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Small Boat Autopilot With Obstacle Override

09/17/2010 5:35 PM

hi everyone

i am in a project of designing an autopilot for a small boat

all sensors (gps, 3 angles of rotation ) and rudder control motor are connected to a computer through a data acquistion card

but there are two main problems

1- i can not find a mathematical model of ship in which the 6 degrees of freedom of the boat is described, since for small boats the usual 4 degrees of freedom model is not effective

2- how could i create a collision sensor for that kind of boat, i just need to get the target direction and range and i will apply obstacle override algorithms and send them to the autopilot to avoid the ships (i think acoustic sensor will be good but where to buy and how to get it to give useful information to the main computer

thanks everyone

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#1

Re: Small Boat Autopilot With Obstacle Override

09/17/2010 8:47 PM

You should start by researching aircraft autopilot systems. That would help your understanding of the problem space.

Aircraft use TCAS (Traffic Collision Avoidance System) for collision avoidance. That system would not be practical for boats (unless a significant number of autopilot boats exist) as it requires every craft to have a transponder broadcasting position, altitude, speed, and trajectory. However, some lessons might be learned from terrain following radar or ground proximity warning systems.

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#3
In reply to #1

Re: Small Boat Autopilot With Obstacle Override

09/18/2010 2:30 AM

first i would like to thank you for your feedback

the main problem for the aircraft model is that all thesis and books i have read assume that i have a huge background of autopilot modeling which is not true

for the obstacle avoidance system, the main goal is that in many times the control wireless signal is lost, so the boat is lost

i wanted to make a system that derives the boat back to me in such case

in its way back it might hit a ship or a floating barrel and cause it to go down or even the other ships propellers may pull the boat and destroy it

the boat is less than 4 meters long only!!!!

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#41
In reply to #3

Re: Small Boat Autopilot With Obstacle Override

09/21/2010 4:48 PM

The best computer I know of for this sort of thing would be the brain (and body) of a Dolphin. Perhaps you could have a Dolphin lead the boat with short range radio autopilot. A Dolphin can do everything you want to do.!!

Otherwise: I just spent a week on a 7 knot cruiser in the San Juan Islands and British Columbia waters. We had limited visibility on several days, but found our way with the use of two chartplotters, a separate GPS, Radar and VISUAL. We never moved without 3 sets of eyes watching the shore line and the surface of the water, as well as traffic.

Had constant run-ins with partially submerged logs, branches and lots of Kelp patches.

I can't think of a sensor that would have done morethan our eyes. ,the sensors were only for backup, even though our radar worked well and was mounted 15 feet above the water.

Talk to the US Navy about your problem. They have lots of experience.

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#42
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Re: Small Boat Autopilot With Obstacle Override

09/21/2010 5:55 PM

I'll be with you next time. GA

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#2

Re: Small Boat Autopilot With Obstacle Override

09/17/2010 9:16 PM

Hello hanyarnaoot,

i think acoustic sensor will be good

Why do you think this? In a marine environment, especially on the small, robotic scale you seem to be talking about, I think there would be an extreme amount of interference. What is the actual size of the boat, and what types of bodies of water will it be operated in?

Mike

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#4
In reply to #2

Re: Small Boat Autopilot With Obstacle Override

09/18/2010 2:45 AM

first i would like to thank you for your comment

the boat is to be used to deliver small spare parts and such stuff between ship it is less than 4 meter (12 feet's) long

the boat may hit another ship or a floating empty barrel or a big piece of wood and so on, which may damage the boat

if at least i managed to determine that there is a ship at a certain direction (by the propeller noise) i will avoid it but how(marine radar cost is high and in the same time the boat is too small and short for one)

if there is any thing in your mind that efficient and low cost please tell me

thank you very much

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#5
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Re: Small Boat Autopilot With Obstacle Override

09/18/2010 10:47 PM

There are marine radar units designed for smaller boats. Although the cost may seem to be high right now but in the long run you may save a lot more by using it.

Noise, not only from the ships props but also the water itself is going to be a huge problem to over come, if acoustics are your choice of detection.

