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 dry 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. One roll of the nip press is typically a hard steel roll while the other is constructed from a metallic shell covered by a polymeric cover. However, in some applications both rolls may be covered or both may be hard steel. The amount of liquid to be pressed out of the web is dependent on the amount of pressure being placed on the web as it passes through the nip region. Later rolls in the process and nips at the machine calendar are used to control the caliper and other characteristics of the sheet. The characteristics of the rolls may define the amount of pressure applied to the web during the nip press stage.

One common problem associated with such rolls can be the lack of uniformity in the pressure being distributed along the working length of the roll. The pressure that is exerted by the rolls of the nip press is often referred to as the "nip pressure. " The amount of nip pressure applied to the web and the size of the nip may determine whether uniform sheet characteristics are achieved. Even nip pressure along the roll is important 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. Excessive nip pressure can cause crushing or displacement of fibers as well as holes in the resulting paper product. Improvements to nip loading can lead to higher productivity through higher machine speeds and lower breakdowns (unplanned downtime).

Conventional rolls for use in a press section may be formed of one or more layers of material. Roll deflection, commonly due to sag or nip loading, can be a source of uneven pressure and/or nip width distribution. Worn roll covers may also introduce pressure variations. These rolls generally have a floating shell which surrounds a stationary core. Underneath the floating shell are movable surfaces which can be actuated to compensate for uneven nip pressure distribution.

Previously known techniques for determining the presence of such discrepancies in the nip pressure required the operator to stop the roll and place a long piece of carbon paper or pressure sensitive film in the nip. This procedure is known as taking a "nip impression. " Later techniques for nip impressions involve using mylar with sensing elements to electronically record the pressures across the nip. These procedures, although useful, cannot be used while the nip press is in operation. Moreover, temperature, roll speed and other related changes which would affect the uniformity of nip pressure cannot be taken into account.

Control instrumentation associated with a sensing nip press can provide a good representation of the cross-directional nip pressure (commonly referred to as the "nip pressure profile" or just "nip profile") and will allow the operator to correct the nip pressure distribution should it arise. The control instruments usually provide a real time graphical display of the nip pressure profile on a computer screen or monitor. The nip profile is a compilation of pressure data that is being received from the sensors located on the sensing roll. It usually graphically shows the pressure signal in terms of the cross-directional position on the sensing roll. The y-axis usually designates pressure in pounds per linear inch while the x-axis designates the cross directional position on the roll. <CIT> describes a system and method for monitoring of a roll with a core and a sheet, and an integrated circuit of the transponder that includes read/write memory for data storage, which is accessed by an external transceiver.

The present invention relates to a system associated with a sensing roll and a mating roll for collecting roll data of the mating roll that includes first and second pluralities (or even <NUM> or more pluralities) of sensors. The first plurality of sensors are located at axially spaced-apart locations of the sensing roll, wherein each sensor of the first plurality enters a region of a nip between the sensing roll and the mating roll during each rotation of the sensing roll to generate a first respective sensor signal The second plurality of sensors are located at axially spaced-apart locations of the sensing roll, wherein each sensor of the second plurality enters the region of the nip during each rotation of the sensing roll to generate a second respective sensor signal. Each sensor of the first plurality has a corresponding sensor in the second plurality which is associated with a same respective axial location on the sensing roll but is spaced-apart circumferentially.

The system also includes a processor to receive a received sensor signal, wherein the received sensor signal is one of the first respective sensor signal or the second respective sensor signal. Upon receiving the received sensor signal, the processor performs a number of operations. In particular, the processor can a) determine a particular one of the sensors of the first plurality or second plurality which generated the received sensor signal, b) determine membership of the particular one sensor based on which plurality of sensors the particular one sensor is a member, and c) based upon a rotational position of the mating roll relative to a reference position, determine which one of a plurality of circumferential tracking segments associated with the mating roll enters the region of the nip substantially concurrently with the particular one sensor entering the region of the nip. The processor can also store the received sensor signal using the determined one tracking segment and the determined membership.

Preferably, each of the plurality of tracking segments are of substantially equal size. According to the present disclosure, they can also be of different sizes. Preferably, the received sensor signal comprises a pressure value, and the plurality of tracking segments associated with the mating roll are a plurality of circumferential segments on the mating roll. According to the present disclosure, they can also be a plurality of time segments of a period of the mating roll.

Preferably, the processor receives the first respective sensor signal for each of the sensors of the first plurality during each rotation of the sensing roll, and the second respective sensor signal for each of the sensors of the second plurality during each rotation of the sensing roll. Preferably, the processor also receives a plurality of sensor signals that include a plurality of the first respective sensor signals and a plurality of second respective sensor signals occurring during a plurality of rotations of the sensing roll. Preferably, foreachoneofthe plurality of sensor signals, the processor identifies: a) its determined one tracking segment, b) an associated mating roll axial segment, and c) a specific sensor of the first or second pluralities of sensors which generated this particular one of the plurality of sensor signals, wherein the processor further determines membership of the specific sensor based on which of the plurality of sensors the specific sensor is a member.

Preferably, the mating roll comprises n axial segments, having
respective index values: <NUM>, <NUM>,. , n; the mating roll has associated therewith m tracking segments, having respective index values: <NUM>,<NUM>,. ,m, and wherein, for each of the first plurality of sensors and the second plurality of sensors, there are (n times m) unique permutations that are identifiable by a two-element set comprising a respective axial segment index value and a respective tracking segment index value.

Preferably, for the plurality of first respective sensor signals and for each of a first plurality of the possible (n times m) permutations, the processor determines an average of all the plurality of first respective sensor signals associated with an axial segment and tracking segment matching each of the first plurality of permutations. Preferably, for the plurality of second respective sensor signals and for each of a second plurality of the possible (n times m) permutations, the processor determines an average of all the plurality of second respective sensor signals associated with an axial segment and tracking segment matching each of the second plurality of permutations.

Preferably, for the plurality of first respective sensor signals and each of a first plurality of the possible (n times m) permutations, the processor determines: a) a number of times one or more of the plurality of first respective sensor signals is associated with an axial segment and tracking segment matching that permutation; and b) a summation of all of the plurality of first respective sensor signals associated with the axial segment and tracking segment matching that permutation. Preferably, for the plurality of second respective sensor signals and each of a second plurality of the possible (n times m) permutations, the processor determines: a) a number of times one or more of the plurality of second respective sensor signals is associated with an axial segment and tracking segment matching that permutation; and b) a summation of all of the plurality of second respective sensor signals associated with the axial segment and tracking segment matching that permutation.

Preferably, the mating roll comprises n axial segments, having respective index values: <NUM>, <NUM>,. , n; the mating roll has associated therewith m tracking segments, having respective index values: <NUM>, <NUM>,. , m, wherein, for each of the first plurality of sensors, there are (n times m) unique permutations, respectively, that are identifiable by a first two-element set comprising a respective axial segment index value and a respective tracking segment index value and, for each of the second plurality of sensors, there are (n times m) unique permutations, respectively, that are identifiable by a second two-element set comprising a respective axial segment index value and a respective tracking segment index value. Preferably, a respective average pressure value is associated with each of the (n times m) unique permutations of each of the first and second sets, wherein each of the respective average pressure values is based on previously collected pressure readings related to the nip.

