Robots and robotic devic es — Col aborati ve robotsThis Te hnical Spe ification spe if ies safety r q ir ment for cola orative ind s rial ro ot syst ems an the work environment, an suppl
General
ISO 10218-2:2011 outlines the safety requirements for integrating industrial robots and robot systems, particularly focusing on collaborative robot systems Unlike traditional robot installations, collaborative robots allow operators to work closely alongside them, with power to the robot's actuators active, enabling potential physical contact within a shared workspace.
Figure 1 — Example of a collaborative workspace
Designing a collaborative robot system necessitates implementing protective measures to guarantee operator safety throughout its operation Conducting a risk assessment is essential to identify potential hazards and evaluate the risks linked to the application of collaborative robots, enabling the selection of appropriate risk reduction strategies.
Collaborative application design
In designing a collaborative robot system and its cell layout, it is crucial to eliminate hazards and reduce risks, which can significantly impact the working environment Key factors to consider include the defined three-dimensional limits of the collaborative workspace and ensuring adequate access and clearance within that space.
1) delineation of the restricted space and collaborative workspaces;
2) influences on the collaborative workspace (e.g material storage, work flow requirements, obstacles);
3) the need for clearances around obstacles such as fixtures, equipment and building supports;
5) the intended and reasonably foreseeable contact(s) between portions of the robot system and an operator;
6) access routes (e.g paths taken by operators, material movement to the collaborative workspace);
7) hazards associated with slips, trips and falls (e.g cable trays, cables, uneven surfaces, carts); c) ergonomics and human interface with equipment:
2) possible stress, fatigue, or lack of concentration arising from the collaborative operation;
3) error or misuse (intentional or unintentional) by operator;
4) possible reflex behaviour of operator to operation of the robot system and related equipment;
6) acceptable biomechanical limits under intended operation and reasonably foreseeable misuse;
7) potential consequences of single or repetitive contacts; d) use limits:
1) description of the tasks including the required training and skills of an operator;
2) identification of persons (groups) with access to the collaborative robot system;
3) potential intended and unintended contact situations;
4) restriction of access to authorized operators only; e) transitions (time limits):
1) starting and ending of collaborative operation;
2) transitions from collaborative operations to other types of operation.
Hazard identification and risk assessment
General
The integrator is responsible for performing a risk assessment for collaborative operations in accordance with ISO 10218-2:2011, section 4.3 This assessment must give special attention to potential intended or reasonably foreseeable unintended contact situations between the operator and the robot system, as well as the expected accessibility for the operator to interact within the collaborative workspace.
User involvement in risk assessment and workspace design is crucial The integrator plays a key role in facilitating this participation and in choosing the right robot system components tailored to the application's needs.
Hazard identification
ISO 10218-2:2011, Annex A outlines key hazards associated with robots and robotic systems, derived from the hazard identification process detailed in ISO 12100 Specific collaborative applications, such as welding, assembly, grinding, or milling, may introduce additional hazards, including fumes, gases, chemicals, and hot materials It is essential to address these hazards individually through a tailored risk assessment for each collaborative application.
The hazard identification process shall consider the following as a minimum: a) robot related hazards, including:
1) robot characteristics (e.g load, speed, force, momentum, torque, power, geometry, surface shape and material);
2) quasi-static contact conditions in the robot;
3) operator location with respect to proximity of the robot (e.g working under the robot) ; b) hazards related to the robot system, including:
1) end-effector and workpiece hazards, including lack of ergonomic design, sharp edges, loss of workpiece, protrusions, working with tool changer;
2) operator motion and location with respect to positioning of parts, orientation of structures (e.g fixtures, building supports, walls) and location of hazards on fixtures;
3) fixture design, clamp placement and operation, other related hazards;
4) a determination as to whether contact would be transient or quasi-static, and the parts of the operator’s body that could be affected;
5) the design and location of any manually controlled robot guiding device (e.g accessibility, ergonomic, potential misuse, possible confusion from control and status indicators, etc.);
6) the influence and effects of the surroundings (e.g where a protective cover has been removed from an adjacent machine, proximity of a laser cutter); c) application related hazards, including:
1) process-specific hazards (e.g temperature, ejected parts, welding splatters);
2) limitations caused by the required use of personal protective equipment;
3) deficiency in ergonomic design (e.g resulting in loss of attention, improper operation).
