as the synchronization of the mating roll is maintained. In particular, combining multiple collection sessions that are separated by gaps in time can be beneficial to help populate the matrices. For example, if the period difference between the two rolls were closer to <NUM> instead of <NUM> time or circumferential segments, the collection would have a tendency to collect only evenly numbered time/circumferential segments in the short term (i.e., evenly numbered segments are those that are offset an even number of segments from a starting segment) until sufficient time has passed to move the collection into the odd numbered time/circumferential segments. Combining collection sessions separated by a long time delay may help to shift the collection so that data is more uniformly captured for all the different time/circumferential segments because there is no expectation that the period of the mating roll will be related to arbitrary time gaps between collection sessions.

The press of <FIG> can be located at a number of different positions within the chain or serial sequence of different components that are part of a modern paper processing operation. <FIG> illustrates an exemplary process and system configuration in accordance with the principles of the present invention in which each of the various circles represents a rotating component (e.g. a roll) that helps propel a web of material <NUM> through the process/system. The process starts at a headbox <NUM> where a fiber slurry is distributed over a wire mesh <NUM> which allows liquid to readily drain from the slurry. From the wire mesh <NUM>, the web of material <NUM> travels to a first wet felt station <NUM> that helps dry the web of material <NUM>. A felt <NUM> at the first station <NUM> is a continuous band arranged to travel in a loop pattern around a plurality of rolls <NUM>. In the example of <FIG>, there are four rolls <NUM>. The felt <NUM> enters a press area <NUM> between one of the rolls <NUM> and a sensing roll <NUM> with the web of material <NUM>. The sensing roll <NUM> may operate similar to the sensing roll <NUM> of <FIG>. Downstream from the wet felt station <NUM> is another wet felt station <NUM> having its own felt <NUM> traveling in a loop pattern around another set of four rolls <NUM>. There is also a second press region <NUM> having a press roll <NUM>, which, in the illustrated embodiment, is not a sensing roll. The last wet felt station <NUM> has a felt <NUM> traveling in a loop pattern around another set of four rolls <NUM>. The felt <NUM> together with the web of material <NUM> is pressed by one of the rolls <NUM> and a second sensing roll <NUM> in a third press region <NUM>. The felts <NUM>, <NUM>, <NUM> are pressed into the web of material in their respective press regions <NUM>, <NUM>, <NUM> to absorb liquid from the web of material <NUM>. In this manner, the web of material <NUM> is drier after passing through the wet felt stations <NUM>, <NUM>, <NUM>. By "drier" it is meant that the fibers in the web of material <NUM> have a higher percentage by weight of fibers after the wet felt stations than before. Additional drying can be performed, however, by separate dryers <NUM> before the web of material <NUM> progresses further downstream in the process of <FIG>. The various felts and rolls of <FIG>, and the spacing between the different stations are not shown to scale but are provided to simplify description of various aspects of different embodiments of the present invention. For example, the web of material <NUM> does not travel unsupported for long distances. Typically, the web of material <NUM> will be removed from one felt and be picked up by a next-downstream felt. In additional, the web of material can be supported by other supporting rolls and by tension between various rolls.

A felt (e.g., <NUM>) can have variations in its material that cause different effects on the web of material <NUM>. For example, seams, worn spots, or even holes, may not be as effective at removing liquid from the web of material <NUM> as portions of the felt <NUM> that are in good condition. Thus, some regions of the web of material <NUM> may have more or less water relative to other regions of the web of material <NUM> due to variations in the felt <NUM>, i.e., a worn portion of the felt <NUM> may not remove as much moisture from a region of the web of material that it engages as compared to a portion of the felt that is in good condition and engages another region of the web material. When a wetter region of the web of material travels through a nip in one of the press regions (e.g. <NUM>), a pressure sensed by a sensor on a sensing roll (e.g., <NUM>) may be greater than when a drier region of the web material <NUM> passes through the nip. Also, the felts <NUM>, <NUM>, <NUM> may be porous in construction and, thus, some portions of a felt may become clogged with debris, fibers, or other contaminants. When a clogged portion of a felt is pressed into, or otherwise interacts with, and affects a region of the web of material <NUM>, not as much moisture will be removed from that region of the web of material as compared with other regions of the web of material <NUM> that were pressed into portions of the felt that were not clogged, or not as clogged. When that region of the web of material that did not have as much moisture removed travels through a nip in one of the press regions (e.g. <NUM>), a pressure sensed by a sensor on a sensing roll (e.g., <NUM>) may be greater than when the other regions that experienced more moisture being removed pass through the nip. Further, when a clogged portion of a felt travels through the nip in one of the press regions (e.g., <NUM>), a pressure sensed by a sensor on a sensing roll (e.g., <NUM>) may be greater than when a non-clogged portion of the felt passes through the nip. Thus, a pressure reading sensed in a nip can reveal effects that a felt had on the web of material <NUM> upstream of that nip in addition to revealing effects from a felt passing through the nip.

<FIG> illustrates a detailed view of the wet felt station <NUM> illustrated in <FIG> in accordance with the principles of the present invention. The felt <NUM> extends in a cross-machine direction into the plane of the drawing sheet and, as described earlier, the felt <NUM> is a continuous band arranged to travel around in a loop pattern around the four rolls <NUM> in a direction shown by arrow <NUM>. Accordingly, the felt <NUM> has a regular period of rotation around this loop pattern. Thus, different portions of the felt <NUM> each periodically travel through a region of the nip <NUM> along with the web of material <NUM>. The region of the nip <NUM> is formed between the sensing roll <NUM> and a mating roll 942A similar to the arrangement described earlier with respect to <FIG>.

The felt <NUM> may be separated into a predefined number of axial segments, such as <NUM> in the illustrated embodiment, such that the <NUM> axial segments of the felt <NUM> are axially aligned with <NUM> axially spaced apart sensors <NUM> provided on the sensing roll <NUM>.

The felt station <NUM> can have a period of rotation that can be divided into different tracking segments in the same manner as the period of rotation of the mating roll <NUM> was divided into <NUM> tracking segments as described earlier. Thus, the tracking segments related to the felt <NUM> can either be a plurality of time segments of the period of rotation of the continuous felt band <NUM> around the loop pattern or a plurality of physical circumferential segments on the continuous felt band <NUM>. The segments of the felt, only segments 1004A, 1004B, 1004C, 1004AA are designated in <FIG> with the remaining segments not being specifically identified, may, for example, be separate circumferential segments with each having an index relative to a fixed reference position <NUM> on the felt <NUM>.

As an example, the reference position <NUM> can make <NUM> complete rotation around the loop pattern in the same amount of time that the sensing roll makes <NUM> rotations. Accordingly, the felt <NUM> can be segmented into <NUM> different physical circumferential segments 1004A - 1004AE or, equivalently, the period of rotation of the felt <NUM> around its loop can be segmented into <NUM> time-based segments. In other words, because the respective portions of the felt <NUM> and the sensing roll <NUM> at a region of the nip <NUM> are travelling at substantially the same linear speed the circumference of the loop of felt <NUM> will, for this example, be about <NUM> times greater than the circumference of the sensing roll <NUM>. In the drawings, as mentioned earlier, various rolls, loops of felt, and wire meshes are not drawn to scale but, instead, are presented so as not to obscure aspects of the present invention.