Preferably, a first respective column average value is associated with each first set axial segment index value, each first respective column average value comprising an average of the m respective average pressure values, from the first set, associated with that first set axial segment index value; and a second respective column average value is associated each second set axial segment index value, each second respective column average value comprising an average of the m respective average pressure values, from the second set, associated with that second set axial segment index value.

Preferably, the processor operates on each of the plurality of received signals. For each one of the plurality of the received sensor signals which defines a pressure reading the processor: a) determines a particular axial segment index value and a particular tracking segment index value, based on that signal's associated axial segment, its determined one tracking segment and whether that signal is generated from the first plurality of sensors or the second plurality of sensors; b) selects the respective average pressure value associated with the particular axial segment index value and the particular tracking segment index value; c) calculates a respective corrected average pressure value by subtracting one of the first respective column average value or the second respective column average value associated with the particular axial segment index value from the selected respective average pressure value; and d) calculates a respective adjusted pressure reading value by subtracting the respective corrected average pressure value from the one received sensor signal. Preferably, the processor also calculates an average pressure profile based on the respective adjusted pressure reading values.

Preferably, the system includes a signal generator to generate a trigger signal on each rotation of the mating roll, wherein the processor identifies the rotational position of the mating roll relative to the reference position based on a most-recently- generated trigger signal.

Preferably, the system includes a third plurality of sensors located at axially spaced-apart locations of the sensing roll, wherein each sensor of the third plurality enters a region of the nip between the sensing roll and the mating roll during each rotation of the sensing roll to generate a third respective sensor signal; and wherein each sensor of the third plurality has a corresponding sensor in at least one of the first plurality and the second plurality which is associated with a same respective axial location on the sensing roll but is spaced-apart circumferentially. Preferably, the processor receives the third respective sensor signal. Upon receiving the third respective sensor signal, the processor operates to: a) determine a particular one of the sensors of the third plurality which generated the third respective sensor signal, b) determine membership of the particular one sensor based on the particular one sensor being a member of the third plurality, c) based upon a rotational position of the mating roll relative to the reference position, determine which one of the plurality of circumferential tracking segments associated with the mating roll enters the region of the nip substantially concurrently with the particular one sensor of the third plurality entering the region of the nip, and d) store the third respective sensor signal using the determined one tracking segment and the determined membership.

Thepresent invention also relates to a method associated with a sensing roll and a mating roll for collecting roll data of the mating roll. The method includes generating a first respective sensor signal from each sensor of a first plurality of sensors located at axially spaced-apart locations of the sensing roll, wherein each first respective sensor signal is generated when each sensor of the first plurality enters a region of a nip between the sensing roll and the mating roll during each rotation of the sensing roll; and generating a second respective sensor signal from each sensor of a second plurality of sensors located at axially spaced-apart locations of the sensing roll, wherein each second respective sensor signal is generated when each sensor of the second plurality enters the region of the nip between the sensing roll and the mating roll during each rotation of the sensing roll. Each sensor of the first plurality has a corresponding sensor in the second plurality which is associated with a same respective axial location on the sensing roll but is spaced-apart circumferentially. The method also includes receiving a received sensor signal, the received sensor signal being one of the first respective sensor signal or the second respective sensor signal. Upon receiving the received sensor signal, the method continues by determining a particular one of the sensors of the first plurality or the second plurality which generated the received sensor signal, determining a membership of the particular one sensor based on which of the pluralities of sensors the particular one sensor is a member; and based upon a rotational position of the mating roll relative to a reference position, determining which one of a plurality of circumferential tracking segments associated with the mating roll enters the region of the nip substantially concurrently with the particular one sensor entering the region of the nip. The method also includes storing the received sensor signal using the determined one tracking segment and of the determined membership.

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.

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.

As illustrated in <FIG>, a sensing roll <NUM> and a mating roll <NUM> define a nip <NUM> receiving a fibrous web <NUM> to apply pressure to the web <NUM>. It is contemplated that, in some cases, a 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>, 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 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 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.

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>, as described below. These data maps can include an average pressure matrix as described more fully below with respect to <FIG>. 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 indicate possible problems with upstream or downstream processing equipment, e.g., upstream rolls 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.

Referring to <FIG>, the sensing roll <NUM> can be, for example, rotating and be instantaneously positioned such that a sensor 26A, located in one of the <NUM> axial segments in the illustrated embodiment, is located in the region of the nip <NUM> simultaneously with mating roll circumferential segment number <NUM> (of <NUM>-<NUM> segments). After a first full rotation of the roll <NUM>, the one sensor 26A may enter the region of the nip <NUM> concurrently with a different circumferential segment, for example segment number <NUM>, on the mating roll <NUM>, see <FIG>. Because the rolls <NUM> and <NUM> have different periods, after a second full rotation of the roll <NUM>, the one sensor 26A may enter the region of the nip <NUM> simultaneously with yet a different mating roll circumferential segment, for example segment number <NUM>, see <FIG>. Because the one sensor 26A enters the region of the nip <NUM> concurrently with different circumferential segments of the mating roll <NUM>, 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 also noted above, variability analysis may indicate 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.

As one particular example, the mating roll <NUM> can be larger in circumference than the sensing roll <NUM>. For example, the mating roll <NUM> has a circumference that is divided into <NUM> substantially equal-length circumferential segments and the sensing roll <NUM> has its own circumference that is smaller than the circumference of the mating roll <NUM>. Differences in circumference and slippage both contribute to a difference in rotational period (period = the time required for a roll to make one full rotation) between the sensing roll <NUM> and mating roll <NUM>. 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, the sensing roll <NUM> may have a period that is <NUM> mating roll time segments less than the period of the mating roll <NUM> (equivalently, the mating roll <NUM> can have a period that is <NUM> mating roll time segments larger 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 less than a complete revolution by an amount equal to <NUM> time segments due to it having a longer 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 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>.

As noted above, in one particular example, the mating roll <NUM> can be larger in circumference than the sensing roll <NUM>. For example, the mating roll <NUM> can have a circumference that is divided into <NUM> substantially equal-length circumferential segments and the sensing roll <NUM> can have its own circumference that may be smaller than the circumference of the mating roll <NUM>. One convenient way to characterize the difference in circumferences is using units-of-measure that measure that difference in terms of the length of the <NUM> mating roll circumferential segments. In other words, a circumference of the sensing roll <NUM> can be described as being x segment-lengths smaller/larger than a circumference of the mating roll <NUM>. For example, the sensing roll <NUM> may have a circumference that is <NUM> mating roll circumferential segment lengths less than the circumference of the mating roll <NUM> (equivalently, the mating roll <NUM> can have a circumference that is <NUM> mating roll segments larger than the circumference of the sensing roll). In such an example, as the sensing roll <NUM> makes one complete revolution, the mating roll <NUM> will make less than a complete revolution by an amount equal to <NUM> circumferential segment lengths due to it being larger in circumference than the sensing roll <NUM> and presuming outer surface portions of the sensing roll <NUM> and mating roll <NUM> in the nip <NUM> both match the velocity of the web <NUM>.

