How to Test Cobot Safety: Force and Pressure Measurement for ISO/TS 15066

Testing cobot safety requires measuring the contact forces and pressures a collaborative robot exerts on the human body, then comparing those values against the limits defined in ISO/TS 15066. The standards tell you what the limits are. This guide tells you how to actually perform the measurements: the equipment, the process, body region mapping, and the documentation an auditor expects to see.

Every cobot installation operating in a shared workspace without physical guarding needs this validation. It doesn’t matter which robot brand you’re running.

What ISO/TS 15066 Actually Requires

ISO/TS 15066 defines two distinct contact scenarios. Both must be measured for every potential contact point in the cobot cell.

Transient contact (impact): The robot strikes a body part and the person can move away. Because the contact is brief and the body absorbs the energy, force and pressure limits are higher than for clamping scenarios.

Quasi-static contact (clamping): The robot traps a body part against a fixed surface. The person can’t escape. Limits are lower because force is sustained and the tissue can’t recover between peaks.

Both contact types apply at every point in the robot’s programmed path where an operator could plausibly be present. That scope comes from the risk assessment, not from guesswork about “obvious” contact points.

One administrative note: ISO/TS 15066 has been integrated into ISO 10218-2:2025. The force and pressure limits haven’t changed, but compliance testing is now part of the core safety standard rather than a separate technical specification. If you’re updating existing documentation, reference ISO 10218-2:2025 alongside the original ISO/TS 15066 tables.

Body Region Mapping

ISO/TS 15066 defines limits for 29 body regions. Each region has a different spring constant because different parts of the body respond differently to impact. The measurement system must simulate the specific body region being tested. A sensor calibrated for the hand doesn’t give valid results for the torso.

These are the spring constants from ISO/TS 15066 Table A.2. Each CoboSafe CBSF transducer matches one of these values. For compliance documentation, always reference the standard directly.

In practice, most cobot contact scenarios concentrate on hands, arms, and torso. Start there. The risk assessment from your ISO 12100 analysis tells you which body regions are realistically exposed; test those first, then work through the remaining identified contact points.

The Testing Process, Step by Step

A few things that matter during test execution and don’t show up in flowcharts:

Test at maximum programmed speed, not reduced speed. The standard requires validation of the actual operating condition. A test run at 50% speed that passes doesn’t tell you anything about the real application.

Test with the actual end-effector installed, including the payload at maximum weight. Tool geometry and mass directly affect impact force. Testing an empty flange is common and wrong.

Test the worst-case scenario: heaviest payload, fastest motion, smallest clearance from fixed surfaces. If the worst case passes, everything else passes. If it doesn’t, you know exactly what to fix.

Record the robot program version tested. When the program changes, the test must be repeated.

Measurement Equipment Options

Three categories of measurement approach exist. They’re not equivalent.

The difference between a purpose-built system and a standard load cell isn’t about hardware sensitivity. It’s about biofidelity. A human skull absorbs impact at 150 N/mm. A human abdomen absorbs impact at 10 N/mm. Those 15x differences in body response change what the transient force reading means. A raw force measurement without the correct spring constant gives you a number that has no relationship to the ISO/TS 15066 limit tables.

A testing service is a valid option for initial compliance validation or for facilities with a single cobot and infrequent changes. The limitation is responsiveness: every program change or tool swap needs re-validation, and scheduling a service provider each time adds lead time to your change management process.

Common Testing Mistakes

Most failed cobot safety audits trace back to a short list of errors.

Testing at reduced speed. The compliance test must reflect real operating conditions. “It passes at 50%” isn’t compliance.

Testing with an empty flange. Tool mass and geometry are part of the impact calculation. Always test with the full end-effector and payload.

Skipping pressure measurement. Force limits and pressure limits are separate in ISO/TS 15066. A contact scenario can pass the force threshold and still fail on pressure if the contact area is small (a sharp edge, a narrow protrusion). Both must pass.

Missing contact points from the risk assessment. Testing only the obvious paths and missing the edge cases found in the ISO 12100 risk analysis. The risk assessment defines test scope.

Not re-testing after changes. Program updates, new tooling, payload changes, and cell layout modifications all require re-validation. Most compliance frameworks require you to document what triggers a re-test; make sure your change management process includes it.

Frequently Asked Questions