What Makes Collaborative Robots Ergonomic?

We talk about collaborative robots being "ergonomic" but what do we really mean? In this post we introduce the basics of ergonomics and find out how ergonomic principles are applied to the design of collaborative robots. We also find out that there's more to cobot ergonomics than first meets the eye.

Look at most of the popular collaborative robots and you will notice some similarities: smooth links, rounded corners, and encapsulated joints. To be able to work alongside humans, collaborative robots are designed to be ergonomic. Rounded corners and links ensure that there are no sharp edges which could cause harm if the robot collides with a person. Encapsulated joints provide no pinch points, which could trap a human hand.

These things are what I think about whenever the term "ergonomics" is applied to collaborative robotics. However, the mechanical design is only one of several ways that ergonomics is relevant to collaborative robotics. In fact, from one perspective, collaborative robotics is all about ergonomics!

In this post we cover the basics of ergonomics and explain how it is an integral part of getting the most from cobots.

The Two Types of Collaborative Robot Ergonomics

The word ergonomics comes from the Greek words "ergo" (meaning work) and "nomos" (meaning laws). The science of ergonomics looks at how products can be designed so that they decrease fatigue and discomfort of human users. It has produced a set of "work laws" which can be applied to reduce injury in the workplace.

In the upcoming International Digital Human Modeling Symposium in June 2016, a paper from researchers at ISIR in Paris explains where collaborative robots fit in to modern workplace ergonomics: "Work-related musculoskeletal disorders (MSDs) present a major health problem in developed countries [and] and affect almost 50% of industrial workers. Assisting workers with collaborative robots can be a solution when a task is physically demanding yet too complex to be fully automatized."

Collaborative robotics is one tool that we can use in the workplace to combat MSDs, and other health problems which are caused by poor ergonomics. The researchers of the paper are looking at tasks where the robot and human are physically interacting with each other, rather than the robot merely working alongside the human as most current cobots do. Physical interaction introduces some more complications: the robot solves ergonomics problems in the workplace, but it could also itself harm the human if not ergonomically designed. However, ergonomics is important even when cobots are not continually interacting with workers.

We can split collaborative robot ergonomics into two parts:

1. The ergonomics of the robot itself, as a product used by humans.
2. The ergonomic issues of the task, which are solved by using the collaborative robot instead of a human worker.

In the rest of this post, we'll look a bit closer at both of these.

The Ergonomics of a Collaborative Robot

Ergonomics should be considered for any products which are designed for humans to physically interact with them. We have all experienced using pieces of technology, often cheap, simple ones, which seem to have been designed by someone who has never used the technology themselves. You can usually tell when something has been ergonomically designed because it feels easy to use, almost like an extension of your own body.

Good product designers incorporate ergonomics by looking at the shapes and proportions of the human body. They often use anthropometric databases, which provide average proportions of the body for different populations of people. There are also many useful guidelines on how to design products ergonomically.

Traditional industrial robots didn't have to incorporate much ergonomics, as they weren't designed for human interaction. Collaborative robots, on the other hand, must interact physically with people. There are a few ways that they can be designed ergonomically, including:

• Smooth mechanical design - Reducing pinch points and sharp edges is a key part of ergonomic product design, and a bare minimum for collaborative robots. If you look at the last joint of a KUKA Lightweight Robot, for example, you will see a rounded gap which is big enough to fit a human hand. This removes a key pinch point of the manipulator and it is likely that designers used antropometric data to design this gap.
• Reducing harmful vibrations - Vibratory hand tools, such as drills, can cause damage as a result of prolonged exposure. This becomes relevant for collaborative robots when there will be sustained physical contact, such as with hand guiding. Robot designers can reduce the effect by ensuring that control systems do not cause excessive vibrations.
• Gravity compensation - Some collaborative robots, such as Baxter, can be programmed by physically moving the arm around. Without some form of gravity compensation, this could cause stresses on the human operator if they had to do it a lot, as robot arms can be quite heavy and awkward to move.
• Contactless control - One way to reduce mechanical stress on users is to use contactless control, such as the research project we reported on in 2014. This is still largely at the research stage but could become more common as the technology improves. However, this approach wouldn't remove ergonomic issues completely, as new issues would arise regarding the gestures and posture of the human operator.

The more that physical interaction becomes part of collaborative robotics, the more that designers will have to incorporate ergonomic factors into the product design.

The Ergonomics of a Robotic Task

The second ergonomic consideration for collaborative robotics are the ergonomics of the task that the robot is performing. Tasks involving repetitive motions, for example, are perfect for a robot because they are often the type of tasks which can cause humans to develop MSDs and other injuries. Reducing ergonomically-related injuries is one of the top benefits of using collaborative robotics, alongside their productivity benefits.

Ergonomics are applicable to many of the tasks which workers carry out in your workplace. Therefore, in order to get the most benefit from a collaborative robot in this regard, you will have to start thinking about the workplace ergonomically. Professionals from the field of ergonomics sometimes talk about having "ergonomics glasses," by which they mean that you start looking at routine tasks from the new perspective of ergonomics.

Once you start thinking how you could reduce a task's physical stresses on human workers, you will begin to notice many places where collaborative robots could be used to help. See our previous post for a list of some of the tasks where collaborative robots can reduce ergonomics problems.

How could collaborative robotics improve ergonomics in your workplace? Are there any ergonomic issues which robots couldn't solve? Have you already had successes in reducing injury with collaborative robots? Tell us in the comments below or join the discussion on LinkedIn, Twitter or Facebook.