AUV BASIC stamp Project

Chayak

I'm working on a micro AUV project in my spare time and I have experience using computers as a control system but not BASIC stamps. I'm looking at using a stepper motor for main propulsion for the power efficiency standpoint. Two servos for control surfaces. A Honeywell 3 axis compass chip, a depth sensor, and a submersible ultrasonic sensor for collision avoidance. There is a possibility of an inertial navigation system later with GPS fixes but thats future development. I've heard that the BASIC stamps can control servos but I've also heard that unlike a servo controller they won't give a continuous signal and the servo will not hold firm.

As for the program... well I haven't decided exactly what I want it to do yet. I'm considering a hunter/killer routine much like a torpedo, searching for a target and flashing a series of red LEDs when it would detonate or going out and then returning after a specified time, flashing the LEDs to signal that it's ready for pickup. The other thought is since it's designed for low power consumption make it do laps in a pool for as long as it can, aborting when it's battery is low or when it gets a leak detect from the internal probes.

Bruce Bates

Chayak -

If I was looking for a high efficiency DC motor, I certainly wouldn't be looking at a stepper motor. Steppers are heavy, notably noisy and prone to vibration, power hungry, produce a fair amount of heat (the UAV will be an enclosed space) and often need to be over-sized to produce the amount of torque required for a given task. I'd look at brushless DC motors similar to those used in electric model airplanes. Plenty of torque when geared down, smooth running, cool, power considerate, and with high efficiency and reliability. Otherwise they wouldn't be used inside of hard disk drives and similar electro-mechanical devices. You would need to use a brushless DC motor controller however to drive them, unless you're only looking for full on and off as the only two speeds.

On a different matter, you may find that a "submersible ultrasonic sensor" is not only difficult to find, but is also quite costly. The only "cheap and dirty" way I can think to get around that is to somehow hack/adapt a fish finder or depth recorder transducer for horizontal use.

Just some thoughts on your project. Good luck with it.

Regards,

Bruce Bates

Chayak

Thanks for the reply. I was looking at a few brushless motors as well, but I'll need to connect a controller and figure out how to program the stamp to work with it. The sonar sensor isn't a problem as I've worked in the sonar world for quite a while and I'm involved with Navy AUVs. I'm just looking for ideas as I'm use to working with much larger equipment. My current vehicle weighs in about two thousand pounds if that gives you an idea of size. I just want to create a low cost hobby AUV for fun. I considered building a RC submarine and replacing it's controls with a gumstix/robostix setup... though RC submarines are expensive so I'm going to make the hull myself as a simple torpedo shape. I've also played with the idea of taking a toy RC submarine and seeing what I can do with it. I am planning to pick up a BASIC stamp and play around with it, though I may need the higher end units for program size issues. I will keep posting updates and code as I'm heavier on the hardware side and I'm still learning programming. The design and code will all be open source as I believe heavily in peer review.
-Chayak

sveenr

Chayak

What type of transducers are you planning to use for this micro-application? I am working on a micro-AUV with my Robotics kids for FIRST LEGO League. We need a transducer with a burst frequency in the 300 kHz range.

Ron

Chayak

I'm using a 600khz micro sensor from Sonatech. I doubt you could get one from them but look at 200LM450 at Hobby Engineering. It was going to be the primary sensor until one of the engineers I work with offered the Sonatech one. The 200LM450 is at 200khz if that will fit your purpose. The only downside is that they are about $120 each. An alternate method is to get an ultrasonic sensor and wire it before encasing it in a sound transparent rubber compound.

On the motor end of things I've been looking at brushless motors and controllers from Hobby-Lobby but the RPMs on those are crazy. I am looking at a Solorbotics GM11 motor. I might also consider using a DUMAS Akula kit as a body and run the stamp control rather than RC

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-Chayak
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"Um, I don't know why it's chasing the cat... it's not programmed to do that."

Robert Kubichek

Bruce Bates said...
Chayak -

If I was looking for a high efficiency DC motor, I certainly wouldn't be looking at a stepper motor. Steppers are heavy, notably noisy and prone to vibration, power hungry, produce a fair amount of heat (the UAV will be an enclosed space) and often need to be over-sized to produce the amount of torque required for a given task. I'd look at brushless DC motors similar to those used in electric model airplanes. Plenty of torque when geared down, smooth running, cool, power considerate, and with high efficiency and reliability. Otherwise they wouldn't be used inside of hard disk drives and similar electro-mechanical devices. You would need to use a brushless DC motor controller however to drive them, unless you're only looking for full on and off as the only two speeds.

