RE: [PSUBS-MAILIST] Control considerations

I'll respond mostly in green.

"Also the control of such thrusters can be wasteful depending of
>the
>electrical configuration of the motor (i.e.. 3 phase brushless
>motors, or
>straight DC motors). Is anyone using PWM to control their
>motors? Anyone
>using brushless motors?"

I've for some time, have watched the development of a new type of electric motor, called a Thin Gap motor.

http://www.thingap.com/

http://www.thingap.com/technology/tgadvantage.htm

This company had developed a special motor for a ring thruster meant to be used in the air. Since I'm interested in ring thruster designs in general, I looked into this company. They have some great electric motors that should make your given power supplies last longer. Here is a quote from there site.

"The innovation of OEM products made possible through the use of ThinGap motors is growing substantially month by month. When your competitors begin offering longer life between battery charges, higher torque in handheld power tools, and ultra smooth operation, chances are there?s a ThinGap motor inside. Our motors are used in a wide range of applications that require high power output in a small package, high efficiency, high power-to-weight ratios, non-cogging operation, high continuous and peak horsepower and torque.

Our patented electromotive coil technology is changing the paradigm for brushless and brush motors and generators. Your products become more powerful, efficient, responsive, controllable and precise. Our technology enables your products to pack more power in a smaller package that weighs less then a conventional motor.

By replacing the iron core and wire windings of conventional motors with a precision machined copper sheet, we have eliminated such issues as hysteresis, cogging and iron losses, while substantially reducing the impact of eddy currents and back emf. The copper sheets allow higher copper density and a higher copper to total volume ratio, creating a very high power density motor.

Our motors deliver a wide range of speed and torque; and generate less heat and electrical resistance. These cool running motors have a wide operational bandwidth and surpass conventional motors in almost every benchmark.' End quote

For controlling these motors and other systems, here is a very interesting link for motion control devices.

http://www.a-m-c.com/

I have a friend that installs and works on computer controlled electric stepper motors for manufacturing machines. From what he's told me, the stepper motors can be controlled very precisely, and that they use allot less energy as well. I will ask him how and if, a small or large stepper motor could be used to control thrusters, compressors, high pressure pump motors for VBTs and sump needs, as well as other control surfaces. Since they can go forward or back in precise amounts there could be some good applications for them. I'm going to see if any of the Thin Gap motors can be used as stepper motors to further increase there efficiency.

"Flying surfaces(dive planes/rudder):
>
> This is the area.....I'm especially interested in. I've gone
>through it
>in my head....and an electrical actuator would be my first choice to
>control
>the dive planes/rudder. The failure of the through hull is less
>likely to happen with a stationary item. The control coordination of
>the
>actuator would then become a problem. The actuator would need to
>know it's
>position to be efficient in it's operation.

Other options perhaps could be some thing like an electric Lenco marine trim tap actuator to move control surfaces. I'm not sure yet what kind if any depth rating can be had or modified to have. But if they control the control surfaces from inside by way of through hulls it should work.

http://lencomarine.com/compareelectricv.html

http://lencomarine.com/

http://victorytrimtabs.com/victory.htm

Here is a great quote from Lenco.

"Lenco Trim Tabs
Powerful, reversing, low-voltage motor, in combination with the ball-screw provides up to 500% more usable power with much lower amperage draw (only five amps) then either of the two best selling hydraulic systems.

Precision Comparison, Electric Vs. Hydraulic

Lenco Trim Tabs are powered by a single wire from the helm. Synchronization is precise.

Hydraulic Trim Tabs require pumps, hoses, and fittings that are susceptible to leaking. When a hydraulic leak develops, the tabs will drift. This requires constant repositioning. Hydraulic synchronization requires same length hydraulic lines. Heavy amp draws puts additional demands on the boats electrical system. Fluctuations in a voltage occur as a result of heavy amp draw.

Lenco Trim Tabs lock in position if they should ever loose power. They can't move or drift. The self-locking ball screw keeps tabs from drifting or pulling under when backing down. With hydraulic trim tabs, a major leak can result in a sudden, rapid movement of the tabs. This can seriously effect a boats operaion, especially in a turn, and can even cause a boat to flip over. Hydraulic trim tabs are known to drift of pull under when backing down."

