Stewart Platform (6 Degrees of freedom) version 2 using (6) EMax Ex08MAII servo linear actuators. I used M3 screws and the servo linkage is formed from 1mmø paper clip wire. I have included my excel calculator along with the files for reference. It calculates the actuator length based on platform displacement in X,Y,Z, X:X, Y:Y, & Z:Z.
Servo Linear Actuator (95-137mm)
Added a few pictures/videos, 7" touch screen platform, X axis retainer.
Spending more time developing the PID control and tuning a bit allows the 6DOFv2 to balance a 0.75" bearing reasonably well. I still plan to fine tune even further. I did end up using an Adafruit STMPE610 (https://goo.gl/uHkAnf) touch screen control to get reliable location readings from the 7" touch screen (https://goo.gl/qONKCV); trying the (4) analog pin method resulted in too much noise and frustration. The (6) servo linear actuaors are driven by a (16) channel Keyestudio PWM driver (https://goo.gl/MrmK1g) connected to an Arduino Uno. While learning to tune a PID I stumbled across youtuber upgrdman (https://goo.gl/TWL8hO, https://goo.gl/hM7X9w) which developed his own telemetry software that reads arduino serial, very helpful!
Arduino sketch and Fritzing schematic posted. I was able to achieve a stable balance that recovers from light disruptions while large disruptions propagate out of control. If anyone is able to contribute or refine it let me know.
Z +/-20mm (Z Home +128mm)