Abstract:
A system or apparatus of monitoring and adjusting the location of a perforation cut during production of a plastic sheet.

Description:
[0001]    This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 60/951,891, entitled “VISION SYSTEM AND METHOD THEREOF,” filed Jul. 25, 2007, which is expressly incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to a system and method for detecting and correcting defects in an automated production system. More specifically, embodiments of the present invention relate to a system and method for automatically detecting and correcting manufacturing defects in plastic bags. 
         [0003]    Plastic bags are typically made from a web or roll of folded plastic film. Seams are applied to the film to form the bag which is separable by a perforation. Typically, the two seams are space a distance (illustratively about an inch) apart. The perforation is then cut between the seams. During manufacturing of the bags the location of the perforation cut can drift to the right or left (relative to the direction of the moving plastic) toward or away from the seams. This causes the perforation to be too close or too far from the seams. 
         [0004]    It would be beneficial to provide a system for correcting this drift during the manufacturing process so the perforation is located in the proper position relative to the seam. 
       SUMMARY 
       [0005]    The present disclosure describes a system for monitoring and correcting the position of a perforation during manufacture of plastic bags and the like. The location of the perforation relative to the seam is constantly monitored with certain deviations causing an alert. When needed, the system includes a correction mechanism that moves the perforation blade to the proper location. 
         [0006]    An embodiment of the present disclosure provides a system for detecting and correcting defects. The illustrative system comprises a data file, wherein manufacturing specifications are stored, a production line, at least one device configured to provide treatment to goods on the production line, at least one sensor configured to capture data from goods passing on the production line, a computer system configured to receive, store, process, and send data, a controller operatively connected to the computer system and configured to send feedback, and an actuator operatively connected to the controller and configured to receive feedback from the controller. 
         [0007]    Illustrative embodiments of the present disclosure relate to a method for detecting and correcting defects and may comprise providing a data file, providing a production line, transporting goods upon the production line, providing at least one sensor, capturing data from the goods with the sensor, communicating the data from the sensor to a computer system, detecting a defect whereby a reference data is compared to the data captured by the sensor, transmitting an output signal to a controller; processing output signals via the controller, generating corrective production specifications, communicating feedback production specifications from the controller to a actuator, and adjusting production specifications via the actuator, wherein the adjustments correct the detected defect. 
         [0008]    Other embodiments of the present disclosure provide a system for detecting and correcting plastic bag manufacturing defects which may comprise a data file, a processing line, a heat welding device operatively connected to the processing line, a perforating device operatively connected to the processing line, at least one sensor configured to gather input from goods passing on the production line, a computer system in communication with the sensor, configured to store a reference and compare an image with said reference, a programmable logic controller operatively connected to the computer, wherein feedback is generated, and a perforation servomechanism operatively connected to the programmable logic controller. 
         [0009]    Another embodiment of the present disclosure comprises a system or apparatus of monitoring and adjusting the location of a perforation during production of a plastic sheet. The system comprises a monitor that captures an image of the perforation cut into the plastic sheet; a computer that processes the image and determines whether the perforation is located in a desired position; and a controller that moves the a perforation blade if the computer determined that the perforation was not in the desired position. 
         [0010]    The above and other embodiments may further comprise: the plastic sheet being a web of a plurality of folded plastic bags; the plastic sheet having a seal located adjacent and spaced apart from the perforation, the monitor capturing an image of the perforation and the seal, the computer determining whether the perforation is located in a desired position relative to the seal, and the controller moving the position of the perforation blade relative to the seal if the computer determined that the perforation was not in the desired position; the monitor being a camera; the camera capturing an image that is transmitted to the computer which includes a reference image that the image is compared to determine whether the perforation is located in the desired position; the controller including a programmable logic controller that receives corrective data from the computer moves the perforation blade if the perforation was not in the desired position; the controller being in communication with a perforation servomechanism that receives commands from the controller to move the perforation blade; movement of the perforation blade ensuring that subsequent perforations in the plastic sheet are in the desired position; the computer issuing a deadband to the controller if the perforation is located in the desired position. 
         [0011]    Another illustrative embodiment is a method of monitoring and adjusting the location of a perforation during production of a plastic sheet. This method comprises the steps of: moving a length of the plastic sheet along a conveyor; monitoring the plastic sheet by capturing an image of the perforation cut into the plastic sheet; processing the image to determine whether the perforation is located in a desired position; and moving the a perforation blade if determined that the perforation was not in the desired position. 