Task identification
In collaboration with the user, the integrator will identify and document tasks related to the robot cell, ensuring all foreseeable task and hazard combinations are recognized Collaborative tasks are characterized by several factors, including the frequency and duration of operator presence in the workspace with a moving robot system, the frequency and duration of contact between the operator and the robot system while energy sources are active, transitions between non-collaborative and collaborative operations, the automatic or manual restart of robot motion post-collaboration, tasks involving multiple operators, and any additional activities within the collaborative workspace.
Hazard elimination and risk reduction
Once hazards are identified, it is essential to assess the risks associated with the collaborative robot system before implementing risk reduction measures These measures prioritize the elimination of hazards through inherently safe design or substitution, followed by protective measures that restrict personnel access to hazards or control them by ensuring a safe state Additionally, supplementary protective measures, including user information, training, signage, and personal protective equipment, should be provided to enhance safety.
In traditional robotic systems, risk is minimized by implementing safeguards that create a separation between the operator and the robot In contrast, collaborative operations focus on risk reduction through the thoughtful design of both the robot system and the collaborative workspace Detailed measures for enhancing safety in collaborative environments are outlined in Clause 5.
5 Requirements for collaborative robot system applications
General
Robot systems with collaborative applications shall meet the requirements of ISO 10218-1:2011 and ISO 10218-2:2011 The information contained in this clause supplements that given in ISO 10218-1:2011, 5.10 and ISO 10218-2:2011, 5.11.
Safety-related control system performance
The safety-related control system functions shall comply with ISO 10218-1:2011, 5.4, or ISO 10218-2:2011, 5.2.
Design of the collaborative workspace
The collaborative workspace design must enable operators to complete all necessary tasks while effectively mitigating risks associated with machinery and equipment, as outlined in the risk assessment It is crucial that the placement of equipment does not create additional hazards Whenever possible, safety-rated soft axis and space limiting measures, as specified in ISO 10218-1:2011, 5.12.3, should be implemented to minimize the restricted space.
To mitigate risks of whole body trapping or crushing between robotic systems and surrounding structures, utilities, or equipment, it is essential to eliminate or safely control these hazards Compliance with ISO 10218-2:2011, section 5.11.3, mandates the provision of adequate clearance to ensure safety.
NOTE The clearance can be different for systems designed to comply with 5.5.4 and 5.5.5.
In a collaborative workspace, if other machines pose a risk, protective measures must be implemented following ISO 10218-2:2011, section 5.11.2 Additionally, all safety-related functions should adhere to the standards outlined in section 5.2.
Design of the collaborative robot operation
General
The requirements for the design of the collaborative robot operation are provided in ISO 10218-2:2011, 5.11 The operating methods in 5.5 may be used singularly or in combination when designing a collaborative application.
In accordance with ISO 10218-2:2011, section 5.3.8.3, any failure detected in the safety-related components of the control system must trigger a protective stop Operations can only resume after a deliberate restart action is taken by the operator, who must be positioned outside of the collaborative workspace.
Protective measures
All persons within the collaborative workspace shall be protected by protective measures Safeguards used in a collaborative workspace shall meet the requirements of ISO 10218-2:2011, 5.10.
Active settings and configurations for collaborative safety parameters must be viewable and documented with a unique identifier, such as a checksum, to facilitate the identification of configuration changes (refer to ISO 10218-1:2011, 5.12.3) Additionally, the process of setting and adjusting these safety parameters should be safeguarded against unauthorized and accidental modifications through password protection or equivalent security measures.
Stopping functions
In a collaborative environment, operators must be equipped with the ability to halt robot movement instantly with a single action or have clear access to exit the collaborative workspace without obstruction.
To halt robot motion, various methods can be employed, including enabling devices, emergency stop devices, and manual stopping for robots equipped with this capability.
The number and location of emergency stop devices shall be determined by risk assessment and shall meet the requirements of ISO 13850.
Transitions between non-collaborative operation and collaborative operation
Effective transitions between collaborative and non-collaborative operations are crucial in collaborative applications It is essential to design these transitions to ensure that the robotic system does not present any unacceptable risks to the operator.
NOTE A visual indicator to identify transitions between collaborative and non-collaborative operations can be used.
Enabling device requirements
ISO 10218-1:2011, section 5.8, outlines requirements for pendant controls, which must include an enabling device (5.8.3) and an emergency stop function (5.8.4) However, if a risk assessment indicates that the risk reduction typically provided by an enabling device can be effectively replaced by inherently safe design measures or safety-rated limiting functions, the pendant control for a collaborative robot system may be implemented without the enabling device.
