News MY PRINCESS

Hello everybody,

After having had fun with my first project ( a seat mover named Docxdof, cf post “Lauching finally a 3DOF (seat mover) instead 6DOF low cost dynamic simulator”,
) that allowed me to understand the different technical aspects, my new one will be MY_PRINCESS (as I have little time for work on this new project, that will take time, but it is also a great pleasure to develop such a project…).


What does MY_PRINCESS mean:
Maximum – Yaw – Pitch – Roll – Immersive – Nucleo_based - Compact – Enhanced - Sixdof – Simulator

Why/how:
Maximum-Yaw-Pitch-Roll:
· by reducing distance between the cardans of the rig,
· by increasing crank arm length (using gear motor with spring assistance + smart geometric bounderies control),
Immersive:
· by better realistic forces simulation (using washout algorithms with tilt coordination)
· and probably VR
Nucleo_based:
· by using a STM32 board (compatible with Arduino IDE, I have already tested), much more power full because 32 bits instead 8, high quartz frequency, included a Floating Point Unit (I have also tested this board with a loop of floating cosinus -> 8000/s with my old arduino Uno3, 520000/s !! with the nucleo…)
Compact:
· by using rotary actuators instead linear,
Enhanced:
· enhanced pitch & roll for tilt coordination, etc
Six_dof-Simulator...

Consideration on actuators:
Electric/hydraulic or pneumatic linear actuators are generally quite cumbersome (very long) so not really compatible with compact simulator. Moreover, with this kind of actuator you need to separate a lot cardans of the rig, so that limits a lot pitch/roll angles (so also surge&sway simulation by using washout algorithm with tilt coordination).
The best compromise for me are electrical rotary actuators (powerfull, wide selection in voltage/rpm/power, less wear, more robust, easier to find, easy to customize torque/magnitude with more or less arm crank length, etc…), and if possible DC 220V (to suppress power supply and make easy the control, I think to develop in this case a triac command board).
BUT it is more complex to design an hexapode with this kind of actuators (difficult to select the good dimension, geometry, to adjust bounderies, etc…) and I do not want to rebuild several time mechanics...
SO the solution is to study the different solutions to find the best one, using a simulator of simulator ... For that I have developed an excel tool.

Simulator of simulator tool:
This tools will help me to finde the best geometry but also to make easy the development of the software on the nucleo board (I will just do portage from excel formula, the test with the same inputs if I obtain the same outputs... I have beginning and it is effectively a pleasure to write the soft and find the bugs...).
Here after a demo:


Drawing:
I will do the drawings after having find the good geometry with the excel tool. But that wil look like that:

So see you soon

Great Scott !!!

Thanks... I have changed the rights with public, could you try again the video...

**** MY PRINCESS - EPISODE 2 ****

Hey mates,
I have finished to optimize the geometry of my future compact 6dof simu, the result is:

=> asymetric hexapode is the best choice (90° instead 60° for motors layout, back cranck arms arround 160mm so longer than side crank arms that will measure arround 130mm),

=> special cardans placed well above the base of the seat, in order to increase the stability, make easier a rotation arround the head (to reduce risk of motion sickness), and always maintain the gravity center of the rig just forward the side cardans (in order to supress worm gear moto backlashes: the 4 legs on the side are always pushing, and the 2 back ones are always pulling with a lower forces than the 4 on the side allowing to use longer crank arms with the same power, arround 600W / 50 or 60 rpm)

=> the maximum moves are +/-35° (pitch/roll/yaw), +/-250mm (surge/sway), and +/-120mm for heave.

I have begun to enter the formula in my excel simulation (easly to transfer to arduino/nucleo code) allowing to check the potential clashes (legs with bottom of the rig). Depending of the size of the special cardans, that mainly gives limitation for yaw (and a little bit for roll and sway). But a short video here below will be better to understand all that.

See you in the next episode (3) = drawings (that will finally be very different than my first idea, see previous post)...

N.B: Comment/advise/etc.. are welcome. I have also a question: are these levels of angles & displacement compatible with VR visu?

video:

Special cardan (roll example)

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25°: