Post by thread:[EE] Beacon system for position location

Would a local version of WAAS work? Use two GPS modules, one fixed and the other mobile. Fixed unit transmits location to the mobile, and the mobile unit calculates relative position. Any drift in the fixed unit should be seen by the mobile unit as well. (Unless due to drift of internal calcs in the GPS module) >>> On 30 Jul 08 at 10:25, in message <spam_OUTPine.LNX.4.64.0807301018280.32109TakeThisOuTshell.dca.net>, Kevin <.....kbenKILLspam@spam@dca.net> wrote: {Quote hidden}> Anybody know of a website or links to a cheap beacon system > for postion location for a mobile robot ? I looked around > the net and everything was pretty expensive. > > I was thinking of trying to use those cheap 315 mhz tx/rx > modules. I want to be able to postion an autonomous lawn > mower within 6 inches or so. I have an acre lot with a house in the > center so line of site is out. > > I have a GPS receiver but that is only good to ten feet > with WAAS enabled. > > Any other suggestions ? > > Thanks, > Kevin

That should work to some degree but not down to 6 inches unless you use specialized differential GPS equipment. I'm afraid that there is no cheap way to do what you want, Kevin. It is a pretty hard problem, especially without line of sight. What I'd be inclined to do is use odometry on the wheels most of the time and just have some system for updating the position at some known points to get rid of drift. For example, you could place several known position markers in the yard and make sure that the robot goes past them at least once per 100 feet of travel or somesuch. Also, you could use a line of sight positioning method and just use odometry to handle the times when there is no line of sight. A final possibility would be to place some markers around the yard which could be seen by a camera on the robot. Depending on which ones it sees at which locations it could figure out is location. Sean On Wed, Jul 30, 2008 at 11:33 AM, Eoin Ross <erossKILLspamchemstation.com> wrote: {Quote hidden}> Would a local version of WAAS work? > > Use two GPS modules, one fixed and the other mobile. Fixed unit transmits location to the mobile, and the mobile unit calculates relative position. > > Any drift in the fixed unit should be seen by the mobile unit as well. (Unless due to drift of internal calcs in the GPS module) > > >>>> On 30 Jul 08 at 10:25, in message > <.....Pine.LNX.4.64.0807301018280.32109KILLspam.....shell.dca.net>, Kevin <EraseMEkbenspam_OUTTakeThisOuTdca.net> > wrote: > >> Anybody know of a website or links to a cheap beacon system >> for postion location for a mobile robot ? I looked around >> the net and everything was pretty expensive. >> >> I was thinking of trying to use those cheap 315 mhz tx/rx >> modules. I want to be able to postion an autonomous lawn >> mower within 6 inches or so. I have an acre lot with a house in the >> center so line of site is out. >> >> I have a GPS receiver but that is only good to ten feet >> with WAAS enabled. >> >> Any other suggestions ? >> >> Thanks, >> Kevin > > > -

what about just teaching it where to go? You would (well..guess with any system) make sure the yard was free of debris, but you put it into learn mode, take it around its path once, then have it repeat it each time. It would have to start at the same place each time but now you just have it programmed to go for x feet, turn so many degrees, go again x feet, etc. Not as fancy, but might be easier to get the job done? --- On Wed, 7/30/08, Sean Breheny <shb7spam_OUTcornell.edu> wrote: {Quote hidden}> From: Sean Breheny <@spam@shb7KILLspamcornell.edu> > Subject: Re: [EE] Beacon system for position location > To: "Microcontroller discussion list - Public." <KILLspampiclistKILLspammit.edu> > Date: Wednesday, July 30, 2008, 9:03 AM > That should work to some degree but not down to 6 inches > unless you > use specialized differential GPS equipment. > > I'm afraid that there is no cheap way to do what you > want, Kevin. It > is a pretty hard problem, especially without line of sight. > > What I'd be inclined to do is use odometry on the > wheels most of the > time and just have some system for updating the position at > some known > points to get rid of drift. For example, you could place > several known > position markers in the yard and make sure that the robot > goes past > them at least once per 100 feet of travel or somesuch. > Also, you could > use a line of sight positioning method and just use > odometry to handle > the times when there is no line of sight. > > A final possibility would be to place some markers around > the yard > which could be seen by a camera on the robot. Depending on > which ones > it sees at which locations it could figure out is location. > > Sean > > > On Wed, Jul 30, 2008 at 11:33 AM, Eoin Ross > <RemoveMEerossTakeThisOuTchemstation.com> wrote: > > Would a local version of WAAS work? > > > > Use two GPS modules, one fixed and the other mobile. > Fixed unit transmits location to the mobile, and the mobile > unit calculates relative position. > > > > Any drift in the fixed unit should be seen by the > mobile unit as well. (Unless due to drift of internal calcs > in the GPS module) > > > > > >>>> On 30 Jul 08 at 10:25, in message > > > <spamBeGonePine.LNX.4.64.0807301018280.32109spamBeGoneshell.dca.net>,> > Kevin <TakeThisOuTkbenEraseMEspam_OUTdca.net> > > wrote: > > > >> Anybody know of a website or links to a cheap > beacon system > >> for postion location for a mobile robot ? I > looked around > >> the net and everything was pretty expensive. > >> > >> I was thinking of trying to use those cheap 315 > mhz tx/rx > >> modules. I want to be able to postion an > autonomous lawn > >> mower within 6 inches or so. I have an acre lot > with a house in the > >> center so line of site is out. > >> > >> I have a GPS receiver but that is only good to ten > feet > >> with WAAS enabled. > >> > >> Any other suggestions ? > >> > >> Thanks, > >> Kevin > > > > > > --