When using a collaborative robot system with safety-rated limiting functions, it is essential that these functions remain active at all times if an enabling device is not present The limits, such as speed, force, or range, must be configured to ensure adequate risk reduction during programming, troubleshooting, maintenance, and other tasks typically conducted with an enabling device.
In the absence of active safety-rated limiting functions within the task-specific configuration, the collaborative robot system must implement an alternative protection method, such as an enabling device that complies with ISO 10218-1:2011, section 5.8.3.
When a robot system does not come with an enabling device, it is essential to include a notification indicating its absence If the enabling device is optional, the manufacturer must provide installation instructions Additionally, a disclaimer should clarify that the robot should only be utilized in applications that incorporate inherently safe design measures or active safety-rated limiting functions.
Collaborative operations
General
Collaborative operations may include one or more of the following methods: a) safety-rated monitored stop; b) hand guiding; c) speed and separation monitoring; d) power and force limiting.
Safety-rated monitored stop
The safety-rated monitored stop feature in collaborative robots ensures that robot motion halts when an operator enters the workspace to perform tasks, such as loading parts onto the end-effector In the absence of an operator, the robot can function non-collaboratively Once the robot system is in the collaborative workspace and the monitored function is active, the operator can safely enter Robot motion can only resume automatically after the operator has left the collaborative area, ensuring a secure working environment.
For safe collaborative operation with monitored stops, robot systems must adhere to specific requirements: a) motion limitations must align with ISO 10218-1:2011, section 5.12; b) robots must be equipped with a protective stop function as specified in ISO 10218-1:2011, section 5.5.3.
The safety-rated monitored stop feature allows the robot system to operate in the collaborative workspace only when no operator is present When the workspace is clear of operators, the robot can function non-collaboratively within that area.
Figure 2 — Truth table for safety-rated monitored stop operations
The collaborative workspace will be designed to comply with ISO 13855 standards, ensuring appropriate distances are maintained The robotic system will feature safety-rated devices to detect the presence of operators within this workspace Additionally, access to restricted areas outside the collaborative workspace will be restricted based on a thorough risk assessment.
Operators may enter the collaborative workspace of a robot system only under specific conditions: firstly, when no hazards, including the robot system itself, are present; secondly, when the robot is in a safety-rated monitored stop (stop category 2) as per ISO 10218-1:2011, ensuring that this stop remains active while the operator is present; and thirdly, when the robot is in a protective stop in accordance with ISO 10218-1:2011, sections 5.4 and 5.5.3.
In the intended use of this function, the robot may decelerate, resulting in a safety-rated monitored stop (stop category 2) in accordance with IEC 60204-1.
When the operator leaves the collaborative workspace, the safety-rated monitored stop function may be deactivated and robot system motion may resume automatically.
Any condition that violates these operational requirements shall result in a protective stop (stop category 0) in accordance with IEC 60204-1.
Hand guiding
In this operational method, an operator utilizes a hand-operated device to send motion commands to the robot system Prior to entering the collaborative workspace for hand-guiding tasks, the robot must reach a safety-rated monitored stop The task is performed by manually controlling guiding devices situated at or near the robot's end-effector.
Robot systems used for hand guiding can be equipped with additional features, such as force amplification, virtual safety zones or tracking technologies.
If the requirements of 5.5.5 are fulfilled in a hand guiding task, then the requirements of 5.5.3 do not apply. 5.5.3.2 Requirements
The robot will implement a safety-rated monitored speed function and a safety-rated monitored stop function, as outlined in ISO 10218-1:2011 A risk assessment will establish the safety-rated monitored speed limit Additionally, if operator safety requires restricting the robot's range of motion, safety-rated soft axis and space limiting will be employed.
The operating sequence for hand guiding a robot system begins when the system enters the collaborative workspace and issues a safety-rated monitored stop, allowing the operator to enter Once the operator takes control using the hand guiding device, the monitored stop is cleared, enabling the operator to perform the task Upon releasing the guiding device, a safety-rated monitored stop is activated again Finally, after the operator exits the collaborative workspace, the robot system can resume its non-collaborative operations.
If the operator enters the collaborative workspace before the robot system is ready for hand guiding, a protective stop (ISO 10218-1:2011, 5.5.3) shall be issued.
Access to the restricted space outside the collaborative workspace shall be prevented in accordance with a risk assessment.
The robotic system must include a guiding device featuring an emergency stop and an enabling device, in accordance with ISO 10218-1:2011 standards, unless the criteria for excluding the enabling device are satisfied.
