How humanoid warehouse robots and their batteries work

HostWe see these videos all the time now of robots that look just like people, walking through aisles and picking up bins. It feels like the future is finally here, but I have to wonder if it's all for show. I mean, why do we need a robot with two legs and two arms just to move a box from a shelf to a truck?

GuestIt comes down to how we built our world. We didn't build warehouses for machines; we built them for us. Think about all the little things we do without even thinking. We step over a fallen piece of wood, we reach onto a high shelf, or we squeeze through a narrow gap between two carts. Most robots in factories today are just boxes on wheels. They're great on a flat, open floor, but as soon as they hit a single step or a bit of clutter, they're stuck. A robot with legs can go anywhere a person can. It can use the same stairs and the same doors. That means a company doesn't have to rebuild its whole building just to use a new tool. They just drop the robot in and it gets to work using the paths we already made.

HostBut surely wheels are easier to deal with in the long run. My car doesn't have to think about how to stand up. It feels like we're making things much harder than they need to be by choosing legs.

GuestYou're right that it's much harder. Walking is a constant battle. When you or I stand still, we don't think about it, but our brains and muscles are doing a ton of work to keep us from falling over. These robots have to do the same. They have dozens of small motors that are constantly firing, making tiny shifts to keep their weight centered. If the robot stops thinking for a split second, it falls. And that's where the energy problem starts. A wheeled robot can just lock its brakes and sit there using almost no power. A two-legged robot uses a lot of juice just to stay upright and not faceplant into the concrete. It's burning fuel even when it's standing still.

HostSo even when it's just waiting for the next job, it's draining its life away? That seems like a huge waste of power. Why can't we just give them a much bigger battery so they can last a full day?

GuestThat's the big trap. It's a loop that's hard to break. If you want the robot to work for eight hours, you need a bigger battery. But a bigger battery is heavy. Now the robot has to carry that extra weight. To move that weight, the legs need to be stronger, which means the motors have to be bigger. Bigger motors eat more power, so now that big battery you just added doesn't last eight hours anymore. It might only last four because the robot is so heavy now. If you add even more battery to fix that, the robot gets so heavy it can barely move or it might even break its own joints. Most of these bots only get a few hours of real work before they have to go back to the wall to charge.

HostThat seems like a deal breaker for a busy warehouse. If a human worker can go for hours but the robot needs a nap every ninety minutes, the math doesn't really add up for a business.

GuestWell, some teams are trying to cheat the system. Instead of waiting for the robot to charge, they're making the batteries easy to swap out. The robot walks over to a station, a machine pops out the dead pack, and slides in a fresh one. It takes about a minute. That keeps the bot on the floor. But there's another issue, which is heat. When you pull that much power out of a battery to move heavy metal legs, the battery gets very hot. If it gets too hot, it can get dangerous or just stop working. So now you need fans or cooling systems, which, you guessed it, weigh more and take up more space. It's a constant fight against the scales.

HostIt's like trying to pack for a long trip but every bag you add makes you too tired to walk to the car. Is there any way around this, or are we just waiting for some new kind of battery that doesn't exist yet?

GuestWe're mostly waiting for better ways to store energy. The batteries we have now are about as good as they can get. We need something that can hold way more juice without being heavy. Until then, the goal is to make the robot move more like we do. Humans are incredibly good at saving energy. We use our bones and tendons like springs to bounce, which saves our muscles from doing all the work. Engineers are trying to build those same kinds of springs into robot legs. If the leg can bounce back like a rubber band, the motor doesn't have to fire as hard. It's a game of saving every little bit of power they can.

GuestThe biggest win will come when a robot can walk for a whole day on a pack the size of a lunchbox.

HostThe dream of a tireless metal helper still seems to be waiting on a better way to store a spark.