Functional safety in human/robot collaborations

One of the major issues associated with Industry 4.0 is making workflows flexible with a closer interaction between humans and machines.

Tobias Maillard writes on how human/robot collaboration (HRC) can be achieved safely. Part of the current move towards more integrated working is a need for humans and machines to work together safely, and in view of this, functional safety will take today’s production systems one step closer to more flexibility.

Productivity is improved as the robot station is mobile and can be used at designated stations as necessary.

There are different forms of automation depending on how humans and machines work together. If the ultimate goal is complete collaboration – where humans and robots share the same workspace and carry out their work at the same time – then it makes sense to develop solutions that employ coexistence or cooperation as initial steps toward this.

Doing this requires not only an in-depth understanding of robotics applications, but also expertise in assessing risks and access to the right portfolio of safety solutions.

Every process in developing HRC systems starts with a risk assessment. To conform to the Machinery Directive, an extensive assessment of possible hazards must be carried out for every machine as defined in EN ISO 12100.

As robot systems have to complete motion sequences that are usually very complex, the robot safety standard EN ISO 10218 also requires that each motion sequence is analysed in addition to hazards being assessed. Environmental factors and basic conditions associated with the HRC application must also be considered and documented in the risk assessment.

These are absolutely essential steps in defining what form the appropriate safety measures should take. Creating solutions for the various safety measures required in human/robot collaborations incorporates a whole range of technology types and components, which have to work together as efficiently as possible and avoid any impact on the workflow – and thus on productivity.

In response to this, SICK offers various harmonised safety solutions that make it possible to map the safety function in full, whether it is being retrofitted in existing plants or integrated into new ones.

Not only that, machine and plant manufacturers – as well as system integrators – are given consistent support when putting their protective measures in place. In this case, a plant walk-through is followed by the risk assessment of the specific HRC solution and a safety concept tailored to suit the exact needs of the application is created.

Types of HRC

Coexistence: this type of HRC could be an insertion station with a rotating table on a welding robot cell, in the automotive industry for example.

Following a risk assessment, the hazard is posed by the rotating table, since the robot is operating in an area which is fenced off and, therefore, secure. For protection, a vertically mounted safety light curtain, such as the deTec4 Prime, functions as a primary protective measure to shut down the rotating table.

A cascaded, horizontally mounted light curtain monitors whether there are any objects in the safety area (presence detection). Productivity improves as the rotating table is able to restart automatically once the horizontal protective field has been released.


This type of HRC could be at a transfer station, where a worker gets preassembled modules ready for an assembly robot. The robot grabs one module each time and brings it to the final assembly process.

Following a risk assessment, it is noted that occasionally the robot and the worker are in the transfer station area at the same time. When the worker inserts the modules, a hazard may be posed by the robot moving at high speed. For protection S3000 safety laser scanners with 4 simultaneous protective fields, combined with the Flexi Soft safety controller (Sim-4-Safety) could be used.

Violating protective fields 1, 2, or 3 triggers a reduction in the robot speed, violating protective field 4 activates a safety-monitored stop. Productivity improves because instead of coming to a complete stop, the robot initially continues working as the worker approaches it. Its movement is stopped safely only once the worker is in the direct vicinity of the transfer station (protective field 4).

Once protective field 4 has been released, the robot continues working. Collaboration: this type of HRC could be attaching non-rigid parts in an electric motor assembly. For example, a safely monitored robot on a mobile work station takes assembly groups from the conveyor belt and presents them to the worker in an ergonomic position.

Following a risk assessment, it’s noted that the robot’s movements may cause collisions, shearing, and crushing. For protection, horizontal hazardous area protection with microScan3 Core safety laser scanner could be used, as well as limiting the Cartesian workspace and the robot’s force and torque; plus monitoring its working speed when the protective field is violated.

Sheathing the robot tool in an ergonomically shaped housing will also reduce hazards. Productivity is improved as the robot station is mobile and can be used at designated stations as necessary. The robot grabs the right devices from the conveyor belt and carries out subsequent steps on the workbench independently.


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