Rise of the DeltaBot
Beckhoff Automation helps AEMK Systems reboot high-performance robot designed for cost- and space-sensitive applications.
Much like the historical progression of computer technology, cost-effective robot technology is steadily advancing into areas that were previously too cost-sensitive to apply it. Food manufacturing, packaging and warehousing are prime areas to experience the next wave of robotics with high performance, low cost robots entering the marketplace from leading suppliers.
One of those suppliers is Waterloo, Ont.-based AEMK Systems. Established in 2006 to commercialize the results of five years of research at the University of Waterloo, the company provides high-speed, vision-based robotics systems for applications in the food industry, packaging and automated warehousing.
The company’s breakthrough product is the DeltaBot, a patented ultra high-speed parallel robot that uses steel cables in place of rigid arms and expensive, high-precision joints. At top speed, AEMK’s three and four-axis models can perform 120 pick-and-place cycles per minute. While fast, the DeltaBot’s main benefit isn’t its speed says AEMK President and University of Waterloo professor Amir Khajepour.
“In order to have the highest market share possible in the robot industry, AEMK strives to provide customers with the most cost effective robots possible with simple integration, low maintenance cost and outstanding customer service,” he says.
The DeltaBot’s cost effectiveness is largely due to its steel cable arms, which reduce moving inertia and mechanical equipment costs. For example, because tension in the robot’s cables helps manage backlash in the gears, more expensive joints can be eliminated and very little maintenance is required to ensure high repeatability. In addition, the cost of components and fabrication is much lower compared to conventional pick and place robots.
And due to its inherently simple design, the DeltaBot can also be installed in many labor-intensive applications with high capital cost barriers to incorporating automation equipment. Since its passive cables control the movement of end effectors, the robot’s workspace can be easily scaled to adapt to any application.
In addition, straightforward construction allows the robots to be easily fabricated for use in the food industry. AEMK Systems has already produced food-grade DeltaBots that comply with strict regulations and are able to withstand the sanitizing substances required for wash-down in the food industry.
When paired with a vision system, the ultra high-speed DeltaBot often eliminates the need for fixtures and dedicated material handling devices, resulting in considerable cost savings for end users.
Robot reboot
For all its speed and flexibility, early versions of the DeltaBot suffered from the limitations of its controller system. While PLC-based platforms were highly deterministic and precise, they lacked flexibility and ease of programming. Instead, the company went with a dual PC-based architecture: one computer served as the real-time robot controller, and the other generated the robot’s path, ran the HMI and connected with vision systems or any other applications that were needed.
“The major drawbacks of the previous system were unreliable communication and the difficulty of running at a consistent, low scan time” says Khajepour, adding that the robot’s motion system featured CANopen as the communication protocol and couldn’t make use of servo drives’ “smart” features. As a result, AEMK decided to run their own control loop using the servo drives in velocity mode to achieve the demands of a high speed robot.
To boost control performance while reducing cost, AEMK’s DeltaBot line was recently upgraded with Beckhoff CX1010 Embedded PCs running TwinCAT PLC software. The DeltaBot is also equipped with EtherCAT I/O terminals for ultra high speed communication as well as the EtherCAT-enabled AX5000 servo drives installed above the pick and place unit.
“Considering the DeltaBot’s previous PC-based controllers, the upgrade to an improved PC-based platform was the natural progression,” Khajepour says. “We wanted the smallest possible footprint for the controller that would also give us the most programming flexibility, but the impressive price-to-performance ratio was the deciding factor in selecting the CX1010 as the DeltaBot’s control centerpiece.”
In addition to the PC controller, Khajepour says Beckhoff’s TwinCAT PLC software platform brings all the best PLC features into a flexible PC-based package. Combined with the PC’s real-time capabilities, the platform gives AEMK more design freedom and much easier programming.
As a result, only a few minor changes were required to accommodate specific features in the new Beckhoff architecture. For example, AEMK had initially implemented a set of external DLL libraries to perform the mathematical tasks related to generating motion paths and controlling the robot. With the Beckhoff architecture, however, the company eliminated the jitter introduced by the communication with those libraries by fully programming its path generator, libraries and feed forward PID control loop directly in TwinCAT.
“TwinCAT’s real-time control system with integrated PLC functionality gives us an all-in-one platform to create high speed, reliable control architectures,” Khajepour explains. “The Structured Text programming language in TwinCAT, one of the system’s many available IEC 61131-3 languages, makes the DeltaBot’s code easy to program.”
EtherCAT keeps the jitter away
With jitter eliminated from its motion programming, AEMK needed the hardware and a communications protocol that wouldn’t introduce bottlenecks of their own. Since the DeltaBot moves extremely fast—most of its paths must be completed in less than 500 milliseconds—it doesn’t permit any time for communication jitter, even in the range of single digit milliseconds.
As a result, the company uses EtherCAT for fast I/O access and Beckhoff’s AX5000 drives to accommodate a wide range of power requirements, drive communication at ‘EtherCAT speed’ and very low cycle times.
“We are able to run the DeltaBot position controller at 2KHz, which came without the hassle of having to integrate various proprietary technologies into the same system,” Khajepour says. “This allows us to increase the DeltaBot’s positioning precision as well as the repeatability at the same robot speed. Due to its deterministic features using its precise timebase, the new DeltaBot system has made great gains in reliability, consequently generating fewer errors than the previous system.”
Multi-channel, EtherCAT communication, low cycle times and flexible architectures allow AEMK to run the AX5000 in position configuration, which in combination with the NC functionalities, employs a very effective PTP positioning system.
“The DeltaBot can run in velocity mode without adding a burden to our control system communication when equipped with the AX5000,” Khajepour says. “Also, a wide variety of Beckhoff servo motor types are available with a wide range of voltages; these are very well suited for the flexibility we need, and the scalability we intend to maintain with the DeltaBot.”
Picking apart system cost
AEMK Systems has successfully implemented DeltaBots in several projects and has introduced the robots as stand-alone products to the market. Due to its reliable nature, Khajepour says the new DeltaBot has greatly reduced testing and integration time. In addition, he says TwinCAT’s ease of programming has decreased the DeltaBot’s development time by nearly 50 percent.
“Our goal at AEMK Systems is to offer flexible automation and, for our robots, Beckhoff offers the ideal solution to run, communicate and interface with nearly any industrial device that we could think to utilize,” Khajepour concludes. “The Beckhoff control architecture will help advance DeltaBot development and help make it the preferred robot solution for many more cost-sensitive applications. ”
www.aemksystems.com
www.beckhoff.ca
