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

[TeslaTony@aol.com]

In a message dated 9/21/00 5:46:51 PM Pacific Daylight Time, 
ststev@uniserve.com writes:

> 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
>  
Hmmm.....I have heard a bit about PID controllers, and the idea of being able 
to control the depth to such a fine range is rather appealing (especially if 
the sub is to go through a hole in something), I'll look into them.

Anthony