Abstract:
An edge detection system including an elongated sheet defining a longitudinal axis and having at least one edge and a sensor positioned relative to the elongated sheet, the sensor defining a scan field having a null zone, wherein the sensor is moveable relative to the sheet in a direction generally perpendicular to the longitudinal axis to align the null zone with the edge.

Description:
PRIORITY 
       [0001]    This patent application claims priority from U.S. Ser. No. 61/059,498 filed on Jun. 6, 2008, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    This patent application is directed to systems and methods for detecting the edge of a moving sheet and, more particularly, to edge detection systems for tracking the camber of a moving sheet. 
       BACKGROUND 
       [0003]    Referring to  FIG. 1 , an elongated rolled sheet  8 , such as a sheet of hard-rolled or soft-rolled steel, often includes a camber C, thereby providing the rolled sheet  8  with a substantially arcuate configuration in top view. The camber C may be defined as the deviation of a side edge  6  of the rolled sheet  8  from a straight line  4 . Therefore, a measurement of camber C may be presented as a distance (e.g., 2 inches) between the side edge  6  and the straight line L, wherein the distance is taken at the center of a section of the rolled sheet  8  having a predefined length (e.g., 20 ft). 
         [0004]    It is often desirable to know the magnitude of the camber C in a rolled sheet  8 . For example, unknown or excessive camber C in a rolled sheet  8  may disable or even damage equipment and machinery used to process the rolled sheet. Furthermore, if the camber C is known, various techniques may be employed to remove or at least minimize the camber C, thereby improving process efficiency and reducing the waste associated with trimming sheets to remove the camber C. 
         [0005]    However, prior art techniques for measuring camber typically require removing a section of the rolled sheet from the line, cutting the rolled sheet section to a predetermined length, determining the center of the length of the rolled sheet section and, using a straight edge or the like, measuring the deviation of the side edge from the straight edge. Such techniques are time consuming and fail to provide real-time data. 
         [0006]    Accordingly, there is a need for a system and method for detecting the edge of a moving sheet and, in particular, an edge detection system for tracking the camber of a moving sheet in real-time. 
       SUMMARY 
       [0007]    In one aspect, the disclosed edge detection system may include an elongated sheet defining a longitudinal axis and having at least one edge and a sensor positioned relative to the elongated sheet, the sensor defining a scan field having a null zone, wherein the sensor is moveable relative to the sheet in a direction generally perpendicular to the longitudinal axis to align the null zone with the edge. 
         [0008]    In another aspect, the disclosed edge detection system may include an elongated sheet defining a longitudinal axis and having at least one edge, a rail disposed over at least a portion of the elongated sheet, the rail extending generally perpendicular to the longitudinal axis, and a high speed profile sensor connected to the rail, the sensor defining a scan field having a null zone, wherein the sensor is moveable along the rail to align the null zone with the edge. 
         [0009]    In another aspect, the disclosed camber tracking system may include an elongated sheet having a first edge and a second edge, wherein the elongated sheet is moving in a traveling direction along a longitudinal axis, a first edge detecting station comprising a first sensor and a second sensor, wherein the first sensor is positioned relative to the first edge of the elongated sheet and defines a first scan field having a first null zone, the first sensor being moveable relative to the elongated sheet generally perpendicular to the longitudinal axis to align the first null zone with the first edge, and wherein the second sensor is positioned relative to the second edge of the elongated sheet and defines a second scan field having a second null zone, the second sensor being moveable relative to the elongated sheet generally perpendicular to the longitudinal axis to align the second null zone with the second edge, a second edge detection station displaced from the first edge detection station by a first distance in the traveling direction, the second edge detection station comprising a third sensor positioned relative to the first edge of the elongated sheet, the third sensor defining a third scan field having a third null zone and being moveable relative to the elongated sheet generally perpendicular to the longitudinal axis to align the third null zone with the first edge, and a third edge detection station displaced from the second edge detection station by a second distance in the traveling direction, the third edge detection station comprising a fourth sensor positioned relative to the first edge of the elongated sheet, the fourth sensor defining a fourth scan field having a fourth null zone and being moveable relative to the elongated sheet generally perpendicular to the longitudinal axis to align the fourth null zone with the first edge. 
         [0010]    Other aspects of the disclosed edge detection system and related camber tracking system will become apparent from the following detailed description, the accompanying drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0011]      FIG. 1  is a top plan view of an elongated rolled sheet material having a camber formed therein; 
           [0012]      FIG. 2  is a top plan view of one aspect of the disclosed edge detection system; 
           [0013]      FIG. 3  is a machine directional view of the edge detection system of  FIG. 2 ; and 
           [0014]      FIG. 4  is a top plan view of one aspect of the disclosed system for tracking camber using the disclosed edge detection system. 