Also, you will need to detect the roll of the boat, as this will inter fear with the auto pilot. Roll will cause the auto pilot to over correct.

Ultrasonic range finders would only be good for very close distance detection. ( I tried this for several years )

The problem I always had, was when the boat would roll it would pickup the water as an object. I tried to mount the sensor within a gimbal it helped but it was not good enough.

I ultimately wound up spending the money on a radar unit (Ratheon)

Good Luck !

Dave

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#8
In reply to #5

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 12:12 AM

With regard to OPs #2).

Why didn't you buffer and average the ultrasound/acoustic data ... and reject any data with less than a 50% hit. This should take care of the waves, if you use a long enough sample time. If the vessel is not a fast mover, it should be appropriate to use a sample size of 3-5 seconds. You could always tweak the hit rate and sample length in real world, if not in real time. IE ... when a 'hit' is detected, lower the sample time and make the hit detection more sensitive .

With that said, an acoustic sensor should be all you need ... I can't see a 4 meter craft used as a cargo vessel used in more than half a meter seas ... otherwise you'd be looking at a sub ... until it hit bottom ... :o0

In fact, a semi-submersible with a tall tower might be a good idea ... depending on the regs in the area of use. (That) should minimize the roll and yaw.

Unfortunately, most maritime regs that I know, prevent unmanned over-the-horizon vessels.

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#15
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 9:49 AM

As I mentioned, Roll was the big issue. In a small vessel it far more a problem. A small boat takes too long to roll back to a horizontal position. I found that often when a wake from another vessel would cross the path, especially at an angle of 45 degrees or less the roll position would last for as long as 30 seconds. in open ocean this was not much of a problem. In a congested area such as a harbor is was unacceptable.

Ultra-sonics' work very well in land base automated for several reasons. One major reason is the control of the vehicle is far more stable and predictable.

Most if not all commercially available autopilot systems that I am aware of, turn the autopilot off and sound an alarm if a collision is detected.

I do not want to discourage anyone from trying to create something that I failed at. My intent is to provide input as to my failures to educate, so that a solution may be discovered.

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#7
In reply to #4

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 12:11 AM

It would be less expensive and time consuming to put rubber bumpers around the boat (or foam ones.) and also to have a reference point guidance system. By your statement, that the boat is for delivery, that suggests the distance is not too great. I would recommend using buoys with radio beacons, and using a standard signal-strength scan and pid loop to steer by. If the distance is only a few hundred yards (like a river), steer by rope and eyelets.

but i do commend your ambition. I think you will have to be committed to learning, and have the time to play with it for .. (years)

chris

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#6

Re: Small Boat Autopilot With Obstacle Override

09/18/2010 10:57 PM

Having sailed a small boat in the open ocean for a number of years in the past, and operated a number of purpose-designed auto-helms and radars, I have a bit of experience in this area.

I am very doubtful that an acoustic sensor is going to give you the information you want, especially if you are operating in relatively rough water. Even a side-scanning sonar operating at relatively high frequencies would be very difficult to direct appropriately to determine with any accuracy where your target would be located. If radar is out of your price range, a quality side-scanning sonar most likely is, as well. You may be able to do something "home brew" with a piezo transducer, but target detection requires some pretty sophisticated signal processing based on the length of time it takes the signal to return to the transducer. Smaller targets, or targets that have low reflectivity characteristics (curved surfaces, tree limbs, etc) are unlikely to result in a strong positive signal.Secondly, although a small radar (say, one limited to an 8 NM range) would probably cost you on the order of $2000 (that is old, old pricing), it would not, due to relatively high motion of the vessel to which it is mounted, give you adequate information about the larger targets, let alone smaller targets like half-submerged barrels or tree trunks.

The next issue is the auto helm itself. The main issue I have had with commercially-available products on smaller vessels is that a relatively small wave can significantly and quickly alter the course of the vessel, and the "brains" get lost. You are most likely going to be running at too slow a speed to rely on GPS to give you rapid enough response to determine how much correction is required. Most systems I have worked with combine GPS and a fluxgate compass, and even these systems find it difficult to find their way back on course at slow speeds, because the heading can change rapidly by far more than the systems are designed to compensate for. This addresses yaw only- when you try to add pitch and roll into the picture, you had better have some pretty sophisticated gimbal mounts for all your sensros/detectors. And some very high-speed data analysis processes.