Continuing with this example, <FIG> illustrate how sensor data for particular circumferential segments (or, alternatively, time segments) corresponding to a same axial location of the mating roll <NUM> are collected for one particular sensor <NUM> of the set <NUM>. Similar data will be collected for each of the remaining sensors <NUM> of the set <NUM>. The left-most column <NUM> represents a number of revolutions of the sensing roller <NUM>. If it is presumed that this particular sensor <NUM> starts when it is concurrently in the region of the nip <NUM> with circumferential segment number <NUM> of the mating roll <NUM>, then after <NUM> revolution, the sensor <NUM> will enter the region of the nip concurrent with segment number <NUM> of the mating roll <NUM>. The second column <NUM> from the left represents the circumferential segment number of the mating roll <NUM> which enters the nip region concurrent with the sensor <NUM> for each successive revolution of the sensing roll <NUM>. For example, after <NUM> rotations, the segment number <NUM> (see element <NUM> of <FIG>) enters the region of the nip <NUM> concurrent with the sensor <NUM>. Only the first <NUM> revolutions are depicted in <FIG>; however, any number of revolutions, e.g., <NUM> revolutions, could be observed to collect even more data.

The two right most columns <NUM>, <NUM> relate to collection of data for <NUM> revolutions of the sensing roll <NUM>. Column <NUM> represents each of the <NUM> segments and column <NUM> represents how many times each of the segments were respectively sampled in the <NUM> revolutions. For example, circumferential segment number <NUM> of the mating roll <NUM> was sampled (i.e., in the nip region concurrently with the sensor <NUM>) by the sensor <NUM> eleven (see element <NUM> of <FIG>) different times during the <NUM> revolutions. <FIG> depicts a distribution chart showing how many times each of the <NUM> circumferential segments were sampled by the sensor <NUM> during <NUM> revolutions. Depending on the difference in circumference (or periodicity) between the sensing roll <NUM> and the mating roll <NUM>, the number of times each of the <NUM> segments is sampled can vary.

As mentioned above, data similar to that of <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 ten <NUM> segments will have passed, e.g., the nip region, from when the trigger signal is made to when the pressure signal is generated. <FIG> is described below in the context of a processor <NUM> generating 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 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.

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> x14 = <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> × <NUM> matrix as depicted in <FIG>. 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 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 segments 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> × <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 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 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> 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> 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 signals, from the sensors <NUM> can be affected by a variety of components in the system that moves the web <NUM>. 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. As more fully described below, a corrected cell value can be calculated by subtracting from each cell in the average pressure matrix its corresponding column average value from row <NUM>. Thus, the average pressure matrix in <FIG> includes average pressure values in each cell and information needed to correct those values in row <NUM>.

Alternatively, one of ordinary skill will recognize that an entirely separate correction matrix (having, for example, <NUM> elements or cells) could be constructed that is filled with already-corrected values from each of the cells of the average pressure matrix. Thus, a correction matrix, as illustrated in <FIG>, could be created that is separate from the average pressure matrix of <FIG>. Each cell (e.g., cell <NUM>) of the correction matrix has a value that is based on the corresponding cell (e.g., <NUM>) of the average pressure matrix. More particularly, the value from each average pressure matrix cell is corrected by subtracting an appropriate column average value found in row <NUM> to determine a corrected value to store in a corresponding cell of the correction matrix of <FIG>.

Individual collection sessions of pressure readings to fill the matrices of <FIG>, <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/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.

Accordingly, a data collection "protocol" or set, e.g., data collection sessions occurring over a <NUM> hour period, can include data from one or more data collection sessions. Each data collection session may typically include continuous collection of data for a brief time (e.g., two minutes, five minutes, ten minutes, etc.) that is repeated periodically (e.g., once every hour). A data collection set can include all of the data collection sessions that occur in a day. When each new data collection protocol or set begins, a counts matrix and a summation matrix from a most-recently-completed data collection set can be reset to zero so that the data for that new data collection protocol or set is independent of previously collected data. However, an average pressure matrix, and optionally a corresponding correction matrix, from the most-recently-completed data collection set may not be zeroed-out but may be stored for use during each of the collection sessions that are part of the new (i.e., next) data collection set. Once this new data collection set is finished, then a new average pressure matrix and correction matrix can be calculated and used to overwrite the stored average pressure matrix and correction matrix. In this way, pressure-related parameters about the mating roll can be collected and compared at different times for diagnostic purposes, for example, or to potentially adjust current operating conditions of the rolls <NUM> and <NUM>.

Other matrices, not shown, can be calculated based on the sensor data used to build the matrices of <FIG>, <FIG>, <FIG> and <FIG>. For example, squaring the pressure values used to build the matrix of <FIG>, and then summing those squared values can be done to build a sum-squared matrix which can be useful in partitioning of variability into cross-directional (CD) variability, rotational variability, <NUM>-dimensional variability, and residual variability. The variability partitions can be trended for operational and/or maintenance purposes.

The average pressure matrix of <FIG> can be generated during a set of collection sessions in an attempt to monitor and measure the operating characteristics of how the web <NUM> is being compressed by the rolls <NUM> and <NUM>. The data from the average pressure matrix of <FIG> or from the correction matrix of <FIG> can then be used during a collection session of a subsequent set of collection sessions to correct raw or real-time pressure readings from the sensors <NUM> for any rotational impact of the mating roll <NUM>. Within the present disclosure the data sensed, or acquired, by a sensor (e.g., <NUM>) can be referred to as either a "signal" or a "reading" as in a "raw pressure reading", a "real-time pressure reading", a "pressure signal", or a "sensor signal". Correction of each of the raw or real-time pressure readings results in a respective "adjusted pressure reading value". These adjusted pressure reading values can be used to initiate or update a real-time average pressure profile for the nip between the rolls <NUM> and <NUM>, as will be discussed below. At the start of each new collection session, the real-time average pressure profile can be reset to zero. The real-time average pressure profile may be used to adjust loading pressures and roll crowns or roll curvature (using, for example, internal hydraulic cylinders) to achieve a flat pressure profile.

As more fully explained with respect to the flowchart of <FIG>, a raw or real-time pressure reading (i.e., sensor signal) can be acquired from each sensor <NUM> each time it enters the nip <NUM>. As noted above, each raw pressure reading, or sensor signal, can be adjusted using the average pressure value information in the matrices of <FIG> and/or <FIG> to calculate an adjusted pressure reading value. In particular, these matrices may have been created from a previous data collection set, such as from a day earlier. The adjusted pressure reading values may then be used by the processor <NUM> to initiate or update a real-time average pressure profile.

The flowchart of <FIG> depicts an exemplary method of generating a real-time average pressure profile in accordance with the principles of the present invention. In step <NUM>, the collection of data is begun. The start of data collection could occur when a sensing roll <NUM> and/or a mating roll <NUM> is first brought online or could occur after a maintenance period or other work stoppage. Accordingly, in some instances, a previously calculated and stored average pressure matrix could be beneficial in adjusting subsequent raw pressure readings and in other instances it may be beneficial to perform data collection without using any previous data about the nip <NUM>.

Thus, in step <NUM>, a determination is made as to whether a stored average pressure matrix exists and whether or not to use it in the current data collection process started in step <NUM>. If the average pressure matrix does not exist, or if it exists and a choice is made not to use it, then in step <NUM> all the cells of the average pressure matrix are zeroed out so that the matrix is initialized to a known state.

Otherwise, values of a stored average pressure matrix are used as described below. As previously mentioned it may be beneficial to have records of different average pressure matrices so that they can be compared to one another to possibly identify trends or issues relating to maintenance or operating conditions. Thus, part of step <NUM> may include presenting an operator with a list of available average pressure matrices that are stored so that the operator can select a particular matrix to be used. In the illustrated embodiment, typically the average pressure matrix from a previous collection session set, i.e., from one day earlier, is selected.

In some instances data collection during a set of collection sessions can be interrupted for various operational reasons. Therefore, it may be beneficial to be able to resume a set of collection sessions without starting over and losing all the data that had been collected before that set was interrupted. In step <NUM>, a determination is made to use existing counts and sum matrices (e.g., <FIG> and <FIG>) of a previously interrupted set of collection sessions. If the determination is to not use these matrices, then the counts matrix and sum matrix are both zeroed out in step <NUM>. If, however, a determination is made to continue with a set of collection sessions, then the existing counts and sum matrices are used in subsequent steps of the data collection.

Step <NUM> starts a new collection session by initializing, or zeroing out, an old real-time average pressure profile. At the end of this new collection session a new real-time average pressure profile will be calculated. The real-time average pressure profile will have a value for each of the axial segments of the sensing roll <NUM> as more fully described below.

In step <NUM>, raw pressure readings, or sensor signals, are collected by the sensors <NUM> of the sensing roll <NUM>. In addition to the raw pressure readings themselves, corresponding time segments (or circumferential segments) of the mating roll <NUM> and axial segment numbers (e.g., <NUM>-<NUM>) are collected for each raw pressure reading. For example, a particular sensor <NUM> will enter a region of the nip <NUM> and acquire a raw pressure reading. Based on the trigger signal <NUM> described above, a determination can also be made as to which of the <NUM> circumferential segments, or <NUM> time segments, of the mating roll <NUM> is also in the nip <NUM>. Thus, based on the determined circumferential segment and the sensor <NUM>, which corresponds to a particular axial segment, one of the <NUM> cells in each of the matrices of <FIG> and <FIG> can be identified. Once those cells are identified, the counts matrix and the sum matrix can be updated, in step <NUM>.

Also, one of the <NUM> cells of the stored average pressure matrix (e.g., <FIG>) can be identified based on the circumferential segment and sensor corresponding to the raw pressure reading sensed in step <NUM>. The average pressure value of that one corresponding matrix cell can be selected, in step <NUM>, and corrected using its corresponding column average value (e.g., from row <NUM> of <FIG>). As discussed above, correcting a cell value from the average pressure matrix can entail subtracting the appropriate column average value from that cell value to determine a corrected cell value (i.e., a corrected average pressure value). This corrected average pressure value can then be used, in step <NUM>, to adjust the raw pressure reading. In particular, the corrected average pressure value from the average pressure matrix can be subtracted from the raw pressure reading.

In those instances when a stored average pressure matrix is not available or a zeroed-out average pressure matrix is used, then the raw pressure reading remains unchanged by steps <NUM> and <NUM>. Also, in those instances where a separate "correction" matrix is created separate from the average pressure matrix, steps <NUM> and <NUM> can be combined so that an appropriate cell value is selected directly from the "correction" matrix and used to adjust a raw pressure reading.

The value from step <NUM> is associated with a particular axial segment of the sensing roll <NUM> (as identified in step <NUM>) and a corresponding axial segment of the real-time average pressure profile. Thus, the value from step <NUM> is stored, in step <NUM>, in order that the real-time average pressure profile can be calculated. Each time a raw pressure reading is adjusted using a corrected average pressure matrix cell value an adjusted pressure reading value, or an adjusted raw pressure reading value, is calculated. That adjusted pressure reading value is summed with all the other adjusted pressure reading values for a particular axial segment acquired earlier during the current collection session and a count of the total number of adjusted pressure reading values used in constructing that sum is stored as well. From this stored data and at the end of the collection session, see step <NUM>, an average pressure value can be constructed for each axial segment of the real-time average pressure profile by dividing the summation of the adjusted pressure reading values by the count of the total number of adjusted pressure reading values.

A determination of whether the collection session is complete is determined in step <NUM>. The determination in step <NUM> can be based on the collection session lasting for a predetermined time period (e.g.,<NUM> minutes) or based on the collection session lasting for a predetermined number of rotations of the sensing roll <NUM> (e.g., <NUM> rotations).

If, in step <NUM>, it is determined that the collection session is complete, then the real-time average pressure profile is calculated and output in step <NUM>. If the collection session is not complete, however, then control returns to step <NUM> and more raw pressure readings are acquired and adjusted to continue building the data to be used to calculate the real-time average pressure profile.

The average pressure matrix (e.g., <FIG>) can be built using data collected across multiple collection sessions (i.e., a set of collection sessions). As noted above, a set of collection sessions may be defined as occurring every <NUM> hours. Thus, in step <NUM>, a determination is made as to whether or not a current set of collection sessions is completed, e.g., has a given <NUM> hour period for a current collection session set ended? If the set of sessions to build a new average pressure matrix is not complete, then a determination can be made in step <NUM> as to whether or not to even continue the process of acquiring pressure readings related to the nip <NUM>. For example, an operator can choose to interrupt the data collection process for a variety of operational-related reasons. Thus, in step <NUM>, the process of <FIG> can be stopped if desired; otherwise, a delay is introduced, in step <NUM>, before the next collection session of the current set is started in step <NUM>. In the illustrated embodiment, each collection session occurs over a predefined time period, e.g., five minutes, and the delay period comprises another predefined time period, e.g., <NUM> minutes.

If the set of collection sessions is complete, however, then in step <NUM> the average pressure matrix for the completed set of collection sessions is built, using the counts matrix and sum matrix that were being updated in step <NUM>. This new average pressure matrix is then, in step <NUM>, stored so that its values can be used in step <NUM> when adjusting the raw pressure readings acquired during subsequent collection sessions of a new set for calculating different real-time average pressure profiles. Once a new average pressure matrix is built, a corresponding correction matrix could be built and stored as well. If such a correction matrix is built and stored, then its values can be used in step <NUM> when adjusting raw pressure readings acquired during subsequent collection sessions of a new set. In step <NUM>, a delay occurs before beginning the building of a new average pressure matrix by starting a new set of collection sessions. For example, the delay may typically equal the delay used in step <NUM> (e.g., <NUM> minutes). After the delay of step <NUM>, the count and sum matrices are zeroed-out in step <NUM> and a first collection session, of a new set of collection sessions, starts with step <NUM>.