         [0012]    The above and other embodiments may further comprise the steps of: moving the plastic sheet which is a web of a plurality of folded plastic bags; providing a seal adjacent to and space apart from the perforation; capturing an image of the perforation and the seal, determining whether the perforation is located in a desired position relative to the seal, and moving the perforation blade relative to the seal if determined that the perforation was not in the desired position; providing a camera to monitor the plastic sheet; capturing an image that is transmitted to a computer which includes a reference image that is compared to the image to determine whether the perforation is located in the desired position; moving the perforation blade with the assistance of a programmable logic controller that receives corrective data from the computer when the perforation is not located in the desired position; providing a perforation servomechanism that receives commands from a controller for moving the perforation blade; moving the perforation blade to ensure that subsequent perforations in the plastic sheet are in the desired position; and sending a deadband if the perforation is located in the desired position. 
         [0013]    Another embodiment includes a method of detecting two variables that are introduced at different points in the process relating to the art of bag making machinery, particularly to rotary bag making machines. The first variable is a heat welding device used to double seal two layers of plastic film together at about 1-inch paralleled seals illustratively perpendicular to the direction of a web path. A second variable can be introduced as a perforating device to perforate the plastic between the adjacent seals. Defects are related to process variables which affect the quality of the product. Quality Control Imaging and pattern recognition algorithms are applied. Once inspection of the variables has been performed, an output signal is used to effect a control action at the rotary bag machine. This method illustratively includes a) an image snapshot capturing the two variables introduced into the process as in claim  1 ; b) an image-capturing device monitors, records and reacts to a preset template of conditions given via computer program, wherein if the variables that pass before the capturing device deviate from the template and the preset measurements are recognized, the system or user is notified of the discrepancy; c) a perforation detector signal used to fire and rest the capturing device, wherein the signal is in close proximity of the capturing device which helps to stabilize the image at high production speeds; d) when a deviation is detected on a captured image, immediate feed back is sent for process corrections creating a closed loop control; e) depending on direction of deviation (upstream, downstream), one of two signals are sent to correct the registered error; f) a deadband control is utilized to eliminate oscillation in the process when no action is required, wherein a no alarm condition exists when the measured process enters the deadband range. 
         [0014]    Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the disclosure as presently perceived. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0015]    The detailed description particularly refers to the accompanying figures in which: 
           [0016]      FIG. 1  is a block diagram of a computer system according to an embodiment of the this disclosure; 
           [0017]      FIG. 2  is another illustrative system according to an embodiment of the this disclosure; 
           [0018]      FIG. 3  is a flow chart of a monitoring system according to an embodiment of the this disclosure; 
           [0019]      FIGS. 4   a  and  4   b  are images of plastic sheeting with target boxes which generally define an area or characteristic of interest; 
           [0020]      FIG. 5  is a flow chart of a detection system according to an embodiment of the this disclosure; 
           [0021]      FIG. 6  is a flow chart of a corrective system in accordance with one embodiment of the present invention; and 
           [0022]      FIG. 7  is a flow chart of a method of detecting and correcting defects according to an embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION  
       [0023]    A block diagram of a computer system  100  according to an embodiment of the present disclosure is shown in  FIG. 1 . Computer system  100  generally comprises a computer  102 . Computer  102  illustratively comprises a processor  104 , a memory  110 , various support circuits  108 , an input/output (“I/O”) interface  106 , and a storage system  111 . Processor  104  may include one or more microprocessors. Support circuits  108  for processor  104  may include conventional cache, power supplies, clock circuits, data registers, I/O interfaces, and the like. I/O interface  106  may be directly coupled to memory  110  or coupled through processor  104 . Additionally, I/O interface  106  may be configured for communication with input devices  107  and/or output devices  109 , such as network devices, various storage devices, mouse, keyboard, displays, and the like. Storage system  111  may comprise any type of block-based storage device or devices, such as a disk drive system. 
