the micro-fulfillment cambrian explosion
=robots =mechanical engineering
Warehouse automation has been very
successful. Here's a typical modern system. As you can see, a tall narrow
robot rides on a single rail at the top and bottom. The linked example is up to
42m tall. Items are stored on top of pallets, and the robot has a telescoping
fork, which might be able to handle 2-deep pallets to improve space efficiency.
Stores are much less automated than warehouses. When you go to a Walmart or
Aldi or Ikea, they don't usually have robots in the back - let alone smaller
stores. There are now many companies selling automation systems for smaller
items and smaller spaces. That's called micro-fulfillment, hereafter "MF".
There are many different configurations being developed and marketed, which
indicates that people haven't yet figured out the best approach. Here are
some approaches I'm aware of.
Kiva/Amazon
Robots lift an entire rack from below, by driving under it then spinning
while turning a ball
screw lifter. The rack is carried to a human picker who typically
transfers several items. This system was developed by Kiva, which was bought
by Amazon and renamed; it now has several clones.
Here's a teardown from 2016.
That Kiva design has some problems:
- That large
ball screw assembly is somewhat expensive for a component.
- The robots
carrying shelving are top-heavy so they can't accelerate quickly.
- The
height of shelving is limited by what workers can reach, which limits
storage density.
- Workers must reach for items that are high up or close
to the floor many times a day. A moderate amount of this isn't a big
problem, but workers at Amazon facilities need to do that so often that it
increases injury rates.
Elevator robots have a rack-and-pinion driven elevator that lifts a rotating platform. The platform has a grabber that reaches around the sides of totes and slides them onto the elevator. The elevator can them push totes onto fixed storage slots, so it can grab multiple totes in 1 trip.
Carrier robots have a set of powered rollers at a fixed height. Totes can be transferred between them and the elevator robots.
AutoStore
Robots ride on rails on top of a storage cube. They have 2 sets of wheels
that can be switched between. Each robot has an elevator system that can
lift/lower totes from above. Deep items are dug out, lifting and
transferring totes above them until they're available.
Alert Innovation
Robots have multiple sets of wheels, letting them drive on a floor,
drive on rails, and move vertically on rails. "Battery-free" probably means
they use supercapacitors.
Zikoo
Per-level flat robots lift pallets from below and move them horizontally.
They have 2 sets of wheels that can be switched between.
Vertically
telescoping forklifts lift pallets from the edge of levels. Pallets are
carried to/from there by the flat robots.
Brightpick Autopicker
Robots carry 2 totes, on a single platform lifted by a belt drive, with
a robotic arm between them to transfer items. The 2 tote slots on the
platform have rollers, and a rolling grabber with vacuum grippers to move
the totes on and off.
Brightpick Dispatcher
Like the Brightpick Autopicker, but with 1 tote and no robotic arm.
EXOTEC
Robots can drive on the floor and grab rails to move vertically. After
climbing to the right height, they use a telescoping fork to transfer a
tote.
Dematic Multishuttle
Elevators lift totes onto a load/unload zone with rollers.
Per-level shuttle robots carry totes horizontally. They ride on rails using
a single set of wheels, and have telescoping arms that grab totes from the
sides or push them.
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So, how has MF been going?
My understanding is, most retailers have been taking a hesitant
approach. They've mostly been waiting for someone else to show economic
success with some system, or doing a small pilot program and seeing how it
works out.
So, how have these pilot programs been working out
economically? My understanding is, they've successfully reduced labor
requirements for picking specific items by 1/2 to 2/3, but are more
expensive than the conventional approach of carting items out to shelves and
letting customers shop for themselves. (You have to be careful looking at
sales material for MF. Brochures will sometimes, for example, compare labor
savings to the purchase cost, but MF systems can also have substantial
maintenance costs and per-item software licensing fees.)
Here's a
study which concluded that (customers shopping online, MF item picking,
and pickup at the store) costs $1.52 per item vs $0.96 for conventional
shopping (for the entire logistics chain), but MF systems are cheaper than
other approaches to online orders. Yes, companies are getting "free labor"
from customers taking their items, but shopping online takes time too, and
being able to physically inspect products has some advantages.
So,
the MF systems might be better if they didn't take up the space used for the
normal restocking process, or if most orders were made online.
Grabbing items is a common task, and analysis of MF systems is a useful
starting point for estimating the costs of other possible applications for
small robots. Some adjustment needs to be done for robot complexity
required, robot utilization rates, task completion speeds, and so on, but
that's easier than starting from first principles.
Suppose there's a
restaurant where many ingredients are stored for chefs. With modern
Transformer systems, it's possible for a chef to verbally request an item,
and for neural networks to convert that audio to text, figure out what item
and task was being requested, and direct a robot to grab a tote with the
right item. Extrapolating from MF system costs, such automation would
probably be $0.20 to $1 per (storage + fetch), depending on utilization
rate, travel distance, etc. Supposing workers cost $30/hour, that would have
to save 24 to 120 seconds worth of labor per (storage + fetch) to be
potentially worthwhile.
Some restaurants
are now using
automated carts to carry meals to customers. These are obviously
mechanically simpler than picker robots, but they do have to navigate a more
unpredictable environment than a warehouse. Compared to an ingredient
picker, those also probably have a higher utilization rate.
In factories, robots are often
doing something that humans can't do as quickly or at all, and often operate
continuously. When you start looking at replacing humans in less-controlled
environments, the tasks are always things that humans can do well enough,
and they're done less continuously than on an assembly line.
Dishwashers and washing machines are unused most of the time, and they're
not particularly expensive per use. The problem is that picker robots can be
100x as expensive to buy, and also have higher operational costs. That's
comparable in cost to a car, but cars aren't a great comparison in general:
they're abnormally cheap for their complexity and power output compared to
other machines, due to a trillion dollars a year of them being made. A
single robotic arm can cost more than a car, too.
If robotic pickers
were better-designed and mass-produced, could the cost be brought down
substantially? Yes, I think so, but I think they'd still be thousands of
dollars. Supposing a picker robot and 2 years of operation could be done for
$5k, and serve 10 picks/hour for 2000 hours/year at a restaurant, that'd be
$0.25/pick.