Collaborative robots: Hazardous zones/ moments for production lines and factories

Robots were invented to help the human beings doing the repetitive tasks and to use the time productively. Large scale manufacturers have most of the production line automated with the help of robots. At the beginning of the industrial robotic history, robots were meant to be sturdy, powerful and enduring and were designed to do the heavy and repetitive tasks. Since then the technological advancement has allowed the robots to work on more sophisticated tasks, but still robot is a machine which cannot replace the human experience and expertise. Industrial experts believed that the production flow can be improved by having the best of robots working alongside the best of humans.

In the year 1996 collaborative robots which are also known as ‘COBOTS’ were invented. The reason why cobot’s were invented was to find a way through which people can safely work with a robot- or robot-like equipment. In simple words collaborative robots (a new kind of robot) is sharing the workspace which is safe enough for humans to work in. The safety is ensured with the help of the sensors attached with the cobot, but still 100% safety cannot be assured. The robotic system and its environment should be meet convinced level of safety, before considering it safe enough to be collaborative. The safety standards that were created for the robots needs to be modified for cobots which can be found in NEN-EN-ISO 10218-1 and NEN-EN-ISO 10218-2. First question which crosses the mind is “how to govern if a potential hazard exceeds acceptable standards for safety or not? The answer is quite simple, by doing ‘Risk Assessment’. Risk assessment is tool of analysing the risk associated with the Cobots and check if they are within the allowable threshold mentioned in the safety standards.

Hazard Identification

Physical/ (structural) hazards Past Present (in use/ life time) Future
Product Environment PH1.  Failing to account for objects. (e.g. sharp objects, hazardous object). PH2. Safety cage placed at improper location, infrastructure not able to provide proper support to the cobot structure. PH3. Complex collaborative workspace creating potential causes for hazards.
Product PH4. Instability in the structure or design. PH5. Demand for Cobots having high capacity leading to hazard. PH6. Advancement in technologies leading complex structure of cobot and difficulties in handling.
Components PH7. Components wear out due to excessive usage, exposed electrical wires. PH8. Errors in programming a cobot. PH9. Cobots connected with IoT (without information about each other) leading to damaged components.

Functional hazards Past Present (in use/ life time) Future
Product Environment FH1. Objects in the surrounding misjudged as humans by cobot’s sensors. FH2. Cobot working with hazardous material or hazardous atmosphere caused damage to sensors. FH3. Collaborative robots working close to each other may act as obstacle to each other and collide.
Product FH4.   Unexpected behavior of robot is likely to happen during tests. FH5.  Worker hits or is hit by the robot due to error in procedure or machine. [6] FH6. Use of AI in Cobot and overruling commands of operator (experience) leading to hazard.
Components FH7. Safety system may be disabled or not working properly FH8. Failure of cobots components such as drive motor, actuators, end-effectors. FH9. When connected to other cobots with IoT can receive multiple signals at a time due to error.
Operational hazards Past Present (in use/ life time) Future
Product Environment OH1.  The operator can accidentally enter robot workspace and collide with the robot moving at high speed. [2] OH2.  The robot collides with an operator while being hand guided by another operator. [2] OH3. Danger of cyber-attacks.
Product OH4. Intentional or intentional misuse of the cobot by unauthorized person. OH5. Operating the cobot without knowing its capacity and capabilities. OH6. Insufficient knowledge of  maintenance worker about new technologies (AI, IoT) introduces error in system.
Components OH7. An operator accidentally engages mode-change button though the collaborative task is incomplete. [2] OH8. Interfacing problem between software and hardware due to upgradation of software. OH9. Hazard situation created due to AI in each cobot working as an individual unit.

