Question Stewart Platform style 6DOF motion range calculator?

I've been thinking about moving from my 2DOF setup to a 6DOF and am trying to do my homework first to see if the motors I have are up to the task. I read over SilentChill's excellent thread detailing a DC motor design (initially at least) and it looks like it is fairly feasible. My big question is in trying to understand the range of motion to expect from different geometry. The FAQ has the motion calculator for 2DOF systems (I already used it on my first build to get range of motion and CTC calculations), but I'm wondering if something similar exists for Stewart platform type 6DOF systems? I did find Eric Middeldorp's kinematics and forces spreadsheet in the FAQs for a 6DOF, which is a great start in at least understanding what kind of accelerations and forces I can expect from my motors, but I would like to close the design loop a little more. The spreadsheet does kick out link lengths at any given position, so I suppose I can get there eventually with a lot of guess and check, but mostly just curious if anyone has already done that before I get too deep into adding some calculations to the spreadsheet.

Did you ever find something to help you with this request? I am looking to do the same investigation to help with determining a base and platform geometry that will meet the motion rage I would like to attain.

Thanks,
Chad

Sort of, I took a couple of different approaches and kind of mashed them all together. The FlyPT Mover software has a really nice visualizer built into it once you figure out how it all works. I used that for a lot of my guess and check work to see if what I was designing in CAD was also making sense in the software. FlyPT does a really nice job of turning actuators red when they exceed their limits, so I used the sliders there to move the platform around and see what kind of range of motion it thought I had. Granted, I think "range of motion" is a bit of a loaded term. By that I mean if I'm only moving in a single axis at a time (say pure lateral side to side motion with nothing else) I might have +- 300mm of movement, but once you start adding any tilt or other motions mixed with that the overall range will decrease, so I'm not sure it really tells you the limits quite the same way I was hoping/thinking, but I found it to be very useful regardless. I built up an assembly in CAD that I was trying to put through similar motions to confirm clearances on my design (namely around the pedal setup as that seems to be the biggest issue going between the front two actuators).

So my general process was design something in CAD, translate those points into the FlyPT software to get a range of motion, put that range of motion back into my CAD and then check for clearances. I haven't had a chance to do much since then though. I bought parts for one test actuator so I could build a test setup on a board and confirm that my control system is going to work, but the project has stalled for the time being due to funds. Hoping I might get some more parts for my birthday soon though, so might be picking up again in the near future.

Just for your info, I created a Stewart platform widget you can use to try your design. You can find it here:
https://www.opensimgear.org/calculators/stewart-platform/

If you have any feature to suggest let me know

I really like your widget. It looks fantastic! But flypt has you beat on visualization of motion. I would love to see something similar on yours. Mover uses sliders that you can move to see the rigs range of motion per axis. This is very useful.

I will give you an example. Let's say I know I want my rig to handle 2 inches of heave, surge, and sway travel, as well as 30 degrees of pitch and roll. I can set these limits in mover then position the rig to its max pitch and see if I still have travel for my 3 translations. If not I need to rearrange my design.

The bummer with mover is the visualization is kinda crappy. Yours is much cleaner, and its web based which is slick.

It would be even more useful to add loops to the motion. For example I could loop my 2 inch heave through its travel constantly while I slider around my pitch or roll and check for issues.

Easy to dream haha.

It's all doable, I have never seen flypt, just some images of it. I was actually planning on adding limits to the length of the actuators so by tweaking the length you can see the motion limits changing.

I'll have a look on flypt to understand all the functionalities. I did not make any progress on the website since I wanted to finish building my control cabinet for the CNC machine. Also I posted this widget in more places and was hoping for some feedback but got none till now

p.s. the widget has sliders already, on pitch for example there is a small bar near the number that you can slide around.

Oh yeah I didnt notice the sliding effect there. Nice. Glad you are going to add the limits. Also rotary actutors would be useful.