In the above description, in steps <NUM> and <NUM>, a raw pressure reading is adjusted using a corrected value from a corresponding cell of the matrix of <FIG> having average pressure values for each of the <NUM> possible permutations. Alternatively, data smoothing could be accomplished by averaging adjacent corrected cells of the matrix of <FIG> before adjusting the raw pressure reading. For the purpose of simplifying a description of possible data smoothing approaches, reference is made below to a separate correction matrix, such as the one in <FIG> that has cell values that already have been corrected using appropriate column averages of the average pressure matrix of <FIG>. For example, in a particular column of the correction matrix, a cell will have adjacent rows that represent adjacent circumferential segments. Accordingly, five cells (for example) could be selected from the correction matrix - a particular cell (associated with a current raw pressure reading) and the two cells above it and the two cells below it. The five values from these five cells can, themselves, be averaged together to calculate an adjustment value to subtract from the raw pressure reading in step <NUM>. Smoothing can be used when some cells in the count matrix (<FIG>) have low values that would tend to cause the average pressure matrix (<FIG>) to be noisy. If a cell in the count matrix has zero counts, then the calculated average pressure corresponding to that cell cannot be made and smoothing is necessary.

Similar data smoothing could be accomplished as well in the axial direction. In this case, three cells, for example, could be selected from the correction matrix of <FIG> - a particular cell associated with a current raw pressure reading, the cell to its left, and the cell to its right. The three values from these three cells could each be averaged together to calculate an adjustment value to subtract from the raw pressure reading in step <NUM>.

<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.

As noted above, 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 <NUM> of sensors <NUM> as shown in <FIG>, <FIG> depicts two pluralities or arrays 24A, <NUM> of sensors 126A, <NUM> on a sensing roll <NUM>. In the illustrated embodiment, the sensing roll <NUM> is separated into <NUM> axial segments. First and second pluralities 24A and <NUM> of sensors 126A and <NUM>, respectfully, are disposed at least partially in the roll cover <NUM>. Each of the first plurality 24A of sensors 126A is located in one of the <NUM> axial segments of the sensing roll <NUM>. Likewise, each of the second plurality <NUM> of sensors <NUM> is located in one of the <NUM> axial segments of the sensing roll <NUM>. Each sensor 126A of the first plurality 24A has a corresponding sensor <NUM> from the second plurality <NUM> located in a same axial segment of the sensing roll <NUM>. The first plurality 24A of sensors 126A are disposed along a line that spirals around the entire length of the roll <NUM> in a single revolution to define a helical pattern. In a similar manner, the second plurality <NUM> of sensors <NUM> are disposed along a line that spirals around the entire length of the roll <NUM> in a single revolution to define a helical pattern. The first and second pluralities 24A and <NUM> of sensors 126A and <NUM> are separated from one another by <NUM> degrees. Each sensor 126A and <NUM> measures the pressure that is being exerted on the sensor when it enters the region of the nip <NUM> between the rolls <NUM> and <NUM>. It is contemplated that the first and second pluralities 24A and <NUM> of sensors 126A and <NUM> 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 <NUM>.

Assuming the above example of <NUM> axial segments and <NUM> circumferential segments, each plurality 24A, <NUM> of sensors 126A, <NUM> may have their own corresponding <NUM> cell matrices of stored values. Thus, the plurality 24A of sensors 126A may have matrices for a number of times a particular sensor 126A and a mating roll circumferential segment were in the region of the nip <NUM> (e.g., a counts matrix), summations of pressure readings (e.g., a sum matrix), average pressure values (e.g., an average pressure matrix) and corrected average pressure values (a correction matrix). The plurality <NUM> of sensors <NUM> likewise may have its own matrices for a number of times a particular sensor <NUM> and a mating roll circumferential segment were in the region of the nip <NUM> (e.g., a counts matrix), summations of pressure readings (e.g., a sum matrix), average pressure values (e.g., an average pressure matrix) and corrected average pressure values (e.g., a correction matrix). In each of the respective cells a value is stored that is associated with a particular sensor 126A, <NUM>, and a particular axial segment and circumferential segment of the mating roll. Accordingly, matrices similar to <FIG>, <FIG>, <FIG> and <FIG> would be stored for each of the different sensor pluralities, or sensor arrays, 24A, <NUM>. However, because the data was collected by sensors separated by <NUM>°, the differences between values in the two sets of matrices may reveal information about rotational variability of the sensing roll <NUM>.

Thus, for the first plurality 24A of sensors, there are <NUM> axially arranged sensors 126A, each of which can be uniquely referred to using an axial segment index value that ranges from "<NUM>" to "<NUM>", and there are <NUM> tracking segments associated with the mating roll <NUM>, each of which can be uniquely referred to using a tracking segment index value ranging from "<NUM>" to "<NUM>", which together create <NUM> (i.e., <NUM> x14 = <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 first two-element set comprising a respective axial segment index value and a respective tracking segment index value. Thus, a raw pressure reading from a sensor 126A can be associated with an axial segment index value and a tracking segment index value which, together, uniquely identify <NUM> of <NUM> cells in each of the matrices shown in <FIG>, <FIG>, <FIG> and <FIG> that are associated with the first plurality 24A of sensors. Based on the particular permutation of an axial segment index value and tracking segment index value, data can be added to, or extracted from, an appropriate cell of one those matrices associated with the first plurality 24A of sensors.

In addition to those <NUM> permutations, for the second plurality <NUM> of sensors <NUM>, there are also <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 still the <NUM> tracking segments associated with the mating roll <NUM>, each of which can be uniquely referred to using the tracking segment index values, which create <NUM> (i.e., <NUM> ×<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 second two-element set comprising a respective axial segment index value and a respective tracking segment index value. Thus, a raw pressure reading from a sensor <NUM> can be associated with an axial segment index value and a tracking segment index value which, together, uniquely identify <NUM> of <NUM> cells in each of the matrices shown in <FIG>, <FIG>, <FIG> and <FIG> that are associated with the second plurality <NUM> of sensors. Based on the particular permutation of an axial segment index value and tracking segment index value, data can be added to, or extracted from, an appropriate cell of one those matrices associated with the second plurality 28A of sensors.

