While robot original equipment manufacturers (OEMs) each offer their own tightly integrated controllers, recent developments now enable control by a programmable logic controller, or PLC. For facilities where PLC-based controls are already used in other machine control applications, the benefits of using one for the robot as well may be a better choice than using an OEM controller, depending on the application.

Speaking robot, simplified

If you're familiar with PLCs, as many engineers are, then you already know how to read, understand, and troubleshoot a PLC-based robot. What the robot should be doing and how to do it is still required knowledge, but the hurdle of learning a proprietary OEM control language disappears, and with it much of the training time previously required.

Moving to PLC-based robotic controls brings additional advantages as well, including common programming controls, software interfaces, program backup and restore methods, and program documentation.

Robotic material handling solutions naturally include robots. In addition, these setups incorporate complex systems that include infeed and discharge conveyors, pallet dispensers, transfer cars, and other equipment. System components are typically controlled via a PLC, so that the robotic controller and system controller must interface, coordinating data and interlocks to achieve the desired functions. Depending on the complexity of the application, this interface can be quite challenging. Several robotics companies are developing control options to simplify matters, including Yaskawa's Motoman Division and KUKA Robotics.

“As we studied the packaging and palletizing markets, we recognized the need for a unified control strategy,” says Steve Barhorst, president and chief operating officer, Yaskawa America Inc., Motoman Robotics Division. “These markets have engineers and technicians with extensive experience and expertise with PLC controls and programming. We view the development of our MLX100 Robot Gateway as an easy way for these users to adopt robotics into their packaging lines without the burden of having to learn a new robot programming language. Users now gain the flexibility that robots offer in a PLC-based platform they already understand. We still offer our standard robot controller, the DX100, for applications requiring process control, like welding, dispensing, and painting.”

PLC-based robotic controls supprt a much wider range of I/O hardware and communications protocols than OEM controllers do, in order to cater to a wide viariety of applications.

When the PLC that controls the robot is the same PLC that controls the other system components, it eliminates this interface point and greatly reduces overall system complexity. In addition, the controls hardware design for a PLC-based robotic controller can now utilize a common controls architecture with the system controls.

“KUKA Robotics worked with Rockwell Automation to develop the capability to control select KUKA four-axis robots to address demands from consumer packaged goods end users who were looking for a single integrated control solution for their packaging machines and robotics,” says James Cooper, KUKA Robotics Corp. “Additionally, they've requested a single point of operator interface for their automation solutions that involve traditional packaging machinery and robotics.”

In addition to shrinking the overall footprint by being housed in the same control panel, the design of the robot controls uses the same drawing nomenclature (for wire numbers and drawing numbers) as all the other hardware in the panel, thereby reducing the overall complexity of the control system design. Other benefits include simplified troubleshooting and maintenance, easier training, and common spare parts.

Flexible I/O and communication protocols

With PLC-based robotic controls, all hardware, I/O, and communications protocols available to the PLC are now also available for use with the robotic controls. This is particularly relevant when considering that large portions of proprietary OEM controller I/O communications are primarily for interfacing the robotic controller with the PLC. With this additional communication no longer required, the only interfacing necessary is to the I/O on the robot, which is as simple as any other I/O in the control system. What's more, PLC-based robotic controls support a much wider range of I/O hardware and communications protocols than OEM controllers, in order to cater to a wide variety of applications.