Patent Description:
C shape sensors are common in web edge detection where the web passes through a gap in the C shape. Sensors are often housed in arms of the C extending at least partially across the web. The sensors may be divided between transmitter and receiver elements. The gap of the C shape sensors extend between the arms and may limit acceptable deviations in the web plane of the traveling web while passing through the C shape sensor. In order to overcome this limitation, C shape sensors may be mounted on or connected to an articulable element, known as a moving sensor guide that allows the C shape sensors to move in response to changes in the width of the material web. In addition, rollers may be employed, such as fixed support bars, close to the C shape sensors enabling better control over the web plane and enabling use of C shape sensors using smaller gaps. A plurality of C shape sensors have been used to guide a single material web, with sensors on either side of the material web, to simultaneously perform edge detection on opposing edges of the material web.

C shape sensors may be used in ultrasonic guiding systems, for example as described in <CIT>. C shape sensors are also used in photoelectric systems as described in <CIT> that uses infrared sensing devices to perform web edge sensing to guide the material web.

Another system has been previously described by Haque et al. , who employed a natural interaction sensor and a sensor controller in order to guide and/or tension material webs (United States Patent Application Publication Pub. No. <CIT>).

Another system has been previously described by Edmiston, who employed a ring redundancy approach in order to provide redundancy within a fieldbus network (United States Patent Application Publication Pub. No. <CIT>).

Line sensors may be used which scan graphical patterns on the web, without performing edge detection, for guiding the material web. Line sensors may capture images and guide the material web based on a comparison of the images and the location of the graphical patterns with a stored set point. Line sensors may have a horizontal field of view that spans a portion or the entirety of the material web between opposing edges. However, the line sensors have a field of view in the web direction of travel that is limited to one pixel and encompasses no more than <NUM>-<NUM> microns of the web in the web direction of travel. Other sensors used in web guiding may include laser curtain sensors, ragged edge sensors, fiber optics sensors, raised feature sensors, capacitance or inductance sensors, and mechanical paddle or finger sensors.

Visual inspection systems for providing quality assurance to moving webs of material currently exist. One visual inspection system is sold under the trademark InPrinttm by Fife Corporation, the assignee of the present patent application. This visual inspection system provides quality assurance by allowing direct, live image viewing of a moving web. In particular, this visual inspection system captures images of a moving web at <NUM> images/second and compares the captured images to a reference image of the web to detect deviations of the captured image from the reference image. When deviations are detected, the visual inspection system sounds an alarm, and/or directs a particular product to an appropriate location to be manually inspected.

Web handling systems include tension control components that are used to control the tension in a web of material. The tension in the web is detected by a load cell bearing sensor on the web of material, and the tension is controlled by a brake or clutch system that can vary the rate of movement of a roller for feeding and/or retrieving of the web of material. The tension control components also include a controller to receive information indicative of the tension in the web of material from the load cell bearing sensor and generate control signals that are transmitted to the brake or clutch system to control the tension in the web. Other tension control components include load cells, load cell-based tension controllers, tension readouts, dancer controllers, magnetic particle clutches and brakes, and permanent magnet brakes and clutches.

In certain applications, web handling systems also include systems for physically modifying or manipulating the web of material. These types of web handling systems include slitting systems used for cutting the web of materials along the web's longitudinal axis, and bowed rolls or spreader rolls used for separating parts of the web of material. Other slitting products include electronic and pneumatic knifeholders, slitter positioning systems, fully automated shear slitting systems, and mechanically linked slitting systems.

In certain applications, web handling systems also include winding products including core shafts, air shafts, expansion shafts, web shafts and core holders, pneumatic brakes, safety chucks, core chucks, shaftless chucks and crushed core restorers.

Various web handling systems can be combined into one or more process line used for guiding, tensioning, slitting, and inspecting one or more webs of material to make predetermined products, such as diapers. These web handling systems have multiple controllers and sensors that are interconnected via a star network topology.

The invention is defined by the web handling system according to claim <NUM>. Further embodiments are set out in the appended dependent claims.

Certain embodiments of the present inventive concepts will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:.

Specific embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. Further, in the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the disclosure. However, it will be apparent to one of ordinary skill in the art that the embodiments disclosed herein may be practiced without these specific details.

In addition, use of the "a" or "an" are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the inventive concept. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

Finally, as used herein any reference to "one embodiment" or "an embodiment" means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment.

