Safety Standards in Industrial Robotics

Industrial robots operate with payloads from a few kilograms to several tonnes, at velocities up to 3 m/s at the tool centre point — energies that can cause severe or fatal injury. The safety of robot systems is governed by a hierarchy of international standards, national regulations, and machine directives that define how risk must be managed.

In most jurisdictions, compliance with relevant standards is not optional — it is a legal requirement for placing machinery on the market (EU Machinery Directive 2006/42/EC, replaced by Machinery Regulation 2023/1230; OSHA regulations in the USA; JIS standards in Japan). Non-compliance can result in product liability, factory shutdown, and criminal responsibility for serious incidents.

Understanding safety standards is therefore not merely an academic exercise — it is a core professional competency for robotics engineers working on real systems.

ISO 10218-2 and ISO 12100 require a risk assessment for every robot installation:

Step 1 — Determine the limits: define the robot's intended use, all reasonably foreseeable misuse, space limits, speed limits, and the population of users (trained operators, maintenance, visitors).

Step 2 — Identify hazards: systematically enumerate hazards — crushing, shearing, entanglement, electrical, thermal, noise, radiation. For each life cycle phase: normal operation, teaching, maintenance, fault recovery.

Step 3 — Estimate risk: for each hazard, assess severity (S1 reversible / S2 irreversible), frequency of exposure (F1 infrequent / F2 frequent), and probability of avoiding the hazard (P1 possible / P2 scarcely possible). This gives a risk level.

Step 4 — Evaluate and reduce risk: if risk is not acceptable, apply measures in order of the safety hierarchy:

1. Eliminate the hazard (design change)
2. Guard against it (fixed guards, interlocked guards)
3. Warn about it (signs, lights, alarms)
4. Provide personal protective equipment

Step 5 — Verify: confirm that measures achieve the required Performance Level (PLr) or Safety Integrity Level (SIL).

ISO 13849 uses Performance Level (PL) — categories a through e — to quantify the reliability of a safety function. PLe is the highest (required for the most critical functions like emergency stop of a large robot at full speed).

PL is determined by three parameters:

• MTTFd: Mean Time To dangerous Failure of each safety channel
• DCavg: Diagnostic Coverage average — how well built-in diagnostics detect dangerous failures
• CCF: Common Cause Failure — protection against single events disabling all redundant channels

IEC 62061 uses Safety Integrity Level (SIL 1–3) — a probabilistic metric for dangerous failures per hour (SIL 3: < 10⁻⁷ per hour). SIL 3 is required for the highest-risk applications (e.g., collaborative robot stopping function in an automotive body shop).

In practice, safety PLCs (Siemens S7-1500F, Allen-Bradley GuardLogix, Pilz PNOZmulti) implement safety functions in hardware-certified IEC 61508 SIL-2/3 firmware, taking inputs from safety light curtains, safety laser scanners, safety-rated encoders, and emergency stop buttons.