Abstract:
Three software programs are respectively run on the main processing constituent of a programmable logic controller (PLC), the network-controlling constituent of the PLC, and a human interface unit. Intelligent (e.g., switch, sensor, control, etc.) devices are distributed within a communications network associated with a vertical package conveyor (VPC). Signals are transmitted between/among the processing constituent, the controlling constituent, the interface and the devices. In an ongoing informational and regulative process, the devices provide input for the processing constituent, which in turn provides output to the devices. In furtherance of human safety, the processing constituent causes VPC operation to stop upon the occurrence of any of the following events: breached light curtain; open machinery access door; inoperable run stop button; inoperable emergency stop button; activated emergency stop button; misplaced package. The processing constituent also dictates the direction (up or down) and mode (constant or variable) of the VPC.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/492,059, filed 29 Jul. 2003, entitled “Control Algorithm for Vertical Package Conveyor,” incorporated herein by reference. 
    
    
     STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BRIEF DESCRIPTION OF THE COMPUTER PROGRAM LISTING APPENDIX 
     Incorporated herein by reference is a computer program listing appendix setting forth inventive embodiments of computer source code. This computer program listing appendix is contained as four documents that were created on 19 Apr. 2004 in a CD-R compact disc that is now situated in the application file. The CD-R compact disc contains three data files in ASCII text file format, entitled “conveyormainprocessorcode.txt” (about 191 KB), “conveyornetworkcontrollercode.txt” (about 62.3 KB), and “conveyorinterfaceunitcode.txt” (about 1.16 MB). The CD-R compact disc also contains one data file in Microsoft Word file format, entitled “conveyorinterfaceunitcode(pictorial).doc” (about 669 KB). The file entitled “conveyormainprocessorcode” pertains to the present invention&#39;s “main processor.” The file entitled “conveyornetworkcontrollercode” pertains to the present invention&#39;s “network controller.” The files entitled “conveyorinterfaceunitcode” and “conveyorinterfaceunitcode(pictorial).doc” each pertain to the present invention&#39;s “interface unit.” 
     BACKGROUND OF THE INVENTION 
     The present invention relates to the conveyance or transportation of objects, more particularly to methods and apparatuses for controlling or regulating the operation of devices such as vertical package conveyors. 
     A “vertical package conveyor” (“VPC”) is a conveyance apparatus typically of a kind that includes one or more (usually, many) horizontal tray components that are physically attached to a movable chain, wherein the chain moves vertically, often on a continual basis, so as to transport bulk materials and other packages from one location (e.g., level or floor) to another. Due to their complexity and dynamism, VPCs are intrinsically dangerous, maintenance-intensive and difficult to troubleshoot. 
     Vertical package conveyors are used aboard some United States Navy ships. According to current Navy practice, vertical package conveyors are associated with a relay controller. A relay type of controller limits the ability to introduce new technology and intelligent sensors to a vertical package conveyance system. A system implementing a relay controller is incapable of being connected to any type of network. Some of the existing electrical components require periodic adjustments to ensure that the system remains reliable and safe. If these adjustments drift or for some reason vary, the conveyor could then have major failures and possibly become unsafe. 
     The U.S. Navy has customarily predicated its ship maintenance systems on time-directed preventive maintenance principles. Recently, the U.S. Navy has been transitioning in favor of “condition-based maintenance” (“CBM”) principles, with a view toward increasing readiness, decreasing maintenance and decreasing manning requirements. Generally, the objective of the U.S. Navy&#39;s transformation from time-directed preventive maintenance to condition-directed maintenance is to optimize readiness while reducing maintenance and manning requirements. The underlying concept of condition-based maintenance (synonymously referred to as “condition-directed maintenance”) is that the utilization of sensors, algorithms and automated reasoning and decision-making models to monitor equipment operations will provide critical analyses to operators that will help prevent impending failure. “Red flags” will appear to operators so that maintenance efforts can focus limited resources on areas most needed to ensure safety and mission readiness, while at the same time minimizing operating costs, labor and risk of mission-degrading failure. It is anticipated that, at optimal capacity, the U.S. Navy&#39;s CBM technology will: detect and classify impending failures; predict the remaining life cycle of equipment; interface with the control system to take action; provide support in performing corrective maintenance; provide data to life cycle management activities; and, update logistics support system. The expectation is that significant improvements in safety, reliability and affordability will ensue. 