Here are some pics I took a couple of days ago, of an interesting propulsion arrange on a home built steel boat. They used Lenco trim taps, MotorGuide Machete weedless props, and what looks like a saltwater type Minn Kota like the Riptide ST motors.

http://www.frappr.com/?a=viewphoto&id=2628470&pid=7077049

http://www.google.com/search?hl=en&rls=com.microsoft:en-US&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=motorguide+machete&spell=1

http://www.cabelas.com/cabelas/en/templates/pod/horizontal-pod.jsp?_DARGS=/cabelas/en/common/catalog/pod-link.jsp_A&_DAV=netcon&rid=&indexId=cat400009&navAction=push&masterpathid=&navCount=3&parentType=index&parentId=cat400009&id=0044153

Hydraulics could be used....but then we have to worry about the
>possibility of environment contamination. Pneumatics are also
>available.....but even harder to control with respect to position."

The yellow 50 passanger Voyager Subs built in Seattle and then sent on to Hawaii, used peanut oil for all ther hydralic fluid, to protect the environment and the passangers in case of a leak. I don't know how well it lubricates the hydralic systems or how often if needs to be replaced, but I can find out from Sam Brown who was the main guy in charge of building Voyager I and II.

Regards,

Brent Hartwig

From:  "Lil Brother LLC" <lil_brother_llc@bellsouth.net>
Reply-To:  personal_submersibles@psubs.org
To:  <personal_submersibles@psubs.org>
Subject:  [PSUBS-MAILIST] Control considerations
Date:  Sat, 21 Jul 2007 17:43:20 -0500
>Although I have not completely read the archives (I'm working on
>it), I have
>some views on the considerations for the sub systems that I've not
>seen
>addressed.
>
>1 atm subs(internal pressure):
>
>    We know the air will be come saturated with CO2, and I know a
>scrubber
>is in the design phase. I haven't seen any response to the
>system.....but
>I'm sure the design team is working on the idea.
>
>    What is the common idea to replacing the used O2 within the sub?
>Pure O2
>or just compressed air? I see compressed air as being a problem and
>waste of
>scrubber material. I guess is it all a cost versus
>design/availability challenge. Also I'm not sure how hard pure O2
>would be
>to purchase. I know you can buy industrial O2, but I'm not sure if I
>want to be breathing it.
>
>    Also what means of relieving the extra pressure within the hull
>are
>being implemented? Compressor?(to the exterior ofcourse) Is anyone
>using a
>device to relieve the internal pressure of added air?     How is it
>controlled and what type of unit?
>
>Propulsion:
>
>    I know many of the designers are using thrusters, be it
>stationary or
>movable, are most people enclosing themselves or buying already
>enclosed
>motors? Internal or external?
>
>    I would like to know, of the ones being enclosed, what amount of
>drag is
>being placed on the output shaft? (seals, etc.)
>
>    Also the control of such thrusters can be wasteful depending of
>the
>electrical configuration of the motor (i.e.. 3 phase brushless
>motors, or
>straight DC motors). Is anyone using PWM to control their
>motors? Anyone
>using brushless motors?
>
>Flying surfaces(dive planes/rudder):
>
>    This is the area.....I'm especially interested in. I've gone
>through it
>in my head....and an electrical actuator would be my first choice to
>control
>the dive planes/rudder. The failure of the through hull is less
>likely to happen with a stationary item. The control coordination of
>the
>actuator would then become a problem. The actuator would need to
>know it's
>position to be efficient in it's operation.
>
>    Hydraulics could be used....but then we have to worry about the
>possibility of environment contamination. Pneumatics are also
>available.....but even harder to control with respect to position.
>
>I know I have a large number of questions.....which I guess is usual
>for the
>"new guy". I'm trying to get a basic consensus of ideas.......and
>work with
>those to implement my design.
>
>
>James Long
>Owner/Designer
>Lil Brother LLC (Instrument Division)
>
>
>
>
>
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