As robotic systems transition from behind improved cages to collaborative, fence-free environments, the complexity of ensuring safety has skyrocketed. A static risk assessment is no longer sufficient for dynamic machines.
Whether you are deploying a traditional 6-axis industrial arm or a fleet of autonomous mobile robots (AMRs), a robust Risk Assessment (RA) is the cornerstone of a safe deployment. Here are the best practices for conducting effective risk assessments in modern robotics.
1. Define Limits Early (The "Use Specification")
Before identifying a single hazard, you must define the limits of the machine. This is the most skipped step, yet it frames the entire analysis.
Spatial Limits: Where will the robot operate? What is the maximum reach including end-effectors and workpieces?
Temporal Limits: How long is the cycle time? What are the maintenance intervals?
Use Limits: Who interacts with it? Is it a trained technician or a bystander? What is the intended use versus the reasonably foreseeable misuse?
Best Practice: Don't just list "welding." Define "welding steel brackets, 24/7 operation, with manual loading by operators every 45 seconds."
2. Assess Tasks, Not Just the Machine
A common mistake is assessing "The Robot." A robot sitting still poses little risk. The risk arises from tasks.
You must break down the lifecycle into granular activities:
- Teaching/Programming: Often requires being inside the cell with power on.
- Normal Operation: Automatic loading/unloading.
- Troubleshooting/Jam Clearing: The most dangerous time, as safeguards are often bypassed or ignored.
- Cleaning & Maintenance: Exposure to sharp edges or hot surfaces.
Best Practice: Create a task-hazard matrix. Map every human interaction point against potential hazards (crushing, impact, shearing).
3. The 3-Step Mitigation Hierarchy
When you find a risk (e.g., "Robot arm can strike operator's head"), ISO 12100 dictates a strict hierarchy for solving it. You cannot jump straight to a warning sign.
Inherently Safe Design: Can you limit the robot's force or speed so an impact doesn't cause injury? Can you eliminate pinch points by redesigning the gripper?
Safeguarding (Engineering Controls): If the hazard exists, separate the human from it. This means light curtains, area scanners, interlocked gates, or pressure mats.
Information for Use: Warning signs, training, and PPE. This is the last resort and the least effective line of defense.
4. Collaborative Robot (Cobot) Specifics
"Collaborative" is a mode of operation, not just a type of robot. Buying a "cobot" does not make your cell safe if it's wielding a sharp knife.
For collaborative applications (per ISO/TS 15066), you must assess:
- Quasi-static Contact: Clamping/crushing (e.g., robot pins hand against a table).
- Transient Contact: Impact (e.g., robot bumps into operator).
Best Practice: You must calculate the permissible force and pressure. If the robot hits an operator, does the energy transfer exceed the pain threshold defined in ISO/TS 15066? If yes, you must lower the speed or pad the robot.
5. Don't Forget "Reasonably Foreseeable Misuse"
Engineers design for how the machine should be used. Safety managers must plan for how humans will use it.
- Will an operator climb on the conveyor to clear a jam?
- Will they tape over the interlock switch to speed up production?
- Will they stand in a "blind spot" to take a shortcut?
Best Practice: Engage operators in the risk assessment. They know the shortcuts. Design safeguards that are harder to defeat or that make the safe way the easiest way.
6. Verification & Validation (V&V)
The risk assessment is just a theory until tested.
Verification: Does the design meet the requirements? (e.g., "Is the light curtain installed at the calculated safety distance?")
Validation: Does the system actually protect the person? (e.g., "If I break the beam, does the robot stop before I can reach the hazard?")
Best Practice: Use a stop-time measurement device to physically validate stopping distances. Document every test.
Summary
Risk assessment in robotics is an iterative process. It doesn't end when the machine is commissioned. Every time you change a gripper, update the software, or alter the cell layout, you must revisit your RA.
By following these best practices, you move beyond "compliance" and creating a culture of safety that enables high-performance automation without compromise.