Key Takeaways of this Article:
✅ How to combine HRI modes with industrial and collaborative robots?
✅ Which fenceless technical alternatives are possible with cobots and robots?
Combination of HRI Modes and Technical Alternatives
By combining the three modes SRMS, SSM and PFL, three different fenceless robot system concepts can be created:
- Concept 1: Industrial Robot in Fenceless Operation
- Concept 2: Collaborative Robot in Hybrid Mode
- Concept 3: Collaborative Robot in Exclusive Collaborative Operation
In the following, these three concepts are further characterized.
Concept 1: Industrial Robot in Fenceless Operation
- Used robot technology: Industrial robot
- Used safety technology: external safety (e.g. laser scanners)
- Used operating modes: full-speed (FS), speed and separation monitoring (SSM) and safety-rated monitored stop (SRMS)
Industrial Robot in Fenceless Operation
The first concept uses an industrial robot with external safety devices. These devices, such as laser scanners, detect the distance between operator and robot and adjust the robot speed accordingly. When a human stands in the white area, the distance is high enough and the industrial robot operates at full speed. As soon as the operator walks towards the robot into the yellow area, the speed and separation monitoring mode (SSM) is activated and the robot operating speed is reduced. If the operator stands close to the robot in the inner red zone, the safety-rated monitored stop (SRMS) is activated and the robot stops moving.
Concept 2: Collaborative Robot in Hybrid Operation
- Used robot technology: Collaborative robot (cobot)
- Used safety technology: external safety (e.g. laser scanners) and on-board safety (e.g. torque sensors)
- Used operating modes: full-speed (FS), speed and separation monitoring (SSM) and power and force limiting (PFL)
Collaborative Robot in Hybrid Mode
For the second concept a collaborative robot with on-board safety in combination with external safety devices is used. This combination enables a similar mode changing behavior like concept 1, with the difference that the cobot continues working in the inner zone by replacing the safety-rated monitored stop (SRMS) by the power and force limiting (PFL) mode. When an operator is present in the white zone, the cobot operates at full-speed. As soon as the operator approaches the robot, the cobot decelerates in the speed and separation monitoring (SSM) mode. In the green zone, the robot operates at the collaborative speed in the power and force limiting (PFL) mode.
The main advantage of this concept over concept 1 is the work continuation in the inner zone: while the industrial robot has to stop in the inner red zone, the collaborative robot can continue working in the inner green zone. The downside of concept 2 is the higher investment, since internal and external safety is used, while concept 1 uses only external safety devices.
Concept 3: Collaborative Robot in Collaborative Operation
- Used robot technology: Collaborative robot (cobot)
- Used safety technology: on-board safety (e.g. torque sensors)
- Used operating modes: power and force limiting (PFL)
Collaborative Robot in Exclusive Collaborative Operation
This concept uses a collaborative robot in exclusive collaborative mode, utilizing only the internal sensor technology without any external safety devices. The cobot is working the whole time at a reduced collaborative speed, independent of any external surroundings, such as person or forklift traffic. This concept is especially useful for dynamic environments like end-of-line palletizing cells, in which a safety fence would limit the accessibility to the system and industrial robots with laser scanners would have to stop frequently because of passenger traffic.
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