Re: [PSUBS-MAILIST] Questions, questions and more questions

["Sean T. Stevenson" <ststev@uniserve.com>]

Just too add to this thread, for my conceptual PSub design I had
originally considered adding PLC controlled auto-altitude
functionality, in addition to auto-heading and auto-depth.  I realized
that there were a couple of problems with this.  First, I needed an
altitude transducer in addition to the main 360 degree sonar, and this
was incredibly expensive.  Second, for accurate altitude control at
speed you need a fairly high frequency ping.  When the bottom gets
stirred up, or if you pass over a halocline or some sort of obstacle,
you will get a false return - this will happen frequently if you want
to operate right over the bottom.  Third - to cut down on false returns
you need to average out the distance over some number of pings, which
reduces the resolution and makes it unsuitable for high speed. 
Solution:  scrap it and just stick with auto-depth.  Depth information
is provided to the controller by a pressure transducer - cheap,
accurate and consistent.  The pilot should be able to see the upcoming
terrain and jog the depth to compensate, or if you are stationkeeping
for a long period of time, to compensate for tidal and weather effects.
 There is a switch on the maneuvering joystick to jog the depth
setpoint up or down.

I would encourage anyone who doesn't have a clue what I'm talking about
to learn about PID controllers.  They give you incredible flexibility
over the control of just about anything on your sub.  As an example,
the auto-depth jog switch I just mentioned could be programmed to jog
the depth setpoint at a rate of 1/2 meter per second for the first five
seconds you hold down the switch, and 1 meter per second thereafter, or
whatever you prefer.

-Sean


On Thu, 21 Sep 2000 15:58:34 EDT, TeslaTony@aol.com wrote:

>In a message dated 9/18/00 6:30:27 PM Pacific Daylight Time, hylands@ibm.net 
>writes:
>
>> What in the world for? For under $100, you can get a pressure gauge that
>>  gives a 0-5 volt analog signal that is directly proportional to depth.
>>  
>>  Translating that signal to something readable by humans is not trivial, but
>>  its certainly doable.
>>  
>>  Later,
>>  Jon
>>  
>That system will measure the pressure, but pressure will change depending on 
>what is going on. (although there is the question of how much does the 
>pressure change with the weather?)
>
>Anthony