ISO/TS 15066

A safety function where the robot stops all motion when a human enters the collaborative workspace. The robot remains powered but stationary until the human leaves the safeguarded space and the system is manually restarted. This is the most basic collaborative mode, effectively creating a dynamic safety zone.

• Key Mechanism: Uses protective stop initiated by external safety sensors (e.g., light curtains, laser scanners).
• Application: Used for tasks where human entry is infrequent, such as loading/unloading a fixture while the robot is idle.

A mode where a human operator directly grasps the robot's end-effector or a dedicated handle and physically guides it through a task. The robot's control system provides zero-gravity-like assistance, moving only in response to the applied force.

• Key Mechanism: Relies on force/torque sensors in the robot's joints or flange to measure the guiding intent.
• Safety Requirement: The guiding device must include a deadman switch that immediately stops the robot if released. This mode is central to kinesthetic teaching for programming by demonstration.

A dynamic safety mode where the robot's speed is continuously controlled to maintain a protective separation distance between the robot and a human. The system calculates a minimum permitted distance (MPD) based on robot speed, human speed, system latency, and intrusion detection capability.

• Core Formula: MPD = (Robot Velocity × System Stopping Time) + (Human Intrusion Velocity × Sensor Response Time) + C, where C is a constant safety margin.
• Application: Enables concurrent operation where human and robot work on different parts of a shared task without physical contact, common in assembly lines.

The mode that permits transient physical contact between the robot and a human. The robot's inherent design or active control limits the biomechanical loadings (force, pressure, energy) to levels considered non-injurious. ISO/TS 15066 provides pain threshold tables for different body regions.

• Key Limits: Includes maximum quasi-static force (e.g., 150 N for the back), transient force/pressure, and clamping energy.
• Implementation: Achieved through inherently safe design (lightweight, rounded edges, compliant joints) and active force feedback control (e.g., impedance/admittance control). This is the defining feature of a true collaborative robot (cobot).

ISO/TS 15066's Power and Force Limiting values are not arbitrary; they are derived from pain sensitivity studies and biomechanical data. The specification provides detailed tables of maximum permissible values for 29 body regions, categorized by pain type.

• Quasi-Static Contact: Prolonged, clamping contact (e.g., being pinned). Limits are based on compression and pain thresholds.
• Transient Contact: Brief, impact-like contact from a moving robot. Limits consider both force and pressure to prevent bruising or fracture.
• Body Region Variability: The hand can tolerate higher forces than the face or neck, reflecting differing biological sensitivity and injury risk.

Implementing these modes requires a holistic safety system, not just robot programming. ISO/TS 15066 mandates a comprehensive risk assessment for each collaborative application.

• Required Components: Safety-rated hardware (PL d/Cat. 3 minimum), validated safety functions, and performance level (PL) calculations per ISO 13849-1.
• Process Steps:
  1. Hazard Identification: Pinpoint all potential contact scenarios.
  2. Force/Speed Estimation: Calculate expected contact forces using physics or simulation.
  3. Validation: Measure actual forces/pressures with a force-pressure measurement device.
  4. Documentation: Create a collaborative operation validation report.
• Critical Note: The integrator, not the robot manufacturer, is typically responsible for the final risk assessment and validation of the collaborative application.

A Collaborative Workspace is the defined area within the safeguarded space where the robot and a human can perform tasks simultaneously during production. ISO/TS 15066 provides critical guidance for its design and validation:

• Definition: It is a subset of the total operating space where collaborative operation occurs.
• Risk Assessment: Hazards within this space must be reduced to acceptable levels using the specified collaborative safety modes (PFL, SSM, etc.).
• Validation: Requires verification that safety functions perform as intended, often involving physical biomechanical testing with force/pressure measurement devices to confirm limits are not exceeded.

Hand Guiding (or Hand-Guided Operation) is a type of collaborative operation where an operator uses a hand-operated device to directly control the robot's motion. ISO/TS 15066 and ISO 10218 specify requirements for this mode:

• Initiation: Requires a dedicated enabling device (3-position switch) that must be continuously activated.
• Control: The robot only moves while the enabling device and guiding handle are activated.
• Speed Limits: Maximum speed is limited (e.g., 250 mm/s).
• Safety: The system must include a safe stop function that engages immediately if the enabling device is released. This mode is distinct from kinesthetic teaching, as it is for direct operational control, not programming.

Safety-Rated Monitored Stop is a collaborative operation mode where the robot comes to a complete stop before a human enters the collaborative workspace. Key characteristics include:

• Stop State: The robot is stopped with motors powered (servos on) but brakes engaged.
• Access: The human can then enter the defined workspace safely.
• Restart: The robot will not automatically restart upon human exit; a manual restart command from outside the workspace is required. This is the simplest collaborative mode and is often used for tasks like part loading/unloading. It does not allow for simultaneous motion, differentiating it from PFL and SSM.