The terminology and phraseology used herein is for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited.

The prior art web handling systems can be improved by providing better networking solutions, and time-based synchronization of the controllers and sensors. It is to such an improved web handling system that the present disclosure is directed.

Referring now to the figures, shown in <FIG> is a web handling system <NUM> for handling a continuous material web <NUM>. The continuous material web <NUM> is passed over a variety of rollers <NUM> in accordance with the present disclosure. The rollers <NUM> may include cylinderically shaped web rollers or other types of rollers, including, but not limited to heat transfer rollers, idler rollers, vacuum rollers, bowed rollers and spreader rollers. The web handling system <NUM> may be used in web guiding, tension control, and quality inspection industries, for example. The web handling system <NUM> includes, by way of example, one or more web guiding systems <NUM>, one or more supply roller <NUM>, one or more tension control systems <NUM>, one or more windup roller <NUM>, one or more slitting systems <NUM> and one or more video web inspection systems <NUM> synchronized by a web handling process logic controller <NUM>. Each of the web guiding systems <NUM>, tension control systems <NUM>, slitting systems <NUM>, video web inspection systems <NUM> has a web handling controller <NUM> (shown by way of example as <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>) in <FIG> that will be discussed in more detail below. The web handling controllers <NUM> are also networked with a web handling process logic controller <NUM>. As shown in <FIG>, the web handling controllers <NUM> are provided with a processor <NUM>, a clock <NUM> and at least two separate network communication ports 34a and 34b. The processor <NUM> is coupled to the clock <NUM> and the at least two separate network communication ports 34a and 34b. The processor <NUM> receives clock signals from the clock <NUM> and may synchronize the clock signals with a master clock, as discussed below. As shown in <FIG>, the web handling process logic controller <NUM> is also provided with a processor <NUM>, a clock <NUM> and at least two separate network communication ports <NUM> (that are designated in <FIG> with the reference numerals 44a and 44b). The processor <NUM> is coupled to the clock <NUM> and the at least two separate network communication ports 44a and 44b. The processor <NUM> receives clock signals from the clock <NUM> and may transmit timing signals the the web handling controllers <NUM> such that the clock <NUM> becomes a master clock for all of the web handling controllers <NUM> within the network, as described below.

As will be described below, the processor <NUM> of the web handling process logic controller <NUM> and the processors <NUM> of the web handling controllers <NUM> are programmed or hardware configured to communicate using a ring-network topology having the ability to detect a fault in the network, and to automatically switch from a network using a ring topology to two separate linear topological networks. Once the web handling process logic controller <NUM> and the web handling controllers <NUM> switch to the linear topological networks, the web handling process logic controller <NUM> sends out a series of neighbor check requests from the communication ports 44a and 44b to cause each of the web handling controllers <NUM> to check to see if the web handling controllers <NUM> can communicate with its neighbors in the linear topological networks. This check can be accomplished by the web handling controllers <NUM> polling neighboring web handling controllers <NUM> and then reporting back to the web handling process logic controller <NUM>. Utilizing a ring topology that can switch to two separate linear topological networks provides the web handling system <NUM> with enhanced communication reliability and redundancy as compared to the prior art web handling systems that utilize a star network topology.

For example, as shown in <FIG>, the web handling controller <NUM>-<NUM> polls the web handling controller <NUM>-<NUM>; the web handling controller <NUM>-<NUM> polls the web handling controller <NUM>-<NUM>; and the web handling controller <NUM>-<NUM> polls the web handling controller <NUM>-<NUM>. Likewise, the web handling controller <NUM>-<NUM> receives the neighbor check request and then polls the web handling controller <NUM>-<NUM>; the web handling controller <NUM>-<NUM> polls the web handling controller <NUM>-<NUM>; and the web handling controller <NUM>-<NUM> polls the web handling controller <NUM>-<NUM>. In this manner, at some point within the network two of the web handling controllers <NUM>-<NUM> - <NUM>-<NUM> will not receive a neighbor check response due to a fault in the network. By polling neighboring web handling controllers <NUM>, the web handling process logic controller <NUM> determines a location of the fault in the network, and also determines the identity of the web handling controllers <NUM> on each of the linear topology networks. For example, as shown in <FIG>, a fault exists between the communication port 34a of the web handling controller <NUM>-<NUM>, and the communication port 34b of the web handling controller <NUM>-<NUM>. In this example, the web handling process logic controller determines the location of the fault, due to the web handling controller <NUM>-<NUM> transmitting a request and not receiving a neighbor check response.

