Does this scenario sound familiar? "We just invested millions of dollars in our business systems and have difficulty synchronizing data with the plant floor." This is a trend that is happening throughout the supply chain.
Businesses are investing millions into ERP and WMS functionality and ignoring the plant floor control systems. This is not intentional, but rather a lack of understanding that a level of sophistication is required in the plant floor control systems in order to take advantage of functionality implemented in the ERP and WMS systems. Technology advances have allowed control systems to not only monitor and control the movement of product from point A to point B, but also to provide real-time data acquisition and reporting, robust maintenance functions for fault detection and isolation, and increased reliability from hardware redundancy.
Industry Norm
Figure 1 shows the traditional control architecture of a typical distribution center, including Enterprise-level systems and a warehouse management system (WMS). Plant floor automation equipment (e.g., conveyors, bar code scanners, photo-eyes) is often not connected at all to the upper-level IT systems or, the connectivity is fragmented and non-integrated. This results in:
- "Islands of automation," groups of automation equipment that do not communicate with each other
- Lost opportunity for data collection and reporting of floor operations
- Lack of visibility into the supply chain
- Poor coordination between operational areas resulting in increased WIP and labor, and reduced operational efficiency.
Figure 1 - Traditional control architectures, showing no plant floor connectivity and fragmented plant floor connectivityIntegrated Plant Floor Connectivity
An integrated warehouse automation control system is able to monitor and control automation equipment and interface to the WMS, allowing data to flow from the plant floor equipment all the way to the enterprise system level as shown in Figure 2.
Figure 2 - Control architecture with plant floor automation control systemThe control system also includes interfaces to most common plant floor equipment as shown in Figure 3. The plant floor control system receives operational data from the WMS or other business systems, buffers it in a local database, formats it for receipt by the plant floor equipment, and transmits it to the automation. The control system also monitors the status of plant floor automation equipment, providing maintenance and operations personnel with real-time, graphical status of plant floor equipment.
Another feature provided by an integrated control system is buffering of data between the upper level business systems and plant floor equipment. If the business systems or facility network goes down, data stored in the control system database allows plant floor operations to continue.
Figure 3 - The Plant Floor Automation Control provides interfaces to a variety of automation equipmentTo facilitate advanced diagnostics and maintenance of automation equipment, the control system performs detailed logging. This allows trained maintenance personnel to review logs offline to resolve issues with equipment or communication.
Another feature of an advanced control system is the heartbeat function. The control system constantly checks the health of its communication connections with both plant floor equipment and the WMS. This allows the control system to notify maintenance personnel immediately if a connection is lost. The control system can even reset the connection automatically when a communication failure is detected.
Plant Floor Control System Checklist
What features should you look for in a plant floor control system? The control system should include a server that both controls the area controllers and interfaces with upper level systems (e.g., WMS). The area controllers monitor and control shop floor equipment and communicate to the control system server. When considering new business systems, include a review of your control systems as well. A categorized list of other recommended features is provided below:
Consider the environment in which your control system server will function:
- Server with interface to WMS
- Server backup capabilities and options:
-- Automatic fail-over
-- Hot backup
-- Cold backup
-- No backup
- Dual redundant processors
- RAID array controller and hard drives
- Hot-pluggable redundant power supply
- Hot-pluggable redundant cooling fan
Area controller features:
- Hardware platform:
-- Industrial PC with soft-PLC (programmable logic controller) capability
-- PLC with Ethernet networking
- Industrial area controller
- Spare area controller
- Redundant power supply
- Removable hard drive cages
Other robustness features:
- Heartbeat between plant floor equipment and area controllers
- Heartbeat between WMS and server
- Data buffering
- Expandability to include more interfaces to shop floor equipment
Maintainability features
- Detailed logging of all processes
- Real-time monitor and control of plant floor equipment
- Real-time maintenance alerts
- Extensive maintenance reports
- Fault detection and isolation
Operations features
- Real-time operations alerts
- Graphical user interface displaying system status
- Extensive operations reporting
- Real-time graphical display of communications status for all networked equipment
- Web-based status tools
- Standard database with open user query tools
Plant Floor Connectivity - How Do I Get There?
We've talked about the industry norm and the full-featured control system. Now, how do you design a control system? Whether you have the in-house staff or engage a consultant/systems integrator, begin by defining the requirements, top-down. Requirements definition should involve all stakeholders, including personnel from operations, maintenance, marketing, and IT. Use the checklist above to select features and design your system around its users, operations personnel.
Plant floor control systems are typically thought of as lower-level functions and given less consideration as compared to upper level business systems. Therefore, when designing new business systems, consider an upgrade to the plant floor control system as an extension of your design. An integrated control system provides comprehensive connectivity between the plant floor and the rest of the enterprise. When considering upgrades in your distribution facility's technology, don't neglect the shop floor.