When positioning the guiding device, it is essential to ensure that the operator is close enough to the robot to directly observe its movements and any potential hazards, such as controls mounted on the end effector Additionally, the operator's position and posture must be safe, avoiding areas under heavy loads or manipulator arms Finally, the operator should have an unobstructed view of the entire collaborative workspace to monitor for any additional individuals entering the area.
The relationship between the motion axes of the hand guiding device and the robot's motion axes must be clearly defined for easy comprehension Additionally, the robot's movement and the end effector's direction should be intuitively grasped and controllable through the hand guiding device.
5.5.3.2.3 Transitions between hand guiding and other types of operation
Transitions between hand guiding operations and non-collaborative or other types of collaborative operations must not introduce additional risks Operators should manage these transitions through deliberate actions, such as activating enabling devices, and by leaving the collaborative workspace Key considerations include ensuring that the halt of robot motion during transitions to a safety-rated monitored stop does not create new hazards, preventing unexpected motion when transitioning back to hand guiding, ensuring all operators have exited the collaborative workspace before resuming non-collaborative operations, and avoiding additional hazards when moving from non-collaborative operations to hand guiding.
Risk reduction is achieved through a combination of operator-controlled motion and safety-rated limitations on speed and position, as identified in a thorough risk assessment This assessment must consider the monitored speed that enables operator control over the robot and associated hazards, the necessary time and distance for the robot to stop when the enabling device is released or a protective stop is initiated, and the potential hazards posed by the workpiece, end effector, peripherals, or application devices.
Speed and separation monitoring
In this operational method, both the robot system and the operator can move simultaneously within a collaborative workspace while ensuring safety A protective separation distance is maintained at all times to minimize risks, preventing the robot from approaching the operator closer than this designated distance If the separation distance falls below the protective threshold, the robot system will halt its motion Once the operator moves away, the robot can automatically resume its operation, adhering to the protective separation distance Additionally, as the robot system slows down, the protective separation distance is adjusted accordingly.
The robot must include a safety-rated monitored speed function and a safety-rated monitored stop function, as specified in ISO 10218-1:2011 To ensure operator safety by restricting the robot's range of motion, it should also feature safety-rated soft axis and space limiting Additionally, the speed and separation monitoring system must comply with the relevant requirements outlined in the standard.
Speed and separation monitoring is essential for everyone in the collaborative workspace The maximum number of individuals allowed in this area will be specified in the usage guidelines, especially if the effectiveness of safety measures is impacted by the number of people present If this limit is surpassed, a protective stop will be initiated.
When the distance between a hazardous component of a robot system and an operator is less than the designated protective separation distance, the robot system must perform a protective stop and activate safety-related functions as specified in ISO 10218-2:2011, 5.11.2 g), such as disabling any dangerous tools.
The possibilities by which the robot control system can avoid violating the protective separation distance include, but are not limited to:
— speed reduction, possibly followed by a transition to safety-rated monitored stop (see 5.4.1);
— execution of an alternative path which does not violate the protective separation distance, continuing with active speed and separation monitoring.
When the actual separation distance meets or exceeds the protective separation distance, robot motion may be resumed.
5.5.4.2.2 Constant and variable speed and separation values
In robotic applications, maximum permissible speeds and minimum protective separation distances can be either variable or constant Variable values allow for continuous adjustments based on the relative speeds and distances between the robot system and the operator In contrast, constant values are established through a risk assessment, identifying worst-case scenarios throughout the application.
The means for determining the relative speeds and distances of the operator and robot system shall be safety-rated in accordance with the requirements in ISO 10218-2:2011, 5.2.2.
During automatic operation, the robot system's hazardous parts must maintain a protective separation distance from the operator, calculated using the minimum distance formula in ISO 13855, while considering speed and separation monitoring hazards For constant speed settings, the safety-rated monitored speed must adhere to ISO 10218-1:2011, 5.6.4, ensuring the constant limit is not exceeded In variable speed settings, the protective separation distance is determined by the speeds of both the robot and the operator, or by calculating the maximum allowed robot speed based on the operator's speed and the actual separation distance This control function must comply with ISO 10218-2:2011, 5.2.2 Additionally, the robot's stopping distance is defined according to ISO 10218-1:2011, Annex B.
The protective separation distance, Sp, can be described by Formula (1):
S p (t 0 ) is the protective separation distance at time t 0 ; t0 is the present or current time;
S h is the contribution to the protective separation distance attributable to the operator’s change in location;
Sr is the contribution to the protective separation distance attributable to the robot system’s reac- tion time;
S s is the contribution to the protective separation distance due to the robot system’s stopping distance;
C is the intrusion distance, as defined in ISO 13855; this is the distance that a part of the body can intrude into the sensing field before it is detected;
Z d is the position uncertainty of the operator in the collaborative workspace, as measured by the presence sensing device resulting from the sensing system measurement tolerance;
Zr is the position uncertainty of the robot system, resulting from the accuracy of the robot position measurement system.