I'm no RFID engineer, but along these lines, what about scattering some RFID tags about the area it would be roaming in? In most areas, have the tags spread in low density (*several* feet/yard/meters apart). As you sense different tags coming and going, you know your relative position. In the areas where you need high precision, bury a few tags separated by some known distance (a small grid, maybe 3x3, of tags). If you're picking up all 9 tags in a small grid, you're pretty well on top of it... if you're only getting a few tags, you're off to the side (and which side you're off to depends on which tags you can read). On Wed, Jul 30, 2008 at 12:03 PM, Sean Breheny <RemoveMEshb7TakeThisOuTcornell.edu> wrote: <snip> > > A final possibility would be to place some markers around the yard > which could be seen by a camera on the robot. Depending on which ones > it sees at which locations it could figure out is location. > > Sean

I'm not sure that it wouldn't work down to 6" or better. There's probably some assumptions I'm making that aren't right? Probably in the area of what resolution you can get out of cheaper GPS modules (I think I answered myself) Basically the system would be a roll-your-own DGPS - The 'fixed' part would have to be just that - never moving in your yard. It will give you some co-ordinates that will drift - but over 2-3 acres (?) I'd imagine an identical GPS unit would have almost identical position drift. In the mobile unit you get the co-ordinates of the fixed unit, take your local co-ordinates, and calculate the offset - there's your position relative to 'home' >>> On 30 Jul 08 at 12:03, in message <e726f69f0807300903x6b051027l22b2fd1d658d46adEraseME.....mail.gmail.com>, "Sean Breheny" <EraseMEshb7cornell.edu> wrote: {Quote hidden}> That should work to some degree but not down to 6 inches unless you > use specialized differential GPS equipment. > > I'm afraid that there is no cheap way to do what you want, Kevin. It > is a pretty hard problem, especially without line of sight. > > What I'd be inclined to do is use odometry on the wheels most of the > time and just have some system for updating the position at some known > points to get rid of drift. For example, you could place several known > position markers in the yard and make sure that the robot goes past > them at least once per 100 feet of travel or somesuch. Also, you could > use a line of sight positioning method and just use odometry to handle > the times when there is no line of sight. > > A final possibility would be to place some markers around the yard > which could be seen by a camera on the robot. Depending on which ones > it sees at which locations it could figure out is location. > > Sean > > > On Wed, Jul 30, 2008 at 11:33 AM, Eoin Ross <RemoveMEerossEraseMEEraseMEchemstation.com> wrote: >> Would a local version of WAAS work? >> >> Use two GPS modules, one fixed and the other mobile. Fixed unit transmits > location to the mobile, and the mobile unit calculates relative position. >> >> Any drift in the fixed unit should be seen by the mobile unit as well. > (Unless due to drift of internal calcs in the GPS module) >> >> >>>>> On 30 Jul 08 at 10:25, in message >> <RemoveMEPine.LNX.4.64.0807301018280.32109spam_OUTKILLspamshell.dca.net>, Kevin <RemoveMEkbenTakeThisOuTspamdca.net> >> wrote: >> >>> Anybody know of a website or links to a cheap beacon system >>> for postion location for a mobile robot ? I looked around >>> the net and everything was pretty expensive. >>> >>> I was thinking of trying to use those cheap 315 mhz tx/rx >>> modules. I want to be able to postion an autonomous lawn >>> mower within 6 inches or so. I have an acre lot with a house in the >>> center so line of site is out. >>> >>> I have a GPS receiver but that is only good to ten feet >>> with WAAS enabled. >>> >>> Any other suggestions ? >>> >>> Thanks, >>> Kevin >> >> >> --

Actually, that gives me another idea. I am not opposed to any solution, just trying to find a cheap one :) I have an invisible fence for the dogs, so maybe I could have one robot follow the invisible fence around the yard kind of like a line following robot. Then that one could relay course and heading to the lawn cutting robot. This would allow line of site control. I downloaded a couple of academic papers on beacons sysems and it is definitly a non-trivial solution to the problem. Thanks to all for the suggestions. Regards, Kevin On Wed, 30 Jul 2008, Eoin Ross wrote: {Quote hidden}> I'm not sure that it wouldn't work down to 6" or better. There's probably some assumptions I'm making that aren't right? Probably in the area of what resolution you can get out of cheaper GPS modules (I think I answered myself) > > Basically the system would be a roll-your-own DGPS - The 'fixed' part would have to be just that - never moving in your yard. > It will give you some co-ordinates that will drift - but over 2-3 acres (?) I'd imagine an identical GPS unit would have almost identical position drift. > > In the mobile unit you get the co-ordinates of the fixed unit, take your local co-ordinates, and calculate the offset - there's your position relative to 'home' > >>>> On 30 Jul 08 at 12:03, in message > <EraseMEe726f69f0807300903x6b051027l22b2fd1d658d46adspamspamBeGonemail.gmail.com>, "Sean Breheny" > <RemoveMEshb7KILLspamcornell.edu> wrote: >> That should work to some degree but not down to 6 inches unless you >> use specialized differential GPS equipment. >> >> I'm afraid that there is no cheap way to do what you want, Kevin. It >> is a pretty hard problem, especially without line of sight. >> >> What I'd be inclined to do is use odometry on the wheels most of the >> time and just have some system for updating the position at some known >> points to get rid of drift. For example, you could place several known >> position markers in the yard and make sure that the robot goes past >> them at least once per 100 feet of travel or somesuch. Also, you could >> use a line of sight positioning method and just use odometry to handle >> the times when there is no line of sight. >> >> A final possibility would be to place some markers around the yard >> which could be seen by a camera on the robot. Depending on which ones >> it sees at which locations it could figure out is location. >> >> Sean >> >> >> On Wed, Jul 30, 2008 at 11:33 AM, Eoin Ross <erossSTOPspamspam_OUTchemstation.com> wrote: >>> Would a local version of WAAS work? >>> >>> Use two GPS modules, one fixed and the other mobile. Fixed unit transmits >> location to the mobile, and the mobile unit calculates relative position. >>> >>> Any drift in the fixed unit should be seen by the mobile unit as well. >> (Unless due to drift of internal calcs in the GPS module) >>> >>> >>>>>> On 30 Jul 08 at 10:25, in message >>> <spamBeGonePine.LNX.4.64.0807301018280.32109STOPspamEraseMEshell.dca.net>, Kevin <KILLspamkbenspamBeGonedca.net> >>> wrote: >>> >>>> Anybody know of a website or links to a cheap beacon system >>>> for postion location for a mobile robot ? I looked around >>>> the net and everything was pretty expensive. >>>> >>>> I was thinking of trying to use those cheap 315 mhz tx/rx >>>> modules. I want to be able to postion an autonomous lawn >>>> mower within 6 inches or so. I have an acre lot with a house in the >>>> center so line of site is out. >>>> >>>> I have a GPS receiver but that is only good to ten feet >>>> with WAAS enabled. >>>> >>>> Any other suggestions ? >>>> >>>> Thanks, >>>> Kevin >>> >>> >>> --