Using the same principles as used when describing the mating roll <NUM> of <FIG>, the felt <NUM> can be segmented into <NUM> tracking segments, for example. As an example and as will be discussed further below, there can be a portion <NUM> of the felt <NUM> located at a circumferential segment 1004AA of the felt <NUM> that defines tracking segment #<NUM> and at an axial location aligned with a pressure sensor 26A (one of <NUM> pressure sensors on the sensing roll <NUM> in the illustrated embodiment) on the sensing roll <NUM> that causes an increase in pressure in the region of the nip <NUM> of approximately <NUM> N/m<NUM> (<NUM> psi) as compared to a pressure increase of about <NUM> N/m<NUM> (psi) for all other portions of the felt <NUM> at different axial and circumferential locations. In a manner similar to how data in <FIG> and <FIG> was collected in a manner time-synchronized with the rotational period of the mating roll <NUM>, sensor readings from the region of the nip <NUM> defined by the sensing roll <NUM> and the mating roll 942A can also be collected in a manner time-synchronized with the period of rotation of the felt <NUM>.

In <FIG>, a processor <NUM> can be present that can receive a trigger signal related to the rotation of the felt <NUM>. Some circumferential segment or position <NUM><NUM> of the felt <NUM> can be indexed or encoded such that a signal generator 900A detects the encoded segment <NUM> and generates a trigger signal each time the signal generator 900A determines that the segment <NUM> of the felt <NUM> completes another full rotation. When the felt <NUM> is rotated such that the circumferential position or segment <NUM> is aligned with a detector portion of the signal generator 900A, then the one of the <NUM> circumferential segments that happens to be positioned in the nip region can arbitrarily be labeled as the first circumferential segment such that the other circumferential segments can be numbered relative to this first segment. This particular rotational position of the felt <NUM> can be considered a reference position. As the felt <NUM> rotates, its rotational position will vary relative to that reference position and the amount of this variance determines which of the <NUM> circumferential segments will be positioned in a region of the nip <NUM>. Accordingly, based on the rotational position of the felt <NUM> relative to that reference position a determination can be made as to which of the <NUM> circumferential segments is in the nip region when a particular sensor 26A generates a pressure signal.

<FIG> is a table of how collecting <NUM> sensor readings from sensor 26A (one of <NUM> pressure sensors on the sensing roll <NUM> in the illustrated embodiment) would be associated with the different tracking segments (e.g., <NUM> tracking segments in the illustrated embodiment with only segments 1004A, 1004B, 1004C and 1004AA being designated in <FIG>) of the felt <NUM>. The data in <FIG> and <FIG> and <FIG> is simulated data and, as noted before, could be generated by rolls and felts having different relative sizes as compared to those depicted in the figures. As a simulation, the data is nicely behaved and the tracking segments advance one segment per sensing roll rotation. Actual data may not be this well behaved as there may be no relation to the tracking segment length and sensing roll rotation period. Actual collections therefore are like to have skips (consecutive readings in non-consecutive tracking segments) and repeats (consecutive readings in the same tracking segment). The result of this is that the tracking segments are not evenly sampled. However, as discussed in more detail in <CIT>, if data is collected for a sufficient amount of time, it is unlikely that any tracking segments will not have corresponding sensed data even if there is unevenness in the data sampling per tracking segment. Similar to <FIG> and <FIG>, the left column 402A is the sequential number assigned to the sensor reading and the next column 404A represents a raw nip pressure reading value when the pressure sensor 26A enters the region of the nip <NUM> defined by the sensing roll <NUM> and the mating roll 942A. As discussed above, each pressure reading value in column 404A can be time-synchronized with the period of rotation of the mating roll 942A by associating that value with one of the <NUM> circumferential segments, see column 406A, of the mating roll 942A that was in the region of the nip <NUM> when the pressure reading was sensed. In addition, each pressure reading value in column 404A can also be time-synchronized with the period of rotation of the felt <NUM> by associating that value with one of the <NUM> tracking segments, in column <NUM>, of the felt <NUM> that was in the region of the nip <NUM> when the pressure reading was sensed.

Similar to the mating roll <NUM> being segmented into axial segments corresponding to the different locations of the sensors <NUM> on the sensing roll <NUM>, the felt <NUM> can be segmented into cross-machine direction (or axial) segments as well, as noted above. <FIG> illustrates a felt <NUM> in relation to a sensing roll <NUM> in accordance with the principles of the present invention. In particular, the view of <FIG> is from the perspective of being below the sensing roll <NUM> and looking upwards towards the felt <NUM>. The felt <NUM> has a width W2 that is substantially similar to a width W1 of the web of material <NUM> that are both typically smaller than the length L of the sensing roll <NUM>. Thus, either or both of the web of material <NUM> and the felt <NUM> can be broken into multiple axial segments <NUM> that each correspond to one of the sensor locations on the sensing roll <NUM>, e.g., <NUM> axial segments in the illustrated embodiment. Accordingly, similar matrices of "counts", "sums" and "averages" as described in <FIG> can be constructed for the data from <FIG> but arranged in a manner time-synchronized with the period of the felt <NUM>. In the example provided above, each such matrix would have (31x14), or <NUM>, cells.

In the example stations of <FIG> and as noted above, not every wet felt station <NUM>, <NUM>, <NUM> necessarily has a press region <NUM>, <NUM>, <NUM> that includes a sensing roll. <FIG> illustrates the wet felt station <NUM> with the press region <NUM> having the sensing roll <NUM> that is downstream from the wet felt station <NUM> that does not have a press region with a sensing roll in accordance with the principles of the present invention.

In <FIG>, the sensing roll <NUM> is associated with the region of the nip <NUM> of the press region <NUM> while the press region <NUM> of the wet felt station <NUM> may not necessarily include a sensing roll. However, the felt <NUM> of the wet felt station <NUM> still rotates as a continuous band in a loop pattern similar to the manner described with respect to the felt <NUM> of <FIG>. Accordingly, the felt <NUM> has a regular period of rotation around this loop pattern. Thus, different portions of the felt <NUM> each periodically contact a region of the web of material <NUM> upstream from the region of the nip <NUM> even though the felt <NUM> itself does not travel through the region of the nip <NUM>.