     A “programmable logic controller” (“PLC”) is a specialized computer device, typically of rugged construction, that reads input signals, runs control logic, and writes output signals. PLCs have been used in industry for over thirty years for effecting “automation” such as involving the exercise of control of a system of machinery in a manner involving the turning on or off of outputs, based on a state of inputs. Typically used for monitoring important process parameters and adjusting process operations accordingly, a PLC is suitable for assembling and concentrating voluminous data (e.g., status information) that is uploaded therein in a compact form. In earlier times, electrical control was based on relays that allowed power to be switched on and off without a mechanical switch. Relays are still used to make simple logical control decisions, but PLCs are more commonly used for effecting more complicated controls. Programmable logic control typically represents a computerized version of a relay control system that can be used to control manufacturing and other systems. The programming is usually performed using “ladder logic,” involving the setting up, inter-linking and timing of sequences in a manner mimicking relay logic. 
     A relay type of vertical package conveyance control system does not lend itself to incorporation of the CBM philosophy recently instituted by the Navy. Some repairs have resulted in inordinate costs due to the failure of this relay-type control system to identify the degrading conditions of components. It would be desirable to practice a vertical package conveyance methodology that is consistent with CBM values. 
     The following U.S. patent documents, incorporated herein by reference, are pertinent to vertical package conveyors: Combs U.S. Pat. No. 6,536,582 issued 25 Mar. 2003; Grond U.S. Patent Application Publication 2002/0014392 A1 published 7 Feb. 2002; Rapell U.S. Pat. No. 6,059,521 issued 9 May 2000; Mulhern U.S. Pat. No. 5,718,322 issued 17 Feb. 1998; Grathoff U.S. Pat. No. 5,320,471 issued 14 Jun. 1994; Franke U.S. Pat. No. 5,350,050 issued 27 Sep. 1994; Pfleger U.S. Pat. No. 5,205,379 issued 27 Apr. 1993; Splitstoser et al. U.S. Pat. No. 4,986,411 issued Jan. 22, 1991; Freeman U.S. Pat. No. 4,219,301 issued 26 Aug. 1980; Eklof et al. U.S. Pat. No. 4,020,953 issued 3 May 1977; Henkel U.S. Pat. No. 3,972,412 issued 3 Aug. 1976. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the present invention to provide method, system and algorithm for effecting vertical package conveyance in a safe, reliable, efficient and economical manner. 
     It is another object of the present invention to provide method, system and algorithm for effecting vertical package conveyance in a manner compatible with and in furtherance of “condition-directed” principles and practices. 
     In accordance with typical embodiments of the present invention, the inventive system is for use in association with conveyor apparatus such as a vertical package conveyor. The inventive system comprises means for controlling the operation of said conveyor apparatus. The controlling of the operation of the conveyor apparatus includes: monitoring whether an unsafe condition exists in the operation of the conveyor apparatus; and, ceasing the operation of the conveyor apparatus upon determining that an unsafe condition exists in the operation of the conveyor apparatus. According usual inventive practice, the controlling of the operation of the conveyor apparatus further includes, after the ceasing of the operation of the conveyor apparatus, at least one of the following: correcting the unsafe condition that exists; and/or re-initiating the operation of the conveyor apparatus. Inventive practice can be concerned not only with operational safety issues but also with standard operational issues. According to many such embodiments, the controlling of the operation of the conveyor apparatus further includes establishing at least one of the following: the direction, in terms of upward versus downward, of the operation of said conveyor apparatus; and/or, the mode, in terms of variability versus invariability of speed, of the operation of said conveyor apparatus. 
     A typical embodiment of an inventive method for controlling a vertical package conveyor comprises regulating the safety condition of said vertical package conveyor. The regulating includes: seeking an unsafe condition associated with the vertical package conveyor; and, causing the vertical package conveyor to stop functioning upon the finding of an unsafe condition. Usually, the inventive method further comprises: connecting a plurality of intelligent devices to the vertical package conveyor; and, connecting a programmable logic controller to the intelligent devices. The regulating of the safety condition of the vertical package conveyor includes inputting from the intelligent devices to the programmable logic controller and outputting from the programmable logic controller to the intelligent devices. Typically, a computer program product is installed in the programmable logic controller so as to provide instructions relating to the regulating of the safety condition of the vertical package conveyor. Normally, an interface unit is connected to the programmable logic controller; one or more persons interact with the programmable logic controller via the interface unit. The regulating of the safety condition usually further includes the elimination of the unsafe condition (e.g., via human intervention) subsequent to the stoppage of functioning of the vertical package conveyor, and the resumption of functioning of the vertical package conveyor subsequent to the elimination of the unsafe condition. 
     A typical embodiment of an inventive computer program product comprises a computer useable medium having computer program logic recorded thereon for enabling a computer to control the operation of a vertical package conveyor. The computer program logic comprises: means for enabling the computer to track at least one safety indicia pertaining to the operation of the vertical package conveyor; and, means for enabling the computer to stop the operation of the vertical package conveyor upon the occurrence of at least one unsafe event. According to usual inventive practice, the means for enabling the computer to track includes means for enabling the computer to observe at least one unsafe event selected from the group consisting of a light curtain breach, an open machinery access door, a stoppage malfunction and a package misplacement. Frequently, the computer program logic further comprises at least one of the following means: means for enabling the computer to govern up-versus-down direction of the operation of the vertical package conveyor; and/or, means for enabling the computer to govern variable-versus-invariable speed of the operation of the vertical package conveyor. 
     The present invention provides an algorithm that, according to typical inventive practice, is used in association with a vertical package conveyor such as those employed aboard US Navy ships. The inventive algorithm exercises control, provides status and condition assessment, and provides troubleshooting information, relative to the vertical package conveyor with which it is associated. The inventive algorithm is a program/code that can be used in conjunction with a processor-controller such as a programmable logic controller (PLC). According to some embodiments, the present invention&#39;s algorithmic system is additionally designed to collect many different data points that can be used for trending and advancing condition-based maintenance (CBM). In furtherance of the condition-based maintenance goals increasingly gaining U.S. Navy emphasis, the present invention is expected to play an important role for the U.S. Navy in terms of providing automated reasoning and decision-making models for data-tracking involving the vertical conveyance of packages. 
     As typically embodied, the present invention&#39;s algorithm provides, for vertical package conveyors (VPCs), decision-making as well as information and guidance pertaining to status, troubleshooting and CBM. Associated with a particular VPC, the inventive algorithm receives inputs via discrete input connections and through a network so as to determine the states and conditions of intelligent devices including switches, photo sensors, ultrasonic sensors and distributed input/output (control) modules. The inventive algorithm uses these inputs to determine what type of operation can be performed by the individual vertical package conveyor system with which the inventive algorithm is associated. If the inventive algorithm determines that the VPC system cannot be operated as configured, that an unsafe condition exists, or that a failure has occurred, the inventive algorithm will then provide information and guidance to the cause of the problem and will even provide corrective actions. 
     The present invention replaces the customary relay-type control system with a network control system that includes a processor-controller (e.g., a programmable logic controller), a human-to-machine interface unit and various intelligent devices connected to several local networks. According to the present invention, various devices are installed in corresponding relationships with a VPC. These installed devices communicate directly with the “controller” constituent of the processor-controller. Various parameters are monitored by the inventive network control system on an ongoing basis in a “ladder logic” manner. The inventive “ladder logic” control algorithm, resident in the memory of the “processor” aspect of the processor-controller, is not a “feedback loop” control algorithm, as such; nevertheless, the inventive “ladder logic” control is analogous to continuous feedback control in terms of monitorial continuity. 
     Typically, the inventive network control system, when installed in relation to a VPC system, provides condition assessment and operational regulation of the VPC system in terms of safety (e.g., regarding personal trespasses, open doors that should be closed, problems relating to run and emergency stops, jammed cargo placements), direction (e.g., whether the VPC moves up or down) and mode of operation (e.g., whether the VPC operates at constant speed versus variable speed). For instance, safety light curtains are installed at all lower levels to dramatically improve personnel safety. These safety curtain sensors and other types of intelligent devices allow for CBM effectuation. 
     The inventive use of PLCs enables the application of technology to the conveyors so as to increase reliability, decrease maintenance and troubleshooting time, and permit future expansion such as involving automation. Troubleshooting capabilities are inventively enhanced by the diagnostic potential of PLCs and intelligent devices (e.g., sensors, switches and controllers), and by fault analysis programming. System problems are more quickly and accurately assessed, and are therefore more expeditiously and effectively resolved. 