Sp(t0) enables dynamic calculation of the protective separation distance, accommodating variations in robot speed during operation Additionally, it can determine a fixed protective separation distance based on worst-case scenarios.
Formula (1) is applicable to all personnel combinations within a collaborative workspace and the robot system's moving components In this environment, one part of the robot may be moving away from a person, while another part may be approaching them.
The contribution to the protective separation distance attributable to the operator’s change in location,
The reaction time (\$T_r\$) of the robotic system encompasses the duration needed for detecting the operator's position, processing the corresponding signal, and activating the robot's stop mechanism However, it does not account for the time required for the robot to come to a complete stop.
The stopping time of the robot, denoted as \$T_s\$, varies based on factors such as robot configuration, planned motion, speed, end effector, and load, rather than being a constant The directed speed of an operator, represented as \$v_h\$, indicates movement within the collaborative workspace towards the robot's moving part and can be either positive or negative, reflecting whether the separation distance is increasing or decreasing Additionally, \$t\$ serves as the integration variable in the relevant formulas.
The quantity \( S_h \) indicates the contribution to the separation distance resulting from the operator's movement until the robot comes to a stop The variable \( v_h \), which depends on time, can change due to alterations in the person's speed or direction The system must be designed to minimize the separation distance by accommodating variations in \( v_h \) In cases where the person's speed is not monitored, the design will assume \( v_h \) to be 1.6 m/s in the direction that most effectively reduces the separation distance However, as per ISO 13855 and IEC/TS 62046:2008, 4.4.2.3, \( v_h \) may differ from 1.6 m/s based on a risk assessment.
A constant value for S h using the estimated human speed (1,6 m/s), expressed in m/s, can be estimated using Formula (3):
The contribution to the protective separation distance attributable to the robot system’s reaction time,
Sr, is expressed by Formula (4):
The integral \( \int_{0}^{\infty} v_r(t) \, dt \) represents the directed speed of a robot in relation to an operator within a collaborative workspace This speed, denoted as \( v_r \), can vary in sign, indicating whether the distance between the robot and the operator is increasing or decreasing.
The quantity \( S_r \) indicates the separation distance contributed by the robot's movement when a person enters the sensing field until the control system triggers a stop The variable \( v_r \) is time-dependent and may change due to alterations in the robot's speed or direction The system must be designed to accommodate variations in \( v_r \) in a way that minimizes the separation distance effectively.
— if the robot’s speed is not being monitored, the system design shall assume that v r is the maximum speed of the robot;
To optimize the robot's performance, the system design should utilize the current speed while also considering the robot's acceleration capabilities, aiming to minimize the separation distance effectively.
— if a safety-rated speed limit is in effect, the system design may use this speed limit if the limit is applicable to the part of the robot under consideration.
A safety-rated speed limit that solely tracks the Cartesian speed of the robot's Tool Center Point (TCP) does not account for other potentially hazardous components of the robot Therefore, it may be necessary to implement a safety-rated speed limit that also monitors the joint speeds to ensure operator safety.
A constant value for Sr can be estimated using Formula (5):
The contribution to the protective separation distance that occurs while the robot system is stopping is expressed using Formula (6):
∫ 0 + + ( ) (6) where vs is the speed of the robot in the course of stopping, from the activation of the stop command until the robot has halted.
Power and force limiting
In collaborative robot systems, physical contact between the robot and the operator can happen both intentionally and unintentionally These systems are specifically designed for power and force-limited operations to enhance safety Risk reduction is achieved by ensuring that hazards remain below threshold limit values, which are established during a risk assessment Detailed guidelines for determining these threshold limits can be found in Annex A.
In collaborative operations involving power and force limiting, contact events between the collaborative robot and the operator's body can occur in several ways: a) through intended contact situations that are integral to the application sequence; b) through incidental contact situations resulting from deviations from established working procedures, without any technical failures; and c) through failure modes that inadvertently lead to contact situations.
Possible types of contact between moving parts of the robot system and areas on a person’s body are categorized in the following manner.
Quasi-static contact refers to scenarios where a body part is pinched between a moving component of a robotic system and a stationary or another moving part within the work cell In these instances, the robotic system exerts pressure or force on the trapped body part for a prolonged duration until the situation is resolved.
