Collaborative Robot Safety
Machine Safety SpecialistsUpdated 10/07/2019
The term “collaborative robots” (“Cobots”) refers to power and force limited robots that are equipped with very accurate and safety approved force sensing capabilities. Collaborative robots can sense unexpected force and stop their motion very quickly if any abnormalities are found. Although they still cannot always avoid bumping into humans, they reduce their impact, preventing certain types of injuries, like crushing and impact injuries. This makes them far safer for human-scaled operations since they can work alongside humans and, in the case of human contact, will not severely injure anyone.
Collaborative Robot Risk Assessments
Risk assessments must be done with any type of industrial machine, whether it is an industrial robot or a collaborative robot (“Cobot”). However, it is especially important for collaborative robots since they operate autonomously, and may operate without any type of fence or guarding. Such risk assessments and resulting risk reduction measures greatly reduce the risk of a robot/human impact injury.
Most robotic safety requirements are taken from standards that are specific to industrial robots. The robotic industry has standards specific to collaborative robots that provide guidelines on the amount of force, pressure, and energy allowable for safe human interaction.
End users and integrators are required to complete risk assessments to prove that risks associated with the robotic application are within acceptable levels.
The term “robotic application” is important, because while the robot itself may have low risk, the entire robotic cell must be considered regarding its particular risks. If the robot has a hot or sharp surface as its end-of-arm tool, it may be dangerous for personnel working nearby. This is why all the aspects of a robotic cell have to be taken into consideration when doing a risk assessment.
What are Collaborative Robots?
Collaborative Robots (“Cobots”) are designed to work effectively directly alongside people in a factory setting, making it possible to deploy in environments which have historically been off-limits to robotic automation. Collaborative Robots combine a number of unique technologies designed to allow deployment without some of the traditional safeguarding described in ANSI, ISO, or other safety standards, based on the application’s risk assessment. Collaborative Robots are designed for:
- Physical interaction between a worker and a Cobot.
- Avoiding accidental contact
- Minimizing forces and stopping safely upon any human contact
Collaborative Robot Features
- Safety by Design: Collaborative Robots operate at human-equivalent speeds which are limited by their inherent design. This makes it easier for integrators to assess the risks associated with robot motion and allows nearby operators to avoid any unintended contact with the robot.
- Machine Safety: Collaborative Robots are designed with many protective features which govern operation and protect those working around them, such as electrical and physical braking systems and manual brake releases for manipulating the arm even without power.
- Contact Detection: Collaborative Robots typically directly measure torque at every joint, monitoring for sudden impacts, soft obstructions, or excess forces or torque.
- Redundant Internal Checking Systems: Various internal systems disable motor power and enable joint brakes if a control error or failure is detected.
Collaborative Robot Safety Standards
ANSI/RIA R15.06-2012, applicable in the U.S., is an ANSI/RIA adoption of ISO 10218-1 & 2. Collaborative Robots are power and force limited by inherent design as described in ANSI/RIA R15.06-2012 and ISO 10218-1: 2011. The most recent edition of ISO 10218-1 does not include these power and force limiting collaborative requirements, but instead points to the requirement in ISO 10218-2 requiring a risk assessment of the entire robotic application, and refers readers to Technical Specification ISO TS 15066:2016 for further guidance.
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