November 18, 2019

Lean production with the helpmate service robot

In the mid 1990s a new service robot was presented to the public, the Helpmate robot. The device was designed to support employees in a hospital. From a technical perspective the Helpmate robot was gorgeous. It was equipped with modern sensors and the onboard software was working error free. Unfortunately, the helpmate robot was from a commercial perspective a failure. Only few amount of customers were interested in the product, and if they bought a robot, they were disappointed.

The problem isn't located in the Helpmate robot itself, but the low productivity of the robot has to do with a certain human machine interaction. To use the robot as a tool to improve the logistics in a hospital a certain management philosophy is needed which is explained in the following blogpost.

The concept is oriented on the Andor switch in lean production which is a robust bottom up technique to organize workgroups in an assembly line. Each robot has a stack light which can be either red which means “error, human intervention is needed” or green which is equal to “everything is ok, no human is needed”.



The picture shows a fictional hospital which contains of 5 helpmate robots plus two human operators. Two of the robots are indicating a problem. They are trapped in the corridor, something with the tray isn't correct or the software has a malfunction. The red indicator signals the human operator that he is needed by the robot. The other three robots are operating within the specification, that means they are executing a delivery job and they doesn't need the attention of a human expert.

It's important to understand that the robot control software which is installed on the onboard computer is only a part of the overall workflow. To use a robot or a machine in a broader context, some kind of execution monitoring is needed in which potential failure are anticipated. In the example picture two human operators are needed to solve smaller and larger problems with the fleet of helpmate robots. Their task is to approach a red blinking robot and fix the issue. It's relative sure, that during 24/7 operation one or more of the helpmate robots will switch from the green status into the red status. It's not possible that a software alone is handle to all situations. The advantage fhe employees is, that at least the helpmate robots who are in the normal mode can work without human intervention. They are doing their job and transport tablets from point A to point B.

The stack light improves the human machine communication. If all the lights are green the robot fleet is working with the maximum productivity. If the robots or the envirionment are in bad situation some of the robots or sometimes all will switch in to the error mode, which means, that the productivity is very low. If the robot doesn't move and if a human operator is needed to fix the issue, the overall work can't be done. That means, the fleet is producing costs but it doesn't provide a service in exchange.

Tool based robotics

Running a robot can be done in two different modes. In the first mode, a robot has the full attention of a human operator. He has switched on the device and likes to observe what the robot is doing. Such a workmode is very common for synthetic robotics challenge, in which the behavior of the robot is evaluated and the audience is interested in every movement the robot is doing. Unfortunately, such a workmode is equal to a low productivity. If one or two human operators are observing the robot all the time, the factory has to pay the human operator. At the end, the overall costs are higher than without a robot in the loop.

Because of this reason a second workmode is needed, in which a robot runs in the background and can be managed as a tool. That means, that no human operator is observing the robot, but the device is in a blackbox and nobody knows what exactly the machine is doing right now. For a realistic workflow used in assembly lines and for real world application in general it's important that the robot is able to switch between the modes. The reason is, that each mode has advantages and disadvantages and for long term operation both modes are needed. What will happen in reality is, that a robot stays for a timespan in mode1 (red) and for a certain timespan in mode2 (green). This allows the financial department which has to calculate if the robots are a great investment to estimate the overall productivity. For example, if a robot stays 90% of the time in the red mode, the costs are too high, and the robot should be replaced by a different model.

Human intervention

The picture shows the robot and the human operator at the same time. The robots have to a task which is deliver something in a hospital, and the humans have to do something as well which is observing the robot during operation. A single robot might be working autonomously, but the overall fleet can't do so. During runtime, it's very common that at least one robot will show the red light. This is the trigger for human intervention. Without the two humans in the loop, the robot fleet of five robots isn't able to work. The reason is, that the onboard software isn't highly enough developed to fix all possible interruption by it's own. Even if the programmer has made a great job and the pathplanner is working robust, it is very likely that in real world application the planner will fail to plan the path sometimes.

Instead of arguing that this situation is not allowed to happen or to estimate that technicans have to improve the software, the better idea is to estimate such situation on a management perspective. The combination of 5 robots plus 2 human operators allows a 100% uptime. That means that the workflow never stops. From the customer perspective this is equal that he can use at any time a robot to deliver something to the destination.