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Hi all,
I put some ideas about this project on paper.
It will be 3 parts, Fish - Sidescan - Controlbox onboard ship.
I would like to present each part as separate post for all to have a look and comment on it.
When we agree on the final plan we can start building.
(better take some time thinking it over than to have to completely change the plans half way through.
Just to make clear.... These posts are suggestions only, when someone has a better idea then we use that idea instead.
Oh yes, please allow for writing errors... english is not my native language.
---------------------------------
General
-------
I think the most important thing the fish should do is running straight and level.
The more it pitches or rolls the more blurry the sonar image will get.
Another problem are the obstacles it might run into.
It would be a pity if we would loose the fish because it goes straight into a wreck.
Therefor I believe we should be able to control the fish from the boat.
Even the depthsounder depth alarm could be used to let the fish do an emergency ascent.
All this requires the fish to have good aero (hydro ?) dynamics.
I feel that a torpedo (basically a rocket) shape will not perform as good as an airoplane shape. (never heard of a F16 rocket... hehe)
So for the shape I would suggest a rectangular body with stubby wings and tail
Ailerons and up/down rudders will be fully operational .
Direction rudder can be fixed because fish is towed.
The wings should be large enough to have lights or marker buoys fitted.
The normal mode for the fish wil be 'autopilot' at a preset depth and angle.
Since the fish will be more complex (expensive) than a normal fish it would be a pity if it is only used to fly the sonar.
I would suggest to make it a standalone unit that can piggyback other modules like Sonar and Camera
A magnetometer would be useless because of the strong magnetic fields generated by the electronics and motors.
Since this is a prototype I would suggets to make extensive use of PIC controllers and/or Basicstamps.
It is easier to adjust some software than to adjust the hardware.
Also the amount of parts used will be less and thus give us more room in fish.
I have thought of the next prerequisites.
1) Body be able to withstand a crash against a obstacle
2) Waterproof up to 50 meters (150 ft)
3) 100 meter cable
4) Fully controlable from boat
5) Autopilot capability
6) 'Rocksteady' run
7) Waterspeed, -temp and depth sensor
Panic button for emergency ascent
Basic Modules needed
--------------------
1) Body
I was thinking of a rectangular airplane shape made
out of plywood or PVC
The size would be about 25x25x130 cm.
This is quite large but the extra space will come in handy (its a prototype)
The towingcable should connect at center of weight point and tail.
Front towing point should release towing cable when force exceeds a set limit.
If fish should get caught in a wreck, even with emergency ascent, the front towing point will release.
When cable start pulling on tail point the fish somersaults and hopefully get released from wreck
To keep the fish waterproof I suggest to use a 1-4 liter diving tank with standard regulator in front part of fish.
The regulator is misadjusted so it will keep the electronics compartment at a slightly higher pressure than the water pressure.
This will just be 1-5 mbars which will prevent water from entering this compartment.
The advantage is that all seals must only withstand a few mbars of pressure.
I do not think that the electronics will be damaged by the high pressure (max 6 bars) inside the hull.
For the non-divers among us : Pressure per 10 meter water increases 1 bar.
So at 50 meters the pressure will be 1 bar sealevel air pressure + 5x1 bar water pressure
During ascent the air inside the hull will expand but this air will be dumped through the exhaustvalve of the regulator.
Since the fish will normally run at preset depth I do not expect the airconsumption will be much.
I thought a 100 meter cable will be enough.
That would give a 45 degree angle at running depth of 50 meters.
Normally the fish wil run shallower.
It is useless to find stuff at deeper levels
50 meter will give us about 15 minutes bottomtime with acceptable decompression times.
For the non divers among us: Decompression time is the time a diver must stop at certain depths during ascent to let his body readjust to the lower air pressure on the surface.
These times depend on how deep and how long the dive has been and can range from 1 minute to several hours
2)Powerpack
A set of 12V/7Ah leadgel should be enough.
An external charge socket would be a good idea.
3)Communication module
This module should provide the communication from/to the fish.
When we want to use only 1 data cable this module will be quite complex.
Communication thru lightpipe is favorite but perhaps Coax will do.
When 1 data cable is used, it must multiplex between sonar/camera data and fish data.
This module will be a challenge... and be well tought over.
It must process quite a lot of data (low freq & High freq)
Have some ideas about it but lets first see what we think about the genaral idea
4) Depth, speed and temperature module
These inputs are needed to create a better image as sound travels differently as these parameters vary
These sensors are controller by a PIC processor
Depth sensor
-----------
To have a clear sonar image I suppose this sensor must have quite a high resolution.
It is not so important that is thinks the depth is 20 meters when it is in fact 22m
What is important is that it senses depth changes of a few cm.
Bill, what resolution do we need ?
Speed sensor
----------
I am not sure what speed is important.
Water speed or ground speed
Bill could you give some info ?
Ground speed can be taken of GPS
Waterspeed can be measured with Pitot tube array.
Temperature sensor
-----------------
A simple lowcost digital thermometer should do the trick
The processor can read its digital display and convert it to our needs
5) Steer module
------------
Pic processor(s) controlling the servo's.
Should be able to run in 3 modes
a) Manual b)Automatic c) Emergency ascent
It also contains the roll and banking sensors.
6) General appliance module
----------------------------
This module should check for flooding, power, airsupply etc.
it will be a simple module.
-----------------------------------------------------
Ok, a long post but better think things over at the beginning than when we are halfway.
I hope there are still people left .... and start taking it appart.
I know there will be errors in my ideas, but we can still change the plans easily.