       
    
    
     DETAILED DESCRIPTION  
       [0015]    Referring to  FIG. 3 , one aspect of the disclosed edge detection system, generally designated  10 , may include a sensor  12 , an articulation device  14  and a rail  16 . As shown in  FIGS. 2 and 3 , the system  10  may be positioned over a sheet  18  having a width W S , a first longitudinal edge  20 , a second longitudinal edge  22  and an upper surface  24 . For example, the width W S  of the sheet  18  may range from about 24 inches to over 8 feet. The sheet  18  may be an elongated sheet of rolled material, such as hot-rolled steel or cold-rolled steel, and may be moving in the longitudinal direction shown by arrow X ( FIG. 2 ), which may define the x-axis of the system  10 . 
         [0016]    The sensor  12  may be any sensor capable of identifying an edge  20 ,  22  of the sheet  18  when the sensor  12  is positioned relative to the sheet  18 . In one aspect, the sensor  12  may be a point laser sensor. In another aspect, the sensor  12  may be a laser line sensor. An example of a sensor  12  useful with the disclosed system  10  is the scanCONTROL 2810 high speed profile sensor available from Micro-Epsilon of Ortenburg, Germany. However, those skilled in the art will appreciate that other sensors, such as non-laser-based sensors (e.g., optical sensors), may be used without departing from the scope of the present disclosure. 
         [0017]    In one aspect, the sensor  12  may include an emitter  26 , a receiver  28  and a processor (or control device)  30 . In response to signals from the processor  30 , the emitter  30  may emit energy, such as light, particularly laser light, that may define a scan field shown by lines  32 ,  34 . The receiver  28  may receive reflected energy from the scan field  32 ,  34  and may communicate appropriate data to the processor  30 . 
         [0018]    The scan field  32 ,  34  may have a width W F  in the y-axis (arrow Y), which may be a function of the distance, in the z-axis (arrow Z), between the sensor  12  and the upper surface  24  of the sheet  18 . Within the scan field  32 ,  34  may be a null zone shown by lines  36 ,  38 . The null zone  36 ,  38  may be substantially centered in the scan field  32 ,  34  and may have a width W N  in the y-axis (arrow Y), which may be a function of the distance, in the z-axis (arrow Z), between the sensor  12  and the upper surface  24  of the sheet  18 . For example, when the sensor  12  is about 12 inches away from the upper surface  24  of the sheet  18 , the scan field  32 ,  34  may have a width W F  of about 5 inches and the null zone  36 ,  38  may have a width W N  of about 2 inches. 
         [0019]    The articulation device  14  may connect the sensor  12  to the rail  16  such that the sensor  12  may move relative to the sheet  18  in the y-axis (arrow Y). In one aspect, the articulation device  14  may articulate the sensor  12  along the rail  16  relative to a known center point  40 . Furthermore, the articulation device  14  may articulate the sensor  12  along the rail  16  in predefined stages, such as, for example, increments of 0.001 inches. Therefore, the precise axial location of the sensor  12  on the rail  16  may be determined at any given time. 
         [0020]    In one aspect, the articulation device  14  may be a servo motor or like device operatively connected to the rail  16 . While not shown, the engagement between the articulation device  14  and the rail  16  may be a sliding engagement, a rack-and-gear engagement, a wheel-and-track engagement or the like. In response to signals received from the processor  30 , the servo motor may translate rotational power from the motor into axial movement of the sensor  12  along the rail  16  in the y-axis (arrow Y). 
         [0021]    It should be noted that while the articulation device  14  is shown as being external of and connected to the sensor  12 , those skilled in the art will appreciate that the articulation device  14  may be integral with the sensor  12 . Furthermore, while the processor  30  is shown and described herein as being integral with the sensor  12 , those skilled in the art will appreciate that the processor  30 , or an additional processor, may be external of the sensor  12  such that the sensor  12  may communicate with the processor  30  by way of communications lines (not shown). For example, in an alternative aspect, the processor  30  may be a stand-alone computer processor that communicates with the sensor  12  and the articulation device  14  by way of physical or wireless communication lines. 
         [0022]    Accordingly, as shown in  FIG. 3 , the system  10  may detect the edge  20  of the sheet  18  by controlling the axial position of the sensor  12  along the y-axis (arrow Y), as described above, such that the edge  20  of the sheet  18  remains in the null zone  36 ,  38  of the sensor  12 . Therefore, a precise indication of the location of the edge  20  of the sheet  18  may be obtained by combining (1) the position of the sensor  12  on the rail  16  relative to the center point  40  and (2) the scan data obtained from the null zone  36 ,  38  of the sensor  12 . 