On a different matter, you may find that a "submersible ultrasonic sensor" is not only difficult to find, but is also quite costly. The only "cheap and dirty" way I can think to get around that is to somehow hack/adapt a fish finder or depth recorder transducer for horizontal use.

Just some thoughts on your project. Good luck with it.

Regards,

Bruce Bates

Could you use one of those portable fish finders that have a side scan display? Also if one was to rotate a sonar sensor to horizontal, would it work just as well???


Bob N9LVU

Bruce Bates

Bob -

I've honestly never tried to, so I can't answer your question reliably. If you can pick one up at a swap meet (left coast) or flea market (right coast) cheaply enough, it might be worth some tinkering though.

Regards,

Bruce Bates

Chayak

Here is an update on sensors for those looking for a submersible ultrasonic www.hexamite.com They have quite a few sensors and signal conditioners.
For RC sub parts, motors, and an automatic level control and depth control that saves some lines of code. www.rcboats.com/submarines_only.html

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-Chayak
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"Um, I don't know why it's chasing the cat... it's not programmed to do that."

Post Edited (Chayak) : 9/28/2005 3:11:45 AM GMT

voodoofish

So I'm not the only one that got stuck on the uw sonar issue....btw, anyone ever consider an ultrasonic stud finder??? it would seem that this can go through a wall to find a stud, so why not be able to use it for collision detection...?? They're as cheap as 20 bux at target so it's not a major loss if you destroy one or two in the name of uw science!!

Just a thought....

Mark

Workin on a homebrue sub myself
I found some useful info at rc-submarines.com
there is a guy who made his sub out of pvc pipe...very creative...

Chayak

OK, an update. I've got the GPS sensor, a Garmin GPS 15 unit as they're inexpensive in case the thing decides to flood or sink. I just have to figure out how to program the stamp to tell the vehicle to transit waypoints. The GPS will output the coordinates so course calculation will be on stamp, possibly a second stamp just to do NAV and inertial with two accelerometers and a compass module when it dives. Each waypoint will contain lat and long in hddd.ddddd format, speed, and depth. If I want it to come up for a fix then I'll set the depth shallow at the waypoint. Below is a link to the GPS unit and it's input/output specs. I can do hardware work all day but I'm not that strong writing PBASIC yet (I'm learning :P) so help will be appreciated.

www.garmin.com/products/manual.jsp?product=010-00240-10

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-Chayak
************************************************************************************
"Um, I don't know why it's chasing the cat... it's not programmed to do that."

voodoofish

As a side to anyone in so cal that is building something like this or considering it and wants to test it in a pool or even want to take it to a lake or even the ocean, I'm a diver and also do video underwater. So if you wanted to test something like this, I could do recovery(as long as it's not too deep) as well as video tape it.

Just a thought [noparse]:)[/noparse]

-MaRk

Chayak

Well I figured out the GPS code with help from a few posts on the board and a couple of articles. The challenge I'm up to now is the intertial navigation system and then getting the two to work together. Calibration for 1G is simple I just need to write the code so the vehicle can determine its position just from inerta. Anyone have ideas?

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-Chayak
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"Um, I don't know why it's chasing the cat... it's not programmed to do that."

mm

The only problem is GPS will not work underwater, the navy has tried it numerous times without any luck.

Presently the only way they can get it to work is by using a buoy with a gps receiver in it and a ultrasonic transmitter above water retransmitting to the UAV. So you need a RF to ultrasonic repeater floating on the water, not impossible but it throws another device into the design.


Mike

Chayak

Mike, that's what the inertial navigation is for... GPS gives it a fix when it is on the surface then it dives and navigates on inertial dead reckoning until it comes up at the next fix. Having been on submarines in the Navy, we use ring laser gyros for submerged navigation and get a GPS fix off a periscope when we come up for comms. The GPS signal is weak as it is and won't penetrate water. Lol, now I'm going to have to throw mine in a ziplock bag and figure out exactly how far it will penetrate just out of curiosity

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-Chayak
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"Um, I don't know why it's chasing the cat... it's not programmed to do that."

mm

Sorry I missed the inert nav part, been skipping thru the post trying to speed read. GPS won't go anymore than a couple of inches down, iv'e tried my waterproof Lowrance in a pond from a canoe. How accurate on distance and heading is the inertial NAV part ?

Chayak

That will all depend on hardware and programming. It stands that the more sensitive the accelerometer the better information you'll get. Then it's all a matter of software to figure out everything else.

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-Chayak
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"Um, I don't know why it's chasing the cat... it's not programmed to do that."

Orion

google for "inertial navigation" had many links to good info, provided you can convert the math to the stamp