In one embodiment, the web handling process logic controller <NUM> and the web handling controllers <NUM> utilizing a device level ring protocol and an ethernet networking protocol to communicate. In this embodiment, the device level ring protocol provides high network availability in a ring topology for the web handling process logic controller <NUM> and the web handling controllers <NUM>. In this embodiment, the communication ports 34a, 34b, 44a and 44b are Ethernet ports with embedded switch technology. The device level ring protocol provides fast network fault detection and reconfiguration in order to support the most demanding web handling control applications.

In one embodiment, the device level ring protocol operates at Layer <NUM> (in the ISO OSI network model). Thus, the presence of the ring topology and the operation of the device level ring protocol are transparent to higher layer protocols such as TCP/IP and CIP, with the exception of a device level ring Object that provides a device level ring configuration and diagnostic interface via CIP.

In one embodiment, the processor <NUM> of the web handling process logic controller <NUM> is programmed with a ring supervisor that monitors traffic on the communication ports 44a and 44b. The ring supervisor can control the traffic on the communication ports 44a and 44b to selectively prevent packets from circulating within the network, as well as to send beacon frames and/or announce frames.

Beacon frames can be sent from both of the web handling process logic controller <NUM> communication ports 44a and 44b to detect cable breaks and/or malfunctions of any one of the web handling controllers <NUM>. The beacon frames can also carry precedence values so that an acting supervisor can be determined on a network with multiple ring supervisors. In one embodiment, by default, Beacon frames are sent out at an interval of <NUM> and during ring state change.

Announce frames are sent from the unblocked port at a predetermined interval, such as once per second, and during ring state change. The announce frames may transmit instructions about topology reconfigurations.

In some embodiments, each of the web handling process logic controller <NUM> and the web handling controllers <NUM> have a unique address, such as a MAC address. When the web handling process logic controller <NUM> receives a packet on one of the communication ports 44a or 44b, e.g., the communication port 44a, the web handling process logic controller <NUM> determines whether the packet needs to be received and interpreted by itself (e.g., the packet has the web handling process logic controller's MAC address) or whether the packet should be forwarded via the other communication port 44a or 44b, e.g., the communication port 44b. Likewise, when the web handling controller <NUM> receives a packet on one of the communication ports 34a or 34b, e.g., the communication port 34a, the web handling controller <NUM> determines whether the packet needs to be received and interpreted by itself (e.g., the packet has the web handling process logic controller's MAC address) or whether the packet should be forwarded via the other communication port 34a or 34b, e.g., the communication port 34b.

The active ring supervisor running on the processor <NUM>, blocks traffic on one of the communication ports 44a and 44b with the exception of few special frames and does not forward traffic from one communication port 44a to 44b to the other communication port 44a to 44b. Because of this configuration a network loop is avoided and only one path exists between any two of the web handling process logic controller <NUM> or the web handling controllers <NUM> during normal operation. In some embodiments, the web handling process logic controller <NUM> is always the active ring supervisor and transmits a beacon frame through both communication ports 44a and 44b at a predetermined interval or random interval, such as <NUM>.

For most implementations, beacon-based device level ring is preferred due to faster fault detection and recovery times. The active ring supervisor also sends announce frames at a predetermined or random interval, such as once per second.

The beacon and announce frames serve several purposes. First, the presence of beacon and announce frames inform the web handling controllers <NUM> to transition from linear topology mode to ring topology mode and vice versa. Second, a loss of beacon frames at the web handling process logic controller <NUM> enables detection of certain types of ring faults. (Note that the web handling controllers <NUM> are also able to detect and signal ring faults). Third, in some embodiments, the beacon frames carry a precedence value, allowing selection of an active supervisor when multiple ring supervisors are configured.

The web handling process logic controller <NUM> and the web handling controllers <NUM> can also be configured to synchronize clocks <NUM> and <NUM> using any suitable protocol, such as a protocol known as precision time protocol. Suitable versions of precision time protocols are described in IEEE <NUM>-<NUM> and <NUM>-<NUM>.

Precision time protocol described in IEEE <NUM>-<NUM> and <NUM>-<NUM> uses a hierarchical master-slave architecture for clock distribution. Under the precision time protocol architecture, a time distribution system consists of one or more communication media (network segments), and one or more clocks, such as the clocks <NUM> and <NUM>. An ordinary clock is a device with a single network connection and is either the source of (master) or destination for (slave) a synchronization reference. A boundary clock has multiple network connections and can accurately synchronize one network segment to another. A synchronization master is selected for each of the network segments in the system. The root timing reference is called the grandmaster. The grandmaster transmits synchronization information to the clocks residing on its network segment. The boundary clocks with a presence on that segment then relay accurate time to the other segments to which they are also connected.

A simplified PTP system frequently consists of ordinary clocks connected to a single network, and no boundary clocks are used. A grandmaster is elected and all other clocks synchronize directly to it.

IEEE <NUM>-<NUM> introduces a clock associated with network equipment used to convey PTP messages. The transparent clock modifies PTP messages as they pass through the web handling process logic controller <NUM>, and/or one of the web handling controllers <NUM>. Timestamps in the messages are corrected for time spent traversing the network equipment. This scheme improves distribution accuracy by compensating for delivery variability across the network.

PTP typically uses the same epoch as Unix time (Midnight, <NUM> January <NUM>). While the Unix time is based on Coordinated Universal Time (UTC) and is subject to leap seconds, in some embodiments PTP is based on International Atomic Time (TAI) that moves forward monotonically. The PTP grandmaster communicates the current offset between UTC and TAI, so that UTC can be computed from the received PTP time.

Synchronizing the clocks, such as by using PTP, in web handling (guiding, tension control, slitter positioning etc.) applications provides the mechanism to synchronize the web handling controllers <NUM> across the network. This is important from a guiding and web handling perspective as this allows sensor signals (such as the position or tension of the web of material) to be collected or generated from any web handling controller <NUM> to be broadcast on the network and shared among specific or all web handling controllers <NUM>.

Each web handling controller <NUM> provides one or more independent closed loop control systems. The nature of closed loop control systems dictate that phase jitter of the sensor signals used as inputs to the control loop be minimized or eliminated. In the presently disclosed web handling controllers <NUM>, very precise timing via any suitable logic, such as FPGA logic, may be used to collect analog signals cyclically at consistent moments in time to prevent signal phase deviations and jitter. Control loop calculations performed in software are also synchronized to the same sampling process by virtue of high priority CPU interrupt mechanisms so calculations are done with the most recent data available. This provides control signals generated at precise cyclical moments to maximize the web controller stability and correction speed.

The timing logic inside each web handling controller <NUM> also contains additional capability to generate and accept signals to synchronize the previously described cyclic signal sampling process of the web handling controllers <NUM> across the network, thus providing the basis for shared guiding signals between units with signals that remain in phase and contain minimum jitter. By maintaining the same signal timing integrity across the network, control loops running in any connected web handling controller <NUM> can use remote sensor data as if the remote sensor data were collected locally without penalizing control loop performance.

The timing logic, using precision time protocol for example, results in clock synchronization. Because the clocks of the web handling controllers <NUM> in the network are precisely synchronized, the closed loop control process previously described is also synchronized. Synchronization implies that a single clock source must become the master to which all other web handling controllers <NUM> seek to mirror. Again the precision time protocol, for example, provides the means to accomplish this by the precision time protocol's use of an arbitration system to determine which device (e.g., the web handling process logic controller <NUM>, or one of the web handling controllers <NUM> will be the master. In order to work in harmony with existing precision time protocol mechanisms that may be present in any given network, the web handling controllers <NUM> described herein may implement precision time protocol in such a way that they will not become precision time protocol masters, however, in absence of other precision time protocol masters in the network, the presently disclosed web handling controllers <NUM> will automatically arbitrate a precision time protocol master when needed in order to synchronize the control loops of the web handling controllers <NUM>.

Several mechanisms are at work inside the timing logic to accomplish synchronization. The timing logic may have the capability to "snap" instantly to a clock value, which is often done when a device (e.g., the web handling process logic controller <NUM>, or the web handling controllers <NUM>) is first powered on with existing precision time protocol clocks already established. As the precision time protocol process runs on the processor <NUM> and the processor <NUM>, for example, the presently disclosed web handling controllers <NUM> may use a control algorithm fed by the amount of correction needed from each adjustment moment to actually tune the timing logic, e.g., FPGA clock frequency. In this embodiment, the clock <NUM> is a FPGA clock. This makes the clock <NUM> of the web handling controller <NUM> seek the same frequency as the master clock resulting in smaller adjustments. In some embodiments, this process runs continuously on the processor <NUM> of the web handling controller <NUM> to maintain synchronization.

