# Multipedal Robot in a Dark Warehouse

How a four\-legged robot senses, finds its way and walks through a warehouse with the lights off

By ycode99

Topic: Machines

[Open the interactive Jig](https://ask.jig.com/j/xmWl9uXzkHSR)

## Transcript

### 1. A night shift with the lights off

This four\-legged robot patrols a warehouse after everyone has gone home\. It has no eyes like ours, yet it can walk the dark aisles without bumping into anything\. Let's find out how\.

Robots like this weigh about as much as a large dog: roughly 30 to 55 kilograms\.

### 2. Seeing with invisible laser light

The spinning cap on its back is a lidar\. It fires pulses of invisible laser light and times how long each takes to bounce back\. Every echo becomes a dot, and the dots build a 3D map, even in total darkness\.

Light is so fast that an echo from a shelf 10 metres away returns in about 67 billionths of a second\.

### 3. Cameras need a lamp

Ordinary cameras need light to see colours or read a label\. So the robot's head carries its own spotlight\. Switch it off: the cameras go blind, but the laser dots keep mapping\.

Some inspection robots carry a lamp of almost 3,800 lumens, brighter than a household bulb\.

### 4. Where am I? Which way now?

The robot compares its new dots with a map of the warehouse it stored earlier, so it knows where it stands\. Then it plans a safe route around anything in the way, like this pallet\.

This trick is called SLAM: building and using a map at the same time\.

### 5. Four legs taking turns

To walk slowly, it lifts one leg at a time and keeps three on the floor, like a careful cat\. To go faster, it trots: diagonal legs move together\. Glowing feet are the ones touching the floor\.

Even trotting, robots like this move at about human walking pace: up to roughly 1\.6 metres per second\.

### 6. Twelve motors, quick decisions

Each leg has three motors: two at the hip and one at the knee, so twelve in all\. A computer adjusts them hundreds of times every second to keep the robot balanced\. Some robots also have springs in their joints to soften each step\.

The knees bend backwards, like the back legs of a dog\.

### 7. Feeling the floor

A power cable lies across the aisle\. Wheels might get stuck, but legs can simply step over\. Sensors in the legs feel when each foot lands, so the robot keeps its balance even on bumpy ground\.

### 8. Home to recharge

After about an hour and a half of patrolling, the battery runs low\. The robot walks back to its charging dock, crouches down and rests until its next round\.

A full recharge takes about three hours\.