         [0024]    Memory  110  stores processor-executable instructions and data that may be executed by and used by the processor  104 . These processor-executable instructions may comprise hardware, firmware, software, and the like, or combinations thereof. Modules having processor-executable instructions that are stored in the memory  110  may include a capture module  112 . Computer  102  may be programmed within an operating system  113 , which may include OS/2, Java Virtual Machine, Linux, Solaris, Unix, HPUX, AIX, Windows, MacOS, among other platforms. At least a portion of operating system  113  may be stored in the memory  110 . Memory  110  may include one or more of the following: random access memory, read only memory, magnetoresistive read/write memory, optical read/write memory, cache memory, magnetic read/write memory, and the like. 
         [0025]    A diagram of system  202  is shown in  FIG. 2 . System  202  generally comprises a monitoring system  204 , a detection system  206 , and a corrective system  208 . System  202  may further include a conveyor belt system  210 , a heat welding device  212 , a perforating device  214 , a sensor  216 , the computer system  100 , a programmable logic controller  220 , and a corrective mechanism  222 . 
         [0026]    System  202  may include an underlying conveyor system  210  being advanced in a production direction, along an extending path, by draw rollers  224 . Omitted for clarity is a complete production line whereby raw materials require sequential steps to render a finished product. This production line is known to those skilled in the art. 
         [0027]    System  202  may also include treatment tools that modify goods. In one embodiment, the system may include a heat welding device  212 . In another embodiment, the system may include a perforating device  214 . In yet another embodiment, the system may include both a heat welding device and a perforating device. The heat welding device  212  is used to double seal two layers of plastic film together at illustratively, one inch paralleled seals perpendicular to the direction of the underlying belt movement. It is appreciated that other sealing configurations may be used. Similarly, perforating device  214  may include a perforation blade or equivalent that is used to perforate the plastic between the adjacent seals. It is understood that a variety of different tools may treat the material as it passes through the production line. For example, tools may provide treatments such as resizing, shaping, cutting and pressing. 
         [0028]    Monitoring system  204  includes at least one sensor  216 . This sensor  216  may be positioned on the conveyor belt system illustratively after the goods receive treatment and before the end of the conveyor belt system. Sensor  216  is configured to capture quality control data from goods advancing on the conveyor belt system. Based on the speed at which goods advance, the sensor may be able to capture data at a high rate of speed. In one illustrative embodiment, sensor  216  may comprise a digital or analog camera that captures images on white or black film. Camera specifications may include, but not limited to, ⅓″ VGA CCD Imager, active pixels 656×494, 5.79 (H)×4.89 (V) active area (mm), 100 frames per second (“fps”) @ 40 MHz, and a minimum illumination of 1.0 lux at 100 fps. Optionally, the sensor may include electric eye sensors, infrared sensors, motion sensors, temperature sensors, vision cameras, and ultraviolet and other visible spectrum light sensors. Alternative embodiments of this disclosure may comprise an analog-to-digital component designed for digitizing analog signals. 
         [0029]    The detection system  206  may include computer system  100 . (See also  FIG. 1 .) Illustratively, computer system  100  is located in close proximity to the sensor to reduce the transfer time. This close proximity configuration may be implemented when data is being captured at high production speeds. Computer system  100  is in communication with the senor through any viable communication medium, such as a serial cable, wireless, Ethernet, Universal Serial Bus (“USB”), or the like, for example. 
         [0030]    Corrective system  208  may comprise a programmable logic controller (“PLC”)  220  and a corrective mechanism  222 . PLC  220  is a digital computer used for automation of industrial processes, such as control of machinery on factory assembly lines. Unlike general-purpose computers, PLC  220  is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. The input/output arrangement may be built into a simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. 
         [0031]    Optionally, PLC  220  and computer system  100  may be combined into one unit. In other words, the functionality of both the computer system and the PLC may be conducted by one computer system. Organizationally, as known to those skilled in the art, the computer system and the programmable logic controller may further be installed in the same location through a rack installation, or similar configuration. 
         [0032]    Corrective mechanism  222  may comprise a mechanism to correct defects generated by the production line. PLC  220  is connected to an electro servo drive which moves or controls the perforation blade. The actuator is usually a physical mechanism, but also may refer to an artificial intelligent agent. In one embodiment, the corrective mechanism may comprise a perforation servomechanism (“servo”). The servo is optimally connected to the production line and, more specifically, to tools that provide treatment to the raw materials or products. For example, the servo can be connected to perforating device  214  such that adjustments may be made when plastic bag seals do not meet specification. 
