Drives and Controls Magazine
Mitsubishi enters cobot fray with precision six-axis arm
Published:  22 October, 2019

Mitsubishi Electric has announced its first cobot (collaborative robot). Although the company is entering the cobot market later than most other major robot-makers, it claims that its RV-5AS-D-S99 Melfa Assista will offer advantages in terms of accuracy and ease-of-programming.

For example, while many other cobots have positioning accuracy repeatabilities of around ±1mm, the Mitsubishi machine offers positioning accuracies down to ±0.02mm – comparable those of high-performance industrial robots. Mitsubishi says that the higher accuracy will open up a wider range of applications involving more delicate operations and smaller parts.

The six-axis cobot has a 900mm reach, a top speed limited to 250mm/s (although it can operate faster in a “co-operative” mode), and can handle payloads of up to 5kg. It complies with the ISO/TS 15066 guidelines on cobots, and has a smooth surface with no “pinch points” that could trap an operator’s hands or arms. The robot has a small footprint and could be used on a desktop or in an industrial work cell for applications such as machine loading, device assembly, testing and inspection.

The robot can be programmed via a PC, a touchscreen HMI, or by hitting a “save” button on the arm and guiding it through the required sequence of movements.

Mitsubishi has developed an intuitive Windows-based environment, called RT Visual, for programming the cobot’s motions. The software allows non-expert users to drag-and-drop icons to define the movements of the arm, and to simulate operations in 3D before the robot actually performs them. Initially available only for the collaborative robot, the graphical programming software will probably be extended to support other industrial robots in Mitsubishi’s portfolio at a later stage. All cables are routed internally, and the arm incorporates torque monitoring to sense any collisions.

A six-colour LED ring that encircles the robot’s “forearm” provides a quick visual indication of its current status, with each colour identifying a different mode of operation, alarms or faults. An on-arm keypad can be used to start and stop the robot, to reset errors, or to teach it tasks.

In a direct control mode, the operator can manipulate the arm into position by hand with controlled force. This position can then be stored and added to a motion sequence or attributed to a command without needing to open the programming tools.

Mitsubishi Electric’s collaborative robot offers similar levels of accuracy to conventional industrial robots

Mitsubishi says that the new cobot will have a similar service life to its other industrial robots – some of which have been operating for more than 30 years.

One reason that company has been slow to enter the cobot market is that it believes that many tasks currently being handled by cobots can be performed faster by using conventional robot arms in conjunction with appropriate safety measures. It says it has won previously business from companies that have tried to use cobots for particular tasks but found them too limited.

“Many potential cobot applications are better handled by a traditional robot with a light guard,” says Mitsubishi’s UK marketing and operations group manager, Chris Evans. “You need to choose the right robot for what you want to do.”

The new cobot is due to go on sale in the first quarter of 2020 at a UK price of around £26,000 ($33,600). Other models could follow.

“Accuracy and ease of use have taken a significant step forward with this product,” says Mitsubishi’s UK robot product manager, Barry Weller. He believes it will “open up new opportunities for cobots in a number of sectors”.