In <FIG>, a portion <NUM> of the felt <NUM> (having corresponding axial and circumferential locations on the felt <NUM>) is shown that contacts the web of material <NUM> in a periodic manner as the web of material <NUM>. passes through the region of the nip <NUM> of the press region <NUM>. Regions <NUM>, <NUM>, <NUM> and <NUM> (each having corresponding axial and circumferential positions on the web of material <NUM>), evenly spaced by a distance d in the circumferential direction, of the web of material <NUM> that were in the region of the nip <NUM> concurrently with the portion <NUM> of the felt <NUM> are shown in <FIG>, i.e., in the illustrated embodiment the felt portion <NUM> engages each of the web of material regions <NUM>, <NUM>, <NUM> and <NUM> at different occurrences or times when in the nip <NUM>. When those web of material regions <NUM>, <NUM>, <NUM> and <NUM> travel through the region of the nip <NUM> of the downstream felt station <NUM>, the pressure readings from the sensing roll <NUM> in the downstream felt station <NUM> can be affected by the impact that the felt portion <NUM> had on the web of material regions <NUM>, <NUM>, <NUM> and <NUM> that it contacted in the upstream nip <NUM>. As explained earlier, the condition of the felt <NUM> as it is pressed into the web of material <NUM> can affect, for example, the amount of moisture that is drawn out from the contacted region of the web of material <NUM> or other characteristics of the web of material <NUM>. Thus, some regions of the web of material <NUM> may be wetter or drier relative to one another and cause higher or lower pressure readings when passing through the region of the nip <NUM>.

The felt station <NUM> can have a period of rotation that can be divided into different time-based tracking segments of the period of rotation of the continuous band around the loop pattern of the four rolls <NUM>. Also, the felt <NUM> can be divided into a plurality of physical circumferential tracking segments on the continuous band. In the illustrated embodiment, the felt <NUM> comprises <NUM> physical circumferential segments, with only four segments 1202A, 1202B, 1202C, <NUM> being designated in <FIG>. The <NUM> physical segments, may, for example, be separate circumferential segments with each having an index relative to a fixed reference position <NUM> on the felt <NUM>. As discussed below, a particular time-based tracking segment, e.g., #<NUM>, may not correspond to a physical circumferential segment having that same index value.

Returning to <FIG>, each of the simulated raw pressure readings from the region of the nip <NUM> that are shown in column 404A can be associated with a specific single time-based tracking segment of the period of rotation of the felt <NUM>. These time-based tracking segments can then be correlated to a specific physical circumferential segment of the felt <NUM> as well. Thus, the table of <FIG> also shows how collecting <NUM> sensor readings from the sensor 26A (one of <NUM> pressure sensors on the sensing roll <NUM>) would be associated with different time-based tracking segments, shown in column <NUM> which, in turn, can be correlated to the different physical circumferential tracking segments (e.g., <NUM> physical tracking segments with only 1202A, 1202B, 1202C, <NUM> being designated in <FIG>) of the felt <NUM>. As described earlier, the left column 402A is the sequential number assigned to the sensor reading and the next column 404A represents a simulated raw pressure reading sensed at the region of the nip <NUM> by the sensor 26A on the sensing roll <NUM>. Each such pressure reading will have a value that is related to the regions of the web of material <NUM> passing through the nip <NUM>. As an example, see <FIG>, the portion <NUM> of the felt <NUM> is located at the circumferential segment <NUM> of the felt <NUM>, which segment <NUM> may define physical circumferential segment #<NUM>, and at an axial location that is axially aligned with the pressure sensor 26A on the sensing roll <NUM> in the downstream nip <NUM>. The felt portion <NUM> may be damaged such that it does not remove as much moisture from a region of the web of material <NUM> it contacts as compared to other felt portions that remove a greater amount of moisture from the web of material regions they contact. Hence, because the felt portion <NUM> removes less moisture content from a corresponding web of material region that it contacts, that web of material region, in turn, causes an increase in pressure in the region of the nip <NUM>, e.g., of approximately <NUM> N/m<NUM> (<NUM> psi) in the illustrated example, as compared to a pressure increase of about <NUM> psi for all other web of material regions.

Time-synchronizing the values in column 404A with the period of rotation of the felt <NUM> can be accomplished by associating that pressure reading value with one of the <NUM> time-based tracking segments of the period of rotation of the felt <NUM> that correspond to when the pressure reading was sensed.

As an example, the reference position <NUM> on the felt <NUM> can make <NUM> complete rotation around the loop pattern around the rolls <NUM> in the same amount of time that the sensing roll <NUM> in the downstream nip <NUM> makes <NUM> rotations. Thus, the felt <NUM> advances by the length of one of the physical tracking segments (e.g., 1202A) for every rotation of the sensing roll <NUM>. As an example and as mentioned above, the portion <NUM> of the felt <NUM> is located at the circumferential segment <NUM> of the felt <NUM>, which segment <NUM> may define the physical circumferential segment #<NUM> and at an axial location that is axially aligned with the pressure sensor 26A on the sensing roll <NUM> in the downstream nip <NUM>.

Thus, a signal generator 900B generates a periodic time reference signal when the reference position <NUM> of the felt <NUM> is adjacent the signal generator 900B. This is the reference signal from which a time-based tracking segment of the period of rotation of the felt <NUM> can be calculated as the sensor 26A on sensing roll <NUM> passes through the region of the nip <NUM>. As one example, when a pressure reading is sensed and generated by the pressure sensor 26A of the sensing roll <NUM>, the processor <NUM> will determine the elapsed time period in <NUM>/<NUM> increments since the last reference signal was generated by the signal generator 900B. If a pressure reading was generated by the sensor 26A of the sensing roll <NUM> twenty-five (<NUM>/<NUM>) time increments from when the last reference signal was generated, this would correspond to <NUM>/<NUM> of the total period of rotation of the felt <NUM>. Thus, the pressure reading sensed at the nip <NUM> can be associated with time-based tracking segment #<NUM>. Thus, the felt rotational period can comprise m time-based tracking segments, each having a respective, unique index value x in the range of: <NUM>, <NUM>,. , m (e.g., m = <NUM>).

In a manner similar to how data in <FIG> and <FIG> and <FIG> was arranged, or stored, in a manner time-synchronized with the rotational period of the mating roll 942A and the felt <NUM>, sensor readings from the region of the nip <NUM> could also be arranged, or stored, in a manner time-synchronized with the period of rotation of the felt <NUM>.

For the felt <NUM>, the time-based tracking segment numbers (e.g., time-based tracking segment #<NUM>) refer to logical segments of the period of rotation of the felt <NUM> which have occurred from when the reference signal was generated by the signal generator 900B until a pressure reading is sensed and generated by the pressure sensor 26A of the sensing roll <NUM>. However, these initial time-based tracking segment numbers do not necessarily correspond to an identical physical circumferential segment on the felt <NUM> as measured from the reference location <NUM>. In other words, a region of the web of material in the region of the nip <NUM> concurrently with sensor 26A may arrive at the <NUM>th time segment of the period of rotation of the felt <NUM> but that region of the web of material <NUM> was not necessarily pressed in the nip region <NUM> by the physical <NUM>th circumferential segment of the felt <NUM> as measured from the reference location <NUM>. There is a delay between felt <NUM> and nip <NUM> impacting the properties of the web and the sensing of this change at a region of the nip <NUM>. In general, variations in the felt <NUM> while in the nip <NUM> can impact the amount of moisture in the region of the web of material <NUM> concurrently in the nip <NUM> and also the thickness of caliper of the web. These differences in moisture and thickness can impact pressure values sensed at the nip <NUM> as the regions of the web of material <NUM> with different amounts of moisture enter a region of the nip <NUM> concurrently with a sensor 26A. Thus, the variations in the felt <NUM> impact pressure values sensed in a region of the nip <NUM>.