         [0033]    A block diagram of a monitor system  204  is shown in  FIG. 3 . System  204  comprises data files  302  and at least one sensor  216 . Data files  302  hold data related to plastic bag manufacturing such as bag size, camera settings, and perforation settings. Specific parameters  306  are utilized to determine the monitoring requirements on a per-job basis. Moreover, data files  302  enable an operator to load a manufacturing run, along with all the customized manufacturing parameters by selecting a specific data file associated with the run. In one illustrative embodiment, sensor  216  may be configured to monitor plastic bag perforations. In another illustrative embodiment, sensor  216  may be configured to monitor plastic bag seals. 
         [0034]    In operation, sensors  216  may be configured to focus on a particular characteristic of the goods. Specifically, a data file or operator may configure a target box whereby sensor  216  focuses on the particular area or characteristic of the plastic sheets. As shown in  FIGS. 4   a  and  b,  an image  404  (see also  FIG. 5 ) is taken of plastic sheeting  320 . A target box  322  which generally defines an area or characteristic of interest is superimposed on image  404 . In this case, target box  322  maintains a fixed distance  329  from perforation  324 . A seam  326  is located inside target box  322 . (Seam  327  is located on the opposite side of perforation  324 .) In an illustrative embodiment, if seam  326  is too close to either the left side  328  or right side  330  of target box  322 , then a corrective function is engaged to adjust the perforation blade. 
         [0035]    As shown in  FIG. 4   b,  once the perforation blade is moved, seam  326  moves back toward the center of target box  322 . As more bags pass under sensor  216  and are photographed, seam  326  should stay close to the center of target box  322 . If, however, perforation  324  drifts (target box  322  stays the same distance from perforation  324 ), seam  326  will drift as well. Once this drift is detected, corrective measures will once again be initiated. 
         [0036]    To accomplish all of this, approximately 1 to 100,000 data points in the image are read. Some embodiments may utilize as many data points as capable and sustainable. A flow chart of a detection system  206  is shown in  FIG. 4 . After sensor  216  captures quality control data, the data may transmit to computer system  100 . Computer system  100 , as described above, may process a computer readable medium having instructions to load a stored reference  402 , to compare with the quality control data. In control systems and used herein, the desired output of a system is called the reference. The computer readable medium may further include quality control imaging and pattern recognition algorithms. In one embodiment, the computer system may store the reference data, which is also called a template or target parameter. The computer readable medium may load a reference  402  and compare it against the recently captured image  404  from sensor  216 . 
         [0037]    In operation, detection system  206  may provide a number of different detection methods. In one embodiment, a defect  406  may be detected by pixel counting whereby the number of light or dark pixels of the reference is compared with the captured image pixels. Additional embodiments may further comprise blob discovery whereby an image is inspected for discrete blobs of connected pixels as image landmarks. In yet another embodiment, defect detection  406  may comprise template matching whereby images are compared by finding, matching, and/or counting specific patterns. In still another embodiment, system  400  may comprise any combination of the above defect detection methods. 
         [0038]    After determining defect  406  exists, computer system  100  may generate an output to PLC  220 . Illustratively, the location of the perforation with respect to defects corresponds to a specific output. For instance (and as discussed with respect to  FIGS. 4   a  and  b ), a perforation to the left  408  may correspond to output 1 at  414 , while a perforation to the right  410  may correspond to output 2 at  416 . In an illustrative embodiment, an alarm may sound when a product defect is detected at  406 . These alarms may include visual and audio alarms to an operator, or any form of an electronic alarm. Examples of electronic alarms may include email, pager, instant message, pop-up, report generation, or the like. In an additional embodiment, the notification can be a series of lights such as green, yellow and red. If the light is green, the perforation is within an optimum tolerance and no adjustment is needed. If red, correction may be needed such as shifting the perforation blade illustratively to the left to get the perforation back within the optimum tolerance. If the light is yellow, correction may also be needed but now the perforation blade may need to be shifted the other way to get the perforation back within the optimum tolerance. 