Regards Jan
I put some ideas about this project on paper.
It will be 3 parts, Fish - Sidescan - Controlbox onboard ship.
I would like to present each part as separate post for all to have a look and comment on it.
When we agree on the final plan we can start building.
(better take some time thinking it over than to have to completely change the plans half way through.
Just to make clear.... These posts are suggestions only, when someone has a better idea then we use that idea instead.
Oh yes, please allow for writing errors... english is not my native language.
---------------------------------
General
-------
I think the most important thing the fish should do is running straight and level.
The more it pitches or rolls the more blurry the sonar image will get.
Another problem are the obstacles it might run into.
It would be a pity if we would loose the fish because it goes straight into a wreck.
Therefor I believe we should be able to control the fish from the boat.
Even the depthsounder depth alarm could be used to let the fish do an emergency ascent.
All this requires the fish to have good aero (hydro ?) dynamics.
I feel that a torpedo (basically a rocket) shape will not perform as good as an airoplane shape. (never heard of a F16 rocket... hehe)
So for the shape I would suggest a rectangular body with stubby wings and tail
Ailerons and up/down rudders will be fully operational .
Direction rudder can be fixed because fish is towed.
The wings should be large enough to have lights or marker buoys fitted.
The normal mode for the fish wil be 'autopilot' at a preset depth and angle.
Since the fish will be more complex (expensive) than a normal fish it would be a pity if it is only used to fly the sonar.
I would suggest to make it a standalone unit that can piggyback other modules like Sonar and Camera
A magnetometer would be useless because of the strong magnetic fields generated by the electronics and motors.
Since this is a prototype I would suggets to make extensive use of PIC controllers and/or Basicstamps.
It is easier to adjust some software than to adjust the hardware.
Also the amount of parts used will be less and thus give us more room in fish.
I have thought of the next prerequisites.
1) Body be able to withstand a crash against a obstacle
2) Waterproof up to 50 meters (150 ft)
3) 100 meter cable
4) Fully controlable from boat
5) Autopilot capability
6) 'Rocksteady' run
7) Waterspeed, -temp and depth sensor
Panic button for emergency ascentBasic Modules needed
--------------------
1) Body
I was thinking of a rectangular airplane shape made
out of plywood or PVC
The size would be about 25x25x130 cm.
This is quite large but the extra space will come in handy (its a prototype)
The towingcable should connect at center of weight point and tail.
Front towing point should release towing cable when force exceeds a set limit.
If fish should get caught in a wreck, even with emergency ascent, the front towing point will release.
When cable start pulling on tail point the fish somersaults and hopefully get released from wreck
To keep the fish waterproof I suggest to use a 1-4 liter diving tank with standard regulator in front part of fish.
The regulator is misadjusted so it will keep the electronics compartment at a slightly higher pressure than the water pressure.
This will just be 1-5 mbars which will prevent water from entering this compartment.
The advantage is that all seals must only withstand a few mbars of pressure.
I do not think that the electronics will be damaged by the high pressure (max 6 bars) inside the hull.
For the non-divers among us : Pressure per 10 meter water increases 1 bar.
So at 50 meters the pressure will be 1 bar sealevel air pressure + 5x1 bar water pressure
During ascent the air inside the hull will expand but this air will be dumped through the exhaustvalve of the regulator.
Since the fish will normally run at preset depth I do not expect the airconsumption will be much.
I thought a 100 meter cable will be enough.
That would give a 45 degree angle at running depth of 50 meters.
Normally the fish wil run shallower.
It is useless to find stuff at deeper levels
50 meter will give us about 15 minutes bottomtime with acceptable decompression times.
For the non divers among us: Decompression time is the time a diver must stop at certain depths during ascent to let his body readjust to the lower air pressure on the surface.
These times depend on how deep and how long the dive has been and can range from 1 minute to several hours
2)Powerpack
A set of 12V/7Ah leadgel should be enough.
An external charge socket would be a good idea.
3)Communication module
This module should provide the communication from/to the fish.
When we want to use only 1 data cable this module will be quite complex.
Communication thru lightpipe is favorite but perhaps Coax will do.
When 1 data cable is used, it must multiplex between sonar/camera data and fish data.
This module will be a challenge... and be well tought over.
It must process quite a lot of data (low freq & High freq)
Have some ideas about it but lets first see what we think about the genaral idea
4) Depth, speed and temperature module
These inputs are needed to create a better image as sound travels differently as these parameters vary
These sensors are controller by a PIC processor
Depth sensor
-----------
To have a clear sonar image I suppose this sensor must have quite a high resolution.
It is not so important that is thinks the depth is 20 meters when it is in fact 22m
What is important is that it senses depth changes of a few cm.
Bill, what resolution do we need ?
Speed sensor
----------
I am not sure what speed is important.
Water speed or ground speed
Bill could you give some info ?
Ground speed can be taken of GPS
Waterspeed can be measured with Pitot tube array.
Temperature sensor
-----------------
A simple lowcost digital thermometer should do the trick
The processor can read its digital display and convert it to our needs
5) Steer module
------------
Pic processor(s) controlling the servo's.
Should be able to run in 3 modes
a) Manual b)Automatic c) Emergency ascent
It also contains the roll and banking sensors.
6) General appliance module
----------------------------
This module should check for flooding, power, airsupply etc.
it will be a simple module.
-----------------------------------------------------
Ok, a long post but better think things over at the beginning than when we are halfway.
I hope there are still people left .... and start taking it appart.
I know there will be errors in my ideas, but we can still change the plans easily.
Regards Jan
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