In the lean management theory a so called Andon light indicates the status of a process. In the easiest case a machine can have the normal status or the error status. This principle allows assign a human operator to a machine or take the human operator away from the process flow. The principle can be used as well for increasing the productivity of a robot control system. The image on the left shows a robot who is maintaining a task under the control of a human operator. That means, the robot isn't autonomous, but a human operator is in the loop.
In the image on the right, the human is not needed and the robot can do the task autonomously. A robot can fluctuate between both states. From the perspective of maximizing the productivity the green status is the goal situation. If no human operator is needed, the costs are much lower. The decision is made not by the human operator but by the robot control system. With a self-monitoring system the robot is able to detect failures by it's own. Detecting if a pick&place operation of a robotarm was successful is much easier than doing the action with a robot.