In addition to the time-based technique described above for identifying different tracking segments, alternative techniques are contemplated as well. For example, the rotating felt <NUM> could include multiple, evenly-spaced marks that could be detected (e.g., optically) as each such mark passes a sensor location. The marks would function so as to separate the felt <NUM> (or <NUM>) into different segments and a counter, or similar circuitry, would increment a count each time a mark was detected so that any collected data could be associated with one of the segments of the felt <NUM>. A reference mark could be distinctive from all the other marks such that when the sensor detects the reference mark, the counter circuitry resets and starts counting from an initial value (e.g., "<NUM>" or "<NUM>"). As an example, each evenly-spaced mark could be a single tick mark, a tick mark of a particular width, or a mark of a particular color. The reference mark could be a double-tick mark, a thicker (or thinner) tick mark, or a mark of a unique color. If the techniques of segmenting the felt <NUM> just described were utilized, then it would be unnecessary to explicitly measure an elapsed time since the most recent generation of a reference timing signal that is generated each revolution of the felt <NUM>. The detectable marks can, for example, be optically detectable, magnetically detectable, detectable using infra-red radiation, detectable using sonic waves, detectable using X-rays, or detectable based on radioactive emissions.

<FIG> provides an exemplary method for relating a time-based tracking segment of the felt <NUM> to a corresponding physical circumferential tracking segment on the felt <NUM>. Felts, such as <NUM> and <NUM> can vary in length, or circumference, between <NUM> to <NUM> meters (<NUM> to <NUM> feet) for example. In an example embodiment, the diameter of the sensing roll <NUM> is <NUM> meter (<NUM> feet) which makes its circumference approximately <NUM> feet. Felt <NUM> has, in this example, <NUM> physical circumferential segments each being equivalent in length to the circumference of the sensing roll <NUM>. Thus, the felt <NUM> is a little more than <NUM> feet in length, LF. The felt <NUM> also rotates as a continuous band around the rolls <NUM> with a period of rotation ρ. In a simple example, the region of the nip <NUM> is located downstream a distance from the region of the nip <NUM> that is an integer multiple of the felt length LF. As <FIG> shows, when the reference location <NUM> is at its position to generate a new time reference signal, there is a segment (e.g., segment #<NUM>) that is touching the web of material <NUM>. In the illustrated embodiment, because segment #<NUM> is the only felt segment ever in the nip <NUM> each time a new time reference signal is generated, it is designated as a "felt touch reference segment. " There are also two other regions <NUM>, <NUM> shown on the web of material <NUM> that were previously in the region of the nip <NUM> concurrently with the "felt touch reference segment" #<NUM>. That is, the web material region <NUM> was in the region of the nip concurrently with the "felt touch reference segment" # <NUM> during one prior rotation of the felt <NUM> and the web material region <NUM> was in the region of the nip concurrently with the "felt touch reference segment" # <NUM> during two prior rotations of the felt <NUM>.

Relative to the web of material region <NUM> and subsequent to the region <NUM> being in the nip <NUM>, there is an adjacent web of material region <NUM> that was in the region of the nip <NUM> concurrently with circumferential segment #<NUM> of the felt <NUM> and adjacent that region <NUM> is a web of material region <NUM> that was in the region of the nip <NUM> with circumferential segment #<NUM> of the felt <NUM>. Ahead of the web of material region <NUM>, there is an adjacent region <NUM> of the web of material that was in the region of the nip <NUM> concurrently with circumferential segment #<NUM> of the felt <NUM> and a web of material region <NUM> was in the region of the nip <NUM> concurrently with circumferential segment #<NUM> of the felt <NUM>. Each web of material region <NUM>, <NUM>, <NUM>, <NUM>, <NUM> has a length of <NUM>/<NUM>th of the length LF of the felt <NUM> corresponding to a time period ρ/<NUM> long.

In <FIG>, at the sensing roll <NUM>, the region <NUM> of the web of material <NUM> is shown in the region of the nip <NUM> with the sensor 26A. Based on the reference signal from the generator 900B, which in the illustrated embodiment is always generated concurrently with the felt touch reference segment #<NUM> of the felt <NUM> being in the nip <NUM>, the sensed reading of the sensor 26A on the sensing roll <NUM> occurs during a first time-based period tracking segment (e.g., <MAT>, which first time-based period tracking segment starts concurrently with the generation of the reference signal by the generator 900B and the value "t" represents an amount of time since generation of that reference signal. If the sensor 26A, however, was in a position to arrive in the nip <NUM> during the next time-based segment of the period of rotation of the felt <NUM>, x = <NUM>, then the reference location <NUM> would have moved by a distance equal to one circumferential segment of the felt <NUM> and the web of material <NUM> would have moved forward substantially the same distance so that a region just behind region <NUM> (and analogous to region <NUM>) would have entered the region of the nip <NUM>. Accordingly, if the sensed reading occurs during the second time period tracking segment <MAT>, then the region of the web of material <NUM> that is in the region of the nip <NUM> was also previously in the region of the nip <NUM> concurrently with the circumferential tracking segment #<NUM> of the felt <NUM>.

Accordingly, each time-based tracking segment can be easily correlated to a physical circumferential tracking segment of the felt <NUM>. If the reading of the sensor 26A on the sensing roll <NUM> takes place between <MAT>, wherein "x" is the index value of a time-based tracking segment of the rotational period of the felt <NUM> measured from the last generated reference signal from the generator 900B, which time-based tracking segment occurs concurrently with the sensor 26A being in the region of the nip <NUM>, then the region of the web of material <NUM> in the region of the nip <NUM> was also previously in the region of the nip <NUM> concurrently with the physical circumferential segment of the felt <NUM> indexed by an index value q, where q = ((# of felt touch reference segment (i.e., #<NUM> in the illustrated embodiment)) + (x - <NUM>)) as measured from the reference location <NUM>. This index value would, of course wrap around to begin again at "<NUM>" when it exceeds "<NUM>", the number of physical circumferential segments.

<FIG> illustrates a slight modification to the arrangement of <FIG> in which the region of the nip <NUM> happens to be, for example purposes, a distance from the region of the nip <NUM> that is not an integer multiple of the length LF of the felt <NUM>. As compared to the arrangement of <FIG>, the distance between the region of the nip <NUM> and the region of the nip <NUM> in <FIG> has an additional span or distance y. In the illustrated embodiment, the amount of time it takes the web of material <NUM> to travel the extra distance y equals <MAT>. A sensor reading from the region of the nip <NUM> occurring during the first time-based tracking segment <MAT> will involve a region of the web of material <NUM> that was also previously in the region of the nip <NUM> concurrently with the circumferential segment #<NUM> (e.g., <NUM> time segments before the "felt touch reference segment" (i.e., #<NUM> in the illustrated embodiments of <FIG> and <FIG>) was in the region of the nip <NUM>. So, more generally:.