I don't mean to discourage you from pursuing this, but I think you need to be aware of the magnitude of the problem. If it were easy, there would be commercial units available on the market at a price that the small boat operator could afford...

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#9

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 1:41 AM

If I am reading you right, you are shipping parts from ship to ship. Are these ships at sea, and what type of distances are there between these ships?

I am wondering based upon your response I hope you provide if there is a much simpler solution.

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#10

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 3:32 AM

By the way, has anyone thought of the military implications of such a craft?

Sounds like a torpedo. I wonder what the cargo is. Seems like a fine way to go blowing up oil rigs.

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#11
In reply to #10

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 3:42 AM

Yes x 4 - hence 'no comment'

& GA

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#17
In reply to #10

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 2:53 PM

Let us not declare war until we are at war. That is the tool of the fear mongers. If we stopped all discussions of technology with military applications, CR4 would be vacant.

I agree it is appropriate to have some sense of the person we share with, and would like to see more of the OP responding... but otherwise, I think we should play it straight.

Terrorism will never be stopped by advanced nations withholding technology. It will be stopped by advanced nations stopping the dissemination of war materiel to warlords, and it will be stopped by advanced nations giving a shit about the poor underpriveleged people of the third world countries, and making strides to help feed, shelter, clothe, and water them, etc etc etc..

/rant off.

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#18
In reply to #17

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 3:46 PM

Caution is the better part of valor

a new member with no real body of work to refer to, asking a question that has some potential for mischief.

can make one reluctant to fire up the "A" game

original posters have to meet certain minimum requirements to get meaningful responses. there have been several new members recently that seemed to have questionable motivations for joining our little goat rodeo.

it's up to our new friend to provide more context for the solution he seeks.

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#19
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 3:55 PM

agreed..

(It is your fault if I'm cranky today anyway...)

chris

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#21
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 3:59 PM

someone has to be

must be your turn, lynlynch is tired :D

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#44
In reply to #19

Re: Small Boat Autopilot With Obstacle Override

09/23/2010 2:59 PM

thank you for your understanding

please read my reply

thanks again

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#45
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Re: Small Boat Autopilot With Obstacle Override

09/23/2010 4:07 PM

I can't find any other reply from you?

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#46
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Re: Small Boat Autopilot With Obstacle Override

09/23/2010 4:09 PM

see number 4

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#47
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Re: Small Boat Autopilot With Obstacle Override

09/23/2010 4:25 PM

thx

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#49
In reply to #47

Re: Small Boat Autopilot With Obstacle Override

09/23/2010 4:58 PM

sorry i thought i have posted it

please read my last reply that is posted on reply to #10

i am a newbie to this site

so do not expect much from me

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#20
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 3:57 PM

Fear is your friend. I have suspicions about the OPs motives. Why boat so small? Why concern with passive sound aquizition of "target"?

CR4 has published interesting cheap tech, even into 100 dollar RC video drones.

Not much of a profile, from OP. I've not changed mine in awhile, but if you look you will find I want to see people from outerspace on the 3D Space TV, and prevent Apocalyptic Riot through airport islands of commerce.

Not sailed much but even in the intercoastals of FLL a 14 foot long motorboat is hard to handle. 26 foot sailboat is biggest I've steered into port. Out it was 6 to 12 foot swells. Below deck I had to stop drinking after two beers and get some air.

Regardless of all wonders realized and available to all, terrorism will continue because it is part of human nature for some humans to hate themselves and others for nothing but their humanity.

Some people simply will never be happy unless they are unhappy, and spreading it around makes them happy to be unhappy.

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#22
In reply to #20

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 4:19 PM

"Some people simply will never be happy unless they are unhappy, and spreading it around makes them happy to be unhappy."

I like that- very insiteful...