DGPS is great for reducing large errors in position, but it will still have a severeal meter error at best. It was meant to correct for the 100+ meter errors introduced intentionally into the GPS system to keep 'the enemy' from using it, but now days it has been turned off. A do it yourself DGPS will certainly improve your accuracy but you will still have several meters of error to deal with. Programming a set route also is not going to work well, as ground conditions will change causing at the very least traction slippage which will quickly add up to large errors as it moves around. What about ultrasonic triangulation? Lets see, speed of sound is 1100ft/s so thats 13,000in/s so a tick rate of 13,000 per second gets you down to an inch of percision. Three transmitters will do it, more if you have an odd area that can't be covered by just three. Another idea is a beacon like an IR led on the robot, and cheap USB cameras looking down. From the position of the LED in the camera's view you can easily calculate it's position. A system to do just that us used to track foul balls in tennis. Then you just need enough cameras to cover the area it will move about in, and a computer to calculate and transmit the position to your robot. -- Ian Smith http://www.ian.org

I'm not an expert in this but I don't think this is quite right. DGPS can be used to correct for errors caused by the ionosphere, which as I understand it is the principal source of error in the present system. As the signals go through the atmosphere, they experience a varying propagation delay. However, if you measure the signals at two points on the earth which are very close, then it is pretty guaranteed that the two paths they took will have been through the same volume of atmosphere/ionosphere, so whatever path length error is introduced will be the same for both, being common-mode error not differential mode error. I'm under the impression that a decent, run of the mill GPS receiver with a full view of the sky typically gets in the 3 to 5 meter accuracy range presently. I also thought that DGPS could get you sub-meter, and that differential carrier-phase GPS could get you to centimeter accuracy (but would cost something like $20k at least). If you have access to the second GPS signal frequency, that can help even further (I think that one is still encrypted). Sean On Wed, Jul 30, 2008 at 5:33 PM, <EraseMEpiclistEraseMEian.org> wrote: {Quote hidden}> DGPS is great for reducing large errors in position, but it will still > have a severeal meter error at best. > > It was meant to correct for the 100+ meter errors introduced intentionally > into the GPS system to keep 'the enemy' from using it, but now days it has > been turned off. > > A do it yourself DGPS will certainly improve your accuracy but you will > still have several meters of error to deal with. > > Programming a set route also is not going to work well, as ground > conditions will change causing at the very least traction slippage which > will quickly add up to large errors as it moves around. > > What about ultrasonic triangulation? Lets see, speed of sound is 1100ft/s > so thats 13,000in/s so a tick rate of 13,000 per second gets you down to > an inch of percision. Three transmitters will do it, more if you have an > odd area that can't be covered by just three. > > Another idea is a beacon like an IR led on the robot, and cheap USB > cameras looking down. From the position of the LED in the camera's view > you can easily calculate it's position. A system to do just that us used > to track foul balls in tennis. Then you just need enough cameras to cover > the area it will move about in, and a computer to calculate and transmit > the position to your robot. > > -- > Ian Smith > http://www.ian.org > -

On Wed, 30 Jul 2008 17:33:19 -0400 (EDT) @spam@piclist@spam@spam_OUTian.org wrote: > What about ultrasonic triangulation? Lets see, speed of sound is > 1100ft/s so thats 13,000in/s so a tick rate of 13,000 per second gets > you down to an inch of percision. Three transmitters will do it, more > if you have an odd area that can't be covered by just three. It will need temperature sensor - sound speed changes quite a lot (about 1% each 5 degrees Centigrade). That's not too much - about 1 meter over 50 m for a 10 degree C change - but still... I'd also worry about reflections against walls and other obstacles. Also, take into account wind direction/speed. A 10 knot wind (18km/h) is about 5 m/s error on the 330m/s sound speed, another 1.5%. > Another idea is a beacon like an IR led on the robot, and cheap USB > cameras looking down. From the position of the LED in the camera's > view you can easily calculate it's position. A system to do just that > us used to track foul balls in tennis. Then you just need enough > cameras to cover the area it will move about in, and a computer to > calculate and transmit the position to your robot. This might get complicated - USB cables only bridge 2m each... And, ideally you'd have to put the cams _above_ the grass to be cut, else resolution errors will cause large positional errors after perspective correction (and I have seen distorsion of cheap camera lenses reach 10%). I don't want this to sound as criticism... I'm as interested as the next man to get my machine do its work solo ;-) (it doesn't - yet) I haven't studied those laser measuring devices I've seen advertised. Maybe they have some digital output that could be used to maintain a constant distance from a wall or so. John

