System challenges for networked, future-proof controls
In the world of manufacturing there is much talk of the Industrial Internet of Things (IIoT) and the future era of Industry 4.0, where cyber-physical systems will revolutionize production. Location systems are becoming increasingly popular as a way to gain visibility into assembly processes and also to create virtualized device controls, especially for automotive assembly.
Sensors across the value chain will monitor the real-time status of the end-to-end operation to optimize flexible process controls, and location systems in automotive assembly create process visibility and virtualized device controls. This is deemed revolutionary since data sources far outside individual processes might influence real-time controls, but it is revolutionary in another sense, too: These distributed sensor and controls networks represent the "IT-ification" of industrial controls, a significant departure from the hardware-oriented, embedded-software reality of the last several decades.
In this future vision, a centralized decision-making engine will gather and assimilate data from distributed sensor networks and, in turn, disseminate decisions to industrial control systems. In this IT-centric world, it will be essential to maintain all the performance, reliability, and scalability that localized controls have made so straightforward. It won't be enough to develop sensors and virtualized controls—that is the easy part. The hard part is to make them operate with better than five 9's reliability, in harsh environments, with all the safeguards in place to make them truly production-critical systems. There is one technology being adopted in automotive assembly that nicely illustrates this challenge and the uphill path that Industry 4.0 technology providers face: Location systems are becoming increasingly popular as a way to gain visibility into assembly processes and also to create virtualized device controls.
Product complexity challenges assembly
A traditional moving assembly line allocates groups of processes to workstations of a fixed length and duration. Every group of processes must be completed within its allocated workstation and therefore within a fixed process time—the "takt" time. For quality reasons, great care is taken to ensure that the right tool executes the right process on the right product in the right workstation. This often is achieved through rigid, mechanical means: Fixed scanners identify the product, limit switches enable and disable tools, and tools may be physically tethered to specific workstations. The whole construct is proven, effective, widely adopted, and completely broken.
In 1913, when Henry Ford invented the modern assembly line, processes could be rigidly controlled: No flexibility is required when the line assembles identical, black Model T Fords. Over the years, engineers created highly elegant processes that allowed some variation in the individual cars assembled on the line, allowing consumers to choose from a number of option packages without violating the fixed takt-time principle of the assembly process.
Today, consumers demand a high degree of personalization, requiring full freedom to choose any combination of options; in parallel, manufacturers strive to control costs by building more cars in fewer factories. The result is that the modern assembly line has to manage trillions of potential variations of one model and also must be configured to simultaneously produce multiple, diverse vehicle types.
Each car on the line is different, and that high degree of variability requires a high degree of flexibility in the way processes are controlled. The fixed workstation is becoming a thing of the past.
Flexibility with virtualization
Quality is paramount as is the need to ensure that the right tool performs the right process on the right product. Rather than physically constraining everything to a rigid workstation, however, a location system can track the relative position of tools and products and create virtual workstations to control devices. In contrast to a tool that is enabled and disabled as a car actuates a limit switch at either end of the workstation, a location system can create a virtual zone which triggers tools as the car is determined to enter and exit the zone.
The process is simple in concept—much like geo-fencing using global positioning system (GPS)—but consequences are far reaching. By virtualizing the control of critical devices, location systems introduce complete flexibility. Manufacturers can tailor workstations in real-time to suit the needs of the product under work: Takt time may vary from one model to the next; workers may temporarily be given more process time to avoid a line stoppage; and processes may overlap or span multiple traditional workstations.
This is a glimpse of the power of Industry 4.0 and an important reminder of what it takes to create distributed, real-time control systems. What is needed to create a production-critical system?
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