by Alex Owen-Hill on Oct 16, 2018 7:00:00 AM
How close can you get to a collaborative robot? Is it always safe to go near one? We explain the 5 spaces around a cobot which determine its safety.
“Yes, but is is really safe?”
This is a common question from first-time cobot users. Collaborative robots are designed to operate safely around humans, but how safe is really safe?
The issue of safety came up a few times at our recent Robotiq User Conference (RUC) in September. Jeff Burnstein from A3 made it clear that collaborative robots aren’t safe in all situations. UR’s Esben Ostergaard questioned whether cobots are too safe (with overly restrictive safety limits).

At the time, both Jeff and Esben were talking about about the maximum force that a cobot is allowed to apply if it collides with a human. But, there is another factor which is just as important when we’re talking about safety: distance.

Getting Too Close to a Cobot

How close should you get to your collaborative robot?

Should you take your cobot to the cinema? Invite your cobot to meet your parents? Or take your cobot on a mini-break to the Caribbean?

I’m joking, but it’s an important question. How close is too close with cobots?

With traditional industrial robots, getting too close can be fatal. But, you can easily tell where the line is: if the robot can reach you, you’re too close. To stay safe, you just put a safety fence around the perimeter of the robot’s workspace. Unless someone jumps over that fence (yes, people have done this!) then the chance of injury or death is slim.

Cobots are designed to work alongside people. They are designed so that they will not inflict harm. However, as our experts at the RUC discussed, cobots are not safe in all situations.

When a cobot is operated within its safety limits, the whole of it’s workspace can be safe. But, you might not want to use these safety limits in all areas of the workspace. You can split the area around the cobot into 5 distinct zones, each of which have different properties when it comes to safety.


2f-85 finger gripper on UR performing pick and place next to a human

Always perform a risk assessment before integrating your robot.

The 5 Spaces Around a Collaborative Robot

The ISO/TS 15066 defines the safety standards for collaborative robots. By following its guidelines, robot manufacturers and integrators can ensure that their cobots do not harm humans. You can find out all about it in our eBook ISO/TS 15066 Explained.

It defines 5 spaces around collaborative robots. As a robot programmer/integrator, it is your job to make sure that you use the right space for particular operations, otherwise the cobot may be unsafe.

1. Maximum Space

This is all the space that the robot is capable of moving in. It is related to the robot’s workspace or working envelope, which you can find on the manufacturer’s data sheet.

The difference between the workspace and maximum space is that the workspace only defines all points that the robot’s end effector can reach. The maximum space includes all points that the robot’s links could potentially enter. For example, you might have a large robot with small workspace (e.g. a delta robot). The maximum space will include the space that the body of the robot could occupy if no limits were in place.

2. Restricted Space

Few robots are able to move within all of their maximum space. In practice, part of its workspace will be unusable due to limiting devices, such as hard limit switches in the workspace, safety-rated axis limits, etc. This is known as the restricted space.

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