In the world of high-performance servo control, robotic motions have traditionally been a processing-intensive task often requiring a separate robot controller and software. But now with core technology upping the processing power of machine controllers, along with the goal of designing robotic mechanisms more tightly into automation equipment, integration of robot motions with the standard controls used on machines has become a growing trend.
The advantages are a familiar mantra: a single software development environment and one machine controller/network. But the overall benefits also extend into a much tighter integration and unification of the overall control hardware, operator interfaces, and network connectivity.
Combining with line controllers
“Robotics is increasingly being adopted in a broad range of industries and applications because of the flexibility and performance advantages that they offer. As part of that, we are seeing machine builder OEMs and end users moving to integrate control of the robot directly into their line controller,” said Bob Hirschinger, principal application engineer at Rockwell Automation, in an interview.
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“The goal is to integrate general automation with robotics. We’ve been helping our customers replace dedicated robot controllers with PAC-based line controllers that have integral kinematics and advanced motion control instruction set capabilities,” he said.
Rockwell Automation has targeted specific robot geometry such as articulated, dependent/independent, SCARA, Delta, and Cartesian robots. The approach is basically using standard controllers with embedded motion instructions linked up to kinematics support to directly control the robot. In some applications, it might be a robot arm using the same type of drives used in the rest of the line, or the controller is interfaced directly to a different vendor’s drives that may come with the robot arm.
The advantages of the integrated control are improved recipe management and better operator interface (EIO) support, which eliminates the need for separate robot-dedicated human-machine interface (HMI) devices. The drives needed for the robot can be integrated with the control panel used for the rest of the line, eliminating the need for the standalone robot controller and panel. The primary motivation is unifying the system hardware, but another advantage is the ability to program the robot using tools the user is familiar with and a single language for control across the line.
Hirschinger said that in many applications, there is also a performance benefit because everything is running synchronously out of the same controller. “Standard robot controllers typically have a standard Ethernet network interface that uses handshaking over the network to coordinate the line and robot controllers. But that can add delays to the system and negatively impact performance,” he said.
Chuck, While packaging automation is a big market for this type of capability, integration of robotic arms into machines is a phenomena that reaches into all types of applications. Especially with the development of technology to create "programmable safety zones", it's now possible for robotics to become more tightly integrated with the machine process. That reduces floor space requirements and enables automation engineers to design around robotic arms to eliminate some custom design. Now with the ability to program the line controls for the machine, plus robotic motions, using the same programming environment on a single machine controller, it's creating more incentive to move machine designs in this direction.
TJ, The most common and popular software approach for these type of systems is based on the IEC61131-3 programming languages, with solutions provided by a wide range of automation vendors. These automation software packages are already wide in used for general machine control, so robotic kinematics is another group of software objects/libraries that can be integrated into the package.
naperlou, for vision I'd agree with you. I've not seen a PAC that tightly integrated vision the way motion has been.
Eventually, it will be; I can see the benefits of merging the two for even better robotics. I haven't seen any of the big automation companies offer a camera yet.
Centralized control does make sense (assuming redundancy is covered properly) when there are numerous devices with similar control requirements. Central control means a single point to adjust programming, and a central point from which supervisory and HMI systems can collect data.
Distributed controls means touching each and every machine to roll out a change (connect, download, verify, disconnect, again and again). It also means a much more complex task for collecting data. In some cases, the number of connections becomes a limiting factor.
ttemple, we use a lot of Rockwell Automation hardware and software (Logix5000).
I've also used AML from Pacific Scientific (a long time ago). Both are an integrated programming environment, and I find I like that, a LOT.
Having to have different suites of software for different parts of a large system can get cumbersome, FAST, especially when the software does not play nice with other packages (Rockwell and Siemens are notorious for this).
Running different suites in their own Virtual Machines is how we handle that problem, but again, it's much nicer to have a single programming environment.
Frankly, I agree with TJ. This becomes a single point of failure. I also am more inclined, in design projects I am involved in, to push the intellgence out to where it is used. There are lots of processors that have specilaized instructions that will handle the computational load at a much lower power level. Vision systems, for example, are tending toward smart cameras. This allows most, of not all, of the processing to be done at the camera, thereby reducing the traffic on the communications link.
The main issue that seems to be addressed here is the comminications latency. There are standard busses that handle this with predictability and high speed.
My company makes control systems using a central PAC for motion control describe in the article. Having a single point of programming makes system development simple and saves time.
However, that central PAC becomes a source of single-point failure unless suitable redundancy is built into the PAC hardware.
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