Thus, the felt <NUM>, or more generally a continuous band, can comprise m (e.g., m = <NUM>) physical circumferential tracking segments relative to a reference location on the continuous band, each having a respective, unique index value q in the range of <NUM>, <NUM>,. , m, wherein each of the m time-based tracking segments can be associated with a corresponding one of m physical circumferential tracking segments. As described above, the index value x of a particular time-based tracking segment can be calculated independently from calculating the index value q of the corresponding circumferential tracking segment (i.e., calculating x of a time-based tracking segment does not depend on first determining q of a corresponding physical circumferential segment).

Additionally, referring back to <FIG> and the equation above, each physical circumferential tracking segment #<NUM> - #<NUM> of the felt <NUM> contacts the web of material <NUM> at an upstream location from the region of the nip <NUM>; and the index value q of each physical circumferential tracking segment #<NUM> - #<NUM> can be calculated based on a) a distance between the region of the nip <NUM> and the upstream location (e.g., the nip <NUM>), and b) the index value x of the corresponding time-based tracking segment. More specifically, one particular circumferential tracking segment contacts the web of material <NUM> at the upstream location substantially concurrently with the signal generator generating the trigger signal and can be considered a felt touch reference segment, and the index value q of each circumferential tracking segment (e.g., #<NUM> - #<NUM>) can be calculated based on a) a distance between the region of the nip <NUM> and the upstream location (e.g., nip <NUM>), b) the index value of the one particular circumferential tracking segment (e.g., #<NUM>, the felt touch reference segment), and c) the index value x of a corresponding time-based tracking segment. In each of the two scenarios for calculating a particular physical circumferential segment index value, q, based on a time-based tracking segment index value, x, just described, a distance between the region of the nip <NUM> and the upstream location (e.g., nip <NUM>) was used in the calculation. As described earlier, it may be beneficial to consider the distance between the region of the nip <NUM> and the upstream location (e.g., the nip <NUM>) to be an integer multiple of the length LF of the felt <NUM> plus some additional span or distance y, wherein the unit of measure for y is in terms of physical circumferential tracking segments.

In addition to the time-based technique described above for identifying different tracking segments, alternative techniques are contemplated as well. <FIG>, <FIG> and <FIG> illustrate an alternative wet felt station 912A with a wet felt 913A traveling around four rollers <NUM> in a direction shown by arrow <NUM>. In this alternative wet felt station 912A, attributes of the felt 913A are used to determine tracking segments. For example, the rotating felt 913A could include multiple, evenly-spaced marks that could be detected (e.g., optically) and counted as each such mark passes a location of a sensor or detector <NUM>. Each time one of the marks travels by and is detected by the sensor or detector <NUM>, the detection of the mark could be considered an "event. " Thus, the detector <NUM> can also include counter circuitry that communicates with a processor 903B and counts or tracks the events that occur. The marks could also be metallic wires or threads that are detectable with magnets or similar switches. The marks would function so as to separate the felt 913A (or the felt <NUM>. ) into different segments and a counter, or similar circuitry, would increment a count each time a mark was detected (e.g., an event) so that any collected data could be associated with one of the segments of the felt 913A. It is also contemplated that the marks may not be evenly spaced.

In <FIG>, the felt 913A may have <NUM> physical circumferential segments 1260A - 1260AK, of which, segments 1260A, 1260X, 1260Y, 1260Z, <NUM> AJ and 1260AK are explicitly referenced in <FIG>. Separating each physical circumferential segment <NUM> is a mark <NUM> (e.g., marks 1264A, 1264X, 1264Y, 1264Z, 1264AJ are explicitly shown in <FIG>). A reference mark <NUM> could be distinctive from all the other marks 1264A - 1264AJ such that when the detector <NUM>. senses the reference mark <NUM>, the counter circuitry <NUM> resets and starts counting from an initial value, or "starting count," (e.g., "<NUM>" or "<NUM>"). Alternately, the reference marks can all be unique and specifically mark certain positions on the felt.

In the wet felt station 912A, one of the rollers <NUM> forms a nip <NUM> with a sensing roll <NUM> that has a wireless device 40A for communicating with the processor 903B and an array of sensors 26A (e.g., <NUM> sensors) spaced axially along the sensing roll <NUM>. When the sensor 26A in one of the axially positions on the sensing roll <NUM> enters a region of the nip <NUM> and senses a pressure reading, then that pressure value can be count synchronized with the rotation of the wet felt 913A by associating the sensor readings at that axial position with a current value of the counter <NUM>. When the marks <NUM> are spaced an equal distance apart circumferentially, the pressure value can also be considered to be time synchronized with the rotation of the felt 913A by associating the sensor reading at that axial position with a current value of the counter <NUM>.

Each time the distinctive reference mark <NUM> is detected by the detector <NUM>, a starting reference signal can be generated that is associated with each rotation of the wet felt 913A. The starting reference signal may, for example, be resetting the value of the counter <NUM> to a starting count such as, for example, "<NUM>". Whenever a pressure reading is sensed by the sensor 26A in the region of the nip <NUM>, the number of tick mark counts, or the number of events, detected by the detector/counter <NUM> since that most-recent starting reference signal, or the starting count, is an indication of an amount the wet felt 913A has rotated around its loop pattern between when the counter <NUM> was reset and the pressure reading in the region of the nip <NUM> occurred. Accordingly, each count (e.g., "<NUM>", "<NUM>",. "<NUM>") can be associated with one of a plurality of count-based tracking segments wherein each count-based tracking segment is associated with a different physical circumferential segment 1260A - 1260AK of the wet felt 913A in one embodiment of the present invention. In the illustrated embodiment, each count-based tracking segment is equal to the count or value of the counter. If the tick marks <NUM> are evenly spaced, then the count-based tracking segments can correspond to time-based tracking segments of the period of rotation of the wet felt 913A or correspond to physical circumferential segments of the wet felt 913A.

Similar to the techniques described above that involved time synchronizing sensor readings for each axially-spaced sensor 26A with one of <NUM> possible time-based tracking segments, associating each of these sensor readings with one of <NUM> count-based tracking segments, when the marks <NUM> are evenly spaced apart, also time synchronizes the pressure data with the rotation of the wet felt 913A.

In the example embodiment of <FIG>, the wet felt 913A travels along with the web of material <NUM> through the nip <NUM> formed with the sensing roll <NUM>. In such an embodiment, a particular value of the detector/counter <NUM> when a corresponding one particular physical circumferential segment (e.g., 1260A - 1260AK) of the wet felt <NUM> is in the region of the nip <NUM> is associated with one of the plurality of count-based tracking segments. As noted above, each count-based tracking segment corresponds to a different physical circumferential segment 1260A-1260AK of the wet felt 913A. Hence, when a sensor reading is generated by one of the axially spaced apart sensors, the processor 903B associates that sensor reading with a current value of the counter <NUM>, associates the count generated by the counter <NUM> with a corresponding count-based tracking segment and stores that sensor reading with a tracking segment corresponding to the count generated when sensor reading occurred.

