RE: [PSUBS-MAILIST] dive plane control scheme

["Stephen Pearce" <sjpearceqld@bigpond.com>]

Hi again Sean

I'm currently working on re-engineering a commercial auto pilot to do
some of the functions you require with two basic functions. Firstly to
keep the Sub level and secondly at a constant depth. I am trying to
replace the flux gate compass with a digital depth gauge and use a
rotary actuator with a pendulum to control the trim.

The system I'm working on is more about taking her down manually to your
desired depth then using this system to maintain that depth than full
automation.

Regards

Stephen Pearce
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Sean T.
Stevenson
Sent: Sunday, 19 February 2006 11:08 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] dive plane control scheme

Thanks Rick.  Yeah - I know about PID controllers, but actually, this 
would all work with proportional only control, apart from the rate 
control for avoiding target depth overshoot.  That could be PID, but I 
wonder if doing some tests and establishing a lookup table would be more

robust?  PID would be well suited for controlling the ballast system, 
though.  There are applications out there which purport to determine the

optimum tuning for any PID system, which might be a better route than 
trial and error.  Do you have any experience with this?  Rather than 
using distributed control, I was thinking that all systems might be 
controlled by a central computer with a backup, since those are required

anyway for other navigation functions, cameras, etc.  I don't know what 
the relative expense would be, but maybe there are important reasons for

going distributed?  I don't know - I'm a mechanical guy, and my controls

background is limited.  Also, I wonder if individual servomotors might 
be a viable alternative to a high pressure hydraulic pump and four 
actuators?  Higher initial expense but less current draw, perhaps?

Good thoughts.

-Sean


rick miller wrote:

> Sean:
>
>    The control system that you describe could be implemented with a 
> plc that has pid controllers built in to the software.a pid controller

> varies its output based upon the speed at which the change to the  set

> point is happening , the distance from the set point and the and the 
> time that the system has been away from the set point. Pid stands for 
> proportional, integral, derivative. Extreame care should be taken when

> tuning these controllers as they can become unstable durring tuning 
> and run away.
>
>    ebaying some used parts and software you would be able to do this 
> control system under about 5000.00$. The only trick is to use a 
> precharged resivor that is in excess of the operational depth of the 
> sub. That allows for the hyd rams to be placed out side the hull. 
> There are several types of feed back systems that you could use. The 
> best for this application would be a feed back system for a rotary 
> actuator that could be place into a oil filled casing, side wire would

> be the cheapest
>
> rick m






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