Releasing the Cobots: Five things you need to know

A robot revolution is on a march. If they have not arrived at a factory near you just yet, they probably will do soon.  With an explosion in the types of compact, lightweight, affordable and adaptable ‘collaborative’ robots, comes the prospect of an off-the-shelf commodity for almost any production hall or warehouse.  

It starts and ends with productivity

The whole point of investing in a robot is to add versatility and flexibility to your workflows. So, you don’t want be forced to implement a safety system that will restrict the very productivity you are trying to improve. 

Implementing safety for a collaborative robot might seem complex or daunting. But, with the right approach, it’s entirely possible to implement a safety system that will protect people without sacrificing machinery uptime, keeping stop-start operations to a minimum and limiting the safe protective area needed around the robot.

A risk assessment is essential

Just because a cobot comes ‘off-the-shelf’ with a safety-rating from its the manufacturer does not mean it is safe for that application. Just as with any other machine, the risk assessment must consider both whether the hardware inherently safe, and whether the application is safe.

The relevant safety standards

The international harmonised standard EN ISO 10218-2 specifies safety requirements for the integration of a robot and, unless the results of the risk assessment determine otherwise, requires the safety-related parts of control systems to be designed to comply with at least PLd (ISO 13849) or SIL2 (IEC 62061). As a supplement to this standard, the technical specification ISO TS 15066 contains further requirements and guidance on the safety of industrial collaborative robots. 

Collaborative means different things

Manufacturers are putting collaborative robots, or ‘cobots’ to work on a variety of tasks, such as machine tending, pick and place assembly and materials loading and unloading. There are different ways in which human and robots can work together, and each will require different safety measures, according to the risk assessment, to meet the relevant standards.

Coexistence:  Someone may still need to enter the robot's workspace, e.g. for maintenance, but there no human intervention during the production process itself.  

Cooperation:  The operator and robot complete stages of a process in the same workspace but at different times.  

Interaction: Humans and robots interact fully in the same process at the same time.

ISO/TS 15066 provides detailed guidance for collaborative robot operations when a robot and people share the same space. It describes a number of methods, or safety features, that can be used to implement safe collaborative operations. 

For example, where humans and robots are fully interacting, the force, speed, and movement paths of the robot must be restricted.  If they are available, inherent safety measures or additional safety measures, such as limiting torque through the drives or safety-related parts of the system controller, can be used to minimize risk. Force, speed, and movement paths must also be monitored and controlled based on the degree of risk. 

There are single-source solutions available

As with any other machinery, it is always wise to seek advice from a manufacturer or integrator about your specific application. However, there are single-source solutions available that could make life easier. 

SICK’s Safe Robots Area Protection is a convenient, easily integrated, single-source safety system for collaborative human-robot applications that satisfies Performance Level PLd/SIL2 in accordance with EN ISO 13849-1/EN 62061.

The solution deploys a SICK safety laser scanner and a SICK Flexi Soft controller to create a warning field outside two protective fields. Depending on how close the person is to the robot, the robot is either slowed to a safe speed or brought to a stop.

Dr Martin Kidman is a product specialist for Machinery Safety at  SICK (UK), FS Engineer (TÜV Rheinland).