     In addition, the inventive implementation of a PLC eliminates all of the electrical single point failures that currently exist in relay-type control systems. Furthermore, the present invention features installation of a variable drive for motor control, which reduces the number of components needed and that affords greater protection, quicker response to over-current conditions, greater reliability, and monitoring capabilities that can be used for CBM. The present invention&#39;s utilization of a PLC and intelligent devices (e.g., sensors, switches, control modules) transforms a vertical package conveyor into an intelligent, networked system in and of itself. 
     Moreover, a typical U.S. Navy ship having vertical package conveyance capability is equipped with many vertical package conveyors. According to some inventive embodiments, not only is each conveyor “intra-networked” (networked within itself), but is also part of an “inter-networked” system. For instance, the conveyors can be networked with respect to a central monitoring system, and/or with respect to the ship&#39;s network. These kinds of “inter-networking” can allow fuller implementation of CBM and trending. 
     Further, the present invention allows for more varied use of conveyors. Conveyors can be used in various unprecedented ways (e.g., at mid levels, for conducting daily breakouts, for striking down of supplies, etc.) without the current need for large numbers of personnel as working parties. The elimination of the single point failures decreases downtime, thus increasing the ability of ship&#39;s force to run the conveyors more often and for longer durations. It is estimated that the present invention&#39;s new VPC control system, if adopted by the U.S. Navy and once installed thereby, will realize savings of over a million dollars, with a relatively short payback period (e.g., less than two years). 
     Other objects, advantages and features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the present invention may be clearly understood, it will now be described, by way of example, with reference to the accompanying drawings, wherein like numbers indicate the same or similar components, and wherein: 
         FIG. 1  is a simplified schematic illustrating the basic system components of a typical embodiment of a vertical package conveyance control system in accordance with the present invention. 
         FIG. 2  is a block diagram of a prototype, being tested by the U.S. Navy, of a vertical package conveyance control system in accordance with the present invention, particularly illustrating various physical components and various electrical and mechanical connections therebetween. 
         FIG. 3  is a simplified flowchart illustrating the basic control logic of a typical embodiment of a vertical package conveyance control system in accordance with the present invention. 
         FIG. 4  is a block diagram of the programmable logic controller (PLC) ladder logic of the inventive algorithmic prototype corresponding to the inventive control system prototype shown in  FIG. 2 . 
         FIG. 5A  through  FIG. 5G  together constitute a table providing explanations of various routines of the PLC ladder logic shown in  FIG. 4 . 
         FIG. 6  through  FIG. 12  are diagrammatic representations of various status, error and troubleshooting screens corresponding to the inventive prototypes shown in  FIG. 2  and  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures, the present invention&#39;s algorithmic VPC control system includes a main processor  100 , a network controller  200 , a human-to-machine interface unit  300  and various local intelligent network devices  400 . Interface unit  300 , a station for human interaction, includes an operator&#39;s panel  301  and a display  302 . Included among the intelligent devices  400  are sensors  401 , switches  402  and a controller (local controller mechanism)  403 . As diagrammatically represented in  FIG. 1 , there are four major, interconnected, functional components of the overall inventive VPC control system, viz., (i) the main processor  100  system component, (ii) the network controller  200  system component, (iii) the interface unit  300  system component, and (iv) the network devices  400  system component. Controller  200  is interconnected with the various network devices  400 , which are local network components. 
     According to typical inventive practice, the processor  100  system component and the controller  200  system component are embodied as integrated processor-controller machinery such as including or included by a programmable logic controller (PLC)  123 . The network devices  400  separately or individually feed into a controller  200  that is a computer card-like device that fits into a slot provided in the PLC  123  main structure and that permits various connections with devices  400  and other network components. According to the U.S. Navy&#39;s inventive prototype, controller  200  is a “DeviceNet” scanner device that is inserted into the major structural portion of PLC  123 ; all of the interconnections between the network components and controller  200  are via a DeviceNet network. 
     The system block diagram of  FIG. 2  provides a broad overview of the electrical and mechanical aspects of the present invention&#39;s conveyor control system. Illustrated are the mechanical and electrical interrelationships among the various physical components of the inventive control system. A solid line indicates a mechanical connection; a dashed line indicates an electrical connection. The present invention&#39;s system control station includes processor  100 , controller  200  and interface  300 . Several intelligent devices  400  are utilized, including the following: proximity switch  402 ; down overtravel device limit switch  402 ; door limit switches  402 ; loader/unloader stow limit switch  402 ; down interlock limit switch  402 ; jam limit switches  402 ; run stop (“run/stop”) switches  402 ; emergency stop (“e-stop”) switches  402 ; safety light curtain muting sensors  401 ; safety light curtain controller  403 ; machinery access door limit switch  402 . 
