Robot Safety in Human-Robot Collaborative Assembly

Human-robot collaborative assembly is revolutionizing manufacturing, blending human dexterity and adaptability with robot precision and endurance. However, ensuring robot safety in these shared workspaces is paramount. This article explores the critical aspects of safety in human-robot collaborative environments, discussing the technologies, standards, and procedures that protect workers while maximizing productivity. This information is vital for anyone involved in implementing or working alongside collaborative robots. The article focuses on industrial environments.

1. What is Human-Robot Collaborative Assembly?

Human-robot collaborative assembly, also known as collaborative assembly, involves humans and robots working together in a shared workspace to complete assembly tasks. Unlike traditional industrial robot setups, where robots operate in isolation behind safety barriers, collaborative robots (cobots) are designed to work alongside humans, often without physical barriers. This approach combines the strengths of both humans and robots.

Humans bring adaptability, problem-solving skills, and dexterity to the task, while robots offer precision, repeatability, and the ability to handle heavy or repetitive tasks. This synergy can lead to increased productivity, improved quality, and enhanced ergonomics for human workers. The key distinction is the shared workspace and the close interaction between the human and the robot.

2. Why is Safety So Critical in Human-Robot Collaboration?

Safety is paramount in any industrial setting, but it becomes even more critical in human-robot collaboration because humans and robots are sharing the same workspace and potentially interacting directly. Industrial robot, traditionally, are powerful machines capable of causing serious injury if contact occurs. Even with collaborative robots designed for safer interaction, the potential for harm remains if safety measures are not properly implemented.

The consequences of a collision between a robot and a human can range from minor bruises to severe injuries, or even fatalities. Beyond the direct physical risks, there are also psychological factors to consider. Workers need to feel safe and trust the robot system in order to work effectively alongside it. Therefore, ensuring robot safety is not only a legal and ethical obligation but also essential for the success of any human-robot collaborative application.

3. What are the Key Safety Standards for Collaborative Robots?

Several international safety standards govern the design and implementation of collaborative robot systems. One of the most important is ISO/TS 15066, which provides specific guidelines for collaborative robot safety. This technical specification builds upon the general safety requirements outlined in ISO 10218-1 and ISO 10218-2, which cover the safety of industrial robots.

ISO/TS 15066 provides detailed information on risk assessment, safety features, and validation methods for collaborative applications. It defines four collaborative operation modes: Safety-rated monitored stop, hand guiding, speed and separation monitoring, and power and force limiting. Adherence to these safety standards is crucial for ensuring that collaborative robot systems meet the necessary safety requirements. These standards often require that detailed information about safety procedures be accessible to workers. The page with information might be temporarily down or it may have moved permanently to a new web address.

4. What are the Main Safety Features and Technologies Used in Collaborative Robots?

Collaborative robots incorporate several safety features and technologies to minimize the risk of harm to human workers. These include:

• Power and Force Limiting (PFL): This is a fundamental safety feature of cobots. PFL robots are designed to limit the force and power they exert, ensuring that any impact with a human remains below safe thresholds. This is often achieved through the use of sensitive force-torque sensors and compliant joints.
• Safety-Rated Monitored Stop: This feature ensures that the robot stops and remains stopped if a human enters a defined safety zone. The robot will only resume operation when the human has left the zone and a deliberate restart command is given.
• Hand Guiding: This allows an operator to manually move the robot by grasping it directly. The robot’s sensors detect the applied force and move the robot arm accordingly. This is often used for teaching the robot new tasks or for fine adjustments during assembly.
• Speed and Separation Monitoring: This strategy uses sensors (e.g., laser scanners, vision systems) to monitor the distance between the robot and the human. The robot’s speed is automatically adjusted based on this distance, slowing down or stopping as the human approaches.

5. How is Risk Assessment Conducted in Collaborative Applications?

Risk assessment is a crucial step in implementing any collaborative robot application. It involves identifying potential hazards, assessing the associated risks, and implementing measures to mitigate those risks. The risk assessment process typically follows a structured approach, such as that outlined in ISO 12100, the general standard for machinery safety.

The risk assessment should consider all aspects of the collaborative application, including the robot itself, the end-effector (tool), the workpiece, the workspace, and the human tasks. It should also take into account potential misuse or unexpected events. The goal is to reduce risks to an acceptable level, ensuring the safety of human workers. The output of the risk assessment informs the selection of appropriate safety features and strategies. The information that page might be temporarily down or it may have moved permanently to a new web address.

6. What are the Different Safety Strategies for Human-Robot Collaboration?

There are several different safety strategies that can be employed in human-robot collaboration, depending on the specific application and the results of the risk assessment. These strategies often involve a combination of the safety features described earlier.