Design for safety

Designing for safety for Physical Hazards

  • Physical Hazard (PH1)’s risk can be eliminated by designing the end-effectors (i.e. different type of end-effectors can easily fit the collaborative robot) which can handle any sophisticated objects.
  • Physical Hazard (PH2) can be removed by designing the base of the robot which will adjust to uneven surface.
  • Physical Hazard (PH4) is not a result of design fault (still its risk can be reduced) and it will be discussed in the control measure section 8.
  • Physical Hazard (PH7) by designing process (i.e. while designing collaborative robot consider design for maintenance as a design aspect) which helps maintenance team to easily maintain the cobot.
  • Physical Hazard (PH5) can be reduced by including placement of proximity sensors in the cobot which while carrying task on heavy loads will stop working if human presence is detected in the collaborative workspace.
  • Physical Hazard (PH9, PH6, PH3) are the situation that can occur keeping in mind the future trends of collaborative robot. They can be eliminated by including a provision in the software were details about existing cobots are installed which help to know the capacity & capability of the other cobots and it does not push it beyond certain point. It can also help the programmer by suggesting the interacting possibilities between two collaborative robots.

Designing for safety for functional hazards

  • Functional hazard (FH1) can be eliminated by installing a temperature (thermal) sensor in the cobot which will activate the stop working if human presence is detected.
  • Functional hazard (FH2) can be reduced by selecting a material for the collaborative robot which can resist the adverse condition in the environment.
  • Functional hazards (FH4, FH5, FH7) will be discussed in the control measures part in the next section 8.
  • Functional hazard (FH8) can be minimized by having a higher factor of safety while designing the collaborative robot which will reduce *the change of functional failure of components.
  • Functional hazard (FH6) can be taken care be designing a “kill switch” in the Collaborative robot which will be used by the operators when the cobots approaching a hazard.
  • Functional hazard (FH9) can be reduced be programming the software in such a manner that if receiving signals are clashed priority will be given to the task given in the preference list by the operator.
  • Functional hazard (FH7) can be removed by using IoT where two collaborative robots working near each other are always aware of each other’s position and if there is a possibility of collision one of them will reduce its speed (delay the operation) till other cobot is out of the way.

Design for Safety for Operational hazard

  • Operational hazard (OH1) can be taken care of by including proximity sensor which will stop when human enters the restricted area during that function.
  • Operational hazard (OH8) can be reduced by making the program in such a manner that it will display “caution message” whenever a software is updated, and the operator can check if any changes happened due to the upgradation.
  • Operational hazard (OH3) does not have a design solution but for a safety purpose if the cyber attack is identified all the systems (cobot) will be automatically switched off until the problem is resolved, and it can only resume its work with the help of operators.
  • Operational Hazard (OH7) can be eliminated by designing a signaling system in the cobot which will tell the operator that the task is still not completed, and he should stay away from the area.
  • Operational Hazard (OH2, OH4, OH5) will be discussed in the control measure section 8.
  • Operational Hazard (OH6) can be reduced by making the IC’s, Components of technologies (AI, IoT) are kept in a casing which can avoid damage to them when maintenance work is done.

Control Measures

Control measures are actions that are taken to prevent or reduce the occurrence of a hazard that has been have identified. Hazards (PH4, FH4, FH5, FH7, OH2, OH4, OH5)’s risk can be reduced by implementing control measures in and around the system and its environment. Control measures are required most when the risk from the hazard cannot be reduced by making changes in design or if they unpredictable or unknown. Current safety standards (ANSI/RIA R15.06 and ISO 10218-2) have begun to consider collaborative robots as a new source of workplace hazards, and a new technical specification (ISO/TS 15066) reports the safety attentions involved in creating a collaborative robot system.

Control measure for collaborative robots are as follows:

  • Comprehensive training for operating the collaborative robots and workshops for imparting knowledge about the new system and technologies to the workforce.
  • Warning signal and sound alarms should be placed to indicate a unsafe area and stop personnel from entering it.
  • Safety cages should be placed around the robot workspace (excluding collaborative workspace) to avoid people entering that zone.
  • Proper safety gears should be issued to the workers to reduce the damage.
  • Safeguarding devices such as sensors should be installed to detect human presence in the restricted area.
  • System or device which will allow only authorized personnel to enter the area.
  • Minimizing the human-machine interaction (i.e. human should be present in the collaborative workspace only for an assigned task).