<FIG> illustrates the felt 913A of <FIG> after it has rotated to a different position and the sensor 26A generates a sensed pressure signal of the region of the nip <NUM>. In particular, the felt 913A has rotated an amount such that the tick marks <NUM>, 1264A, 1264B and 1264C have been detected and counted by the detector/counter <NUM>. Thus, if the counting of the tick marks starts with "<NUM>" as the distinctive tick mark <NUM> is detected, an example count for the position of the felt 913A of <FIG> would be "<NUM>" when the sensor reading from sensor 26A is captured. This count value would correspond to one of the <NUM> (for example) tracking segments that each of the sensor readings will be associated with and each such tracking segment (or count value) would correspond to a different physical circumferential segment 1260A-1260AK of the wet felt 913A. As shown in <FIG>, corresponding to this count value of "<NUM>", the physical circumferential segment 1260F of the felt 913A is in the region of the nip <NUM>. Accordingly, a plurality of sensed pressure readings from the region of the nip <NUM> associated with the tracking segment, or count reading, of "<NUM>" could all be associated with the physical circumferential segment 1260F of the felt 913A. Continuing with the example of <FIG>, when the felt rotates such that the tick mark 1264D is detected and counted, the tracking segment, or count value, will be "<NUM>" and will correspond to pressure readings sensed when physical circumferential segment <NUM> is in the region of the nip <NUM>.

The embodiment of <FIG> could be modified as well such that the felt <NUM> includes tick marks and the wet felt station <NUM> includes a counter/detector instead of the time-based-signal generator 900B. The pressure readings sensed in the region of the nip <NUM> could by count synchronized with the rotation of the wet felt <NUM> based on a count value rather than an elapsed time. Thus, the count-based tracking segment determination and count synchronization described with respect to <FIG> could be applied to either a felt that travels through a nip where pressure values are sensed or a felt that is upstream from the nip where the pressure values are being sensed.

<FIG> depicts a portion of the wet felt 913A that is traveling around in a loop pattern in a direction shown by the arrow <NUM>. The portion of the felt 913A in <FIG> shows a distinctive reference mark <NUM> and four other nearby marks 1264A, 1264B, 1264AJ and 1274AI that are evenly space relative to circumferential segments 1260A, 1260B, 1260AJ, and 1260AK of the wet felt 913A. As an example, each evenly-spaced mark could be a single tick mark (e.g., 1264A, 1264B, 1264AI and 1274AJ), a tick mark of a particular width, or a mark of a particular color. The distinctive reference mark <NUM> could be a double-tick mark, a thicker (or thinner) tick mark, or a mark of a unique color. Such tick marks can also be used to encode positional information (such as the numbers <NUM> to <NUM>) associated with each segment. If the techniques of segmenting the felt 913A (or <NUM>) just described were utilized, then it would be unnecessary to explicitly measure an elapsed time since the most recent generation of a reference timing signal that is generated each revolution of the felt 913A; instead, detection and counting of tick marks (e.g., 1264A - 1264AJ) since the distinctive reference mark <NUM> could be used to define a plurality of count-based tracking segments.

The position of the marks, <NUM>, 1264A, 1264B, 1264AJ, and 1264AK in <FIG> is provided merely by way of example. They can extend along the entire axial width of the felt 913A, be localized next to one or both edges of the felt 913A, or be located in the middle of the felt 913A. They are located such that they can be detected by the detector/counter <NUM> as the felt 913A travels past a location proximate to the detector/counter <NUM>.

One of ordinary skill in this technological field will recognize that identifiable tick marks or other types of markings can be provided in a variety of different ways without departing from the scope of the present invention. For example, each mark may be encoded such that each is uniquely identifiable. An appropriate sensor would, therefore, not necessarily "count" the tick marks but merely identify which tick mark is presently passing by the sensor. Thus, each tick mark could be associated with or define a value, possibly a unique value, that can be sensed between when a most recent starting reference was generated and when a sensor (e.g., 26A) enters a region of a nip where a pressure reading, or other reading, is being sensed. Accordingly, one of a plurality of tracking segments associated with the continuous band can be identified based on this value.

In addition to being on a surface of one of the felts, the tick marks, or similar marks or openings, could be included on a disk coupled to a rotating shaft or on the shaft itself associated with one of the multiple rotating components that help drive the felt around its continuous loop. Such an arrangement may be used to provide a rotary encoder beneficial in identifying respective tracking segments of a felt or other continuous band. As one example, a shaft encoder of this type could provide a value that corresponds to a count of the number of tick marks or openings that were detected between when a most recent starting reference was generated and when a sensor (e.g., 26A) enters a region of a nip where a pressure reading, or other reading, is being sensed. Accordingly, one of a plurality of tracking segments associated with the continuous band can be identified based on this value.

In addition to the above examples, each respective tracking segment of a continuous band, which could be either time-based segments of a period of rotation of the band or physical circumferential segments of the band, can also correspond to a value that occurs between when a most recent starting reference was generated and when a sensor (e.g., 26A) enters a region of a nip where a pressure reading, or other reading, is being sensed. Each such tracking segment could correspond to a different value such as, for example, an index number of the tracking segment as measured from a reference such as a time-based reference signal or a reference location or position of the band.

Returning to the felt <NUM> of <FIG>, the felt <NUM> can be segmented into cross-machine direction (or axial) segments similar to the felt <NUM> being segmented into axial segments corresponding to the different locations of the sensors 26A on the sensing roll <NUM>. Thus, the felt <NUM> can be broken into multiple axial segments that each correspond to one of the sensor locations on the sensing roll <NUM> and data similar to that of <FIG> can be collected for each axial segment. Accordingly, similar matrices of "counts", "sums" and "averages" as described in <FIG> can be constructed for the data similar to <FIG> for each axial segment but arranged in a manner time-synchronized with the period of rotation of the felt <NUM>. In the example provided above, each such matrix would have (<NUM>×<NUM>), or <NUM>, cells because the felt <NUM>, or more generally a continuous band, comprises n axial segments, having respective index values: <NUM>, <NUM>,. , n (e.g., n = <NUM>) and the felt rotational period comprises m time-based tracking segments, each having a respective, unique index value x in the range of: <NUM>, <NUM>,. , m (e.g., m = <NUM>) which creates (n times m) unique permutations that are identifiable by a two-element set comprising a respective axial segment index value and a respective time-based tracking segment index value. So, as mentioned above, for a plurality of respective sensor signals and for one or more of the possible (n times m) permutations, each cell of a matrix can be calculated that represents an average of all the plurality of respective sensor signals associated with an axial segment and time-based tracking segment matching each of the one or more permutations.

