HRC is not equal to HRC

In human-robot collaboration (HRC), humans and robots work directly together without a safety fence. This opens up enormous potential. But HRC is not always equal to HRC. There are four possible scenarios of how humans and robots can work together effectively. Thus, there is a suitable HRC application for every requirement. Always in the focus: employee safety.

  1. Monitored Stop

The safety fence becomes superfluous as the robot stops immediately as soon as the human enters the collaboration room. To make this work, a safety sensor is installed. It ensures collision avoidance. In this case, it triggers the safe stop of the robot. The advantage of this type of HRC is that classic industrial robots can also be used here. This type of HRC is particularly suitable for applications in which human access to the working area of the robot is not normally expected and touching the moving robot is not necessary.

  1. Speed and Distance Monitoring

This type goes beyond the monitored stop. The robot makes its speed dependent on how close the human comes to the robot. It only moves so fast that it stops safely when the human reaches the robot. Latency times and braking distances and times are included in the calculations required for this. The corresponding relationships are described in the TS15066 standard. This type of HRC is particularly suitable for applications that are somewhat more time-critical and where people occasionally enter the robot’s workspace. The aim is to keep the loss of time caused by human access as small as possible.

  1. Hand Guiding

The contact between humans and robots is becoming more and more direct: humans guide the robot by hand at monitored, safe speeds. The permissible speed has been defined in advance by a risk assessment. The robot only moves when a three-stage enabling switch is actuated. Collision avoidance is ensured by the fact that human consent is only given if no collision between human and robot can occur. This type of HRC is particularly suitable for applications in which the human being guides the robot and brings it into a desired position. This can be the case for joining tasks when the robot is used as an intelligent lifting aid, for example when mounting batteries in electric vehicles.

  1. Power and Force Limitation

Unlike the other three strategies, the focus here is on collision control. Collisions between humans and robots are permitted, whereby certain biomechanical limits must be adhered to. These are listed in the TS15066 standard for technical specifications for different body regions. The technical specification distinguishes between two cases

  • Quasistatic contact: These are processes such as crushing or clamping that must be prevented. A safe force monitoring system is often installed for this purpose.
  • Transient contact or dynamic impact: Here the “collision” between robot and human is permitted. If, for example, the robot touches the hand of a human being, it is merely pushed aside. The prerequisite for this is that the robot has no sharp edges. In such processes, the force and pressure values transmitted to the human body are determined by the speed of the robot system. The values are maintained by the correct selection of the maximum, safely monitored robot speed. This form of HRC is suitable for tasks in which man and robot work together. These can be assembly tasks in which the robot holds one part and the human inserts another part or performs a small machining step.

 

In human-robot collaboration, man and machine work hand in hand. Read more about this topic at KUKA here.

 

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