Flexible real-time robotics control with POWERLINK
Robots for injection molding machines used in global industries such as automotive, semiconductor and packaging must be extremely reliable and user-friendly, with control software as versatile and easy to use as it is powerful. These characteristics demand a bus with the performance to handle complex motion control algorithms that also provides high-speed communication between devices positioned throughout the line. With a new architecture based on POWERLINK, the VISUAL2 control platform from injection molding specialist SEPRO is now able to provide optimal control performance and accuracy for robots of any size and payload. POWERLINK’s real-time performance and hardware-independence open up more flexible architectures and allow more sophisticated motion control.
SEPRO specializes in the automation of injection molding machines for the plastics industry and develops robots that are used in a wide variety of fields – from the automotive and semiconductor industries to packaging for food and beverages, pharmaceuticals and cosmetics.
Looking to enhance the motion control of its robots for many years, SEPRO faced the challenging objective of finding an optimum balance between performance and accuracy. Another goal was for a single CNC system, SEPRO’s VISUAL2, to provide optimum control for any robot, regardless of its size and payload.
"However, the most promising solutions for motion control would require extremely fast communication over longer distances to allow devices to be positioned optimally on the machine," recalls Francis Columeau, R&D manager in charge of electronics and software design at SEPRO.
In order to continue improving the quality of its robotics control, SEPRO knew it would need a bus solution with better bandwidth that could handle a larger number of connected nodes. This bus system would also have to incorporate a mixture of real-time and asynchronous frame traffic, along with additional safety frames.
With the development of a new system architecture based on POWERLINK, SEPRO was able to overcome these limitations and gain the freedom to implement even the most demanding algorithms. This has expanded VISUAL2’s boundaries for real-time management between the CNC system and the numerous real-time devices that make up the heart of SEPRO’s digital control system.
"For me, the greatest benefit is to have the capability to place a slave module anywhere on the robot without having to worry about wiring," says Columeau. "This gives us the freedom to create new architectures with optimum placement of embedded motion drives, controllers, I/O modules etc. while maintaining flexibility toward the various perimeters and allowing them to be addressed with the same platform."
SEPRO also takes advantage of POWERLINK’s ability to combine real-time, safety and asynchronous processes on a single bus to simplify the overall solution while lowering its total cost. "In addition to its exceptional performance, one of POWERLINK’s biggest strengths is its ability to combine various types of information on the same medium," explains Columeau. Free access to the open source code, which is the same for both masters and slaves, gave SEPRO the freedom to develop an optimal solution with both POWERLINK master and slave implemented on the same stack.
The major challenge SEPRO faced in the transition was porting open source code developed for a Linux environment to the QNX Neutrino real-time operating system used by SEPRO. "POWERLINK’s full POSIX compliance made implementation of our POWERLINK master a very straightforward process," recalls Columeau, "and the excellent architecture of the software stack is perfect for easy porting to any hardware and operating system."
As a successor to classic fieldbus technology, POWERLINK provides uncompromising performance and real-time capabilities based on the established global standard, Ethernet. The open-source nature of POWERLINK plays a key role in managing development times and ensuring the quality of results of SEPRO.
SEPRO has begun its transition to POWERLINK by implementing a managing node on its CNC platform. This will be followed by the ongoing replacement of existing CAN bus systems in all new developments in order to base the new system architecture entirely on POWERLINK.
One of the key criteria leading up to the new solution was compatibility with SEPRO’s existing CANopen protocol. By providing this compatibility, POWERLINK allows the company to continue using their existing CANopen libraries. "This feature made the transition quite simple for us," says Columeau, "and thanks to efficient support from the EPSG and training on implementing controlled nodes in an FPGA, we hardly lost any time at all."
SEPRO joined the EPSG (Ethernet POWERLINK Standardization Group) in 2012, as did its drive supplier, INFRANOR, who developed a new drive architecture based on SEPRO’s specifications, which clearly defined POWERLINK as the communication bus.
According to Columeau, implementing POWERLINK is a strategic move for SEPRO in general and an important step in the evolution of the VISUAL2 platform in particular: "With POWERLINK, we have achieved a near optimal situation: an economic, versatile, fast and open communication bus."
In the future, SEPRO plans to complete its transition to open-source communication technology by modernizing its safety solution. Replacing its hard-wired relays with a modern, integrated openSAFETY solution will allow SEPRO to benefit from higher productivity, faster commissioning and easier maintenance, while also reducing the footprint of their machines.