     At least one intelligent device  400  is causative of the cessation of the vertical package conveyor. The present invention&#39;s jam limit switches  402  can involve a tripwire design. The safety light curtains implemented by the present invention can utilize known technology for protecting people from hazardous areas such as machinery complexes or elevator doorways (e.g., elevator doors that are closing). For instance, a light curtain apparatus can project many invisible infrared light beams (e.g., in grid-like fashion) defining a geometric plane that demarcates a boundary between permissible and impermissible presence; the light curtain is instantaneously activated when a person or object (even a small object) intercepts any of the beams. 
     As shown in  FIG. 3 , the controlling by processor  100  is effected in an essentially ongoing process (while the overall system power is on) in two aspects or phases of VPC operation, viz., (I) the safety of VPC operation and (II) the vertical direction and variability mode of VPC operation. Processor  100  monitors whether an unsafe condition exists in the operation of the conveyor, and stops (ceases operation of) the conveyor upon the discovery by processor  100  of the existence of such an unsafe condition. According to many preferred inventive embodiments such as the U.S. Navy&#39;s inventive prototype, processor  100  monitors conveyor operation for the occurrence of several conditions indicative of safety deficiency, viz.: a breach of a light curtain; the open state of a machinery access door (e.g., a machinery room door adjacent to the conveyor); the inoperability of a run stop button (e.g., push button); the inoperability of an emergency stop button (e.g., push button); the activation by a person of a run/stop button (e.g., push button); the activation by a person of an emergency stop button (e.g., push button); the misplacement of cargo with respect to the conveyor. Upon the occurrence of any of these safety-threatening conditions, processor  100  causes the conveyor to cease operation, thereby permitting human intervention to fix the problem and to subsequently re-start the conveyor. It is noted that either a run stop button or an emergency stop button may be humanly actuated due to a humanly perceived exigency. 
     In addition, processor  100  governs the direction of operation of the conveyor in terms of upward conveyor movement versus downward conveyor movement. Further, processor  100  governs the “mode” of operation of the conveyor in terms of variable conveyor speed versus invariable (constant) conveyor speed. According to the U.S. Navy&#39;s inventive prototype, a condition precedent to normal operation is that exactly two conveyor doors (e.g., one top door and one other door) be open. If fewer or greater than two conveyor doors are open, human intervention is needed to ensure the openness of two doors only and to then re-start the conveyor. The orientations of the loader/unloader trays relate to the selection of the vertical direction (upward or downward) in which the conveyor moves. The speed mode can be either “continuous” mode (wherein the conveyor moves at a constant speed) or “index” mode (wherein the conveyor can be controlled so as to move at variable speeds). The present invention thus advantageously affords the option of varying conveyor speeds—an option that is less feasibly implemented in a relay-type VPC control system. 
     Processor  100 , controller  200  and interface unit  300 , which communicate with each other, each have software installed therein (resident in its memory). Processor  100  contains in its memory the present invention&#39;s main processor source code, such as that which is exemplified by the electronic document entitled “conveyormainprocessorcode.txt,” set forth herein in the computer program listing appendix. Network controller  200  (a “DeviceNet” scanner, according to the U.S. Navy prototype) contains in its memory the present invention&#39;s network controller source code, such as that which is exemplified by the electronic document entitled “conveyornetworkcontrollercode.txt,” also set forth herein in the computer program listing appendix. Interface unit  300  contains in its memory the present invention&#39;s human interface source code, such as that which is exemplified by the electronic documents entitled “conveyorinterfaceunitcode.txt,” and “conveyorinterfaceunitcode(pictorial).doc (which includes inventive screen portrayals), further set forth herein in the computer program listing appendix. 
     Main processor  100 , in combination with the main processor code installed therein, is the primary decision-maker of the inventive VPC control system. The programmable logic controller (PLC) ladder logic block diagram of  FIG. 4  diagrammatically represents the inventive embodiment of main processor  100  source code that is electronically contained in the computer program listing appendix of this disclosure as the document entitled “conveyormainprocessorcode.txt.” The tabular representation of  FIG. 5A  through  FIG. 5G  describes various routines that are illustrated in  FIG. 4  and included in the “conveyormainprocessorcode.txt” source code embodiment. The processor  100  code is executable on processor  100  so that a data representation for access by the processor code is storable in the memory of processor  100 . The data representation is capable of being generated by processor  100  so that processor  100  is capable of controlling the operation of the vertical package conveyor. In particular, processor  100  regulates, in an essentially ongoing manner, the safety condition of the vertical package conveyor. 
