Pairing Programmable Automation Controllers and Networks

When using a programmable automation controller (PAC) that combines a processor and FPGA, the processing components offer different advantages, lending themselves to different communication tasks.

Michael Sopko, National Instruments
Michael Sopko, National Instruments

Industrial networking issues are often treated separately from controller discussions in that the network simply serves the purpose of delivering data to and from the controller. But with next-generation controllers, such as PACs, the two separate processing units—CPU and FPGA—found within these controllers creates a variety of networking options.

For example, a processor running a real-time operating system is well-suited for communicating with distributed systems, storing measurement data, implementing complex control algorithms, and managing data from I/O, according to Michael Sopko, product marketing engineer for National Instruments’ CompactRIO. “An FPGA is incredibly fast and reliable, making it ideal to pre-process I/O, implement custom triggering between I/O channels, develop high-speed control and DSP algorithms, as well as custom digital protocols for unique sensors and transducers,” he says.

With the flexibility of the FPGA, a range of I/O can be integrated into the control system and synchronized on the hardware level. “This means that developers can choose from a range of analog I/O such as high voltage and current measurements, digital I/O ranging from high speed TTL to 24V industrial digital, as well as numerous industrial communication busses,” Sopko adds.

As manufacturing applications become more complex, PACs will require an ecosystem of components, each with their specific functions.  The controller must communicate with each of these devices.  Depending on the complexity of the application, a system may require many additional components or just a few to make up the industrial network.

Which brings us to how we think of an industrial network. In an office, PCs, printers, servers, etc. are all connected together.  Each component of the system can talk to the other, transferring data back and forth. This is the same basic setup for industrial networks connecting PLCs, sensors, motors, actuators, and other devices.  However, in industry, these systems use different protocols for faster data rates, low latency, and deterministic communication, notes Sopko. “Each industrial network protocol is specifically designed to optimize these characteristics.  This is one of the primary differences between office and industrial networks. Though the premise behind each is the same, the requirements differ dramatically,” he says.

It is the ability to work with these differences that are driving PACs, with their multi-processor capabilities, to increasingly become the controllers of choice in many manufacturing industries.

In the automotive space, for example, the CAN protocol meets many of the industry’s specific application requirements. “Due to the number of subsystems in automotive applications, CAN’s ability for subsystem communication makes it ideal for this industry,” Sopko says. And PACs’ abilities to handle these subsystem communications are one of the major factors leading to their growing use in this industry.

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