SPRK: A low-cost stewart platform for motion study in surgical robotics

To simulate body organ motion due to breathing, heart beats, or peristaltic movements, we designed a low-cost, miniaturized SPRK (Stewart Platform Research Kit) to translate and rotate phantom tissue. This platform is 20cm × 20cm × 10cm to fit in the workspace of a da Vinci Research Kit (DVRK) surgical robot and costs $250, two orders of magnitude less than a commercial Stewart platform. The platform has a range of motion of ± 1.27 cm in translation along x, y, and z, and of ± 15° in roll, pitch, and yaw directions. The platform also has motion modes for sinusoidal motion, breathing-inspired motion, and multi-axis motion. Modular mounts facilitate pattern cutting and debridement experiments. The platform's positional controller has a time-constant of 0.2 seconds and the root-mean-square error is 1.22 mm, 1.07 mm, and 0.20 mm in x, y, and z directions respectively. Construction directions, CAD models, and control software for the platform are available at github.com/BerkeleyAutomation/sprk.