Safety solutions for intelligent human-robot collaboration

Human-robot collaboration (HRC) describes a work scenario in which humans and automated machines share a workspace. Driven by Industry 4.0, this model of collaboration promises highly flexible workflows, maximum system throughput and productivity, and economic efficiency.

One of the major issues associated with Industry 4.0 is making work processes flexible. At the extreme end of the spectrum, this may involve manufacturing unique items on a conveyor belt. This type of factory where products and production processes are one with state-of-the-art information and communication technology is becoming home to machines that are increasingly intelligent and autonomous.

Interaction between humans and machines is also set to increase in industrial manufacturing. Machines that are autonomous but primarily interact with humans require new safety concepts that provide effective support for making production processes more flexible.

Human-robot interaction: a question of space and time

Industry 4.0 is seeing a third form of interaction shifting increasingly into the spotlight: collaboration between humans and robots. This involves both humans and robots sharing the same workspace at the same time. An example of this is a mobile platform with a robot that takes parts from a belt or a pallet and transports them to a workspace, where they are presented and given to the worker stationed there. In collaborative scenarios such as this, the conventional safe detection solutions used for coexistence or cooperation are no longer sufficient — instead, the forces, speeds and travel paths of robots now need be to monitored, restricted and stopped where necessary, depending on the actual level of danger. The distance between humans and robots is therefore becoming a key safety-relevant parameter.

The risk assessment is always the first step — even for ‘cobots’

No two examples of human-robot collaboration are the same. This means that an individual risk assessment for the HRC application is required even if the robot concerned has been developed specifically to interact with humans. ‘Cobots’ like this therefore have many features of an inherently safe construction, starting from their basic design. At the same time, the collaboration space also has to meet fundamental requirements such as minimum distances to adjacent areas with crushing or pinching hazards. General standards such as IEC 61508, IEC 62061 and ISO 13849-1/-2 are one way in which the foundations for the functional safety of HRC applications are laid.

It is also important to give particular consideration to ISO 10218-1/-2, which concerns the safety of industrial robots, and ISO TS 15066, which relates to robots for collaborative operation. Developers and integrators of robot systems not only have to perform thorough checks on the structural safety measures taken by robot manufacturers, but must also consider any hazards or risks that may remain. This means carrying out a risk assessment in accordance with EN ISO 12100 for the robot system.

Safety-related operating modes of collaborative robot systems

These technical specifications can be used to discern four types of collaborative operation. The ‘safety-related monitored stop’ prevents robots from interacting with humans, while ‘hand guiding’ ensures safe HRC by guiding the robot manually at an appropriately reduced speed. The third type of collaboration, ‘power and force limiting’, achieves the required safety by reducing the power, force and speed of the robot. This takes place regardless of whether there is unintentional or intentional physical contact between robots and humans.

The ‘speed and separation monitoring’ type of collaboration is based on the speed and travel paths of the robot and adjusted according to the working speed of the operator. Safety distances are permanently monitored and the robot is slowed down, stopped or diverted when necessary.

Functional safety for HRC: expertise, portfolio and implementation from a single source

Safety-related sensor and control technology is facing new challenges, to ensure that HRC operations are unimpeded. The more the requirements imposed on the safety of shared work spaces, the more collaborative future work situations will become.

As a manufacturer of sensor, control and system solutions for functional safety, and a supplier of comprehensive safety services that range from risk assessment and safety concepts through to system solution implementation, SICK has extensive expertise in designing safe robot applications.

SICK offers a range of sensors and controllers that have developed along with the requirements of safe robot applications over the decades. Safety solutions based on various technologies are becoming more intelligent, making new HRC applications possible.

HRC only accounts for a small share of all applications involving human-robot interaction. Innovative solutions for functional safety in robot applications, like those developed and implemented at SICK, can help to increase this share significantly in the foreseeable future.