<FIG> shows an exemplary method that may be run by the processor <NUM> of the web handling controller <NUM> to synchronize a slave clock to a master clock in accordance with the present disclosure. In this example, an Offset and Network Propagation Delay used by processor <NUM> of the web handling controllers <NUM> to synchronize the clock <NUM> with the clock <NUM> can be calculated as follows:
<MAT>
<MAT>
<MAT>
<MAT>.

In some embodiments, the processor <NUM> of one of the web handling controllers <NUM>, or the processor <NUM> of the web handling process logic controller <NUM> acting as a slave clock (referred to herein as the "slave clock") synchronizes the clock <NUM> or the clock <NUM> to the master clock of the network by using a bidirectional multicast communication as shown in <FIG>. In some embodiments, the synchronization of the clock <NUM> or the clock <NUM> can be accomplished as follows. The processor <NUM> of the one of the web handling controller <NUM> or the processor <NUM> of the web handling process logic controller <NUM> acting as the master clock (referred to herein as the "master clock") issues a synchronization packet containing a timestamp of the time when the synchronization packet left the master clock via one of the communication ports 34a, 34b, 44a, or 44b. The master clock may also, optionally, issue a follow-up packet containing a timestamp for the synchronization packet. The use of a separate follow-up packet allows the master clock to accurately timestamp the synchronization packet on networks where the departure time of a packet cannot be known accurately beforehand. For example, collision detection and random backoff mechanisms of ethernet communication prevents the exact transmission time of a packet from being known until the packet is completely sent without a collision being detected, at which time it is impossible to alter the packets content. A slave clock receives the master clock synchronization packet and timestamps the packets arrival using the slave clock's own clock <NUM> or <NUM>. The difference in the synchronization packet's departure timestamp and the synchronization packets arrival timestamp is a combination of the slave clock's offset from the master clock and the network propagation delay. By measuring and storing the offset and using the offset to adjust the slave clock by the offset measured at this point, the offset between the master clock and the slave clock can be reduced to the network propagation delay only.

In some embodiments, the processor <NUM> of the web handling controller <NUM> or the processor <NUM> of the web handling process logic controller <NUM> acting as the master clock operates under an assumption that the network propagation delay is symmetrical. That is, the delay of the packet sent from the master clock to a slave clock is the same as the delay of a packet sent from the slave clock to the master clock. By making this assumption, the slave clock can discover and compensate for the propagation delay. The slave clock accomplishes this by issuing a request packet which is time stamped on departure from the slave clock. The request packet is received and timestamped by the master clock, and the arrival timestamp is sent back to the slave clock in a delay packet. The difference in the two timestamps is the network propagation delay.

By sending and receiving the synchronization packets, the slave clocks can accurately measure the offset between the slave clock's clock <NUM> or <NUM> and the master clock. The slave clocks can then adjust their clocks by this offset to match the time of the master clock.

The foregoing description provides illustration and description, but is not intended to be exhaustive or to limit the inventive concepts to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the methodologies set forth in the present disclosure.

Claim 1:
A web handling system (<NUM>) comprising:
a plurality of web handling controllers (<NUM>), each of the web handling controllers (<NUM>) running a control loop, and having a web handling processor (<NUM>), a first clock (<NUM>), a first communication port (34a) and a second communication port (34b); and
a web handling process logic controller (<NUM>) having a processor (<NUM>), a second clock (<NUM>), a third communication port (44a) and a fourth communication port (44b), the first communication port (34a), the second communication port (34b), the third communication port (44a) and the fourth communication port (44b) being connected to form a ring network, the processor (<NUM>) of the web handling process logic controller (<NUM>) being configured to determine whether a fault exists within the ring network, and responsive to determining that a fault exists within the ring network, to generate and send signals throughout the ring network to switch the configuration of the ring network to at least one linear network;
wherein the web handling processors (<NUM>) are configured to determine whether a master clock exists within the ring network, and responsive to determining that no master clock exists within the ring network, to automatically arbitrate a precision time protocol master in order to synchronize the control loops of the web handling controllers.