Similar, in concept, to having two sensor pluralities 24A, <NUM> on the sensing roll <NUM> is having one sensor array <NUM> on the sensing roll <NUM> (referred to as a first sensing roll in this embodiment) as shown in <FIG> but also having a mating roll 11A (See <FIG>) with an array <NUM> of sensors <NUM> so as to define a second sensing roll, wherein the mating roll 11A replaces the mating roll <NUM> in <FIG>. Thus, in addition to the sensors <NUM>, there would also be the array <NUM> of sensors <NUM> that enter the region of the nip <NUM> during each rotation of the second sensing roll 11A. As in the case of two sensor arrays 24A, <NUM>, a respective counts matrix, sum matrix, average pressure matrix and correction matrix could be built for the first sensing roll <NUM> and the second sensing roll 11A. One difference from the above description, however, is that a separate signal generator 900A and a separate trigger signal 901A (shown in phantom in <FIG>) may also be associated with the first sensing roll <NUM> so that its period can be broken into different time segments (or circumferential segments) that are associated with pressure readings when one of the sensors <NUM> from mating or second sensing roll 11A enters the region of the nip <NUM>.

Thus, for sensor array <NUM> on the first sensing roll <NUM>, there are <NUM> axially arranged sensors <NUM>, each of which can be uniquely referred to using a first axial segment index value that ranges from "<NUM>" to "<NUM>", and there are <NUM> tracking segments associated with the mating or second sensing roll 11A, each of which can be uniquely referred to using a first tracking segment index value ranging from "<NUM>" to "<NUM>", which together create <NUM> (i.e., <NUM> ×<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 first two-element set comprising a respective first axial segment index value and a respective first tracking segment index value. Thus, a raw pressure reading from a sensor <NUM> can be associated with a first axial segment index value and a first tracking segment index value which, together, uniquely identify <NUM> of <NUM> cells in each of the matrices shown in <FIG>, <FIG>, <FIG> and <FIG> that are associated with the sensor array <NUM>. Based on the particular permutation of the first axial segment index value and first tracking segment index value, data can be added to, or extracted from, an appropriate cell of one those matrices associated with the sensor array <NUM>.

In addition to those <NUM> permutations, for sensor array <NUM> there are also <NUM> axially arranged sensors <NUM>, each of which can be uniquely referred to using a second axial segment index value that ranges from " <NUM>" to "<NUM>", and there are <NUM> tracking segments associated with the sensing roll <NUM>, each of which can be uniquely referred to using a second tracking segment index value ranging from "<NUM>" to "<NUM>", which create <NUM> (i.e., <NUM> ×<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 second two-element set comprising a respective second axial segment index value and a respective second tracking segment index value. Thus, a raw pressure reading from a sensor <NUM> can be associated with a second axial segment index value and a second tracking segment index value which, together, uniquely identify <NUM> of <NUM> cells in each of the matrices shown in <FIG>, <FIG>, <FIG> and <FIG> that are associated with the sensor array <NUM>. Based on the particular permutation of the second axial segment index value and second tracking segment index value, data can be added to, or extracted from, an appropriate cell of one those matrices associated with the sensor array <NUM>.

The process of <FIG> is substantially the same even when there are multiple arrays or pluralities of sensors and multiple sets of matrices such as, for example, if there are two sensing rolls <NUM>, 11A or there are two arrays, or sets, (24A, <NUM>) of sensors on a single sensor roll <NUM>. Similar to step <NUM>, the raw pressure reading from a sensor entering the nip <NUM> is still being acquired. However, the appropriate counts and sum matrices that will be updated also take into account which plurality (e.g., 24A, <NUM>) or array (e.g., <NUM>, <NUM>) the sensor is a part of. Similarly, when adjusting the raw pressure reading, an average pressure value is selected from the appropriate average pressure matrix that corresponds to that sensor plurality 24A, <NUM> or array <NUM><NUM>, see step <NUM>. As for the real-time average pressure profile data that is stored, the adjusted pressure readings can be averaged into its appropriate axial segment value of the profile regardless of the sensor plurality 24A, <NUM> or array <NUM><NUM> used in acquiring that reading. Also, in an embodiment having multiple sensor pluralities or arrays, steps <NUM> and <NUM> are completed for each sensor plurality or array; in other words, a respective average pressure matrix is built and stored for each plurality (e.g., 24A, <NUM>) or array (e.g., <NUM><NUM>) of sensors.

<FIG> is a flowchart of one example modification to show a data collection session according to <FIG> may change when multiple sensor pluralities or arrays are used in collecting nip pressure data in accordance with the principles of the present invention. As described with relation to <FIG>, a new collection session begins in step <NUM> with zeroing out an old real-time average pressure profile.

In step 914A, a raw pressure reading is collected when a sensor from any of the pluralities (24A, <NUM>) or arrays (e.g., <NUM>, <NUM>) enters a region of the nip <NUM>. Accordingly, a determination is made of which sensor plurality or array that sensor belongs to, a time (or circumferential) segment (i.e., a tracking segment) associated with the raw pressure reading, and an axial position associated with the raw pressure reading. Which sensor plurality or array a particular sensor belongs to can be referred to as the "membership" of that sensor; or, in other words, which array or plurality that sensor is a "member" of.

When the sensing roll <NUM> includes two (or more) pluralities or arrays of sensors, then the time (or circumferential) segment number of the mating roll <NUM> is determined based on the time that has elapsed since the last trigger signal from the mating roll <NUM> (as described above). However, when the mating roll 11A is itself a sensing roll, then the time (or circumferential) segment number associated with any raw pressure readings collected by sensors <NUM> of the mating or second sensing roll 11A are determined based on the time that has elapsed since the last trigger signal from the first sensing roll <NUM>. Thus, when there are two sensing rolls <NUM>, 11A, their respective roles vacillate between being a "sensing" roll and a "mating" roll. When a raw pressure reading is acquired by a sensor <NUM> of the second sensing roll 11A, then that roll 11A is acting as a sensing roll and the first sensing roll <NUM> is actually considered as a "mating" roll whose surface is being mapped. Similarly, when a raw pressure reading is acquired by a sensor <NUM> of the first sensing roll <NUM>, then that roll <NUM> is acting as the sensing roll and the other sensing roll 11A is actually considered as a "mating" roll whose surface is being mapped. So, even if a roll is explicitly labelled a sensing roll in the above description, such as rolls <NUM> and 11A, that particular roll can sometimes be acting as a "sensing" roll and at other times be acting as a "mating" roll.

In step 916A, for each raw pressure reading generated by a sensor 126A, <NUM><NUM>, <NUM>, the counts matrix and sum matrix associated with the sensor plurality (24A, <NUM>) or array (<NUM>, <NUM>) of which that sensor is a member is determined and an appropriate cell in each of those matrices is determined based on the time (or circumferential) segment number and the axial position associated with the sensor that generated the raw pressure reading. These cells in the appropriate counts and sum matrices can then be updated.

In step 917A, the stored average pressure matrix corresponding to the sensor plurality or array of the sensor (i.e., the membership of the sensor) that collected the raw pressure reading is determined and an appropriate cell is selected based on the time (or circumferential) segment number and the axial position determined in step 914A. As described above, an average pressure matrix can include a row of column averages which can be used to correct each cell value of the average pressure matrix when it is selected in this step.

