Safe collaboration of operators and industrial robots

When a person enters the workspace of an automatically running robot, the traditional solution to ensure safety is to stop the robot by using protective stop or emergency stop. Protective stop and emergency stop cut the servo power, which is a foolproof way to stop the robot. However, restarting can be laborious, since it must be done outside of the robot workspace. In addition, stopping a full speed running robot takes time, since the braking distance of the robot is quite long. Long stopping distance cause a long safety distance between a person and the robot. If the robot maximum speed can be reduced, the braking distance and also required safety distance is decreased drastically. To have practical safety distances in robot cells, the robot speed must be reduced before there is a need to stop the robot. Monitored safety-rated stop allows quick and even automatic restart, but to ensure safety, stopping performance needs to be monitored adequately. Typical solution for monitoring the stopping performance is robot's safety controller. VTT has developed a dynamic safety system, which monitors the speed and separation between persons and the robot in order to keep the stopping distance of the robot small enough to avoid collisions. The dynamic safety system enables safe continuous working beside the robot, automated restarting after a stop and switching tasks of the robot according to human position. The collaborative operations described in standards allow also power and force limiting in small robots or controlling the motion manually i.e. hand guiding, enabling device or hold-to-run buttons.