On Wed, 30 Jul 2008, John Coppens wrote: > This might get complicated - USB cables only bridge 2m each... And, > ideally you'd have to put the cams _above_ the grass to be cut, else > resolution errors will cause large positional errors after perspective > correction (and I have seen distorsion of cheap camera lenses reach 10%). > > I don't want this to sound as criticism... I'm as interested as the next > man to get my machine do its work solo ;-) (it doesn't - yet) I wouldn't post ideas if I didn't expect them to get poked with a stick. :) I read some papers on optical tracking using cameras and one of the techniques is to move an object around the cameras field of vision and track it's real location with the screen position. You make up a grid of mappings, and when you are done you just interpolate between all the points so you end up with a matrix of screen to position values. The studie found that if youi are just interpolating between small areas of the screen, a simple linear model works perfectly, no fancy math involved. USB cable length is an issue, alas. And wireless cameras are not exactly cheap to throw half a dozen around to cover the yard if it stretches around your entire house. Hmm. -- Ian Smith http://www.ian.org

> Anybody know of a website or links to a cheap beacon > system > for postion location for a mobile robot ? I looked around > the net and everything was pretty expensive. Somewhat internally redundant content follows ... LineS of sight may work for you. Mower has a modulated tx beacon and eg rotating sensors at various points that deduce the angle to the beacon. You require enough sensors such that 3 can always see the mower. You can also have multiple stationary senders and a single scanning receiver on the mower. Probably cheaper and easier. TX's could be coded eg IR sources but with care you may be able to use simple uncoded omnidirectional sources and some extra information from knowing the beacon position relationships. If you use RF AND you can "see" through the building then you can use radio direction finding - probably again with a rotating sensor. If you can't 'see' through the building then placing more sensors, with some outside the covered area if necessary, allows lines of sight / RF that never intersect the building. Simple variant. Spinning IR "line of light" mounted on tower (just a pole would do) high above the house so it 'looks down' on mower. A detector on the mower and a knowledge of tx position tells where the mower is on an angle around the house. A second tx on another tall tower (tree, power on fence etc) does similarly. Maybe a few of these on boundary only. Turns back into original system with enough beacons. You can also implement (as some have) a multi transmitter phase measurement system to create your won GPS style system. Not for the faint hearted. R

Robin Very cool demo of infrared dot tracking Thanks cc {Quote hidden}> On Jul 30, 2008, at 4:30 PM, Robin D. Bussell wrote: > > > > >> Another idea is a beacon like an IR led on the robot, and cheap USB >> cameras looking down. From the position of the LED in the camera's > view >> you can easily calculate it's position. A system to do just that us > used >> to track foul balls in tennis. > > Maybe this chap's wii remote hacking projects will be of use, he's > tracking things very well: > > http://www.cs.cmu.edu/~johnny/projects/wii/ > > Although you'd need a PC or similar with Bluetooth on the mower I > suppose... does the mower need to know where it is or does an outside > control system need to track the mower? > > Cheers, > Robin. > > P.S. the stuff on this page is fantastic! (though nothing of any > use for > lawnmower tracking :) ) > > http://www.cs.cmu.edu/~johnny/projects/thesis/

A few "brainstorming" thoughts... The big one: Make the rover as dumb as possible. Putting this intelligence in the mower is silly... Build this in an older PC or similar, and then have the radio control simply provide direction to the mower. That is, the PC will determine where the mower is now, and where it needs to go, and tell the mower to move say left or right or forward or backward. So, then you simply have to know where the rover is, within a few inches. Ideas: 1) Use radio direction finding. Place a "beacon" on the mower - just a transmitter on a specific frequency, no modulation or anything. In the yard area place one or more receivers which can detect phasing differences between two antennas. The simplest way to do this is with a pair of antennas and an antenna switch to switch between them, hooked into a FM receiver on the same frequency. With suitable signal processing, this will give you an angle from the antenna where the rover is. 2) Use high resolution video and some sort of video processing... You will need to ensure something like 1 inch per pixel or similar and then write some code to locate the mower. You should be able to make this easy to locate by painting it fluorescent orange or similar. Of note, a 1024x768 camera should be able to handle an 85x64 ft yard if you can mount it in the right spot and one inch per pixel is sufficient resolution (subject to experimentation). These are commonly available for less than $40 in the form of a USB webcam. I think this is where I would start.. The loop would look something like: grab a picture, look for orange. Figure out where it is in relation to where it needs to be. Command the mower. Repeat. -forrest

