[Dan Royer] has noticed that most university projects involving a Stewart platform spend more time building a platform than on the project itself. He hopes to build a standard platform universities can use as the basis for other projects.
Stewart platforms are six degree of freedom platforms often seen hefting flight simulators or telescopes. The layout of the actuators allows movements in X,Y,and Z as well as pitch, roll and yaw. While large platforms often use hydraulic systems to accelerate heavy loads quickly. [Dan] is looking at a smaller scale system. His platform is built of laser cut wood and uses six steppers to control motion.
One of the harder parts in designing a platform such as this is creating a mechanical system that is strong, precise, and smooth. With so many linkages, it’s easy to see how binding joints could bring the entire thing to a grinding halt. [Dan] is currently using RC helicopter ball joints, but he’s on the lookout for something even smoother.
For locomotion, stepper motors are more than adequate – providing both the quick acceleration and holding torque needed to control the platform. Adafruit’s stepper motor controller boards provide the drive from an Arduino. The bottleneck in all of this is the i2C link with control of 6 steppers limiting the overall speed of the platform.
Software is another big issue on Stewart platforms. Kinematics of 6 DOF platforms are no easy task. To this end, [Dan] has gone open source. His Gcode demo is available at github.