New Controller Handles High Speed Motion of Multiple Axes

Over the past 50 years, control vendors have developed various controls to meet specific industry needs. Distributed Control Systems (DCS) met process industry needs for controlling pressure, temperature, and flow. Programmable Logic Controllers (PLC) meet applications where sequencing, count, and timing are key metrics. Industrial PCs (IPC) came about to take advantage of the easy programming and HMI benefits of personal computers. Programmable Automation Controllers (PAC) emerged to combine the functions of both PLCs and PCs to handle the higher loop rates, need for advanced control algorithms, analog interfacing, and integrate more seamlessly with the enterprise network. PACs typically have redundant processors, a single database, function block language, high-speed logic, component architecture, and online programming.

According to control developer Omron Industrial Automation, the latest industrial applications challenge the functions of these controllers, fostering the need for a new controller. As automation technologies take over the movement of product during setup and production, there’s a need for a control that can handle high-speed motion with multiple axes. In this type of application, movement must be fast and accurate. Controllers not designed around motion often have inherent architecture barriers to performance when used to increase throughput, yield, and uptime. Consequently, machine manufacturers are forced to coordinate and synchronize the controller across motion, vision, logic, and safety actions.

“We started a new category called Machine Automation Controller (MAC) where the most important attribute is motion performance,” said Bill Faber, commercial marketing manager for automation products at Omron Industrial Automation. “A MAC can handle applications that require a high level of synchronization and determinism as it integrates multiple technologies: motion, vision, logic and I/O—all without sacrificing performance. Omron’s NJ-Series controller is an example of the emerging MAC.”

A MAC features an advanced real-time scheduler to manage motion, network, and the user application updates all at the same time to ensure perfect synchronization.

Updating all three in the same scan is unique to the NJ Series MAC, claims Omron. System synchronization occurs when the user application program coordinates with the motion scheduler, the network servo drives, and ultimately controls the motor shafts. With each motor shaft synchronized with each other, what is true for two axes is true for nine, 17, or even 64 axes.

“There are many 8-axis and 16-axis controllers on the market,” noted Faber. “If there is a need to expand the coordination of motion beyond that number of axes, another motion module is typically added. However, this is where many other controllers fall short, because the application requires synchronization across expansion and scalability of motion, through to the network, and back to the application program into the motion scheduler. MACs have this capability.

The controller must be deterministic to accurately coordinate all axes in the system. All this points back to the main driver: to increase throughput, the system requires the axes to remain synchronized with great repeatability to guarantee higher throughput, yield, and uptime.

Over the past 50 years, control vendors have
developed various controls to meet specific industry
needs, ranging from Distributed Control Systems (DCS),
to Programmable Logic Controllers (PLC), to Industrial
PCs (IPC), and finally to Programmable Automation
Controllers (PAC). The latest addition to this lineup is
the Machine Automation Controller (MAC) where the
most important attribute is motion performance.

Noted Faber, “Uptime is not necessarily just a factor of the equipment itself. It’s also a factor of the production process. If motion is not accurately controlled to match the process, when speeds are increased, the result is bad parts as the machine goes slightly out of control. This clearly impacts uptime because upstream and downstream processes need to be readjusted as well. For the next generation of platforms, machine builders need to be assured their architecture will allow them to expand throughput and yield without the platform becoming a bottleneck.”

The MAC integrates multiple, specialized controllers with exacting system synchronization to deliver high performance throughput on a single controller. For example, here’s how the MAC would function in a simple application such as a vision guided, Cartesian pick-and-place robot.

There are two parts: the setup and actual production. The coordinate system of the camera must match with the coordinate system of the Cartesian robot. To get the camera data to the controller in a coherent form, a lot of time is spent developing the protocol. Previously, this might have taken the combined efforts of an articulated-arm robot manufacturer, a third-party vision system engineer, and a PLC vendor. There could be three different systems from three different companies using three different technologies. At this point there would be three engineers in a room to figure out how the systems can communicate with each other for commissioning. A MAC allows these technologies to converge together so protocol development can be completed in a matter of hours. A real-time network passes vision data to the motion system without losing a scan. But this capability is only possible if vision and motion are on the same network.

Consider another challenge—adjusting servo parameters on the fly. This challenge can create performance loss if the whole system gets overloaded with a high number of axes moving at high speed with full synchronization. According to Atef Massoud, motion and drive engineer for Omron Industrial automation, “With a lot of machine controllers, there is a loss of speed if synchronized motion control is combined with a large number of axes, and there is a need for adjusting servo tuning at the same time. Non-MAC systems require additional CPUs to accomplish this.”

Today’s benchmark to qualify for the MAC category is processing 32 axes and updating in 1 millisecond. “There were many earlier attempts to create a multidisciplinary controller,” said Shawn Adams, Omron’s Director of Marketing. “PACs were the most prominent. There were attempts to apply them to process control, to cell control, and to machine control; but the PAC had to have an extensive operating system. Also, for really high-speed motion control, that controller and configuration required many CPUs. The performance of motion control will drop as the number of axes increases.”

Where MAC Applies
According to Faber, the market for MACs is where the motion market, the vision market, and the PLC market have common requirements.

The MAC integrates multiple, specialized controllers with exacting system synchronization to deliver high performance throughput on a single controller.

Imagine yogurt packs traveling on a conveyor. They get inspected, checked, picked up by a series of spider robots, put in boxes, lined up in cartons, and so forth. Before the MAC, this line would have many controllers, each needing to be coordinated—the vision controller, the robot controller, the motion controller, and, on top, the PLC that sequenced all of them.

This is a typical application where customers have been asking for one controller and one software application that gives information on what is happening on the production line from vision inspection, to pick-and-place, to synchronization of the robot with the conveyor, to packing and palletizing at the end of the line. MAC meets these requirements, streamlining operations by reducing the amount of equipment and integration traditionally required when different systems are linked together.

Machine innovation exposed controller inefficiencies that led to the development of machine automation controllers. Now that MACs have emerged, further machine development incorporating their advances will continue evolving, with motion at the core.

::Design World::