Transient contact, also known as "dynamic impact," occurs when a moving part of a robot system impacts a person's body part, allowing for a quick recoil or retraction without clamping or trapping the contacted area This brief interaction is influenced by the inertia of both the robot and the person's body part, as well as the relative speed between them.
NOTE 1 The relevant inertia of the robot is the moving mass as computed at the contact location This might be anywhere along the length of the kinematic chain (i.e the manipulator arm, linkages, tooling and workpiece), so estimating this value makes use of the specific robot pose, link speeds, mass distribution and contact location or uses a worst case value.
NOTE 2 The inertia of human body parts is addressed in reference documents listed in the Bibliography.
5.5.5.3 Risk reduction for potential contact between robot and operator
To ensure operator safety in robotic systems, risk reduction must focus on preventing harmful contact between the operator and the robot This involves identifying potential contact scenarios, assessing the associated risks, designing the robot and workspace to minimize contact frequency, and implementing measures to maintain contact situations below acceptable limits.
In risk assessment, it is crucial to recognize that the operator lacks any risk reduction measures, such as personal protective equipment, during potential contact events The identification process must take into account specific criteria related to these potential contact scenarios.
— origin of contact events, i.e intentional action as part of intended use vs unintentional contact or reasonably foreseeable misuse;
— probability or frequency of occurrence;
— type of contact event, i.e quasi-static or transient;
— contact areas, speeds, forces, pressures, momentum, mechanical power, energy and other quantities characterizing the physical contact event.
Objects with sharp, pointed, shearing or cutting edges, such as needles, shears, or knives, and parts which could cause injury shall not be present in the contact area.
NOTE 1 Suitable housings, covers or separating planes can be used to mitigate potential hazards.
NOTE 2 There can be other hazards besides contact, including process hazards.
Contact exposure to sensitive body regions, including the skull, forehead, larynx, eyes, ears or face shall be prevented whenever reasonably practicable.
5.5.5.4 Passive and active risk reduction measures
Risk reduction strategies for quasi-static and transient contact can be categorized as either passive or active Passive safety measures focus on the mechanical design of the robotic system, while active safety measures concentrate on the control design of the robotic system.
Passive safety design methods include, but are not limited to: a) increasing the contact surface area:
3) compliant surfaces; b) absorbing energy, extending energy transfer time, or reducing impact forces:
3) compliant joints or links; c) limiting moving masses.
Active safety design methods include, but are not limited to:
— limiting velocities of moving parts;
— limiting momentum, mechanical power or energy as a function of masses and velocities;
— use of safety-rated soft axis and space limiting function;
— use of safety-rated monitored stop function;
— use of sensing to anticipate or detect contact (e.g proximity or contact detection to reduce quasi- static forces).
The application of these and other related measures shall address the expected exposure of the operator, as determined by a risk assessment.
A combination of safety functions may be necessary, as the force limiting safety function is only effective up to a specific speed limit Therefore, implementing an additional speed limiting safety function is essential for enhanced safety.
If passive or active risk reduction measures fail to sufficiently mitigate risk, additional strategies such as guards or safeguarding may be necessary.
In any clamping situation involving a collaborative robot and human body parts, it is essential that individuals can easily and independently free themselves from the clamping condition.
5.5.5.5 Power and force control limits
The robot system will be engineered to minimize operator risks by adhering to the established threshold limit values for both quasi-static and transient contacts, as outlined in the risk assessment For guidance on determining these threshold limit values, refer to Annex A.
Robots designed for collaborative operations can be equipped with configurable limiting thresholds for various parameters, including forces, torques, velocities, and mechanical power To reduce risks associated with transient contact, it is essential to limit the speed of moving components, such as the robot, tooling, or workpiece, and to consider the design of their physical characteristics, like surface area Additionally, for quasi-static risks, implementing speed limits and similar design considerations is crucial, particularly for components that may pose a trapping or clamping hazard to operators.
The analysis of limit values for contact events on exposed body regions must focus on the most stringent thresholds These "worst case" limit values for transient and quasi-static events are essential for assessing the necessary risk reduction measures Appropriate design and safety measures should be implemented to ensure that the effects of identified contacts do not exceed these threshold limit values.
Figure 4 — Graphical representation of acceptable and unacceptable forces or pressures
To ensure safety in robotic operations, it is crucial to limit the robot's speed if its motion could potentially clamp or pin a body part between the robot and other items in the cell This limitation allows the robot system to adhere to protective boundaries for exposed body areas Additionally, the robot must be equipped with a manual mechanism for the operator to safely extricate any body part that may become trapped.
