In RT-101: Real-Time Operating Systems (RTOS), I provided readers with a brief description of the many benefits that systems running an RTOS can provide in harsh and demanding environments. The bigger question is: in an industry saturated by PLCs (Programmable Logic Controllers), PACs (Programmable Automation Controllers), Field Point controllers, Microcontrollers and many others, why should an engineer choose an RTOS PAC (Programmable Automation Controller) platform above all the rest? To address this issue we will take a look at a comparison between two distinct camps Programmable Logic Controllers and RTOS Programmable Automation Controllers.
Traditional PLC platforms are based on a reliable and easy to use scanning architecture. PLC software has historically been confined to a sequence of scanning inputs, running control code, updating outputs, and performing housekeeping functions. Automation programmers only develop the control code because the other functions (input cycles, output cycles, and housekeeping cycles) are all concealed. This rigid architecture allows engineers to quickly and efficiently design and program basic control systems. However, the PLC’s greatest strength, a robust and rigid scanning architecture, can become its most obvious weakness, inflexibility when custom applications require advanced operations.
- Incorporate extremely high speed measurements (hundreds of thousands or millions of samples per second)
- Vision acquisition and processing
- Software defined hardware (by incorporating FPGA, field programmable gate arrays)
Most important, a Real-Time PAC platform can incorporate vision, high speed measurements and other data acquisition with logic and motion control and eliminate the need for engineers to integrate multiple dissimilar hardware and software platforms. Instead, all these functions are designed and programmed within a single software environment. This makes RTOS PAC software adaptable and appropriate for complex applications that require advanced structures, programming techniques, or hardware level control, but more difficult for basic applications.
The “80/20 rule” can be used to simplify this dilemma. In general, 80 percent of industrial automation tasks can be efficiently completed using a basic PLC to provide digital I/O, a small number of analog I/O points, and generic programming techniques (i.e. ladder logic). The other 20 percent of applications, however, require advanced programming algorithms, extremely high loop rates, deterministic execution, and access to low level hardware drivers for customization. Programmable Automation Controllers running Real-Time operating system are designed for the “20 percenters” who need more freedom and functionality to solve complex control problems.
RT-301: Capabilities of Distributed LabVIEW Real-Time
Learn more about DMC's LabVIEW programming for Real-Time and FPGA.