The pressure readings in column 404A of <FIG> involve less than only <NUM> different sensor readings from one sensor 26A. However, if data from over <NUM>, <NUM> or even <NUM> sensor readings from each of the sensors in a sensing roll is collected, then the time-synchronization of data can reveal effects that different stations, e.g., wet felt stations <NUM>, <NUM> and <NUM>, in the process/system line of <FIG> can have on those pressure readings. The values in column 404A correspond to different sequential sensor readings as numbered in column 402A. However, depending on how those pressure reading values are associated with periodically repeating tracking segments, patterns in the pressure readings may become apparent.

As shown by element <NUM> in column 406A, there can be <NUM> mating roll tracking segments such that each pressure reading (from column 404A) is associated with one of those tracking segments. As described earlier with respect to the matrices of <FIG>, each sensor reading in column 404A can be associated with only one axial position (or sensor position of the one sensor generating those pressure readings) and any one of a number of tracking segments (e.g., <NUM>-<NUM>) of a monitored component in the process/system of <FIG>. In the following discussion, an assumption is made that the example axial segment is "Axial Segment #<NUM>". Every pressure reading in column 404A that is associated with mating roll tracking segment <NUM> is added together. The number of those segments can then be divided into the sum to arrive at an average pressure reading for tracking segment <NUM>. A similar average can be calculated for each of the <NUM> other mating roll tracking segments as well. Similar averages can be calculated for all of the <NUM> mating roll tracking segments corresponding to the remaining axial segments, i.e., Axial Segment #<NUM> through Axial Segment #<NUM>. Thus, an average pressure matrix, such as the one described with respect to <FIG>, can be constructed for the mating roll 942A.

<FIG> illustrates an average pressure matrix for the mating roll 942A constructed by extending the simulation data of <FIG> to <NUM>,<NUM> pressure readings. Column <NUM> represents the tracking segments of the mating roll 942A with each row representing one of those <NUM> tracking segments. Each column <NUM> represents one of the axial positions of the sensors <NUM> (for example, <NUM> axial positions). The extended pressure reading data in column 404A of <FIG> represents one particular axial position such as "Axial Segment <NUM>" and, thus, is used to calculate the value in a single column 1506A of the matrix of <FIG>. A value <NUM> in row <NUM> of the matrix is an average of all the pressure readings of column 404A that are associated with tracking segment <NUM> of the mating roll 942A.

<FIG> illustrates an average pressure matrix for the felt <NUM> constructed by extending the simulation data of <FIG> to <NUM>,<NUM> pressure readings. Column <NUM> represents the tracking segments of the felt <NUM> with each row representing one of those <NUM> tracking segments. Each column <NUM> represents one of the axial positions of the sensors <NUM>. The extended pressure reading data in column 404A of <FIG> represents one particular axial position such as "Axial Segment <NUM>" and, thus, is used to calculate the value in a single column 1516A of the matrix of <FIG>. A value <NUM> in row <NUM> of the matrix is an average of all the pressure reading of column 404A that are associated with tracking segment <NUM> of the felt <NUM>. In particular, the average value in row <NUM> is significantly higher than the values in the other rows of column <NUM> and could represent a defect of the felt <NUM> such as a plugged spot that is periodically causing lower water removal.

<FIG> illustrates an average pressure matrix for the felt <NUM> constructed by extending the simulation data of <FIG> to <NUM>,<NUM> pressure readings. Column <NUM> represents the time-based tracking segments of the felt <NUM> with each row representing one of those <NUM> tracking segments. Each column <NUM> represents one of the axial positions of the sensors <NUM>. The extended pressure reading data in column 404A of <FIG> represents one particular axial position such as "Axial Segment <NUM>" and, thus, is used to calculate the value in a single column 1526A of the matrix of <FIG>. A value <NUM> in row <NUM> of the matrix is an average of all the pressure reading of column 404A that are associated with time-based tracking segment <NUM> of the felt <NUM>. The time-based tracking segment <NUM> does not necessarily correspond to physical circumferential tracking segment <NUM> of the felt <NUM> being in the nip <NUM> concurrently. However, as described above, the physical circumferential segment of the felt <NUM> in the nip <NUM> corresponding to the time-based tracking segment <NUM> can be calculated. In particular, the average value in row <NUM> is approximately <NUM> psi higher than many of the values in the other rows and could represent a defect in the felt <NUM>, such as a region of the felt that is plugged or a thin spot of the felt <NUM> that does not remove water as readily as surrounding areas of the felt <NUM>, that is periodically affecting the web of material <NUM>.

<FIG> illustrates graphically the different time-synchronized arrangements of the same sensor data readings in accordance with the principles of the present invention. In particular the waveforms of <FIG> represent the <NUM> sensor readings taken by a single sensor 26A on the sensing roll <NUM> used to construct columns 1506A, 1516A and 1526A of the matrices of <FIG>.

The waveform <NUM> has the mating roll tracking segment index as its x-value and the corresponding average pressure reading from column 1506A of the matrix of <FIG> for that segment index as the y-value. The waveform <NUM> has the felt tracking segment index of the felt <NUM> as its x-value and the corresponding average pressure reading from column 1516A of the matrix of <FIG> for that segment index as the y-value. The waveform <NUM> has the felt <NUM> time-based tracking segment index as its x-value and the corresponding average pressure reading from column 1526A of the matrix of <FIG> for that segment index as the y-value. The peaks of the waveforms <NUM> and <NUM> correspond to the values <NUM> and <NUM> from <FIG> and <FIG>.

As mentioned above, the average pressure matrices, or their corresponding waveforms, can be analyzed to identify potential issues with one or more stations in the process/system of <FIG>. The waveform <NUM> reveals a sinusoidally changing pressure value based on which tracking segment of the mating roll 942A is traveling through the region of the nip <NUM> at an axial location corresponding to pressure sensor 26A, which sensor 26A corresponds to Axial Segment <NUM>. This, for example, could be caused by the mating roll 942A having an oval cross-sectional shape at that axial position, rather than a circular cross-section. The waveform <NUM> reveals a significant pressure pulse associated with tracking segment #<NUM> of the felt <NUM> at an axial location corresponding to pressure sensor 26A as compared to the other <NUM> tracking segments of the felt <NUM> at that axial location. The waveform <NUM> reveals an identifiable pressure pulse associated with time-based tracking segment #<NUM> of the period of rotation of the felt <NUM> at an axial location corresponding to pressure sensor 26A as compared to the <NUM> other tracking segments of the felt <NUM> at that same axial location.

