How Does Star Wars’ BB-8 Work?
Ian Wright posted on December 14, 2015 | 27315 views

Unless you’ve been living in an ice cave on Hoth for the last two years, you should know of the upcoming release of Star Wars: The Force Awakens on December 18th.

The movie was destined to be a box office smash from the moment it was announced, but whether it will have the same technological influence as its predecessors remains an open question.

One of the most impressive engineering feats from the new film is R2-D2’s spiritual successor: BB-8. Unlike the droids from the previous films, BB-8 is portrayed by a remote-controlled robot rather than an actor wearing a costume or device.

To bring BB-8 to life at home, the Disney Corporation turned to Sphero—a company with ample experience building spherical robots. ENGINEERING.com got the chance to meet Sphero’s BB-8 first hand.

How does BB-8 Work?

On the inside, BB-8 is basically the same as Sphero: a balancing robot housed in a spherical shell. Both devices use four wheels mounted on two rotary joints and one prismatic joint to rotate the shell around the robot.

Inside BB-8 (Image courtesy of Sphero.)

Inside BB-8 (Image courtesy of Sphero.)

The control system is powered by an ARM Cortex M4, which utilizes an inertial measurement unit (IMU). This consists of an accelerometer and gyroscope for balance and control.

BB-8 communicates with a phone or tablet, using Bluetooth Low Energy (LE), as a remote control. That and the free-moving head are the major differences between BB-8 and Sphero.

The head itself contains two magnets corresponding to oppositely polarized counterparts mounted on a small post attached to the main internal body. The magnets keep the head aligned with the balancing mechanism inside, while two small rollers enable it to move freely on the sphere’s outer surface.

Another notable feature—also shared by Sphero—is the induction coil that is wrapped around a ballast weight in the robot’s bottom. This lets BB-8 charge wirelessly simply by placing it on its base.

As a whole, BB-8 illustrates an interesting optimization puzzle for engineers. In brief, the issue is how heavy the ballast weight must be for the robot to rotate its shell. If it’s either too heavy or too light, the motor will simply rotate within the shell rather than the rotate the shell itself.

How to Engineer and Build BB-8

The first prototype for BB-8 was delivered to Disney in 48 hours, an achievement Sphero chief scientist Adam Wilson credits to the company’s ample experience with similar technology.

“When we saw the pictures of what they wanted, we told Disney ‘We could totally 3D print a little dome-shaped head and attach it,’” said Wilson.

Although the BB-8 model that appears on screen was built by Lucasfilm, Wilson stated that Sphero took its programming inspiration from watching the puppeteers.

“We looked at the way they piloted it and used that as basis for our software design. Based on the personality they put into it, we asked ourselves what we would have to put into the design to get it to behave in a similar way,” said Wilson.

BB-8 comes pre-loaded with a number of macros based on earlier programming for Sphero. The major difference between the two is the modifications for taking the head’s movement into account.

“The control system has been customized to give the BB-8 personality as it turns,” said Wilson. “It’s not just a matter of keeping the head balanced, but making its movement look natural.”

He added, “It banks into the third dimension, similar to the way a fighter jet lowers its bottom when it banks.”

Sphero uses the Makerbot Replicator 2 to 3D-print its prototypes, as well as the Replicator Z18 for higher volume orders. The Formlabs Form 1+ gave Sphero the capability to print clear components for high-definition pieces inside the chassis.

All the technical files for BB-8 were done in Adobe Illustrator. Sphero is currently transitioning to using SolidWorks for CAD design, however, they used PTC Creo to design BB-8 in order to stay consistent with its manufacturer.

Surprisingly, one of the most impressive things about BB-8 is the manufacturing process behind its decoration.

Skeptical? I find your lack of faith… disturbing.

BB-8 on its charging station.

BB-8 on its charging station. (Image courtesy of Sphero.)

Each BB-8 takes over 100 pad print hits to fully decorate. For comparison, the maximum number on a Lego figure is roughly 20.

Six symbols are distributed evenly between the two hemispheres of BB-8’s outer shell. Each symbol consists of an outer orange ring with a black line around it and a unique silver pattern in the center.

Four of the six symbols are bisected across the hemispheres, which means that the symbols need to line up precisely when the two halves are joined.

“It seems simple if you just consider one pass of the printer,” said Wilson. “But when you have to flip it around between passes it gets a lot more complicated. We had to create a lot of robotic assistance with jigs to make it work right within the factory.”

BB-8 is the Droid STEM Education is Looking For

For the aspiring engineer or STEM enthusiast, BB-8 offers a glimpse into being a software or systems engineer. Users can create their own programs for the droid by connecting it to the Sphero SPRK app.

BB-8 is automatically recognized by the SPRK app. (Image courtesy of Sphero.)

BB-8 is automatically recognized by the SPRK app. (Image courtesy of Sphero.)

Padawans start by simply dragging and dropping directions for the robot to perform into the program. True Jedi Masters will be able to create their own blocks of code from scratch.

This is quite similar to the way many modern software and systems engineers operate: using system-level design software like Simulink and MapleSim. Engineers design a system from a library of validated code blocks, which they can drag and drop into a simulation. Engineers can then create or edit code blocks when needed.

BB-8 Hands On

Sphero’s BB-8 made quite the impression around the ENGINEERING.com office. Phones came out for pictures as soon as its box was opened and the little robot attracted a lot of attention as we struggled to learn to drive it.

Putting it into patrol mode lets BB-8 wander about on its own without user intervention. While it does, a connected device will display information such as distance travelled and internal temperature. This autonomy is what really brought out BB-8’s charm.

Working at my desk, I’d hear the odd clank from underneath as BB-8 bumped into a wall or cabinet. On one such occasion, I looked down to find it sheepishly peeking out from behind my garbage can.

Honestly, that’s the only way I can describe it: a robotic ball with an empty plastic head looked like it was embarrassed.

BB-8 is an undeniably impressive piece of technology and a great (albeit expensive) holiday gift for Star Wars fans, STEM enthusiasts and anyone who isn’t a scruffy-looking nerf herder.

For more information, visit Sphero’s BB-8 website.

(Story Thumbnail courtesy Walt Disney Studios Motion Pictures)

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