Safety technologies and tools

ISO 10218, which applies to human-robot collaboration (HRC) in the industrial sector, describes four collaboration scenarios. Each scenario has specific requirements for the capabilities of safety-related components. However, a lack of expert knowledge about legal requirements often makes companies reluctant to start using HRC. Many HRC stations use force and power limits as a safety mechanism. This results in slower speeds, unclear cycle times and an uncertain return on investment.

To help companies, Fraunhofer IPA has developed an HRC catalog. The catalog assesses the type of HRC, evaluates combinations of safety components, and recommends a suitable safety principle on the basis of a list of questions.

The HRC assessment tool makes it easier to estimate the cycle time for a specific HRC use case. With the help of the Excel tool, processes can be simulated, and cycle times and investment costs calculated. This gives companies a sound basis for making decisions about their planned HRC application.

With the help of a questionnaire, the HRC readiness check first examines whether the general conditions in a company are suitable for deploying cobots and then describes the necessary capabilities to implement collaborative robot systems.

Companies receive an assessment of the readiness level of their planned HRC application, enabling them to pinpoint any gaps between the actual and target state. A recommendation on the use of cobots is based on this. In addition, various scenarios can be considered so that modifications to the workflow or to safety measures can be evaluated.

Making robot grippers safe is often still a major challenge. The Balanced Decoupling Unit (BDU) enables non-collaborative robots to identify collision potential between the originally unsafe gripper and its environment. The BDU can be used for contact situations in the z joining direction. This makes it possible to increase the approach speed during assembly processes while complying with force and pressure limits at the same time. The BDU also transforms the clamping contact into a free impact: Because ISO TS 15066 specifies higher biomechanical limits for this, the performance of the application is improved.

Configuration:

• Permanent magnet generates force of 200 N
• Pneumatic cylinder generates counterforce of 100 N with a pressure of 4 bars
• Resulting decoupling force of 100 N to ensure assembly process without locking mechanism

BDU cover:

• Covers sharp edges
• Prevents human hands from coming into contact with the moving fixing plate

For safety reasons, the rising degree of automation in production invariably results in the spatial separation of man and machine. Consequently, very few conventional heavy-duty industrial robots have been used in collaboration with humans up to now. This is because the human body is unable to absorb the high kinetic energy of the robot in the event of a collision.

Researchers at Fraunhofer IPA have therefore developed a coupling unit that significantly reduces the kinetic energy transferred when a collision occurs. The coupling unit is intended for transient contacts in the x-y direction. During the collision, the mass of the robot is decoupled from the mass of the workpiece and/or tool. The conversion to transient, i.e. only short, contact situations enables the HRC cell to be designed with higher force values and speeds. The use of magneto-rheological fluids results in reaction times in the millisecond range in the joints of the decoupling unit.

The technology is patented for use in HRC applications. By adjusting the magnetic fields, the coupling can also be used as a Remote Center of Compliance, enabling a local joining force to be set for joining operations, for example.

Up to now, the risk assessment, optimization and configuration of an HRC cell has mostly been carried out manually. This is an extremely time-consuming process and requires the necessary expert knowledge. IPA researchers have now developed a tool that not only automatically identifies and evaluates hazards but also selects suitable safety measures for the HRC cell: Simulation-based Automated Risk Assessment (SARA).

To start the assessment, SARA needs a 3D layout of the workplace and a description of the processes. It then uses machine learning to initiate the automated identification and assessment of hazards. The proposed safety measures are optimized in terms of cost, cycle time and flexibility.

The current version identifies transient and static hazards and also makes recommendations about configuring safety measures. In practice, risks are still assessed and rated manually, but the IPA team is working on an automated solution.

The Failsafe PLC Configurator helps safety engineers program safety PLCs (F-PLC) for robot applications. The idea behind this is to standardize design processes and map machine safety as a safety state. Programs can be created on the basis of a safety specification. The F-PLC Configurator makes it easier to identify F-PLC inputs and outputs. It also provides a checklist for validating the final program. This speeds up the process for safety engineers because knowledge about the structure of the safety program and safety resources is stored in databases.

Technical implementation:

• Simple GUI with input parameters (components from the application and safety principles)
• This is based on model-driven databases already implemented by IPA

Output:

• Specification regarding safety configuration on safety PLCs
• Checklist including description of the test to be performed to validate correct implementation of the safety configuration, e.g., to check that the robot stops moving when someone enters the laser scanner field.

The tool links input information and compliance with all safety conditions.