Motion controllers are getting better simply because state-of-the-art industrial automation needs more capable controls. That’s the message coming from motion-industry veterans these days.
“The amount of programmable features that can reside in FPGAs continues to rise,” said Joseph Profeta, control systems group director at Aerotech Inc., supplier of motion control, positioning and automation systems for medical, industrial, military, and research applications. “This four-to-eight-fold increase over the last several years lets far more functions be loaded into the FPGA on startup, so a variety of feature sets can be delivered on the same hardware platform.”
Curt Wilson, vice president of Engineering at Delta Tau agreed. “Rising speed and density of digital logic in both ASICs and FPGAs has opened up new avenues for processing the inputs and outputs required in motion control,” he said.
More capable electronics also let end users customize feedback signals for closed-loop control. An example comes from Delta Computer Systems’ Bill Savela. “Delta controllers now can switch between redundant sensors if one should fail, so production can continue. This provides a degree of fault tolerance to machines in harsh environments and lets maintenance take place on a schedule rather than when things break. Delta controllers can also switch between sensors that respond to different measurement ranges or those that provide different sensitivities,” he said.
And some industries been catalysts for improving controller designs. To handle applications in sawmills, for example, Delta Computer added instructions for curves and splines that make it easier for movable saws to process curved logs. Delta Computer also gives its controllers the ability to synchronize multiple axes to let forest products processing equipment vary log processing speed in real time to help mills deal with logs of varying quality.
Similar trends are making packaging equipment more productive. “The packaging equipment industry continues to build in more motion control, driven by the need for packaging machines with higher throughput and more flexibility in their features,” said Aerotech’s Profeta. “Additionally, test and inspection applications are utilizing more motion control. It takes sophisticated motion to thoroughly test equipment and materials. In that regard, many testing machines—for stress and strain testing as an example—are considering linear motors with motion control to replace mechanical or hydraulic actuation. The ability to apply sophisticated motion profiles and higher forces (or torques) to the test sample has motivated the transition to servo-driven test machines.”
Electro-hydraulic testers are seeing a similar transition. “Simple machines applied pressure or force in a sinusoidal pattern to a device under test for a certain number of cycles. Closed-loop motion controllers now improve precision and repeatability using various test-load profiles. They also gather data regarding the way devices respond to the stress – an important factor in validating new material compounds and in improving the efficiency of structural designs,” said Delta Computer’s Savela.
Delta Tau’s Curt Wilson pointed out that the manufacture of dental prostheses—crowns and implants—is another area benefiting from advancing servo technology. Dental molds traditionally go off to a central lab that creates the prostheses with a turnaround measured in weeks. This whole process is moving into the dental office with a turnaround of an hour or two. Advanced controllers now run small, inexpensive, but highly capable dental milling machines that dental technicians can operate right in the office.
Wilson also said huge increases in computational speed and memory capacity are making it possible for modern controllers to perform extensive real-time monitoring and analysis in many different areas. These include analyzing servo error patterns both for adaptive control and for problem identification (such as excessive vibration). Multi-core CPUs permit the use of a separate core for redundant safety monitoring, and automatic servo tuning algorithms are becoming increasingly common, he said.
Similar sentiments come from David Goodin, owner of motion system supplier AllMotion. “DSP technology has also improved. Higher processing speeds as well as the incorporation of peripherals that are necessary for controlling motors have made drivers smaller and more capable,” he said. “The ability to do things in smaller packages is also promoting the use of advanced automation. For instance, our newest four-axis driver controller has native Delta-robot support. That is, you simply feed the desired XYZ coordinates to the board. It takes care of moving the end effector to the necessary location, calculating the trajectory and the transformation of the motor angles in real time.”
At Trio Motion Technology LLC, significant trends include the addition of IEC 61131-3 programming and Ethernet-based drive interfaces, said Trio N.A. sales manager Ed Novack. The lines are blurring between the traditional PLC and motion controller as both become more full-featured machine control platforms. In addition, the IEC programming standard has over the past several years brought PLC-style programming into the motion world. The result is more incentive for PLC-savvy engineers to consider using a motion controller in situations that might not have been candidates in the past, Novack said.
Trio also sees rapid growth in Ethernet-based drive interfaces. One reason is that this type of drive interface is flexible and can cut costs by simplifying wiring. The main protocol Trio sees in ascendance is EtherCAT. Originally developed by Beckhoff Automation, EtherCAT has been adopted by over 130 drive companies and continues to grow. Other Ethernet-based protocols, such as Allen Bradley’s EtherNet/IP, are used as well but don’t excel in high-speed deterministic servocontrol, Novack said.
In particular, as the motion control needs of machine builders and manufacturers continue to become more complex, there has been a shift to PC-based controls. “Industrial PCs and DIN rail-mountable embedded PCs are making good use of multi-core technology,” said Reid Beilke, industrial PC product specialist at Beckhoff Automation.
“For example, programs for multiaxis motion control, PLC, CNC, robotics, HMI, and more can run on one industrial PC through dynamic software platforms such as TwinCAT 3 which assigns separate tasks to individual cores, evenly distributing the CPU workload,” Beilke explained. Thanks to multi-core technology, it is common to run entire machines and a robot with one PC-based hardware controller. “Entire machines and multiple machine modules in a plant can share one hardware device depending on the application,” he said.
All in all, PC-based motion systems are starting to look a lot like self-contained systems. And that is changing, to some degree, how they are sold and distributed. Aerotech and AllMotion both said that regardless of how a manufacturer sells, application engineers still end up assisting users in selecting motion control components and often have a significant role in the subsequent application of the equipment. Trio Motion, however, pointed out that the more total machine control a motion system can handle, the more likely it is that the hardware and software will be bundled and offered as a solution. And this kind of bundling lends itself to sale via distribution rather than direct from manufacturers. This bundling also drives future feature development. As an example, one distributor requested better HMI support, according to Trio’s Ed Novack. “So we introduced an integrated HMI system. Often distribution drives product development this way to better meet industry needs.”