How to define a Rig?

I have a 3DOF motion platform with one dc motor in the front and two dc motors in the back. I assume that's a "3DOF with 3 rotating actuators"?

I'm completely baffled about how to configure the Rig part of PT Mover for the platform... I'm using a serial interface to kangaroo/sabertooth drivers for each motor. I've successfully configured the source (DCS) and i get values in the pose module which I can modify there, but I don't really know how to approach the rig module.. any help would be greatly appreciated!

Pictures of my current config attached. I must confess, I dont fully understand what I'm doing in the Pose and Rig screens yet. My challenge is understanding how to determine appropriate gains and ranges in Pose and then appropriately configure the rig based on those settings...

Totally missed that first thread, I'll check it out. I did see the 2nd but didn't go too far in that one as I thought it was for 6DOF setups, but I'll see what I can learn from it.

how about a photo of your physical rig? maybe '3dof with 3 rotating' isnt the best to start from

I'm travelling at the moment, so cant take a picture, but this would be the closest picture I could find on the web... 2 motors in the back, one in the front. Corners are raised and lowered by levers on the motors with about a 80-90 degree range of motion.

Yep if your rig looks like that and the motor axles and upper frame pivots can be described as lying on circles of radius R1 and R2 that will work.

from your description, you might be going about it backwards. define the rig before you define the poses. the rig will not change.

then, without powering the physical rig, bring up the 3d viewer so you can see what the effects are. using the pose sliders, determine the absolute maximum physical travels on heave, pitch and roll. the links in the 3d picture will turn red when they get there. lets say its 200mm, and 30deg for each tilt. then, enter HALF of those in the limits on the rig (100mm, 15deg- because you want other axes available when you are at a single axis limit) i also like to set the pose filters to LOGISTIC(VALUE;100;1) and LOGISTIC(VALUE;15;1) so it approaches those values gently.

on all the pose positions, set everything to Manual except heave. run the game, fly/drive in extreme conditions, and see what the movement will be like. (still with the 3d viewer, not the real rig!) use input gain so that the slider isnt going off the ends and turning red. then modify the filters and output gains so those move at the speed you like and dont go overlimit there either. set heave to Manual at 0 and then repeat with pitch, and then roll all by themself.

Then, turn off manual mode. When you are happy with the 3d viewer motions, run power to your motors and hang on!

@smitty Great post! thank you, that guidance will help, although it creats some more questions too

I'll start by trying to ensure I define the rig as closely as possible first. IF i understand correctly, in my case...

- Range is the allowable angle carved out by the lever attached to the motor axis (80 degrees or so between limit switches)
- Middle is the angle of the shaft with respect to the ground when the motion platform in the neutral position (0 degrees in my case since the the lever is parallel to the floor in the neutral position)
- Crank is the length of the lever from the center of the motor axle to the center of the rod connected to the chair (40mm for me)
-Rod is the length of the rod or arm from the end of the motor lever to the bottom of the platform (270mm for me)
-R1 and R2 I need to work out still...

Once these Rig values are correct, I need to move the heave, pitch, and roll sliders in the pose dialog and adjust the pose limits values in the rig dialog to prevent any red (set values to 1/2 the value that caused the red to leave room for other aces). Pose limits for heave are in mm, and pose limits for pitch and roll are in degrees. Add Pose Filtering, then test using the game and the 3d visualization , not the actual platform.

Did I get all of that correct?

Thanks for your help!

Yes but i think range is +/- so if your full travel is 80 you'd put 40 in the range box

I'm still a little lost... I have my rig set up as follows, however with 0 in every pose value the rig shows an actuator position of 9.7. I would have expected it to be 0?

second question is the behavior of the heave slide doesnt seem to be symmetric. if I change the pose limit for heave to 20, then when I move the slider to the right i get different behavior than if I move the slider to the left... shouldn't the behavior be symmetrical?

yes, 9.7 is correct, as its based on the +/- limits of heave. the geometry of the crank means that the angle swept to go from midpoint 0 to +30mm is less than going from midpoint to -30mm, so it starts a little higher.

hmmm, maybe I have the rig geometry a little wrong then, or I am just having trouble visualizing. My crank on the actual rig is parallel to the ground when in the middle position (or at least what I call the middle position - half way between the limits of the range).

What in the rig definition should I be looking at to correct that?

first off, changing first angle from 0 to 60 changes the actuator center postion from 9.1 to 1.3.. i dont know why that would matter, or what is going on with the geometry calculation, pmvcda will have to explain that.

looking at you definitions again - Middle: this is the angle from the ground where there is symmetric angular travel of the shaft. has nothing to do with where the heave midpoint is.

i drew a diagram. the calculations are close to what is reported in flypt.
if your crank moves equally 40deg up and down to its hardstops, then your middle angle is 0.

note how the heave travel is +/- 25.71 from some point. THAT is your mid-travel point or "default height".
trace those crank/rod lines back, and youll see the travel midpoint is 4.38 degrees up from horizontal.

@smitty , thank you, the visual helps. If R1 & R2 a radius or diameter measurement? I'm assuming radius since they use the letter R

Yep you can look at the drawing in the rig page (little arrows on the bottom left) to see the definitions

I ended up with the following rig and pose settings so that nothing goes out of range when the pitch, roll, and heave sliders are moved to their extremes individually. However I can force out of range conditions by moving more than one of those sliders to their extremes. Is this normal or do I need to eliminate those? The ranges seem much smaller than I would have expected. Maybe I'm still missing a basic understanding of how all of these values interplay with each other. I might need some remedial training from someone on discord for 10 or 15 minutes lol.

Any insight to the numbers below would be greatly appreciated.

those rig limits are pretty small.. is the crank limited to moving less than +/- 40 degrees?



also your rig is referencing "Pose from motion (1)" but your graphic shows "pose from motion" so those sliders will have no effect.

post some pictures of your rig, and maybe a detail of the motor/crank area.

sorry, I had the wrong window in front. update attached. Yes I agree, very small limits. The motor crank has a full range of almost 90 degrees, I used 80 to build in a little safety margin... so yes 40 degrees in each direction.

I will post some pictures in a bit.

picture of motor detail...