How risk-tailored safety solutions protect robots, just like sunscreen protects humans from the sun
The human body can only produce the vital nutrient vitamin D through exposure to the sun. But without protective measures, this poses serious risks, which people alleviate by means of protective measures tailored to their environment—like sunscreen, umbrellas, hats, and protective clothing. Such “risk-tailored safety solutions” are also necessary for robots, which are appearing more frequently into our work and daily lives.
Robots are used in a variety of environments, from intralogistics to service, and are becoming increasingly diverse in their size, weight and speed. To achieve a suitable and appropriate level of machine safety for said robots, SICK conducts the legally required process of a risk assessment as efficiently as possible. Once the assessment is complete, the company’s comprehensive safety portfolio makes it possible to implement the most economically optimal solution in any case.
When it comes to a risk assessment, a risk must be reliably categorized before precisely analyzing the hazard it poses. This applies always, and to all areas, of human life. In the case of a risk assessment for sun exposure on human skin, for example, the safest option for avoiding UV radiation would be to sit in a dark room. But since humans run a serious risk of falling ill without sunlight, they’ve contemplated the risk and have developed several solution strategies. Depending on the intensity of the radiation, they might wear long sleeve, light colored clothing; stay in the shade, and/or use sunscreen with a suitable UV filter.
Scale your safety systems with SICK’s comprehensive portfolio
In the industrial and service-oriented world of work, classifying the measures according to the specific environmental factors when choosing protections is the key to success. At SICK, scalability means precisely adapting the safety solution to the identified hazard and having a portfolio that can adequately cater to the diverse range of applications.
The company’s offerings range from products, systems, and services with a high-risk reduction capability to solutions that can protect against lower risk hazards.
Higher risk
Performance level e (Pl e): safety light curtains
Pl d: safety laser scanners
Lower risk
Pl c: safety multibeam scanners
Pl b: safety distance sensors
Furthermore, individual components can also be incorporated into a system solution to provide protection that is tailored to customer and application-specific requirements (AOS object detection system).
The preliminary risk assessment starts by defining the limits of the machine functions and identifying hazards. The subsequent risk estimation and assessment follows this rule of thumb: risk is equal to the extent of damage times likelihood of occurrence.
Risk = extent of damage × likelihood of occurence
Depending on the application, this gives either a high or low risk, and is then classified into the required performance level (PL r) according to ISO 13849-1.
What happens after the risk assessment?
As a solution for reliable collision avoidance and protection of people when using heavy mobile robots with PL d, for example, SICK will always recommend using the nanoScan3 with its low space requirements and the rugged microScan3. Whether or not a solution for PL d is required for an application with a mobile robot is determined from a thorough analysis on a case-by-case basis.
Questions to determine this include, but are not limited to:
- Does the application involve an automated area with restricted access where only trained staff are present?
- How fast does the vehicle move?
- How heavy is it (when loaded)?
- How long is the braking distance?
In addition to answering these questions, the expert teams of mobile robot manufacturers and SICK safety experts will investigate how the risk could affect the severity of injury, how frequently and for how long the risk arises, and what the possibilities are for avoiding it.
What is severity?
When looking for a solution that is precisely tailored, adequate for the specific requirements, and nevertheless safe, it is necessary to first determine the “severity,” i.e., the degree of severity of the risk. Automated guided carts (AGCs), which carry only a small load and are narrow, light, and slow, fall at one end of the scale. Fast and large vehicles with a high weight and heavy load represent the other extreme.
Different requirements of safety functions will apply depending on the vehicle characteristics. The main direction of travel of heavy vehicles, for example, can be protected using a microScan3. But how can reversing of the same vehicle be adequately protected? Vehicles generally travel more slowly in this direction, which has a large effect on the degree of severity of the risk. A risk assessment might determine that the safety function for reversing can be adequately protected with PL c, or even PL b.
A similar concept applies for stationary applications for access and presence control, for example: pick-and-place robots. Lower risk severity levels apply for non-hazardous machine functions, light workpieces, and the application of very low forces during processes. Risk-tailored safety solutions are therefore able to achieve an optimum balance between the competing aspects of risk reduction, according to severity and cost effectiveness.
What is probability and risk?
Probability, i.e., the likelihood that hazardous situations will arise, is another aspect that needs to be considered when determining safety solutions. A low risk exists, for example, for cleaning robots operating after hours in a shopping mall or airport with no customers or foot traffic, and only trained cleaning staff present. In these cases, a risk-tailored safety solution based on PL c would be perfectly suitable for protecting the application.
Based on just a few examples, industry-typical standard solutions are not always technically necessary and economically sensible. Only by determining the actual risk can an efficient solution be found that is also safe, economical, and productive. Furthermore, this approach opens the door for new possibilities and intelligent applications beyond mobile applications.
How can you overcome your functional limitations?
With its comprehensive portfolio of sensors, SICK offers a scalability that can overcome functional limitations. For example, SICK has expanded its TiM series of 2D LiDAR sensors with safety sensors that meet PL b standards. Being safety sensors, the TiM7xxS variants also deliver safety-related measured values, thereby opening up new possibilities besides the familiar protective field. This makes it possible to not only detect the presence of a person, but also their position.
For example, a possible use case might be a position-dependent speed reduction to reduce the minimum distance of a safety-related switch-off and to optimize the availability of the mobile platform. This benefits users with a lower investment cost and a faster time-to-market.
Risk minimization with the primary goal of protecting people also opens further possibilities and can offer added benefits. Back to the example of avoiding UV radiation, if a person protects themselves against excessive UV radiation by using an umbrella, the surrounding materials will also benefit from this, e.g., the patio furniture and building materials will have a longer service life. Likewise, risk-tailored safety solutions can also help avoid property damage in human-robot collaboration.
The key to the productivity of each of these solutions is a tailored, precise analysis and a clear classification of the risks. SICK has a complete range of systems, products and services for this, and provides tailored and on-site advice to enable intralogistics specialists and AGV manufacturers to avoid over dimensioned and unnecessary solutions.