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#23
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 4:24 PM

"Once you start down the dark path, forever will it dominate your destiny, consume you it will." Yoda

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#24
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 4:43 PM

Since destiny is chosen, while fate happens to you, all that flows from the acceptance of your destiny is better than what fate hands you.

Less of course if your destiny is to chose to be bad.

Hitler accomplished a lot of bad doing. Considering he was a WWI vet for the entire war on a losing side doing some long time in bad fighting during a time when mass murder and genocide, and even fair fights were as awful as it gets you gottah wonder why he lived to fight another day.

What would my friends recommend I do to do as much good as Hitler did bad?

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#25
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 4:47 PM

Transcendia is a good start. Nothing worthwhile comes easy...

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#26
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 6:34 PM

Hitler had many positive qualities. That is why he was so successful.

I would suggest that if your aim is what you state, that you do as he did, only change the message to correspond to your beliefs.

Speak plainly, with passion.

chris

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#27
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 6:37 PM

WITH PASSION.

Anything done without passion is only half done...

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#31
In reply to #27

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 11:54 PM

Passion is overrated.

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#32
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 11:57 PM

Passion is not over-rated- we are just too old to participate any more...

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#33
In reply to #32

Re: Small Boat Autopilot With Obstacle Override

09/20/2010 12:12 AM

Speak for your self :D

do it like you mean it...

intention shows

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#34
In reply to #33

Re: Small Boat Autopilot With Obstacle Override

09/20/2010 12:19 AM

Some of you are younger than some of us. When you get a little more experience under your belt, I hope I am still around to say, "I told you so..."

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#35
In reply to #31

Re: Small Boat Autopilot With Obstacle Override

09/20/2010 1:20 AM

I assume you are kidding.. but, you wanted to know... so why argue with what worked/works?

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#48
In reply to #10

Re: Small Boat Autopilot With Obstacle Override

09/23/2010 4:52 PM

first if all i am so sad for what you have said

my intention are far away from what you have said

and i want to tell you something

an enemy of the US may read your comment and decide to make an attack thanks to you (remember that the idea of what happened in 11/9 was taken from a movie)

also those people use a different, autopilot than what we are discussing they are the suicidal boomers ( USS COOL was destroyed by one)

second

using it to destroy an oil rig is none sense because small boat like this will not go that far to be in a range of a one

third

it is not a torpedo such small boats will not go faster than 10 knots, otherwise it will cape size

nearly all military ships in the world exceed 30 knots easily (how come it will be on third of its speed)

I must clear things much more for every one

I have recently got my master degree in automatic control

but i was very theoretical and i did not feel that i have learned a lot

for those who are specialized in such stuff it was about the relation between system state controllability-observability and system state sensitivity to change in system parameter (quiet boring is not it)

my professor told me that there is a PHD scholarship but there is a large number of candidate for it

so i wanted to come up with something real big and astonishing

in the same time applicable and will be a very good additive to my CV to work as a professor after my PhD

the idea came to me because a close friend had a boat renting facility for diving and such stuff

and in many case the rented boat my suffer from a mechanical problem an need a new spare part like spark plugs,fuel hoses.....even sometimes fuel when the renter does not estimate the distance enough, food, water ,wine, extra diving gear

so he had to keep one boat from 4 not rented fro such cases

so a huge boat is used to deliver a fuel hose of 1 feet long

so i talked to myself and said a small boat that is to carry a cargo of not more than 100 lib. will be fine

but my friend is too fat

and really the boat may not withstand him

so it came up in my mind why do not i make such a boat to go to the designated area where my friend boat is located to deliver the needed spare parts,wine,water,fuel......

and my friend liked it very much and told me he will fund the project within the range of one of his boat price (he will not pay to the boat operator)

(by the way it could not be used in smuggling because it will not withstand open sea state)

and people Will be amazed because it is a huge project

and most important of all i will learn much about applicable automatic control

and get a free scholarship , become a professor

in brief life will be so good

has any one any objection on that

thanks to any one who tried to help me

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#50
In reply to #48

Re: Small Boat Autopilot With Obstacle Override

09/23/2010 5:07 PM

Welcome to CR4

home of the cranky old guy

Your project makes much more sense with the additional information.