General
See ISO 10218-1:2011, Clause 7, and ISO 10218-2:2011, Clause 7, for information for use requirements.
Information specific to collaborative robot operations
The documentation for a collaborative robot system is tailored to a specific application and must be provided by the integrator, ensuring users have the necessary information for safe operation This includes essential safeguards and mode selection for collaborative functionality Additionally, the integrator must supply details on system design, adhering to ISO 10218-2:2011, Clause 7, which encompasses the manufacturer or integrator's identity, any testing organization involved, a brief description of the robot type and its collaborative application, as well as the name of the workplace where the collaborative robot is utilized.
Description of the collaborative robot system
It is essential to maintain the following documents: a) specification data detailing the use of the collaborative robot, including descriptions, drawings, and images; b) a comprehensive description and specification data for the safeguards implemented in the collaborative workspace, the entire workplace, and the collaborative robot system; c) a clear description of the controls for selecting and deselecting the relevant types of collaborative operations.
Description of the workplace application
The required documents include a description of the spatial environmental conditions, including entries, exits, and traffic routes; a detailed account of the equipment, installations, machines, optional tools, and production goods relevant to the application, along with their positioning, particularly that of the robot system; and comprehensive drawings and images.
Description of the work task
The documentation must include a detailed description of the operator's relevant work activities and the collaborative robot system's operations, along with a chronological sequence of all work activities, particularly those occurring within the collaborative workspace Additionally, it is essential to document hazardous robot-to-person distance measurements throughout all work phases and provide a description or drawing of the collaborative workspace.
Information specific to power and force limiting applications
For robot systems meeting the requirements of 5.5.5 by following the guidance in Annex A, the following requirements shall be documented: a) information specific to the robot, tooling and workpiece (see A.3.6), including:
2) the total mass of the moving parts of the robot (M); b) anticipated and reasonably foreseeable contact situations between the robot system and the operator, including:
1) the specific body area(s) that could be contacted (see Table A.1);
2) a declaration as to whether the contact is transient or quasi-static;
3) the anticipated surface area or geometric conditions associated with the contact surfaces;
4) the maximum permissible biomechanical limit(s) associated with the contact (see Table A.2); c) the proposed risk reduction measures selected:
1) active or passive risk reduction measures recommended (see 5.5.5.4);
2) if safety-rated speed control is used, the safety-rated speed limit value shall be documented (see A.3.6).
Robot systems that comply with the requirements of 5.5.5 and utilize alternative methods to those outlined in Annex A must provide pertinent data and information to support the establishment of the power and force limiting function.
Annex A (informative) Limits for quasi-static and transient contact
ISO 10218-2:2011, section 5.11.5.5, mandates that a risk assessment must establish the parameters of power, force, and ergonomics for power and force limited robot systems Additionally, details regarding the design of the collaborative robot system can be found in section 5.4.4.
This annex offers guidance on establishing threshold limit values for collaborative robot systems, focusing on power and force limiting applications It emphasizes that these limits can be derived from pain sensitivity thresholds at the human-machine interface during contact By utilizing a body model, pressure and force limit values for different body areas can be determined, which helps in setting energy transfer limits at the interface Additionally, speed limits for robots in collaborative workspaces can be defined to ensure that force and pressure remain below the pain sensitivity threshold in the event of contact with an operator.
The limit values in this annex are based on conservative estimates and scientific research on pain sensation.
The guidance in this annex is intended as an informative means to outline a method by which integrators can set limits in power and force limiting applications.
A premise of a risk assessment for power and force limited collaborative robot applications is that incidental contact between parts of the collaborative robot system and operator can occur.
In risk assessment, it is essential to identify the specific areas of the operator's body that may come into contact with the robot This is crucial because various body regions have distinct thresholds for tolerating biomechanical loads, which can affect the likelihood of sustaining minor injuries.
This specification introduces a body model that encompasses 29 distinct body areas organized into 12 body regions Figure A.1 illustrates the contact areas within the body model, while Table A.1 categorizes the specific body regions into general classifications, indicating their positions on either the front or back of the body.
Biomechanical limits are established to minimize the risk of injury to operators by controlling the biomechanical load generated by robot movements during interactions.
Pressure values can be utilized to estimate transient pressure and force limits based on conservative estimates from previous studies By modeling the transfer energy from hypothetical contact between a robot and a human, and considering fully inelastic contact along with the robot's payload capacity and the specific body part involved, we can determine appropriate speed limits for robot motion This ensures that the transfer energy remains below a threshold that could cause minor injury to a human during interactions in a collaborative workspace.
