Every time I start thinking about robot design, I keep finding myself running into the same design constraint. Since I know that I'm going to be invoking this rule over and over again in my coming blog posts, I thought I should articulate it in detail early on. This way, in future posts, I can just say "The WID Rule".
The Wild Iris Discovery Design Rule for Industrial Robotics is defined by the following observation. "It makes no economic sense to replace a worker with a robot if that robot's total cost-of-ownership is not competitive with the total cost-of-labor for the worker it is going to replace."
I use the phrase "total cost-of-ownership", but I'm not really happy with it. It's just that I can't think of any better umbrella term that encompasses, in one phrase, the combined cost of everything that using a robot is going to entail.
Such as the purchase price factored over the life of the robot, the cost of operation and maintenance, and the labor costs to have someone in the field to monitor the robots as they work. There are other costs that most people won’t think about, like the cost of the barn or stable facilities where robots will be parked when not in use. There will have to be some kind of tractor-trailer carrier for moving the robots back and forth from one field to the next, and the labor cost of the driver to operate it. Then of course there will be registration and license fees and the cost of liability insurance for each of the robots. OSHA will no doubt get involved with certification and training requirements for anyone going to work around robots. Anyone who has worked in industry can probably go on and add many more examples of owner/operator type expenses that will go along with the introduction of robots to the farm workforce. So I’ll just stop here.
But anyway, back to the discussion at hand. If I asked any of my fellow engineers about this observation, they would, without a doubt, unanimously say, "yes, of course that's true." But I've never seen this observation reflected in any of the robot design specs that I've read about.
Here is an example of how a corollary of the WID Rule gives rise to a design specification.
WID Rule, Corollary:1, when designing a robot, it is the worker you want to duplicate, not the worker’s task.
To illustrate what this means, I’ll divide industrial robots into two classes. The assembly-line factory floor-mounted robot arm characterizes the first class. In this case, you have a robot intended to replace a stationary worker doing a single repetitive task.
Now move from the factory, outdoors to the farm, construction site, logging or mining operation. The first thing to note is that workers in this second “outdoor” category are not stationary. As an example from my own younger days as a logger, it was not uncommon at all for me to run/walk five miles or more a day as part of my job.
Another aspect of this second “outdoor” category is that tasks are never exactly repetitive; everyday and every work site always brings something new about it.
And a final aspect of this second category is that workers in these occupations are constantly called upon to do multiple tasks. As an example, consider the picking of organic leaf lettuce.
Since organic fields are smaller, they are not harvested using the harvesting platforms you would see in the larger non-organic fields. In this case, harvesting, cleaning, inspection, packing and loading are all done by the field workers themselves. Designing a robot that does just one of these tasks doesn’t help the farmer, since he/she will still have to have additional workers or additional specialized robots in the field to do the rest of the remaining jobs. Thus violating the WID Rule!
So to bring this observation back to the question of agricultural robotics, a design engineer needs to look at all  of the tasks a field worker is called upon to do during a day’s work and design to that. To focus on a specific task, such as “picking a strawberry” and then design a robot to do just that one thing might be a very worthwhile educational experience, but it will never give rise to a robot that will find a productive life outside of the engineering lab.
 "All" in this case means literally all. This includes everything from getting off of its carrier by itself, walking out to the field on its own, taking verbal instructions, working autonomously for hours at a time, and walking back to its carrier at the end of its work day.