In <FIG>, the sensing roll <NUM> is associated with a region of a nip 212A of the pressing region <NUM> of the felt station <NUM> that, in this example, is closest to the wire mesh <NUM>. However, pressure values can be sensed at other, further downstream stations as well without departing from the scope of the present invention. Similar to the felts <NUM> and <NUM>, the wire mesh <NUM> rotates as a continuous band in a loop pattern around rolls <NUM> and <NUM>. Accordingly, the wire mesh <NUM> has a regular period of rotation around this loop pattern. Thus, different portions of the wire mesh <NUM> each periodically contact corresponding regions of the web of material <NUM> upstream from the region of the nip 212A even though the wire mesh <NUM> itself does not travel through the region of the nip 212A. The region of the nip 212A is formed between the sensing roll <NUM> and a mating roll 940A in the wet felt station <NUM>. The sensing roll <NUM> includes a wireless transmitter 40B (substantially similar to the wireless devices <NUM>, 40A described above) and a sensor array having a plurality of axially spaced apart sensors <NUM> (substantially similar to each sensor <NUM> described above), with only a single sensor 1302A at one corresponding axial location illustrated in <FIG>. In a similar manner to that described with respect to <FIG>, a processor 903A receives signals from a signal generator 900C and the wireless device 40B in order to time synchronize sensor readings from the sensing roll <NUM> with the periodic time reference signal from the signal generator 900C. In the example embodiment of <FIG>, a simple, single wire mesh <NUM> is described; however, other elements may be associated with the wire mesh <NUM> such as a top wire and/or a vertical former. One of ordinary skill will recognize that a variety of other elements can be associated with the wire mesh <NUM> of <FIG> such as additional rolls that contact an inner surface of the mesh <NUM> to carry the mesh <NUM> evenly and prevent it from sagging and vacuum boxes and foils (not shown) can be provided to pull moisture from the slurry through the mesh <NUM>.

In <FIG>, a portion <NUM> of the wire mesh <NUM>, having a corresponding axial and circumferential location, is shown that contacts the web of material <NUM> in a periodic manner as the web of material <NUM> is carried by the wire mesh <NUM>. Identified web of material regions <NUM> and <NUM> are evenly spaced and were in contact with the portion <NUM> of the wire mesh <NUM>. When one of those web of material regions travels through the region of the nip 212A, the pressure reading from the sensing roll <NUM> can be affected by the impact that the wire mesh portion <NUM> had on the web of material <NUM> that it contacted. Similar to the explanation relating to felts, the condition of the wire mesh <NUM> that contacts the web of material <NUM> can affect, for example, the amount of moisture that is able to drain from the contacted region of the web of material <NUM>. Thus, some regions of the web of material <NUM> may be wetter or drier relative to one another and cause higher or lower pressure readings when passing through the region of the nip 212A. Changes to the web of material <NUM> are caused by gravity, vacuum and foils and vacuum pulling water from the slurry through the wire mesh <NUM>. Both water weight (moisture) and dry weight of the slurry can be impacted. Plugs in the wire mesh <NUM> may cause solids of the slurry to shift position. Holes of worn areas in the wire mesh <NUM> may cause solids in the slurry to be lost and pass through the mesh <NUM> and result in a light weight region.

The wire mesh <NUM> can have a period of rotation that can be broken into different time-based tracking segments in the same manner as the period of rotation of the felt <NUM> was broken into <NUM> time-based tracking segments as described earlier which each could also be translated into a corresponding one physical circumferential tracking segment of the felt <NUM>. Thus, the tracking segments related to the wire mesh <NUM> can either be a plurality of time-based segments of the period of rotation of the continuous band around the loop pattern or a plurality of physical circumferential segments on the continuous band. Segments <NUM>, as shown in <FIG>, may, for example, be separate physical circumferential segments with each having an index relative to a fixed reference position <NUM> on the wire mesh <NUM>.

As an example, the reference position <NUM> can make <NUM> complete rotation around the loop pattern in the same amount of time that the sensing roll <NUM> makes <NUM> rotations. For example, if the sensing roll <NUM> is about <NUM> feet in circumference, then in this example, the circumference of the wire mesh <NUM> would be about <NUM> feet (e.g., <NUM> * <NUM>). Using the same principles as used when describing the felt <NUM> of <FIG>, the mesh <NUM> can be segmented into <NUM> tracking segments, for example. As an example, the portion <NUM> of the wire mesh <NUM> that, for example, has a circumferential tracking segment and an axial location, may cause a pressure pulse in the region of the nip 212A as compared to all other portions of the wire mesh <NUM> if it is plugged or a pressure dip in the region of the nip 212A as compared to all other portions of the wire mesh <NUM> if it has a hole worn in it.

Thus, a signal generator 900C generates a periodic time reference signal when a reference position <NUM> of the wire mesh <NUM> is adjacent the signal generator 900C. This is the reference signal from which a time-based tracking segment can be calculated as the sensor 1302A passes through the region of the nip 212A. As one example, when any of the web of material regions <NUM> or <NUM> passes through the nip 212A and is sensed, the processor 903A can determine the elapsed time period since the last reference signal was generated in a manner similar to that described above with respect to felt <NUM> in <FIG> and <FIG>. Thus, the pressure readings sensed at those times can all be associated with the same time-based tracking segment of the period of rotation of the mesh <NUM>. The portion <NUM> of the wire mesh <NUM> that corresponds to this time-based tracking segment can be calculated in a manner similar to that described above with respect to felt <NUM> in <FIG> and <FIG>. Thus, the pressure readings from the region of the nip 212A that are associated with different time-based tracking segments can also be associated with corresponding circumferential tracking segments of the mesh <NUM> relative to the reference position <NUM>.

In a manner similar to how data in <FIG> and <FIG>, <FIG> and <FIG> was collected in a manner time-synchronized with the rotational period of the mating roll <NUM>, the felt <NUM>, and the felt <NUM>, sensor readings from the region of the nip 212A could also be collected in a manner time-synchronized with the period of rotation of the wire mesh <NUM>. Also, similar to the tick marks and count-based tracking segments described in <FIG> and <FIG> with respect to the felt 913A, a similar count-based technique can be utilized with respect to the wire mesh <NUM> in order to collect sensor data in a manner time-synchronized with the rotation of the wire mesh <NUM>.

Claim 1:
A system associated with a sensing roll (<NUM>, <NUM>, <NUM>) and a mating roll (<NUM>, 940A, 942A) for collecting sensor signals comprising:
the sensing roll and the mating roll located relative to one another to create a nip (<NUM>, 212A, <NUM>) therebetween, wherein a web of material travels through the nip from an upstream direction to a downstream direction and a continuous band, arranged to travel around in a loop pattern, contacts at least a region of the web of material at the nip or upstream from the nip;
a plurality of sensors (<NUM>, 26A, 1302A) located at axially spaced-apart locations of the sensing roll, wherein each sensor enters a region of the nip during each rotation of the sensing roll to generate a respective sensor signal;
a structure (900A, 900B, 900C) for generating a periodically occurring starting reference associated with each rotation of the continuous band around the loop pattern; and
a processor (<NUM>, 903A) to receive the periodically occurring starting reference and the respective sensor signal generated by each sensor and, after receiving the respective sensor signal, the processor operates to:
determine a particular one of the plurality of sensors which generated the respective sensor signal, and
based upon an amount of time that has elapsed between when the respective sensor signal was generated and a most recent starting reference, identify one of a plurality of tracking segments associated with the continuous band, wherein each of the plurality of tracking segments is, respectively, associated with a different amount of elapsed time, and
store the respective sensor signal to associate the respective sensor signal with the identified one tracking segment.