Small Kat Quadruped
The SmallKat project is a low cost, opensource, 3D printed quadrupedal platform designed and made by 2 WPI students (Keion Bisland and Xavier Little) along with framework code prepared by Kevin Harrington. The intention of the platform was to make a dynamics quadruped for the education/research and high-end toy markets. Using hobby servos and common electronics allows the overall price point to remain very low in comparison to its competitors.
SmallKat comes in 3 sizes, micro, small and xl. Micro is the smallest and at one pound, is the same size and weight as a kitten. Small is the current product offering and is availible in 2 different electronics solutions. XL is a research grade platform and is the product of an MQP at WPI.
The simple electronics platform is a single ESP32, 16 servos, 3 switch mode BEC's and a BNO055 IMU. This platform is easiest to source assemble using of OTS parts plus printed pieces. This platform streams sensor data up, and servo positions down, using the WiFi built into the ESP32. This configuration is easy to develop for because the code kinematics/walking gait code runs on a nearby PC. Kinematics and walking gait/body controllers can be swapped out on-the-fly without restarting SmallKats controller making development fast. Once algorithms are finalized and published to Git, they can be loaded by the second configuration and run in a tight real-time loop with the hardware. A downside to this configuration is that it is only as stable as your WiFi signal in the room.
The advanced configuration uses the same control coda as the Wifi version, except it loads a headless kernel and runs it on a RasPi onboard of the robot. This configuration uses an STM32 to connect to the BNO055 and servos, and bridge them directly to the onboard RasPi over HID. The first variant used a Teensy, but we wish for the full stack to be fully open source and so are switching to a custom STM32 board. This solution will be more expensive, and development loops will include pusing to a git server and re-starting the robots control stack to load new code. These trade offs suggest that both electronics solutions ought to exist as options, and researchers might want both in a given lab. Toy markets would only be interested in this type of fully stand-alone electronics, since it requires no setup to start the robot running.