Tell us more about the parameters of the project

budget

range

power source

....

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#12

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 4:26 AM

You could consider investing in this and tie it into your gps,

http://www.systron.com/products/motionpak%C2%AE

As for a collision sensor a seperate ultrasonic system would seem to be one way to go.

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#13

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 5:06 AM

Here is another link which could be of intrest.

http://www.ocean-server.com/compass.html?gclid=CIGvr4SRk6QCFQ25bwodUwsuHg

Not to expensive.

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#14
In reply to #13

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 5:25 AM

"Here is another link which could be of intrest." (interest)

"Not to expensive." (too)

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#16
In reply to #14

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 11:03 AM

Well caught , such observation. here is a link for you.

http://www.worldwidewords.org/qa/qa-nit1.htm

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#28
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 7:26 PM

I suspect as methods were improved, as in medicated shampoo, the 'ole' way was laughed at ... and one who was a practitioner of the 'ole' way, was was belittled.

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#29
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Re: Small Boat Autopilot With Obstacle Override

09/19/2010 7:43 PM

But equally; I never seem to find them when I don't read and think about a post.

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#30

Re: Small Boat Autopilot With Obstacle Override

09/19/2010 11:17 PM

You could consider using a vision system - a camera and appropriate software - especially since you already have a computer on board.

Laboratory robots have been using vision systems for guidance and obstacle detection for years. Of course, you will need to experiment a lot. There are no readymade available solutions. But I believe (especially after reading the posts re sonars and radars) that a vision system would do the job better. You could also use the acquired images (or the video stream) to detect any changes in direction so that you could apply appropriate corrections to the course. It will not be easy but could be done.

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#36
In reply to #30

Re: Small Boat Autopilot With Obstacle Override

09/20/2010 8:04 PM

Agreed: under many (I think "most") conditions, vision will be far better than sonic/ultrasonic sensing. It will have less noise - but still plenty - and automatically increases the importance of nearby objects over far-away ones due to apparent size in the view. If you can combine vision with direction input, you don't need the actual range: you need to find targets, and see whether their direction relative to yours changes. The old saying is, "Constant bearing means collision." So if the direction is changing, ignore that target. If not, change your own direction or speed to make it happen from your own end.

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#37
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Re: Small Boat Autopilot With Obstacle Override

09/20/2010 8:51 PM

I think the task is next to hopeless.

First, a small boat probably will have a small vertical profile, so any sensor will have a very limited range of view. Water will have swells, wakes, and waves to contend with.

Second, some obstacles may be semi-submerged, such as a water soaked logs, rocks, reefs, sea life, or debris that may float at the water line level. These obstacles will be nearly impossible to detect in advance.

You may have a better chance (and cheaper) of simply making the boat robust to collision with some form of inflated ring that will absorb any impacts.

On-board software could detect when forward progress has stopped and perform an evasion or escape procedure where the boat backs up and takes a tangental course to work around the obstruction.

Maybe DARPA has some prior art that was granted from the military. They clearly have been doing this over land and I would bet that there are a number of studies and research trials for water based automated resupply vessels.

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#38
In reply to #30

Re: Small Boat Autopilot With Obstacle Override

09/20/2010 8:53 PM

I also agree. I use vision systems to detect failed part in many forms. They work well once set up. Excellent suggestion!

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#39

Re: Small Boat Autopilot With Obstacle Override

09/21/2010 1:24 PM

Rumba Boat. Taps something, remembers it, goes around it.

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#40
In reply to #39

Re: Small Boat Autopilot With Obstacle Override

09/21/2010 2:20 PM

Do you mean Roomba? If not, what DO you mean?

If you do mean Roomba, how do the situations correspond: the vacuum cleaner works in a relatively unchanging environment and repeats its path, or tries, but the boat is in a constantly-changing situation and may never be called upon to repeat a path. One has three degrees of freedom, and the other has six - which is sort of why this thread got started, if I understand correctly.