     Unlike the algorithmic main processor  100  source code and the algorithmic interface  300  source code, the network controller  200  source code is not, strictly speaking, algorithmic in nature. The controller  200  code defines the network makeup, including the addressing and types of all of the devices  400  on the network, the speed of the network, and all of the input/output (I/O) mapping. The controller  200  code routes all of the I/O information to distinct locations in the memory of controller  200  so that referencing by the main processor  100  and the interface unit  300  can take place. Some code resident within processor  100  and some code resident within interface  300  are set up such that they will look to those specific memory locations to obtain the proper information needed for assimilation and display of information by interface unit  300 . The embodiment of controller  200  code entitled “conveyornetworkcontrollercode.txt,” disclosed herein as an electronic document in the computer program listing appendix, pertains to operation of a seven-level VPC system. In the light of the instant disclosure, the ordinarily skilled artisan will be capable of practicing the present invention for any number of VPC levels. 
     As shown in  FIG. 6  through  FIG. 12 , interface unit  300  is informative and facilitative of human interaction, both manual and visual. Interface unit  300  provides status information, error information and troubleshooting information to the operation and maintenance personnel who manipulate panel  301  and view display  302 . The interface  300  code defines numerous items relating to the various visual indications appearing on its display  302 , including the physical look and layout of the various informational screens, the colors that are used, the error messages, the troubleshooting aids, and the parts information.  FIG. 6  through  FIG. 12  depict the following screens, respectively: conveyor status; level diagnostic; diagnostic; system setup; motor information; alarm history; light curtain identification (“ID”). An example of color cueing that can be manifested is such screens is portrayed by  FIG. 6 , which indicates three permissive run modes, viz., “up continuous,” “up index” and “down continuous”; the three circles (encompassed by a rectangle) situated next to these three permissive run mode indications each turn either red (for “off”) or green (for “on”) in color. 
     Processor  100  receives all of the inputs from the various network intelligent device components  400  within the inventive VPC control system. The inventive algorithm that is installed in processor  100  then decides, from those inputs, if the conveyor is safe to operate. If the processor  100  algorithm determines that the conveyor can be safely operated, then the processor  100  algorithm analyzes the position and status of conveyor doors and various other components to determine what direction and mode of operation the conveyor is set up to run in. If the processor  100  algorithm determines that the conveyor is set up for a certain mode of operation, processor  100  awaits a start input. When the start input is received, processor  100  then sends out start and speed commands for motor control of the conveyor. 
     All three inventive source codes—viz., the processor  100  code, the controller  200  code and the interface  300  code—work and interface with each other to be informative about and regulatory of the VPC. According to typical inventive practice, these three pieces of source code are necessary components to achieve safe control and provide display of status and error information. All communication between and among the three source codes is carried out over the inventive network that is associated with the VPC. Main processor  100  processes the input information and then sends out the proper output information to the proper components in the network. This output information could include, for instance: a “start” command to the motor; and/or status information to interface unit  300 ; and/or error information to interface unit  300 ; and/or corresponding steps to take to correct errors so that operation of the conveyor can begin. While the conveyor is running, the transfer of data continues to determine if any conditions have changed that would require the conveyor to be stopped. Conveyor operation continues until the main processor  100  source code determines, based on the information that main processor  100  has received, that the conveyor motor should be stopped. 
       FIG. 4  shows a significant diagrammatic flow into “ICAS” (acronymous for the “Integrated Condition Assessment System”). As distinguished from a localized network (e.g., a DeviceNet network) that is specific to an individual conveyor, ICAS is a central, ship-wide network (e.g., an Ethernet network) that receives information from each of the localized, conveyor-associated networks. Within each localized inventive conveyor control system and network, the main processor  100  code assembles information that is sent out over the ship&#39;s ICAS network for data collection and trending. All of the important data is sent out over the ICAS network for monitoring and trending by an assessment system. 
     The present invention is not to be limited by the embodiments described or illustrated herein, which are given by way of example and not of limitation. Other embodiments of the present invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. Various omissions, modifications and changes to the principles described herein may be made by one skilled in the art without departing from the true scope and spirit of the present invention, which is indicated by the following claims.