Explainers
Robot Safety Standards and Safety-Rated Stops: Where Humanoids Fit
A robot stopping when someone walks nearby may look safe, but the engineering question is more precise: what detected the person, which safety function commanded the stop, how is standstill monitored, and under what conditions can motion resume? Industrial robot safety standards address systems and applications, not just the appearance or shape of the machine.
What ISO 10218 covers
OSHA's robotics standards page describes ISO 10218-1 as covering the inherent safe design, protective measures, and information for use of industrial robots. ISO 10218-2 addresses integration of the robot into a complete system, including end effectors and related equipment. That distinction matters because a robot can be supplied with protective capabilities yet become hazardous when fitted with a tool or installed beside other machinery.
The publicly accessible OSHA material summarizes the scope of these standards; it is not the complete paid standards text. OSHA also notes that ISO 10218 is directed at industrial robots, not every service or consumer robot. Its safety principles may still be useful elsewhere, but applicability cannot be inferred merely because a machine has two arms or walks on legs.
ISO/TS 15066:2016 supplies safety requirements specific to collaborative robots and robot systems, as a supplement to the industrial robot standards; OSHA's standards page notes it was adopted in the U.S. as RIA TR R15.606. Calling a robot “collaborative” therefore requires more than an informal description of it sharing a room with people.
A protective stop is not the same as an emergency stop
An emergency stop is an operator-initiated protective measure for emergencies. A protective stop can be triggered by a safeguard, such as an intrusion detected by a presence-sensing system. OSHA discusses both in its industrial robotics guidance, alongside interlocked barriers, speed and separation monitoring, and other risk-reduction measures.
One particular concept is a safety-rated monitored stop. OSHA explains that this is also called a monitored standstill and describes it as a Category 2 stop in the NFPA 79-2017 terminology referenced by its manual. Power to the actuators is retained while the robot remains in a monitored stopped state. That can support a quicker resumption of operation than repeatedly removing actuator power, but it depends on continued monitoring and appropriate safeguards.
Do not treat the term “Category 2” as a generic label for every safe stop. It identifies a specific stopping behavior in the cited context. Nor should a software pause button be assumed to implement a safety-rated function. The safety system must be designed, assessed, and validated for the application.
Four ways collaborative operation can be organized
OSHA's technical manual describes several approaches. Speed and separation monitoring uses protective sensing to detect workers and can slow or stop a robot as separation decreases. Hand-guided controls allow a worker to direct motion using an appropriate hold-to-run control. Power and force limiting permits certain contacts only when the application controls the resulting forces and pressures. OSHA also discusses the safety-rated monitored stop, while noting that it is used with other collaborative techniques rather than by itself.
These modes are not interchangeable. A robot that avoids contact by stopping when a worker enters a zone is addressing a different interaction from one designed to tolerate limited contact during motion. The correct combination follows from the tasks and hazards identified in a risk assessment.
OSHA specifically emphasizes that the relevant contact includes the robot, end effector, and workpiece. A rounded arm carrying a sharp tool or heavy part cannot be evaluated on arm geometry alone. Protective measures can also include padding, elimination of sharp projections, limiting devices, and presence-sensing safeguards.
Cobots versus humanoids: different labels, same questions
A cobot usually refers to a robot intended for collaborative applications, often a stationary manipulator. A humanoid describes a body form, not a safety classification. The categories can overlap in principle, but neither label independently establishes a safe application. OSHA distinguishes collaborative industrial applications by their designed direct interaction with workers, not by whether the robot has a humanlike silhouette.
Consider a fixed collaborative arm that loads parts beside a worker. Its risk assessment must cover the shared workstation, tool, part, and anticipated contacts. Now consider a mobile humanoid that walks through the same plant carrying a crate. The assessment must additionally consider travel paths, changing contact locations, loss of balance, and falling loads. These are application-specific hazards; simply importing a fixed-arm safety claim would leave important questions unanswered.
OSHA separately discusses industrial mobile robots and recognizes that mobile platforms can carry manipulator systems. That provides a useful comparison for walking robots, but it does not mean every humanoid automatically falls within one specific standard's scope.
Risk assessment determines the safeguards
OSHA describes a task-based process: identify intended use and foreseeable tasks, identify hazards, estimate risk, choose risk-reduction measures, and validate the result. It also calls for checking stopping performance and safety distances and reassessing the application when conditions change. Training and procedures complement engineering safeguards; they do not replace them.
For a factory buyer, the practical questions are concrete. Which stop functions are safety-rated? What sensors trigger them? Is standstill monitored? Can a restart occur automatically, and under what conditions? What happens to a carried object when motion stops? Which edition and scope of each standard is the integrator claiming, and what evidence supports that claim? Those answers matter more than whether the robot is marketed as a cobot, an industrial humanoid, or a general-purpose assistant.