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.
To replace the analog motion controller, Eastman wanted a programmable digital software platform that was easy to program and maintain using a well-supported software development environment. The company also wanted the platform to provide industry-standard I/O interfaces to devices such as servo amplifiers and motion sensors. With cost savings due to economies of scale as an additional goal, the PC platform was a natural choice to fulfil the customer’s basic hardware requirements.
To make it all work, however, Eastman needed capable motion software that is easily customizable in order to accommodate various customer requests, such as adding more motion axes to support proprietary components such as a custom labeler, or punch to the main cutting head unit. RSI’s RMP soft motion controller filled the bill.
To satisfy the customer’s requirement for flexible addition of devices to the cutting machine, RSI’s software supports most EtherCAT-compatible devices. The software automatically detects the add-on hardware during system initialization, speeding the setup process. If a drive should stop working in the field, it can simply be replaced with a new one and the network will seamlessly reconfigure itself, minimizing machine downtime. Likewise, if a network failure should occur, the RSI system is designed to keep functioning, while providing advanced diagnostic information to help resolve the problem. If a network failure should occur, the RSI system will provide advanced diagnostic information to help resolve the problem.
High-speed, real-time processing is required in order to enable Eastman’s machine to cut material with high precision unrivaled by other manufacturers. To achieve this task, the hardware streams positions, velocities, accelerations, and time trajectory data into the RMP motion controller. The data received by the motion firmware is then processed and relayed to multiple synchronized axes at a very high sample rate. The higher the sample rate, the shorter the time difference between the trajectory points, resulting in finer, precise cuts. The RMP controller leverages the INtime RTOS for this realtime critical task.
To verify machine functionality, Eastman has implemented a feature called Motion Analyzer, which runs every time the machine starts, and analyzes and records motion performance. The data is used to detect any mechanical components that are at risk of failing and notify the operator accordingly. RSI’s technology illustrates how multi-core PC architecture can host a very powerful multi-function motion system, with the ability to add functionality that would otherwise require additional computing platforms, increasing system costs. The economic advantage that this brings will continue to drive the migration from hardware-centric motion control solutions to software-centric ones.
This article was written by Kim Hartman of TenAsys Corp. For more information, Click Here .