         [0023]    Referring to  FIG. 4 , a system for tracking camber, generally designated  100 , may employ the disclosed edge detection system  10 . In one aspect, the camber tracking system  100  may include a moving sheet  102 , a first edge detection station  104 , a second edge detection station  106  and a third edge detection station  108 . The sheet  102  may move in the longitudinal direction shown by arrow X′ and may include a first side edge  110  and a second side edge  112 . Furthermore, the sheet  102  may have a measurable camber, as shown by the generally arcuate shape of the sheet  102  in  FIG. 4 . 
         [0024]    The first edge detection station  104  may detect the location of the first side edge  110  of the sheet  102  using a first edge detection system  114  and the second side edge  112  of the sheet  102  using a second edge detection system  116 . In one aspect, the first edge detection station  104  may generally continuously detect the location of the first and second side edges  110 ,  112  of the sheet  102 . In another aspect, the first edge detection station  104  may periodically (e.g., every 5 seconds) detect the location of the first and second side edges  110 ,  112  of the sheet  102 . 
         [0025]    Therefore, as the sheet  102  moves in the longitudinal direction shown by arrow X′, the first edge detection station  104  may determine the width W(x) of the sheet  102  at longitudinal position x by comparing the location of the first side edge  110  with the location of the second side edge  112 . The following equation may be used to calculate the width W(x): 
         [0000]        W ( x )= Y 1 1 ( x )− Y 1 2 ( x )  (Eq. 1) 
         [0000]    wherein Y 1   1 (x) is the location (in the y-axis) of the first side edge  110  at longitudinal position x and Y 1   2 (x) is the location (in the y-axis) of the second side edge  112  at longitudinal position x. 
         [0026]    Once the width W(x) of the sheet  102  is known, the following equation may be use to calculate the center point Y 1   C (x) of the sheet  102  at the first edge detection station  104  at longitudinal position x: 
         [0000]        Y 1 C ( x )=½ W ( x )+ Y 1 1 ( x )  (Eq. 2) 
         [0000]    wherein Y 1   1 (x) is the location (in the y-axis) of the first side edge  110  at longitudinal position x. 
         [0027]    The second edge detection station  106  may be positioned a predetermined distance L 2  downstream of the first edge detection station  104 . For example, the second edge detection station  106  may be positioned about 10 feet downstream of the first edge detection station  104 . 
         [0028]    The second edge detection station  106  may detect the location of the first side edge  110  of the sheet  102  relative to the process centerline using a third edge detection system  118 . However, those skilled in the art will appreciate that whether the system  100  detects the first side edge  110  or the second side edge  112  at the second edge detection station  106  is purely a matter of design choice. 
         [0029]    The following equation may be use to calculate the center point Y 2   C (x) of the sheet  102  at the second edge detection station  106  at longitudinal position x: 
         [0000]        Y 2 C ( x )=½ W ( x )+ Y 2 1 ( x )  (Eq. 3) 
         [0000]    wherein Y 2   1 (x) is the location (in the y-axis) of the first side edge  110  at longitudinal position x. 
         [0030]    The third edge detection station  108  may be positioned a predetermined distance L 3  downstream of the second edge detection station  106 . For example, the third edge detection station  108  may be positioned about 10 feet downstream of the second edge detection station  106 . Therefore, the system  100  may track the camber of the sheet at a longitudinal position x relative to a segment of the sheet  102  having a predetermined length L 1  (e.g., 20 feet), wherein L 1  is the sum of L 2  and L 3 . 
         [0031]    The third edge detection station  108  may detect the location of the first side edge  110  of the sheet  102  relative to the process centerline using a fourth edge detection system  120 . However, those skilled in the art will appreciate that whether the system  100  detects the first side edge  110  or the second side edge  112  at the third edge detection station  108  is purely a matter of design choice. 
         [0032]    The following equation may be use to calculate the center point Y 3   C (x) of the sheet  102  at the third edge detection station  108  at longitudinal position x: 
         [0000]        Y 3 C ( x )=½ W ( x )+ Y 3 1 ( x )  (Eq. 4) 
         [0000]    wherein Y 3   1 (x) is the location (in the y-axis) of the first side edge  110  at longitudinal position x. 
         [0033]    The center points Y 1   C (x), Y 3   C (x) at the first and third edge detection stations  104 ,  108  may define a straight line. Therefore, the camber of the sheet  102  at longitudinal position x may be calculated as the distance between the straight line defined by center points Y 1   C (x), Y 3   C (x) and the center point Y 2   C (X) at the second edge detection station  106 . 
         [0034]    The collected data points discussed above, as well as the calculated camber, may be presented as a report (e.g., in a table, on a graph or the like). 
         [0035]    Although various aspects of the disclosed edge detection system have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present patent application includes such modifications and is limited only by the scope of the claims.