A collaborative robot is defined less by what it is than by where it is allowed to be: inside a workspace shared with people, without the safety cage that fences off a conventional industrial robot. That permission has to come from somewhere, and in the U.S. it comes from a consensus standard OSHA names directly. On its robotics page, OSHA lists "RIA TR R15.606 (TR 606), Collaborative Robot Safety," and describes it as explaining "safety requirements specific to collaborative robots and robot systems" that is "supplemental to the guidance in ANSI/RIA R15.06." The same entry states the lineage plainly: "TR 606 is the U.S. National Adoption of the ISO/TS 15066:2016." So the document behind cobot safety is the U.S. adoption of the international technical specification ISO/TS 15066.

The reason a separate document was needed is that the main robot standard, R15.06 (the U.S. adoption of ISO 10218), was written around the assumption that the robot and the worker are kept apart by guarding. Collaboration breaks that assumption: the whole point is that a person and a moving robot occupy the same space. ISO/TS 15066 supplies the missing piece — the requirements that make shared space safe — which is why OSHA describes TR 606 as supplemental to R15.06 rather than a replacement for it. The two are read together: R15.06 governs the robot and the cell, and ISO/TS 15066 governs the conditions under which the cell can be a shared, uncaged one.

RIA TR R15.606 ("TR 606"), Collaborative Robot Safety. Explains safety requirements specific to collaborative robots and robot systems, and is supplemental to the guidance in ANSI/RIA R15.06. TR 606 is the U.S. National Adoption of the ISO/TS 15066:2016.— OSHA, Robotics — Standards, source

Power-and-force limiting is the core idea

The defining technical contribution of ISO/TS 15066 is the concept of power-and-force limiting (PFL). In a power-and-force-limited collaborative application, the robot is permitted to make contact with a person — including unintended contact — provided the force and pressure of that contact stay below limits the standard specifies. Rather than preventing all contact, PFL bounds how hard a contact can be, so that a touch or even a bump from the robot cannot cause injury beyond a defined threshold. This is the mechanism that lets a cobot operate without a fence: it is engineered so that the energy it can deliver to a human body is capped.

OSHA's page names the companion standard that closes the loop on PFL: "RIA TR R15.806 (TR 806), Testing Methods for Power & Force Limited Collaborative Applications," which it describes as a document that "describes methods to test and verify that the forces exerted by a collaborative robot system remain within the allowable limits described in TR 606 (ISO/TS 15066)." That pairing matters. ISO/TS 15066 sets the force-and-pressure limits; TR R15.806 defines how to measure a real cobot application against those limits. A claim that a collaborative cell is safe under power-and-force limiting is therefore a testable claim, with a published method for the test, not an assertion.

The other modes, and why PFL gets the attention

Power-and-force limiting is the most distinctive collaborative method, but it is not the only one the standards recognize. The R15.06 / ISO 10218 framework that ISO/TS 15066 supplements describes a set of collaborative techniques — including a safety-rated monitored stop (the robot halts when a person is present), hand-guiding (an operator moves the robot directly), and speed-and-separation monitoring (the robot slows or stops as a person approaches, maintaining a protective separation distance). PFL is the one that allows genuine simultaneous contact-tolerant operation, which is why it draws the most engineering attention and why ISO/TS 15066's force-and-pressure data is the part most often cited.

How the standard fits the broader stack

OSHA places ISO/TS 15066 inside a larger family of robot documents, and the surrounding entries clarify what it does and does not govern. The agency lists ISO 10218-1, covering "the inherent safe design, protective measures, and information for use of industrial robots," and ISO 10218-2, covering "the safe integration of an industrial robot into a complete robot system, which includes end-effectors and other related equipment." OSHA adds that "in the U.S., ISO 10218-1 has been Nationally Adopted as the single U.S. standard ANSI/RIA R15.06-2012." The collaborative technical specification sits on top of that base, which is why OSHA labels TR 606 "supplemental" rather than standalone.

End-effectors get their own attention, which matters because the gripper or tool at the end of a cobot's arm is often what actually contacts a worker. OSHA lists ISO/TR 20218-1, "Safety Design for End-effectors," describing how a robot system "should handle and manage end-effectors (end-of-arm tooling or EOAT) to maintain human safety, in either a collaborative or non-collaborative industrial environment," and ISO/TR 20218-2 on the design of a safe "Manual Load/Unload Station." A power-and-force-limited application has to account for the whole moving assembly — arm plus tooling plus workpiece — not just the robot body.

The consensus standards also carry a status caveat OSHA states plainly. The agency notes these documents "are NOT OSHA regulations," though "they do provide guidance from their originating organizations related to worker protection," and it groups them with related adoptions such as the Canadian CSA Z434, "Industrial Robots and Robot Systems." So a cobot cell is enforced through the binding general-industry rules, while ISO/TS 15066 and its testing companion supply the engineering content — the force-and-pressure limits and the methods to verify them — that gives a safety claim about an uncaged collaborative robot something concrete to be measured against.

For a plant integrating cobots, the document chain mirrors the industrial-robot case but with the collaborative layer added. The general OSHA rules — machine guarding under 29 CFR 1910.212 and lockout/tagout under 29 CFR 1910.147 — still apply, because a cobot is still a machine with hazardous energy. The robot and cell are still built to R15.06 / ISO 10218. And the collaborative operation specifically is governed by ISO/TS 15066, adopted as RIA TR R15.606, with force-and-pressure limits verified using the methods in RIA TR R15.806. The reason a cobot can stand uncaged next to a worker is not that it is inherently harmless — it is that this stack of standards defines, and provides a way to test, exactly how hard it is allowed to push.