         [0039]    A flow chart of corrective system  208  is shown in  FIG. 5 . Computer system  100  sends a defect output  502  to PLC  220 . Illustratively, PLC  220  includes communication ports such as 9-Pin RS232, RS485, Ethernet, and the like. Communication protocols used may include Modbus, DF1, and other communication network protocols. By employing these communication capabilities, the PLC is able to receive notification from the computer system. 
         [0040]    In control theory, a closed-loop, also called a feedback control system, uses feedback to control states or outputs of a dynamical system. In operation, process inputs have an effect on the process outputs, which is measured with sensors and processed by the controller, wherein the result is used as input to the process, closing the loop. Embodiments of the present invention may provide a controller comprising a closed-loop architecture. Optionally, the system may comprise a closed-loop and open loop control simultaneously, wherein the open-loop control is termed feedforward and serves to further improve reference tracking performance. 
         [0041]    After PLC  220  receives defect  503  output from computer system  100 , it processes the particular output at  504 . Processing may include determining what corrective actions need to be taken. Corrective parameters are then sent at  506 . Illustratively, programming gives an output signal to control overshooting when correcting the defect. The output and/or notification may be in any form capable of conveying corrective parameters to an actuator. 
         [0042]    PLC  220  further comprises a deadband, which is an area of a signal range or band where no action occurs (the system is dead). When no defects are detected, computer system  100  does not send an output so PLC  220  takes no corrective actions. Most commonly, deadband is used in voltage regulators, thermostats, and alarms. The purpose for deadband is to prevent oscillation or repeated activation-deactivation cycles (called “hunting” in proportional control systems). 
         [0043]    The actuator receives corrective parameters  508  from PLC  220 . In an illustrative embodiment, the perforation servo serves as the actuator. Based on the parameters received, the perforation servo may adjust production to correct the position of the perforation blade at  510 . Illustratively, receiving a corrective parameter may cause the perforation servo to initiate a correction sequence that adjusts the perforation blade so no more seal defects occur. It is understood to those in the art, however, that any device that may provide control of a desired operation through the use of feedback may serve as an actuator. 
         [0044]    A flow chart of a method of detecting and corrective defects is shown in  FIG. 6 . The method 2 is described with respect to the system  202  disclosed in  FIG. 2 . Illustratively, production output includes providing a data file at  602  that may comprise a plastic bag that has been heat sealed and perforated. Optionally, the production output may comprise any goods, product, or material subjected to a quality assurance process. 
         [0045]    At step  604 , the method captures data of the production output. As discussed in more detail above, there are a variety of methods to capture data. The method used to capture data will depend on a number of factors, including cost, the subject matter, and accuracy. In one embodiment, an image may be captured with a photographic device using white film. Illustratively, an image may be captured with a photographic device using black film, or even digitally using no film. The capturing device focuses on a particular area or feature, and adjusts itself ensuring it captures that particular area or feature. 
         [0046]    At step  606 , the computer system loads a stored reference from its memory. This reference may comprise the target parameter for determining if a defect exists. Illustratively, the stored reference may comprise an image of a plastic bag with a seal and perforation within a target box. Optionally, the step of loading a stored reference  608  may utilize other computer systems and/or network topologies. 
         [0047]    At step  610 , the method detects if a defect exists. To accomplish this step, the reference is compared with the captured data. Illustratively, the detection may occur using an application programmed to focus on the alignment of a seal. In addition, the application may focus on the perforation to determine if there is a defect. This detection comprises a pixel examination of images and attempting to develop conclusions with assistance of knowledge bases and features such as pattern recognition engines, and the like. Optionally, systems may be programmed to perform tasks such as counting objects on a conveyor, reading serial numbers, and searching for surface defects. When no defect is determined, the method may be completed, such that no corrective action takes place (deadband). Alternatively, if a defect is detected, the method performs other steps. 
         [0048]    Step  612  comprises sending an output to a controller. The format for sending an output may comprise analog, digital, audio, visual, or the like. Illustratively, a computer system may send an output to PLC  220 . Optionally, if the computer system and the PLC functionality are combined within one unit, sending an output to a controller would comprise internal computer system communication. 
         [0049]    At  614 , an actuator, or the like, receives feedback from the PLC and may provide adjustments at  616  to mechanisms within the system. A perforation servomechanism where, depending on the feedback, adjustments to the perforating device are made to correct misaligned perforations. Another illustrative embodiment includes a heat welding device being adjusted by the servomechanism.