You may want to rethink the problem a little when it comes to GPS. You don't need to know the absolute position of the lawn mower only that cuts the whole yard and not one segment and it is in your yard. w.. Kevin wrote: {Quote hidden}> Anybody know of a website or links to a cheap beacon system > for postion location for a mobile robot ? I looked around > the net and everything was pretty expensive. > > I was thinking of trying to use those cheap 315 mhz tx/rx > modules. I want to be able to postion an autonomous lawn > mower within 6 inches or so. I have an acre lot with a house in the > center so line of site is out. > > I have a GPS receiver but that is only good to ten feet > with WAAS enabled. > > Any other suggestions ? > > Thanks, > Kevin > > -

On Thu, 31 Jul 2008, Walter Banks wrote: Some good brainstorming ideas ! Couple of issues I should mention, I don't think I could get a camera looking down because of several large trees in the yard. Also, the yard is half level, the other half has a fall of probably 10 ft in 60 ft. So, one section is a steep hill. That may be a problem for a transmitter pole or sensor on top of the mower. I plan on making the mower as dumb as possible. I will have my computer perform the processing and relay course and direction to the mower through my wifi network or something similiar (zigbee, bluetooth, etc...). Thanks, Kevin {Quote hidden}> You may want to rethink the problem a little when it comes to > GPS. You don't need to know the absolute position of the lawn > mower only that cuts the whole yard and not one segment and > it is in your yard. > > w.. > > > Kevin wrote: > >> Anybody know of a website or links to a cheap beacon system >> for postion location for a mobile robot ? I looked around >> the net and everything was pretty expensive. >> >> I was thinking of trying to use those cheap 315 mhz tx/rx >> modules. I want to be able to postion an autonomous lawn >> mower within 6 inches or so. I have an acre lot with a house in the >> center so line of site is out. >> >> I have a GPS receiver but that is only good to ten feet >> with WAAS enabled. >> >> Any other suggestions ? >> >> Thanks, >> Kevin >>

Your yard sounds like it has a number of interesting topological features! I wonder if you could put a triple axis accelerometer and triple axis magnetometer in the mower to get the vector of the ground surface and the magnetic field. If you map out your entire yard you may find that between those two vectors you can roughly identify the location of the mower. Place some large metal or magnetic objects underground in areas where the sloping is not so great. Or put magnetic loops underground with time-varying fields. Turn your yard into a giant Wacom tablet! I like the ultrasonic transducers idea, though. There's a lot of literature out there about using ultrasonic transducers for measuring distance. All you need (heh heh heh - there's that trivializing phrase again!) is to place a dozen transducers around the yard, each listening to each other and transmitting a code at a particular time. Since they can be synchronized to each other, then you can gaurantee that no transitter will be transmitting at the same time as another (time slots). The robot can hear at least 4 at any given time, and reflections can be dealt with by only paying attention to the first sound heard. If a reflection is messing up one of the transmissions, there's lots of redundancy, so you can safely ignore that one. Since they can hear each other, wind speed, direction, and temperature can all be calculated and accounted for on a per measurment basis. Or reverse that and have the robot beep with transducers around the yard picking the sound up - but then you'll need auxiliary beeps to determine wind speed, direction, and temperature. Fun stuff to think about... -Adam On 7/31/08, Kevin <.....kbenspam_OUTdca.net> wrote: {Quote hidden}> On Thu, 31 Jul 2008, Walter Banks wrote: > > Some good brainstorming ideas ! Couple of issues I should > mention, I don't think I could get a camera looking down > because of several large trees in the yard. Also, the yard > is half level, the other half has a fall of probably 10 ft > in 60 ft. So, one section is a steep hill. That may be > a problem for a transmitter pole or sensor on top of the > mower. > > I plan on making the mower as dumb as possible. I will have > my computer perform the processing and relay course and > direction to the mower through my wifi network or something > similiar (zigbee, bluetooth, etc...). > > Thanks, > Kevin > > > > You may want to rethink the problem a little when it comes to > > GPS. You don't need to know the absolute position of the lawn > > mower only that cuts the whole yard and not one segment and > > it is in your yard. > > > > w.. > > > > > > Kevin wrote: > > > >> Anybody know of a website or links to a cheap beacon system > >> for postion location for a mobile robot ? I looked around > >> the net and everything was pretty expensive. > >> > >> I was thinking of trying to use those cheap 315 mhz tx/rx > >> modules. I want to be able to postion an autonomous lawn > >> mower within 6 inches or so. I have an acre lot with a house in the > >> center so line of site is out. > >> > >> I have a GPS receiver but that is only good to ten feet > >> with WAAS enabled. > >> > >> Any other suggestions ? > >> > >> Thanks, > >> Kevin > >> > > -

