The world of collaborative robots, or cobots, is making headway. According to a recent report by the International Federation of Robots (IFR), along with Loup Ventures, global robotics spending will reach $13 billion in 2025. Currently, collaborative robots only make up about 3% of all robot sales. This number is expected to jump to 34% in 2025 [1]. These robots allow us to combine the repetitive performance of robots with the individual skills and ability of people. They are a great way to relieve employees from monotonous and strenuous tasks, and typically a company will create a return on investment with these robots within three to eight months. The major benefits of collaborative robots include:

• Better robot-human interaction and efficiency 
• Suitable for small-scale and mid-scale production
• Safer work environment
• Very easily programmed
• Greater flexibility in the human environment

It is important to be aware of the various safety hazards that are present in a collaborative robot system because a lack of safety can hinder the exponential growth that is underway. By creating an effective Hazard Analysis and Risk Assessment (HARA), the risk can be mitigated to a level that allows collaborative robots to reach their full potential.

Hazard Identification

In order to perform an effective HARA, the hazard analysis assessment should be performed collaboratively with the integrator (robot hazard identification) and the user (task identification).

Robot Hazard Identification

• Robot-related hazards
• Hazards related to the robot system
• Application related hazards

Task Identification

• The frequency and duration of operator presence in the collaborative workspace with the robot system
• The frequency and duration of contact between an operator and robot system with the drive power or application-related sources of energy active
• Transitioning between non-collaborative operations and collaborative operation
• Automatic or manual restart of robot system motion after the collaborative operation has been completed
• Tasks involving more than one operator
• Any additional tasks within the collaborative workspace

Biomechanical Limits

We must also look at the parts of the body that are being influenced. Different parts of the body have different pain thresholds, and the cobot must be designed accordingly. Biomechanical limits are set forth to prevent biomechanical load initiated by robot motion to create a potential for minor injury to an operator in the event of contact between the operator and robot. To properly analyze the biomechanical limits, the following need to be considered:

• The body region exposed to the hazard (fingers, hand, lower arm)
• Critical region avoidance – robot program MUST avoid head and neck body region
• Contact pressure; this is the most significant predictor of pain
• Contact area; a larger contact area will decrease the pressure

Power and force limited collaborative operation requires robot systems specifically designed to consider contact between the robot and the operator. This considers both intended and unintended contact situations. When biomechanical limits are exceeded, changes need to be made. This can include reducing the robot force function limit, redesigning a part or gripper to increase the contact area, or adding passive risk reduction measures. 

Watch Hazard Assessment and Risk Analysis of Collaborative Robots to learn more about this topic

[1] Robotics online marketing team, Collaborative Robots Market Update 2018, Robotics Online, February 2018