Wheeled quadrupeds have long been an exciting topic to me, and so with Quadruped V3 (gold/red) being objectively better than Quadruped V2 (blue), I decided to start experimenting with the concept by upgrading the old robot before investing in a totally new design.

Hardware-wise, there’s nothing special. I used the same design as Stride’s lower legs and same motors, but found smaller and lighter wheels (which got matching custom wheel hubs).

One of the early painpoints was that I had to redo the SPIne firmware completely to reliably handle 4 motors per bus (previous implementation leveraged the fact that there are 3x CAN outgoing mailboxes for the 3 CAN devices used). A few robot explosions later, and a lot of firmware changes, and now the SPIne firmware is much more adaptable (running 7 motors for the arm) now.

As for controls I’ve been trying some naive implementations to get started. Things like, commanding 0 X velocity to the minimally modified Mini Cheetah WBIC MPC, and handling X velocity and Z angular velocity mostly in the wheels. It functions but there’s certainly room for improvement. It also doesn’t help that I haven’t modified the dynamics to include the much higher leg inertias or that this robot still uses the medicore IMU.

Unfortunately the hardware (mostly the re-used actuator gears) for QV2 isn’t the most reliable so I’ve had a bit of a frustrating time testing on this robot. I’ll revisit this project in the future with a new robot likely.