When developing its new collaborative robot, Mitsubishi Electric needed to take a number of design aspects into consideration – not only from a productivity point of view but also, perhaps more importantly, to ensure complete safety for the end user. Rachael Morling reports



obots have been used in industry for many years, automating such tasks as

manufacturing and assembly in a wide range of industries, from automotive to electronics production. When you think of a robot in operation, however, you may picture a machine surrounded with safety guarding systems to protect personnel against injuries. But, for some applications, a certain degree of interaction between the robot and user is necessary – users have been known to remove safety guards in order to do this. Robot technology has moved on greatly over

time, enabling the machines to be used for even more tasks, but one of the most recent developments is robots which are capable of working safely alongside humans – without the need for physical safety guards. So when Mitsubishi designed its new range

of collaborative robots there were a number of points that needed to be taken into consideration. For a start, the robot needed to offer the highest levels of safety – after all, it needs to be helpful while allowing a high degree of autonomous interaction with a human operator. As Mitsubishi explains: “Unlike an assistive arm used frequently for manipulation of heavy objects on car assembly lines, for example, or an industrial robot that works at high speeds but merely slows down or stops in the presence of a human operative, a cobot has to be interactive.” Another design aspect was ease of use –

teaching the robot how to carry out tasks would need to be both quick and intuitive for the user. Alongside these features, of course, were the need for flexibility, high positional accuracy and reliability. The company has therefore designed and built


the RV-5AS-D-S99 MELFA Assista collaborative robot. According to Barry Weller, product manager: “Accuracy and ease of use have taken a significant step forward with this product, which is the culmination of technical development as well as many hours of field testing and user feedback. I believe our latest MELFA Assista collaborative robot opens up new opportunities for cobots in a number of sectors.”

UNDER DEVELOPMENT So how did Mitsubishi meet the requirements when building the new cobot? With safety one of the key customer

demands, a sophisticated solution that guarantees operational safety alongside flexibility and high positional accuracy was the aim for the design team. As a result, payloads are relatively low as the arm is force limited for safety. Being responsive in terms of touch sensitivity limits the overall speed. Positioning accuracy, however, is comparable with industrial robots, the company explains. The safety features and technical specifications

of the new robot are therefore in accordance with ISO/TS 15066 guidelines on ‘Robots and robotic devices – Collaborative robots’. To meet the demands for ease of use, the

robot can be programmed in a number of ways: via a PC, touch screen HMI, or simply by pressing the ‘save’ button and teaching the arm through the required sequence of movements. As Mitsubishi explains: “Adjusting the sequence

or the positions held is just as quick and easy which makes the robot an adaptable, easy to teach, assistant that is totally consistent with its repeatability. This makes it ideal for complex and/or delicate assembly, work holding or pick and place tasks where the operator will have a

preferred way of working and will benefit from the robot’s assistance to complete the task or sequence of operations. This is particularly true of high-value manufacturing such as jewellery, electronics and life-science applications.” Furthermore, with positioning accuracy

repeatability as low as ±0.02mm, the new robot is comparable with high performance industrial robots, opening it up to use in a wider range of applications that deal with delicate operations and smaller parts. Additional features built into the machine

include a six-colour LED ring on the robot’s ‘forearm’ that shows the arm’s current status, with each colour used to identify a different mode of operation as well as alarms or faults. This feature sits next to the keypad that provides an intuitive interface to ‘teach’ the robot a task to perform, as well as to start and stop the robot or reset errors. This position can then be stored and added to the existing motion sequence or attributed to an individual command without the need to open the programming tools. It is also possible to programme motion

sequences via a new and intuitive programming environment, called RT Visual, that can run on conventional PC operating systems. According to Mitsubishi, the new RV-5AS-D-

S99 MELFA Assista collaborative robot will allow companies to automate a broad range of production line processes – from machine loading, device assembly, kitting and un- kitting of parts, to testing and inspection. It is due for commercial release in the UK during the first quarter of 2020.

Mitsubishi Electric


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