With the increased processing power that PCs have attained, a complex machine that used to require an expensive and dedicated hardware-based motion control solution can now be accomplished on a multicore PC running on a real-time operating system (RTOS).
The power and flexibility of PC hardware can support closed-loop motion controls and integrate other processes such as machine vision, industrial networking, supervisory control, and the human interface for a machine work cell. By consolidating these processing workloads on a single multicore platform, a machine builder can greatly reduce hardware costs, simplify software development, and reduce maintenance operations. The secret to combining processing environments is embedded virtualization: the ability to run standard applications on multiple guest operating systems of different types on the same platform, without sacrificing real-time determinism.
RSI Motion of Chicago, IL, helps its customers build smarter machines faster. RSI’s soft motion controller, the RMP, provides benefits to companies in industries such as medical electronics manufacturing, surgical robots, material cutting, semiconductor, packaging, military, and aerospace applications.
“There are three key elements that contribute value to the solution that we provide,” said Raj Bhasin, Director of RSI. “Obviously, real-time processing needs are critical in motion control, so having a real-time operating system (RTOS) is the number-one priority. Second, leveraging the abundance of Windows tools and applications provides customers with an easy-to-design-with platform for building control applications and powerful human interfaces. Third, the system provides an open and industry-proven network that supports interfacing with everything from motor drives to enterprise networks and the Internet.”
RSI targets any machine developer who wants to be able to engineer a highly customized application, drawing from a broad range of software products from many manufacturers, without requiring any proprietary hardware. The company’s RapidCode software libraries support motion application development in C++, C#, or Visual Basic .NET framework.
In order to bring reliable real-time functionality to the PC platform, RSI selected the INtime RTOS by TenAsys Corp. of Beaverton, OR. INtime for Windows runs alongside Windows, and is able to meet the timing demands of high-performance, multi-axis motion control by explicit hardware partitioning of the underlying processor architecture to give real-time processes direct control over their own core(s). The hardware partitioning is done using standard Windows application programming interfaces (APIs), enabling Windows to run without any modification on its own assigned core(s). Such a virtualized system (virtualized in the sense that Windows thinks that it has complete control of all resources of the underlying processor) makes very efficient use of processor resources compared to other multi-OS configurations requiring hypervisors, as there is no hypervisor layer that consumes computing cycles. INtime has been enhanced to make optimal use of the constantly evolving Intel Architecture hardware and software platforms, including providing ongoing support for the Microsoft Visual Studio development environment and INtime-APIs to create Windows HMI (human-machine interface) and controller applications.
“The great thing about INtime is that it literally runs in the background,” said Bhasin. “A user does not need to interact with it. Our motion library handles the real-time interaction with the RTOS and all user application development uses standard Windows tools.”
Figure 1 shows the architecture of a typical motion system using RSI’s software. The real-time portion of the system typically runs on one processor core, whereas the rest may run on as many as three cores in a quad-core PC. Bhasin estimates that a quad-core Intel i7 processor can support up to 64 motion axes operating simultaneously with a loop time of 0.25 to 1 milliseconds. The system in Figure 1 uses EtherCAT (Ethernet for Control Automation Technology), an open fieldbus protocol, to interface with motor drives.
“Other real-time operating systems require use of separate computing platforms for development and execution of the application software,” said Bhasin. “INtime’s seamless integration with Windows allows users to focus on developing their applications in a familiar programming environment while real-time processes are being handled behind the scenes on the same processor platform.”
One of RSI’s customers is Eastman Machine Company, a Buffalo, NY-based manufacturer of high-performance, ultra-precise equipment for cutting a variety of materials including upholstery, vinyl, fiberglass, carpet, canvas, and even carbon fiber and Kevlar. The company’s goal in developing a new conveyor cutting system (Figure 2) was to build an automated cutting machine that would be guaranteed to satisfy the performance and flexibility requirements of any type of customer application. The performance and reliability of the company’s previous machines were limited by an inflexible architecture and an analog motion controller. As a result, the machine required a large number of cables, making it very difficult to customize and troubleshoot.