Automated coil handling and in-process inventory system, страница 2

System components

Automation hardware and software was chosen with an emphasis on reliability. As CHIPS and AGVS are plant-wide systems, they are required to run 24 hours per day, seven days per week. The need to move coils is continual; even if all the process lines are scheduled for maintenance downturns at the same time, there would still be coils to move for the purposes of shipping, receiving or optimizing a given coil field.

CHIPS is actually five computer systems: a CHIPS supervisory system to control one automatic crane, manage the operator interface for the manual cranes, and maintain an inventory and event database for coil movements; two CHIPS automatic storage and retrieval systems (ASRS), each to control two automatic cranes; a CHIPS development computer with full simulator environment so that control software changes may be fully tested prior to use; and a computer system to control the movement and traffic flow of the 14 AGVs.

Computer system — DEC/Compaq Alpha computers running OpenVMS operating system and utilizing disk shadowing provide the platform for the level 2 system. Each system has a backup Alpha computer that can be brought online without any cable changes in the event there is a problem with the primary processor. These systems are of the rack-mount style and include redundant power supplies. Application software for these systems was written using Fortran and C languages. DECmessageQ is the tool used for communication between systems. DataConcepts’ PDS software allows the Alpha computers to communicate with the Siemens PLCs on the automatic cranes and the PLCs used for safety interlocks. The database on the supervisory system is Oracle. Each of the Alpha computers uses Liebert Corp. software to monitor the state of the uninterruptable power supply (UPS) and to bring the system down gracefully in the event of a power loss before the UPS runs out of battery backup power.

HMI system — Intellution FIX32 is used for operator screens (Fig. 2). A pentium-class PC is used for the supervisory control and data acquisition (SCADA) server node. There are nine view nodes for operator use at various locations in the plant. The FIX screens allow the user to see an inventory overview, find a specific coil, monitor automatic cranes, add coil moves, reprioritize coil moves and view the event log.

In addition to the FIX screens, there are many ANSI screens which may be run on any network PC with a terminal emulation package such as WRQ's Reflection. Many of the FIX screen functions are duplicated in these Reflection screens for redundancy. CHIPS includes maintenance screens for changing routing and other coil movement parameters. This table-driven scheme allows on-the-fly modifications to be made without software program changes.

Manual crane operators use Teklogix hand-held terminals with an integrated barcode scanner. These terminals are capable of running the ANSI CHIPS screens. There are unique screens for each manual crane, customized to the functions specific to that crane's operation. Barcode scanners are used to update a coil's location in CHIPS. Each coil at Rockport Works has a barcode identity label and each coil location has a barcode identity plate. By scanning the barcode on the coil and the coil location, the hand-held terminals update the CHIPS inventory database.

Teklogix terminals communicate to one of five receivers in the plant via narrow band licensed frequencies. Hand-held units will communicate to the strongest signal at any given time. Receivers are network devices connected to a Teklogix controller, which actually controls the Telnet login sessions.

Automatic cranes — There is one automatic crane at the exit of the cold mill, two in the packaging warehouse (Fig. 3) and two in the distribution building. Positioning lasers at each end of the crane bridge are aimed at huge reflective targets at the end of the buildings. There is a positioning laser on the crane endtruck aimed at a target on the trolley. These lasers constantly report distance to the crane PLC. The hoist has encoders to measure the position of the tongs. On the tongs are toe-pad and leg-plate switches to signal contact with the sidewall and inside diameter of the coil for safe pickup.

Each coil location under an automatic crane has a set of bridge, trolley and hoist coordinates. CHIPS sends these coordinates to the automatic crane PLC in steps to perform a move. Automatic storage and retrieval system (ASRS) buildings have two cranes sharing a runway, so each of these cranes also have positioning lasers aimed at the other crane. .These lasers are tied to anti-collision emergency stops. There are several layers of level 2 software protection to prevent the cranes from getting close to each other. ASRS control also uses several "no-fly" and "bridge-only" zones where it is critical to keep the automatic crane out of the way of people and equipment, which may interfere.