From Control Engineering magazine:
The notion of 'real-time,' or determinism, can apply to sensing, logic, actuation, and communications that connect the three.
In sensing, it means measuring and acquiring data about a process quickly enough to accurately reflect reality: taking samples too slowly can distort understanding. In devices and software performing logic, real-time decisions happen when information is collected fast enough to meaningfully influence the process. Real-time actuation, of course, means changing the process in time to keep measured parameters within desired setpoints. Networks have to transmit information in a known, or determined, period, so information travel time can be factored into calculations. A process that does this is said to be deterministic.
'What real time or determinism means in manufacturing depends on context. Programmable controllers, robotics, CNC motion, vision systems, and other devices all have vastly different requirements for each and even among each,' says Ron Sielinski, Microsoft industry technology strategist. Microsoft targets real-time applications with its Windows XP Embedded and Windows CE 5.0.
Following is a round up of real-time technology advances.
Numerical control for machine applications: IndraMotion MTX from the Bosch Rexroth Corp. Electric Drives and Controls division, uses Wind River VxWorks real-time operating system in a PLC that executes 1,000 statements in 60 Ķs; the CNC guarantees a maximum interpolation time of 1 ms when controlling eight axes. www.boschrexroth-us.com
Fast data exchange: GE Fanuc Automation PACSystems Control Memory Xchange allows users to share data in real time at rates up to 174 Mbytes per second with node-to-node latency as low as 450 nanoseconds. Users can realize updates on 10,000 data tags from input controller to second controller or screen display in as little as 1 millisecond. www.gefanuc.com
PLC and Microsoft Window XP Embedded: MDSI (Manufacturing Data Systems Inc.) offers the 'FlashCNC complete machine control system,' which combines MDSI's high-speed open architecture software, compact hardware, and digital machine interface. It supports up to 256 I/O points and manages up to 10 axes. www.mdsi2.com
Development software and operating system: National Instruments LabView with the LabView Real-Time Module and NI Real-Time hardware offers deterministic, real-time performance for data acquisition and control systems. Using graphical programming, applications can be developed on a desktop machine, then downloaded and executed on an independent hardware target, based on speed and I/O requirements. www.ni.com
In-field software updates: Sauer-Danfoss and Texas Instruments Inc. (TI) announced availability of eight 'Plus 1' hardware modules, based on TMS320F2810 and F2812 digital signal controllers. Processors are TI C/C++ efficient 32-bit TMS320C28x DSP core, F2810 and 2812 controllers integrate up to 128 Kilowords (Kw) of on-chip flash memory for reprogramming during development and in-field software updates. www.ti.com
VXWorks or Linux development: Wind River Workbench reportedly is the first and only integrated development environment that enables companies to standardize on one development tool for VxWorks and Linux. Wind River Workbench 2.0 is said to offer flexibility and openness. www.windriver.com