The SWERVE
"The road to success and the road to failure are almost exactly the same." — Colin R. Davis
In 2023, I became the captain of the rookie FTC team 22042. Of course, instead of choosing a safe route, I decided to take a massive risk and oversaw the creation of the holy grail of FTC drivetrains—the swerve drive.
01 THE AMBITION
At the start of the development process, I created a V1 test rig to test the FDM vs. SLA gear manufacturing process, overall performance, and durability.
Spoiler alert: it failed miserably, not even lasting an hour of testing.
02 HUMBLE BEGINNINGS
The second test rig improved tremendously on its predecessor. It was rigid, used off-the-shelf angular contact bearings, and successfully endured over 1500 cycles carrying about 3.5 liters of water up and down. This is equivalent to over 3 kilometers or 1.8 miles of travel. The success of this rig paved the way for the full-scale drivebase prototype.
03 GLIMMER OF HOPE
Over the course of about two years, the swerve went through six major iterations. Starting with a tubular carbon fiver chassis, moving to aluminum tubes, and later, a custom sheet metal chassis made from 2mm AW5754 aluminum with over 1000 holes for weight reduction.
V1
V2
V3
V4
04 ENDLESS ITERATIONS
05 CODE SHENANIGANS
The main milestone was the swerve kinematic algorithm. At every wheel, it adds up the base drive vector with each wheel’s rotational vector to get the final output vector. The current angle and speed of each module are calculated from it’s motor encoders and run through independent PIDF loops to achieve a new target angle and speed.
There are also a couple optimizations to this algorithm. In short, if the robot is driving really fast, the turning should be slow and gentle, but if the robot is standing still, we want the wheels to turn as fast as possible.
06 REDEMTION
Every journey has a beginning and an end, and the Swerve is no exception. After years of development, it competed in Italy and many other local competitions, proving its reliability over and over again. It was a true manifesto of innovation in the FTC world.
Team 22042 Center Stage technical documents: