Submarine touble

[SS-310]

So I set up my hydrofoils on my submarine and when it submerges, the bow lifts up at about 50 degrees. I tried adding lead but it doesnt help. I've never made a submarine before, so I might just be an idiot.

[SS-310]

My hydrofoils are right on the CoM too.
If the PID settings help, here they are
kP Gain: .500
Ti. Integral time: 3.00
Td. Derivative Time: 1.500
No test stims
Altitude Hydrofoil

[Rampant Rabbit]

Set one of the test stims to the depth you want, otherwise the PID doesn't know what depth to shoot for. Also check bouyancy if you've got airpumps. You should be able to see centre of bouyancy as well as mass (green cross vs blue for mass). And if that doesn't work, check you've got hydrofoils balanced front and rear. If there's more downforce from the rear, nose will lift.

[SS-310]

The test stims dont stay when I put them in, and in the PID it says somethings saturated? I dont know how to fix that.

[Rampant Rabbit]

try increasing Td to 3-5 and watch the graph.. tweak those until the lines settle down and it shouldn't get saturated. The test value should save, but noticed it didn't first time on the sub I tweaked in the other sub thread. Might be a bug, but it's saved on my campaign subs.

[SS-310]

Alright, i'll try it out

[SS-310]

Well it isnt saturated anymore, but the bow still comes up and the test stim isnt keeping a steady depth

[SS-310]

Its diving, gets to the set depth, and jumps out of the water

[Rampant Rabbit]

Your gain may be a bit high, and have you clicked the button for 'use test stim'? Sounds like it's either overcompensating on the planes, or just not balanced.. Hard to tell without having a look at it from the workshop.

[SS-310]

http://steamcommunity.com/sharedfiles/filedetails/?id=1120977675

[Rampant Rabbit]

So.. choice of sleep, or helping a sub in trouble.. And I like the design :)

Suggest a couple of tweaks..

Add another PID and set it to control pitch hydrofoils.
Add same amount of hyrofoils at the rear of the sub as you do at the front.. BUT make sure they're pointing backwards. Then the pitch control can set the rear planes to lift and front to dive to balance it out. The depth control PID will still keep it at the right depth.

I set the pitch PID to 5.5 & 5.5 for the last two values and pitch stayed around +/-2

If it rolls too much when turning, use some downward facing props set to roll LHS and RHS to stabilise that.. And if you want to... complicate stability, can also pair up & down roll thrusters to turn faster.. Or 'manouever agressively and unpredictably' if the PIDs give up..

[SS-310]

I dont know if I understand but I'll try anyways

[SS-310]

Alright, she works! Thanks man!