In step 918A, this corrected average pressure value can be subtracted from the raw pressure reading to calculate an adjusted pressure reading value. Based on the axial position of the raw pressure reading, the adjusted pressure reading value can be stored, in step 920A, with the other adjusted pressure reading values for that axial position collected during the current collection session in order to calculate a real-time average pressure profile at the appropriate time. Hence, when multiple sensor pluralities or arrays are used, adjusted pressure reading values from the multiple sensor pluralities or arrays at each axial position are summed together to determine an average pressure value for each axial position when determining the real-time average pressure profile.

For the embodiment comprising first and second pluralities 24A and <NUM> of sensors 126A and <NUM> on a sensing roll <NUM>, each time a raw pressure reading from one of a pair of sensors 126A and <NUM>, positioned at a same axial segment of the sensing roll <NUM> and circumferentially spaced apart, is adjusted using a corrected average pressure matrix cell value, that adjusted pressure reading value is summed with all the other adjusted pressure reading values for that particular axial segment acquired earlier by that sensor pair (126A, <NUM>) and during the current collection session and a count of the total number of adjusted pressure reading values from that sensor pair used in constructing that sum is stored as well. From this stored data and at the end of the collection session, an average pressure value can be constructed for each axial segment of a real-time average pressure profile for the nip region of the sensing roll <NUM> and mating roll <NUM> by dividing the summation of the adjusted raw pressure reading values by the count of the total number of adjusted pressure reading values.

For the embodiment comprising a first array <NUM> of sensors <NUM> on the first sensing roll <NUM> and a second array <NUM> of sensors <NUM> on the mating or second sensing roll 11A, each time a raw pressure reading from one of the sensors <NUM> on the first sensing roll <NUM> is adjusted using a corrected average pressure matrix cell value, that adjusted raw pressure reading value is summed with all the other adjusted raw pressure reading values for that particular axial segment on the first sensing roll <NUM> acquired earlier by that sensor <NUM> as well as with all the other adjusted raw pressure reading values for a corresponding or same axial segment on the mating roll 11A acquired earlier by a sensor <NUM> on the mating roll 11A at the corresponding axial segment on the mating roll 11A during the current collection session and a count of the total number of adjusted raw pressure reading values from that sensor <NUM> and its corresponding sensor <NUM> at the same axial segment on the mating roll 11A used in constructing that sum is stored as well. Likewise, each time a raw pressure reading from one of the sensors <NUM> on the second sensing roll 11A is adjusted using a corrected average pressure matrix cell value, that adjusted raw pressure reading value is summed with all the other adjusted raw pressure reading values for that particular axial segment on the second sensing roll 11A acquired earlier by that sensor <NUM> as well as with all the other adjusted raw pressure reading values for a corresponding or same axial segment on the first sensing roll <NUM> acquired earlier by a sensor <NUM> on the first sensing roll <NUM> at the corresponding axial segment on the sensing roll <NUM> during the current collection session. From this stored data and at the end of the collection session, an average pressure value can be constructed for each axial segment of a real-time average pressure profile for the nip region of the first and second sensing rolls <NUM> and 11A by dividing the summation of the adjusted raw pressure reading values by the count of the total number of adjusted pressure reading values. As an alternative, a separate real-time pressure profile can be calculated for each of the sensor arrays <NUM>, <NUM>. Calculating separate real-time pressure profiles may allow calibration of the sensors which comprise the arrays <NUM>, <NUM>. Sensor calibration can be checked and adjusted by comparing, for each axial segment of the pressure profile, the pressures of two sensors, one from each array <NUM>, <NUM>, that are in the nip at the same time. The sensor values can be adjusted, or calibrated, so that each sensor provides the same reading. Once the arrays <NUM>, <NUM> of sensors are calibrated, then the separate real-time pressure profiles can be combined into a single real-time pressure profile.

The process can then continue with step <NUM> (see <FIG>) to determine if a collection session is completed or not. When all collection sessions for a set of collection sessions are completed, then a new average pressure matrix can be built using the counts and sums matrices. In an embodiment with multiple sensor pluralities or arrays, a respective new average pressure matrix is built corresponding to each sensor pluralities or array and can be used in subsequent collection sessions (e.g., the next day). That is, a separate new average pressure matrix is built for each sensor plurality or sensor array.

The above description of the flowchart of <FIG> assumed that the sensing roll <NUM> and the sensing roll 11A each had been logically divided into the same number of axial segments (e.g., <NUM>) defined by the number of sensors on the opposite sensing roll. The above description also assumed that both sensing rolls <NUM>, 11A had also been segmented into the same number (e.g., <NUM>) of tracking segments. Accordingly, the matrices associated with each of the sensing rolls were all of the same size (e.g., <NUM>,<NUM> cells). One of ordinary skill will recognize that each of the sensing rolls could have respective numbers of axial segments and tracking segments that are different from one another. The steps of the flowcharts of <FIG> and <FIG> would remain substantially the same but the corresponding matrices associated with each sensing roll would be different sizes.

In the case where the two rolls have the same number of axial segments (e.g., <NUM>) but different numbers of tracking segments, the sensing roll that has more tracking segments will contribute, for each axial segment, more data samples to the real-time pressure profile calculated in <NUM>; but the steps of the flowchart remain the same.

In the case where the two sensing rolls have different numbers of axial segments, then the collection of data and the building of various matrices for each sensing roll remains the same but the method of calculating the real-time pressure profile using that data may be modified. For example, if all the sensors on both rolls were evenly-spaced and the sensing roll <NUM> had twice as many sensors as the sensing roll 11A, then one axial section of the nip will be associated with two sensor readings from the sensor roll <NUM> and only one sensor reading from the sensor roll 11A. Various techniques can be used to combine these three values in a manner that provides a beneficial real-time pressure profile value for that axial section of the nip. As a general principle, each separate axial section of the nip will be associated with one or more sensors on one sensing roll and one or more sensors on the other sensing roll. Creation of the real-time average pressure nip profile is performed by determining which sensors are associated with which axial segment of the nip and combining the values from those sensors in a statistically appropriate manner.

As mentioned above, there arc ways for synchronizing sensor measurements other than using the signal generator <NUM> (or 900A) to generate respective trigger signals <NUM>. In general, a trigger signal is associated with the mating roll <NUM> being in a known reference position such that the time that has elapsed since the most-recent trigger signal allows the processor <NUM> to identify a present rotational position of the mating roll relative to that reference position. Alternative techniques that allow the processor <NUM> to calculate a rotational position of the mating roll <NUM> relative to a reference position can also be utilized. For example, a pulse generator could generate <NUM> pulses per each rotation of the mating roll <NUM> and a counter could count the pulses such that after the count reaches <NUM> the counter is reset to start-over counting from "<NUM>". By considering the position of the mating roll <NUM> to be at the "reference position" when the counter starts over, a current pulse count value when a sensor signal is acquired can be provided to the process <NUM> and used to determine a rotational position of the mating roll <NUM> relative to the reference position.

When more than one sensing roll is used, there are other alternatives to the signal generators <NUM> and 900A providing respective trigger signals <NUM>, 901A to the processor <NUM> in order to determine time segments or circumferential segments. In particular, the timing of sensor data from each of the sensing rolls <NUM>, 11A could also be used for a similar purpose. For example, acquiring raw pressure readings from the sensors <NUM> of the sensing roll 11A can be synchronized with respect to the rotation of the sensing roll <NUM>. One of the fourteen sensors <NUM> of the sensing roll <NUM> can be selected to indicate a full rotation of the sensing roll <NUM> such that each time that one sensor <NUM> enters the region of the nip <NUM> the sensing roll <NUM> is considered to have made a rotation and a periodically occurring first time reference is established. Rather than measuring time since an externally applied trigger signal, time since the most recently occurring first time reference can be used. Each time that one sensor <NUM> enters the region of the nip <NUM>, measurement of a time period can be re-started such that the elapsed time in the current time period is indicative of which of the tracking segments associated with the sensing roll <NUM> is presently in the region of the nip <NUM>. Thus, when a sensor <NUM> from the sensing roll 11A enters the region of the nip <NUM> and acquires a raw pressure reading, the elapsed time period since that one sensor <NUM> of the sensing roll <NUM> last entered the nip <NUM> can be used to identify an appropriate time segment or circumferential segment of the sensing roll <NUM> to associate with that raw pressure reading. In accordance with this alternative, the pressure measurements communicated by the wireless transmitters <NUM>, 40A to the processor <NUM> can also include timing information to allow the processor <NUM> to perform the appropriate time-based calculations.

A similar approach can also be used to also measure the raw pressure readings acquired from sensors <NUM> synchronously with respect to rotation of the sensing roll 11A. In this approach, one of the fourteen sensors <NUM> of the sensing roll 11A can be selected to indicate a full rotation of the sensing roll 11A such that each time that one sensor <NUM> enters the region of the nip <NUM> the sensing roll 11A is considered to have made a rotation and a periodically occurring second time reference is established. Rather than measuring time since an externally applied trigger signal, time since the most recently occurring second time reference can be used to synchronize sensor measurements by sensors <NUM> with respect to the rotational period of the sensing roll 11A.

Also, three or more sensor arrays may be arranged on a single sensing roll or two or more sensor arrays can be arranged on a pair of sensing rolls that form a nip. Thus, one of ordinary skill will appreciate that acquiring data from two sensor arrays, as discussed herein, is provided merely by way of example and that data from more than two arrays of sensors may also be acquired without departing from the scope of the present invention. Each sensor array will have its own associated matrices as shown in <FIG>; however, the steps of the flowcharts of <FIG> and <FIG> will remain substantially the same for each sensor array regardless of the number, and configuration, of the multiple sensor arrays.

The various example arrangements of rolls described above included arrangements of two rolls; however, it is possible to arrange three or more rolls in such a way as to move webs of material. For example, one sensing roll could be located between two mating rolls such that the sensing roll forms two separate nips, one with each mating roll. In such an arrangement, a sensor of the sensing roll will rotate through two nips during each rotation of the sensing roll and respective pressure readings can be acquired from each nip. Thus, the matrices of <FIG> and a real-time average pressure profile can be calculated for each nip in accordance with the principles described above. Even though only one sensing roll is actually present, the collection and analysis of data is functionally equivalent to two sensing rolls and two mating rolls forming separate nips such that the method described in the flowchart of <FIG> would be implemented separately for each mating roll.

Similarly, three sensing rolls could also be arranged such that a central sensing roll forms separate nips with two outside sensing rolls. The matrices of <FIG> and a real-time average pressure profile can be calculated for each nip in accordance with the principles described above. Even though only three sensing rolls are actually present, the collection and analysis of data is functionally equivalent to two different pairs of sensing rolls forming separate nips such that the method described in the flowcharts of <FIG> and <FIG> would be implemented separately for each hypothetical pair of sensing rolls.

One of ordinary skill will readily recognize that there a many different ways to arrange a plurality of sensors or sensor arrays on a sensing roll. One example of such an arrangement, not falling within the scope of the claims, is provided in <CIT> where arrays of sensors are "interleaved". In other words, each sensor of a first array of sensors is associated with a respective axial segment of a sensing roll while each sensor of a second array of sensors is associated with a respective axial segment of the sensing roll. In particular, however, each the respective axial locations associated with a sensor of the first array of sensors is located in-between a pair of respective axial segments associated with a pair of sensors of the second array, to create an "interleaving" of the sensors of the two different sensor arrays. In accordance with the principles of the present disclosure, the example methods described with respect to <FIG> and <FIG> can be utilized with such an arrangement of interleaved sensors. If for example,which is an example not falling within the scope of the claims a first sensor array had x sensors and an interleaved second sensor array had y sensors, then various real-time nip pressure profiles could be constructed in accordance with the principles of the present disclosure. Two separate nip profiles, for example, could be generated with one nip profile having x axial segments corresponding to sensor readings from the first sensor array and a second nip profile having y axial segments corresponding to they sensors of the second sensor array. A composite nip profile that has (x + y) axial segments could then be constructed by combining the two separate nip profiles and graphically presented to an operator.

Alternatively, the two arrays of sensors could be treated, in accordance with the principles of the present invention, as a single array having (x + y) sensors and, therefore, (x + y) corresponding axial segments. Accordingly, a single nip profile could then be constructed, and graphically presented to an operator, that has (x + y) axial segments.

Claim 1:
A system associated with a sensing roll (<NUM>) and a mating roll (<NUM>) for collecting roll data of the mating roll comprising:
a first plurality of sensors located at axially spaced-apart locations of the sensing roll (<NUM>), wherein each sensor of the first plurality enters a region of a nip (<NUM>) between the sensing roll (<NUM>) and the mating roll (<NUM>) during each rotation of the sensing roll (<NUM>) to generate a first respective sensor signal;
a second plurality of sensors located at axially spaced-apart locations of the sensing roll (<NUM>), wherein each sensor of the second plurality enters the region of the nip (<NUM>) during each rotation of the sensing roll (<NUM>) to generate a second respective sensor signal, wherein each sensor of the first plurality has a corresponding sensor in the second plurality which is associated with a same respective axial location on the sensing roll (<NUM>) but is spaced-apart circumferentially; and
a processor (<NUM>) to receive a received sensor signal, the received sensor signal comprising one of the first respective sensor signal and the second respective sensor signal, and, upon receiving the received sensor signal, the processor (<NUM>) operates to:
determine a particular one of the sensors of the first plurality or second plurality which generated the received sensor signal,
determine membership of the particular one sensor based on which plurality of sensors the particular one sensor is a member,
based upon a rotational position of the mating roll (<NUM>) relative to a reference position, determine which one of a plurality of circumferential tracking segments associated with the mating roll (<NUM>) enters the region of the nip (<NUM>) substantially concurrently with the particular one sensor entering the region of the nip (<NUM>), and store the received sensor signal using the determined one tracking segment and the determined membership.