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#43

Re: Small Boat Autopilot With Obstacle Override

09/21/2010 9:43 PM

Use your eyes.

Don't sleep on such a boat, unless it is docked or on the land. If you want to eliminate collisions, look out and steer it by hand. Once I thought I was on a rescue mission in the North Sea to rescue a Jet Ski with 2 persons on board.

Why?

Because they left 3 hours earlier, with only 90 minutes fuel.

So I took a small rubber dinghy with a 5 Hp outboard and went into the ocean.

After 10 minutes, I spotted them, moored against a boat, full with boobs and booties. To show me what an idiot I was, they came to splash around my gummi boat, but instead of avoiding me, the pilot maneuvered the Jet Ski straight onto my dinghy.

Probably with a speed of 40 Mph plus. No damage to me and/or the dinghy

A flying passenger that took a launch of 50 meter through the air and made a very rough landing on the water. The pilot only had to get 5 stitches, nicely divided under the lower lip.

This proves the idea of a Canadian Fellow poster.

The first rule on the ocean or on the waters that you share is to not be a danger for the other users. You need to know the laws of the water.

Your first issue: Correcting displacements automatically with such a small boat: forget it unless you are very fast and can afford lots of wasted fuel. Also the coastguard may consider you (a)drunk.

You need to anticipate the incoming waves on beforehand, or you might find yourself upside down from time to time. So be PRO Active, not Re active.

To not sound to negative today:

you could work with some infrared cameras, or put a night vision scope (waterproof with wipers) on your nose. They work pretty well with fog too.

Or install some tweeters on the boat and make them auto balancing (horizontally) and, send some high audio frequencies away from you in different directions and listen to the reflecting sound.

In fog, use a bell or fog horn- others are supposed to do that also.

Then in the dark you should use navigation lights and also watch for them on other vessels. They give you the size and direction to anticipate on too.

If there is a lot of dangerous wreck stuff, make a deviator or deflector in the water on your boat (with shock ab- or adsorber) You can push them or detect them or even catch and collect them.

A standard GPS helm should work on calm seas, even on a floating motorized bath, bed and beyond. Listen to Tina Turner songs at home.

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#51

Re: Small Boat Autopilot With Obstacle Override

09/24/2010 2:12 AM

thank you Garthhthe

the boat itself which is most expensive component is old fiber glass boat with an electric motor that was used by children to play with in nearby water

range is less than 2 miles (including the working instrument power usage, go back journey and 20% of battery power as a reserve)

the main problem is that the power to weight ratio (for batteries) is low

and by mounting additional batteries the cargo decreases dramatically

does any one know a better electrical power source than ordinary batteries

i was thinking of fuel cells

but i do not know about the cost, space needed, power to weight ratio

on the other hand changing the electric motor with a fuel powered motor will cost a fortune (motor price, hull modification, redistribute weights to maintain boat stability -that why i do not wish to put a sensor that requires a tall mast like radars-) and also the the vibration may be another problem

budget is about 40 grant (i wish to make it as small as possible)

by the way no one asked me about the way with which the boat will work

how would i get it to work

i thought of a radio on each of my friend ship to tell him what they need and their current location, so my friend will put what they want on my boat and enter the location and required way points to the boat computer and the boat will go on its way

but there is a problem

if the boat is heading for a limited maneuverability ship the people onboard that ship must have some sort of short range remote control to guide it to the ship because

1-even if a GPS on L2 frequency or a differential GPS are used there still a position error for the main boat or the small boat

2-as far as i know all available autopilots keeps you in a circle (usually 1 to 3 times the boat length) not in a point, no one managed to do better than that

3- the main ship itself may change its position a little bit for any reason

Remote control making is not a big deal

i will just connect the receiver unit on the small boat to a transistor or a relay to pass a signal to the moving motor

by the way the most suitable stuff for are the satellite moving motors

and if any one wants i could post how to connect them to rudder and speed regulator arm

and how to get a feed back of their position to a computer and how to initiate motion through computer joystick and a simple circuit mounted to computer parallel port

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