A.3.2 Maximum pressure and force values
Table A.2 provides quantitative maximum values for quasi static and transient contact between persons and the robot system.
The contact data in Table A.2 does not reflect any use of personal protective equipment or anything other than clothing typical of any working environment.
Although Table A.2 provides data for contact with face, skull and forehead, contact with these areas is not permissible See 5.5.5.3.
Body region Specific body area Front/Rear
Skull and forehead 1 Middle of forehead Front
Back and shoulders 6 Shoulder joint Front
Upper arms and elbow joints 12 Deltoid muscle Rear
Lower arms and wrist joints 14 Radial bone Rear
Hands and fingers 17 Forefinger pad D a Front
20 Forefinger end joint ND a Rear
24 Back of the hand D a Rear
25 Back of the hand ND a Rear
Thighs and knees 26 Thigh muscle Front
Lower legs 28 Middle of shin Front
29 Calf muscle Rear a D = dominant body side; ND = non-dominant body side.
Body region Specific body area
Quasi-static contact Transient contact Maximum permissible pressure a ps
Maximum permissible force multi- plier c
Face d 3 Masticatory muscle 110 65 not applicable not applicable
Upper arms and elbow joints
Lower arms and wrist joints
A study conducted by the University of Mainz established biomechanical values related to pain onset levels, utilizing advanced testing techniques on 100 healthy adults across 29 body areas The maximum permissible pressure values represent the 75th percentile of recorded values, indicating the pressure at which pain sensation begins These values are derived from a specific test apparatus and may vary with different equipment Additionally, maximum permissible force values, based on an independent study referencing 188 sources, aim to prevent minor injuries, adhering to the Abbreviated Injury Scale (AIS) criteria Future research is expected to refine these values for collaborative robots Furthermore, studies indicate that transient contact limits can be at least double those of quasi-static values for force and pressure.
Body region Specific body area
Quasi-static contact Transient contact Maximum permissible pressure a ps
Maximum permissible force multi- plier c
25 Back of the hand ND 190 2
Lower legs 28 Middle of shin 220
The biomechanical values presented are derived from a study by the University of Mainz, focusing on pain onset levels in 100 healthy adults across 29 body areas While the research utilized advanced testing techniques, it is based on a single study in a relatively under-researched field, with expectations for future studies to potentially revise these values The maximum permissible pressure values represent the 75th percentile of recorded values, indicating the pressure at which pain onset is felt, measured with a 1 mm² resolution on a specific test apparatus Additionally, maximum permissible force values, sourced from an independent study referencing 188 sources, are designed to prevent minor injuries, adhering to the Abbreviated Injury Scale (AIS) to avoid more severe damage Future research is anticipated to provide more specific values for collaborative robots Furthermore, studies indicate that transient contact limits can be at least double those of quasi-static values for force and pressure.
A.3.3 Relationship between pressure and force
For the purposes of evaluating the contact scenario for a collaborative robot risk assessment, both the force and pressure values need to be calculated and considered.
In a running robot system, if an operator enters the tool area, their hands may be caught by the tool or workpiece, potentially generating a force that is below the established threshold limit In this scenario, the pressure limit is likely to be the primary constraint.
In cases where a padded machine surface makes contact with a body area that has a larger surface area or a higher concentration of soft tissue, such as the abdomen, the pressure generated can be significant.
To minimize the pressure exerted on the operator, it is essential for the robotic system and the workpiece to maximize their surface area Incorporating additional padding can enhance this surface area, leading to a reduction in pressure.
Contact between rigid robot system components and human body parts can result in uneven pressure distribution, leading to pressure peaks on the contact surface In these situations, the peak pressure in the contact area becomes a significant factor.
The pressure and force limits outlined in this Technical Specification apply universally and are not confined to any particular surface or edge curvature For details on restrictions related to collaborative robot system components with sharp edges, such as knives or needles, refer to section 5.5.5.3.
A.3.4 Relationship between biomechanical limits and transfer energy during transient contact
The values in Table A.2 can be used to validate the performance of a collaborative robot system during quasi-static contact situations using measurement devices on the robot system.
For collaborative tasks involving transient contact, the contact scenario can be effectively modeled by following the outlined procedure This modeling relies on the understanding that the body contact region and contact area between the robot and operator are predetermined, allowing for the modification of energy transfer by adjusting the robot's velocity at the contact point.