On the camera thing... Nothing precludes you from using several cameras scattered around...perhaps linked back to the base using wireless transmissions. Same with other location ideas. Kevin wrote: {Quote hidden}> On Thu, 31 Jul 2008, Walter Banks wrote: > > Some good brainstorming ideas ! Couple of issues I should > mention, I don't think I could get a camera looking down > because of several large trees in the yard. Also, the yard > is half level, the other half has a fall of probably 10 ft > in 60 ft. So, one section is a steep hill. That may be > a problem for a transmitter pole or sensor on top of the > mower. > > I plan on making the mower as dumb as possible. I will have > my computer perform the processing and relay course and > direction to the mower through my wifi network or something > similiar (zigbee, bluetooth, etc...). > > Thanks, > Kevin > > > >> You may want to rethink the problem a little when it comes to >> GPS. You don't need to know the absolute position of the lawn >> mower only that cuts the whole yard and not one segment and >> it is in your yard. >> >> w.. >> >> >> Kevin wrote: >> >> >>> Anybody know of a website or links to a cheap beacon system >>> for postion location for a mobile robot ? I looked around >>> the net and everything was pretty expensive. >>> >>> I was thinking of trying to use those cheap 315 mhz tx/rx >>> modules. I want to be able to postion an autonomous lawn >>> mower within 6 inches or so. I have an acre lot with a house in the >>> center so line of site is out. >>> >>> I have a GPS receiver but that is only good to ten feet >>> with WAAS enabled. >>> >>> Any other suggestions ? >>> >>> Thanks, >>> Kevin >>> >>> > >

- A wire grid would relatively easy to install ("mole plow" insertion) and probably as easy and accurate to drive as any other system. - A small UAV 1 flies a search grid looking for the mower. or 2 carries a camera which views the mover and targets for location. - A hot air ballon on a cable, powerd by a heater which allows it to always stay aloft ... - Hmm. Mower. Microphones mounted on the house ... . - An ultrasonic ranger on the mower identifies IR beacons and calculates their distance. or Utrasonic rangers detect the mowers location using a beacon on the mower. - A ... Sounds like fun. ____________________________ If somebody wanted me to show them a demo working within a week I'd consider going for the mower carrying a rotating optical detector with N modulated beacons. Demos in no time are easy. Making the final product work is another matter. R

Please send us an update when you achieve 99.999% success ( or sooner even ) cc {Quote hidden}> On Jul 31, 2008, at 8:18 AM, Kevin wrote: > > On Thu, 31 Jul 2008, Walter Banks wrote: > > Some good brainstorming ideas ! Couple of issues I should > mention, I don't think I could get a camera looking down > because of several large trees in the yard. Also, the yard > is half level, the other half has a fall of probably 10 ft > in 60 ft. So, one section is a steep hill. That may be > a problem for a transmitter pole or sensor on top of the > mower. > > I plan on making the mower as dumb as possible. I will have > my computer perform the processing and relay course and > direction to the mower through my wifi network or something > similiar (zigbee, bluetooth, etc...). > > Thanks, > Kevin > >

An autonomous robot to push the mower. Comes complete with beer/ chips ingesting orifice ( for energy ) , expandable thorax filled with beer/chips ( for additional traction ). cc {Quote hidden}> On Jul 31, 2008, at 9:42 AM, Apptech wrote: > > - A wire grid would relatively easy to install ("mole plow" > insertion) and probably as easy and accurate to drive as any > other system. > > - A small UAV > > 1 flies a search grid looking for the mower. > or > 2 carries a camera which views the mover and targets for > location. > > - A hot air ballon on a cable, powerd by a heater which > allows it to always stay aloft ... > > - Hmm. > Mower. > Microphones mounted on the house ... . > > - An ultrasonic ranger on the mower identifies IR beacons > and calculates their distance. > or > Utrasonic rangers detect the mowers location using a beacon > on the mower. > > - A ... > > Sounds like fun. >