• No Physical Contact Intended: In this scenario, the robot and human work in the same general area but are not intended to come into direct contact. Safety is typically ensured through speed and separation monitoring and safety-rated monitored stops.
• Occasional Physical Contact Possible: This strategy acknowledges that occasional contact between the robot and human may occur, but the robot is designed to limit the force and power of such contact to safe levels. Power and force limiting is a key feature in this scenario.
• Deliberate Physical Contact Intended: In some applications, such as hand guiding, deliberate physical contact between the robot and human is required. Safety relies on the inherent safety features of the robot, such as force-torque sensors and compliant joints. Human-robot cooperation has a great influence on safety and ergonomics in industrial collaborative robotics.

7. How Does the Robot Controller Contribute to Safety?

The robot controller is a critical component of the safety system. It is responsible for monitoring the robot’s sensors, processing safety-related signals, and controlling the robot’s motion. The controller must be designed and certified to meet relevant safety standards.

The controller implements the chosen safety strategy, such as speed and separation monitoring or power and force limiting. It continuously monitors the robot’s position, speed, and force, and it will initiate a safety stop if any predefined limits are exceeded. The controller also manages safety-related inputs and outputs, such as emergency stop buttons and safety light curtains. Controller is used to ensure safety.

8. What Role Do Sensors Play in Collaborative Robot Safety?

Sensors are the “eyes and ears” of the safety system, providing crucial information about the robot’s environment and the presence of humans. Different types of sensors are used, depending on the specific safety strategy.

• Force-Torque Sensors: These sensors are typically integrated into the robot’s joints or end-effector and measure the forces and torques being applied. They are essential for power and force limiting and hand guiding.
• Laser Scanners: These sensors create a two-dimensional safety zone around the robot. If a human or object enters this zone, the scanner detects it and sends a signal to the robot controller.
• Vision Systems: Cameras and image processing software can be used to detect the presence and position of humans in the workspace. This information can be used for speed and separation monitoring or to trigger other safety functions.
• Robot Skin: Sensor used to detect touch.

These sensors provide real-time data to the robot controller, enabling it to react quickly to potential hazards and ensure the safety of human workers.

9. What are the Specific Safety Procedures for Collaborative Assembly?

In addition to the technical safety features, specific safety procedures are essential for safe operation in collaborative assembly. These procedures should be clearly defined and communicated to all personnel working in the collaborative workspace.

• Training: Workers must be thoroughly trained on the operation of the robot, the safety features, and the emergency procedures.
• Workspace Design: The workspace should be designed to minimize the risk of collisions and to provide clear visual cues about the robot’s operational area.
• Regular Inspections: The robot system, including sensors and safety devices, should be regularly inspected and maintained to ensure they are functioning correctly.
• Emergency Procedures: Clear procedures must be in place for responding to emergencies, such as a robot malfunction or a collision.

These procedures, combined with the technical safety features, create a comprehensive safety system that protects workers in human-robot collaborative environments. Safety procedures must be accessible to all members of the team. The website may be temporarily down or it may have moved permanently to a new web address.

10. What is the Future of Safety in Human-Robot Collaborative Systems?

The field of human-robot collaboration is constantly evolving, and safety technology is continually advancing. We can expect to see several trends in the future:

• More Sophisticated Sensors: Advances in sensor technology, such as 3D vision systems and tactile sensors, will provide even more detailed information about the robot’s environment, enhancing safety.
• Artificial Intelligence (AI): AI can be used to improve the robot’s ability to predict and react to human movements, making interactions safer and more intuitive. Machine learning algorithms can be trained to recognize potentially hazardous situations and trigger appropriate safety responses.
• Adaptive Safety Systems: Future safety systems may be able to adapt to changing conditions in the workspace, adjusting safety zones and robot behavior in real-time based on the specific task and the human’s actions.
• Improved Human-Robot Interaction: Advances in user interfaces and communication methods will make it easier for humans to understand and interact with robots, reducing the risk of misunderstandings and errors.

These advancements will further enhance the safety and efficiency of human-robot collaborative systems, paving the way for even broader adoption of this technology in various industries.

Key Takeaways

• Human-robot collaborative assembly involves humans and robots working together in a shared workspace.
• Safety is critical due to the potential for collisions and injuries in close human-robot interaction.
• Key safety standards, such as ISO/TS 15066, provide guidelines for collaborative robot safety.
• Collaborative robots use safety features like power and force limiting, safety-rated monitored stops, and speed and separation monitoring.
• Risk assessment is crucial for identifying and mitigating potential hazards.
• Different safety strategies are employed based on the level of interaction between humans and robots.
• The robot controller plays a vital role in implementing safety functions and monitoring sensors.
• Sensors, such as force-torque sensors, laser scanners, and vision systems, provide crucial safety information.
• Specific safety procedures, including training and workspace design, are essential for safe operation.
• The future of safety in human-robot collaboration involves more sophisticated sensors, AI, adaptive systems, and improved human-robot interaction.
• The website with safety information may be temporarily down or it may have moved permanently to a new web address. We need to be ready for such situations.