ISO/TS 15066 sets biomechanical force and pressure limits for 29 body locations, grouped into 12 body regions, to control hazardous contact by power- and force-limited collaborative robots [S1][S7].
The technical specification supports risk assessment for collaborative industrial robot systems and supplements ISO 10218, with power and speed guidance for applications where incidental human-robot contact may occur [S2][S5].
What ISO/TS 15066 Controls
ISO/TS 15066 defines power and force limiting, or PFL, as one of four collaborative-operation safeguarding modes and establishes limits intended to prevent contact from producing biomechanical stress beyond the onset of pain [S1].
Its force and pressure data cover 29 body locations across 12 body regions. The values guide robot design and integration when human-robot contact is permitted, while the specification also addresses maximum allowable robot-system power and speed for PFL applications [S2][S7].
The scope is application-specific. ISO/TS 15066 covers a collaborative robot system, not merely a robot arm: the end effector, workpiece, operating speed, contact geometry, protective measures and surrounding work environment all affect the assessment [S5]. A collaborative robot can still be used in a non-collaborative application if the end effector creates hazards beyond the assumed limits [S5].
Force, Pressure and Contact Geometry
ISO/TS 15066 separates transient impact exposure from sustained or quasi-static clamping, because the same actuator force can produce different injury risks when the robot surface strikes a body or traps it against another object [S1].
The specification includes a force and pressure chart developed by the University of Mainz, while a later human-subject study involved 112 subjects and tested 28 body locations. Pressure-based limits apply to clamping contact involving a semi-sharp robot surface, while impact limits address striking contact [S1][S2].
A later human-subject study involved 112 participants and 28 tested body locations. Contact force was increased until each subject reported a slightly painful sensation, and the results showed that pain thresholds differed between sexes in specific body regions [S1]. That finding matters because a single generic force setting cannot represent every worker or every body location.
Risk assessment must therefore match the limit to the relevant body region and contact type. Force gauge instrumentation can support verification of contact force, while the selected tool, workpiece and fixture determine whether the robot presents a blunt, flat, sharp or clamping surface [S1][S4].
Power and Speed Limits
ISO/TS 15066 provides recommended robot-system power and speed limits for PFL operation, making kinetic capability part of the safety calculation rather than treating force limiting as a stand-alone feature [S2].
The power and speed guidance supports the design of collaborative applications intended for power- and force-limited operation. It does not authorize unrestricted motion: speed, mass, payload, contact surface and stopping behavior still have to be considered within the application risk assessment [S2][S5].
The four collaboration modes differ materially. Safety-rated monitored stop requires motion to stop before human entry; hand guiding uses a force-recording sensor for direct human guidance; speed and separation monitoring uses monitored zones to adjust robot speed as a person approaches; PFL permits motion to continue while the system limits contact force [S4].
For a PFL application, the correct sequence is to identify the exposed body regions, determine force or pressure limits for those regions, calculate whether robot speed and mass remain compatible with the contact model, and then verify that the complete system can maintain those limits after tooling and payload changes [S1][S5].
Comparison of Collaborative Operation Modes
Safety-rated monitored stop, hand guiding, speed and separation monitoring and power and force limiting solve different hazards and should not be treated as interchangeable safeguarding methods [S4][S5].
On cost, implementation complexity and contact tolerance, monitored stop is generally the simplest production sequence, hand guiding requires a dedicated sensing interface, speed and separation monitoring depends on spatial monitoring, and PFL depends on controlled contact mechanics [S4]. On workspace flexibility, PFL and speed and separation monitoring can outperform a permanently stopped sequence, but neither permits the risk assessment to be skipped [S5].
Applications and Required Controls
Assembly and packaging are established PFL use cases because force and pressure limits can govern contact during handling, placement and tool interaction [S3]. A robot that feels an abnormal force and stops is not by itself compliant; the system must demonstrably reduce contact energy and maintain the applicable limits throughout the task [S4].
Validation requires more than a nominal payload figure. The assessment should examine tool geometry, workpiece mass, grip pressure, approach direction, contact point, human body region, robot speed, emergency stopping and the consequences of a dropped or trapped part [S1][S5].
The collaborative workspace remains inside the safeguarded space, and a risk assessment is still required even when a power- and force-limited arm is installed [S5]. Other safeguards may therefore remain necessary, including separation from sharp tools, restricted access during hazardous process states, and controls for material handling or process hazards outside human-robot contact.
Limitations and Failure Modes
Most biomechanical limits in ISO/TS 15066 are preliminary because they were derived from a literature survey, although the underlying Mainz study tested 100 subjects [S1][S2]. The values therefore provide an engineering basis for risk assessment, not a guarantee that every contact below a threshold produces no injury.
Several failure modes follow from that limitation. A tool change can replace a compliant surface with a sharp edge, increasing pressure for the same actuator force. Added payload can change dynamic energy and stopping distance. A body-region mismatch can apply a generous limit to a sensitive location. A control fault can permit contact force or robot speed to exceed the validated envelope [S1][S5].
The 112-subject, 28-location study also showed sex-dependent pain thresholds in particular body regions and proposed a regression model for limits fitted to a chosen percentile of a mixed workforce [S1]. That evidence supports application-specific validation rather than replacing the ISO/TS 15066 tables with a generic force number.
How to Verify a Compliant PFL Application
The first verification step is to document the robot, controller, end effector, workpiece, operating cycle, contact surfaces and human body regions, then map each credible contact to the applicable force or pressure limit [S2][S5].
The second step is to test the complete configured system at the intended speed and payload, including grip force, approach angle, stopping behavior and the effect of wear or assembly variation. Measured contact force can be checked with calibrated instrumentation such as a force gauge, while speed and motion behavior should be verified through the robot’s safety controls [S1].
The third step is to preserve the validation envelope through change control. A modified gripper, higher payload, faster tool, lighter workpiece or relocation of the process can invalidate earlier contact assumptions, so each change should trigger a documented reassessment of power, speed, force and pressure [S2][S5].
Two signals provide a trackable control point for maintainers: the documented separation between measured contact limits and the applicable biomechanical threshold, and the number of production changes accepted without a renewed risk assessment.