Simplifying Automation System Hierarchies

  • November 30, 2012
  • Feature

November 2012 By Bill Lydon, Editor The automation industry has been centered on a five layer hierarchical architecture for years but new technology is making it possible to streamline this model to eliminate layers, increase performance, and lower software maintenance costs.  A commonly used architecture model to define Manufacturing Operations Management is the five level Purdue Reference Model (PRM), which later formed the basis for the ISA-95 standard.  The model is typically expressed as: Level 5 - Business Systems Level 4 - Plant Level (ERP, MRP, and MES) Level 3 - Operation Unit Level Level 2 - Machine/Process Automation Level Level 1 - Controller Level Level 0 - Sensor/Actuator Level Existing automation systems generally reflect this architecture with software running on general purpose computers at levels 2, 3, 4, and 5. Levels 2, 3 and 4 typically have database and communications interfaces that buffer and synchronize information between each level in addition to associated HMI and user interfaces. The constraints of computing costs and networking bandwidth dictated this configuration based on past technology. The multilevel computing model however is complicated and creates a great deal of cost, ongoing configuration control and lifecycle investment. Fortunately, this model is changing to enable a more efficient and streamlined automation system architecture.  In the new model, controllers can communicate information to all levels directly using the appropriate methods and protocols. Ethernet communication has become the high speed and pervasive technology used by industrial automation protocols and business systems. More controllers are supporting multiple Ethernet ports to interact directly with industrial and business networks that exist throughout industrial plants. Historians, analytics, real-time maintenance monitoring and other functions are now being incorporated in controllers. This simplifies the applications of these functions and eliminates level 2 and 3 software costs, complexity, performance drag, and ongoing software maintenance. More powerful controllers and communications enable the coordination between controllers without requiring a separate computer to coordinate them as well. A good example is controllers that incorporate complete ISA88 batch function, i.e. simply receive batch orders and execute them, thus improving production throughput and response. Internet of Things The “Internet of Things” is becoming a reality with sensors and actuators embedded in physical objects - from roadways to pacemakers - and are linked through wired and wireless networks, leveraging the Internet Protocol (IP). Industrial controllers are starting to follow this trend by providing data refinement, local historians, analytics, and advanced control at the source end devices. Modern controllers are communicating with all levels of systems using the “IP plumbing” that is pervasive in manufacturing plants, including capabilities to send Email, FTP files, and serving up WEB pages. Open communications is being supported using XML, SOAP, SNMP, and OPC UA. New Breed Over the past ten years there have been tremendous technological innovations and refinements that are starting to be deployed in level 0 and level 1 devices. These devices incorporate powerful new CPU chips to simplify automation architectures. The rapid increase in the power, memory, and communications integrated on CPU chips with associated lower costs is driven by high volume production of smart phone and tablet computers. In 2008, over 10 billion CPUs were manufactured with approximately 98% embedded in devices. In 2010 overs 1.39 billion mobile phones were shipped.  Cell phones reflect this change having started in 1983 with the first hand held cell phone.  The Motorola  DynaTAC 8000X was 13 x 1.75 x 3.5 inches in size, weighed 1 ¾ pounds, offered 30 minutes of talk time and 8 hours of standby power, and sold for a retail price of $3,995 ($9,281.84 in 2012 dollars).  Now smart phones are a fraction of the cost and offer significantly more power. The new breeds of industrial controllers and embedded industrial end devices are incorporating this power and adding features that include embedded Web Servers, Email clients and Web Services.  These capabilities enable these level 0 and 1 devices to communicate directly with level 4 and 5 systems. It is common to now see dual core CPU’s in controllers and a number of companies have announced quad core-based controllers. For example, the new Intel Multicore Atom processors are starting to be incorporated in industrial controllers. These more powerful industrial controllers are becoming automation computing engines that are starting to collapse the typical 5 level model and make automation systems more flexible and responsive. Bloat ware The incorporation of higher level functions directly into these new breed of powerful industrial controllers is starting to eliminate the need for middle level software. Middle level software and computers have served their purpose of buffering, synchronizing, translating, and refining sensor and controller information.  But they have also created a great number of middle level computers, databases, and software that is expensive and difficult to maintain. The interim solution is the migration to more powerful computers and the virtualization of existing middle level software.  This migration and virtualization improves performance and centralizes software maintenance and configuration control. Over time the functions of this middle level software is being taken over by the new more powerful controllers. Holistic & Adaptive The new high level of communications and computing at end devices is opening the possibilities for holistic and adaptive automation to increase efficiency. This is a logical evolution in step with the “Internet of Things” trend and will lead to more responsive and efficient production.

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