Web-based design tool for better cobot safety

The safety of people interacting with robots has top priority, especially when humans and robots are working side by side instead of being separated from each other by safety fencing. The Fraunhofer Institute for Factory Operation and Automation has created a free web-based design tool that helps companies design their cobot implementations. The Cobot Designer helps minimise the risk of accidents and increases employee safety.

Humans and robots are sharing workspace in more and more sectors, whether they be manufacturing, logistics or medicine. Safety plays a major role in this. Up to now, range-finders on robots have prevented severe impacts or crushing when collisions occur but these sensors do not function when humans and machines have to stand close to each other, for example in subassembly — this requires other solutions. The Fraunhofer IFF web-based application, Cobot Designer, ascertains the robot speeds that ensure safe collaboration. The design tool helps programmers design cobot workstations safely. The project was contracted by the German Social Accident Insurance Institution for the Woodworking and Metalworking Industries (BGHM).

Anyone acquiring cobots for their business must perform a legally required risk assessment: companies must identify specific potential hazards and foreseeable misuse by employees beforehand. The maximum speed a robot is permitted to reach is measured when it is certified for safety — a special device measures impact forces and pressures that act on anyone who comes into contact with the robot. The limits set in the ISO/TS 15066 standard may not be exceeded, otherwise, the robot’s speed would have to be reduced to prevent injuries to employees caused by clamping or impact.

However such measurement is costly and requires expertise, and the robot must then be programmed accordingly.

“Small businesses in particular can’t afford this,” said Dr Roland Behrens, research scientist at the Fraunhofer IFF. “What’s more, measurements are taken too late since the robot has already been purchased. This is where our Cobot Designer for digital hazard prevention comes into play.”

Companies can use the interactive tool before a making a purchase to assess whether the robot’s speed suffices to perform a particular job productively and, above all, safely.

“The amount of force is contingent on the robot’s speed,” said Behrens. If limits are exceeded, productivity subsequently suffers. “Let us assume the robot has to pre-sort a pallet in one minute. If the speed has to be reduced by 50% for safety reasons, the cycle time increases to two minutes, reducing the robot’s economic efficiency 50%. That’s why being able to perform an economic feasibility analysis before purchasing a robot would be desirable.”

The Cobot Designer is intended to prevent bad purchases and more potentially necessary measurements. Using the design tool will enable businesses to reduce their engineering work significantly when they implement future HRC applications.

“The goal is to use computer simulation, as the Cobot Designer does, to dispense with measurements entirely in the future,” said Behrens.

The tool is available for free online to anyone designing an HRC workstation, and runs on all browsers. The user merely has to enter the parameters for the robot, the hazard and the tool used, eg, a gripper. The Cobot Designer automatically computes the effect of contact between a human and the robot as well as the robot’s maximum permissible speed. The tool also provides the option of loading proprietary, custom robot models.

Various biomechanical robot and hazard models constitute the technological basis. The user can combine different robots, hazard situations and tools, thus compiling and continuously expanding a catalogue. All the data entered can be downloaded and reused at a later time, and inputs are not stored on the Cobot Designer’s server to protect data.

The biomechanical model precisely simulates the extent to which clamping and impact stress a person. It comprises all 29 relevant body parts where a person can feel pain, including the head, for instance. This model draws from the results of the one and only human subject study in the world to ascertain biomechanical limits, which was conducted by the Fraunhofer IFF and contracted by the German Social Accident Insurance DGUV and the BGHM. The Fraunhofer IFF validated the results of the Cobot Designer’s simulation experimentally in stress tests with human subjects together with physicians from Otto von Guericke University Hospital’s Traumatology Clinic and with the involvement of the appropriate ethics commission. The tests ran from 2015 to 2019.

Image: Users can combine different robots, hazard situations and tools with the design tool, thus compiling and continuously expanding a catalogue. © Fraunhofer IFF.