Outdoor robot navigation - GPS or robot lawn mower fence?
I've bought a WildThumper, will get it in a week or so.
Q1: For autonomous navigation on my lawn, would you recommend GPS (have a PAM-7Q GPS) or using an existing buried wire fence for my Robomow RL-1000?
GPS might be easier to get started with, but is it reliable enough to prevent the robot to drive out on the street or in a ditch? Using the buried wire somehow seems safer but more complicated to build.
Q2: Can I use PropScope to find the frequency in the wire? Once I've found it, what circuit should I build?
With both options I'd need to have obstacle avoidance sensors to avoid flower beds, our outdoor pool etc. Laser sensor perhaps combined with ultrasound and/or IR sensor comes to my mind, have them in my toolbox.
Also have several Project and Activity Boards, compass module, LSMDS1 9-axis IMU, Ping, IR leds etc. If this project ever flies, it would be close to 100 % Parallax-driven :-)
Q3: Don't have the Sharp IR sensor, would IR even be reliably outside?
Q4: As I'll travel to Santa Clara in a week, I'd be able to order some parts from Parallax and have them delivered to my hotel, anything I'd need for this project?
Appreciating guidance and recommendations
Q1: For autonomous navigation on my lawn, would you recommend GPS (have a PAM-7Q GPS) or using an existing buried wire fence for my Robomow RL-1000?
GPS might be easier to get started with, but is it reliable enough to prevent the robot to drive out on the street or in a ditch? Using the buried wire somehow seems safer but more complicated to build.
Q2: Can I use PropScope to find the frequency in the wire? Once I've found it, what circuit should I build?
With both options I'd need to have obstacle avoidance sensors to avoid flower beds, our outdoor pool etc. Laser sensor perhaps combined with ultrasound and/or IR sensor comes to my mind, have them in my toolbox.
Also have several Project and Activity Boards, compass module, LSMDS1 9-axis IMU, Ping, IR leds etc. If this project ever flies, it would be close to 100 % Parallax-driven :-)
Q3: Don't have the Sharp IR sensor, would IR even be reliably outside?
Q4: As I'll travel to Santa Clara in a week, I'd be able to order some parts from Parallax and have them delivered to my hotel, anything I'd need for this project?
Appreciating guidance and recommendations
Comments
GPS is rather too vague for lawn-edge precision, but it could qualify zones for the buried wire, to cut false positives.
What I'll start with now is to just hook up my GPS to a Activity Board with a LCD-screen, take it outside and see how consistent readings I get at different corners of the lawn.
FYI: Not building another lawn mower robot, already have one 10 years old, what I have in my mind was to make a smaller robot that would be airing the lawn, e.g. with a couple of nails. How to build the airing mechanism is a later part, the navigating part needs to be solved first for the whole project to make sense. Still snow and ice on the lawn, have 8 months time
Related to navigation, as this robot would 'work' only on our lawn, I thought I could pre-program the map of the lawn with the GPS-coordinates of each corner (there are plenty of them due to the diamond shape of our lot). 'Connecting' these corners would then give the boundaries inside which the robot should stay. This is feasible only if the GPS is consistent enough which it might not be.
I'll bet Ken & Team Parallax would roll out the red carpet and you'd easily win the man-mile award, coming from Finland!
I'd be surprised if the Colorpal worked well in this application. I think it's intended to find the color of things up close.
A low res camera would probably be a better choice but the interfacing might be a problem. What the world really needs is a camera chip that transfers the image to a block of memory that can then be accessed via SPI.
It might also be worth taking a look at Phil's Redeye project, using a linear imaging sensor: The Parallax/TAOS TSL1401-DB is a vision sensor that sees in one dimension using a 128x1 array of light sensors, along with an imaging lens.
http://forums.parallax.com/discussion/117941/redeye-a-linescan-imager-based-boe-bot-line-follower
I'm not however sure how I could utilize the linear imaging sensor in my outdoor project. The buried wire is...well buried and if I put another wire on the surface it will either get buried within some months or cut into pieces by the robot lawn mower. OTH, if I find some type of wide, somewhat flexible and thin enough material with suitable color and that would not easily get buried, this type of sensor could be useful. Don't know how aesthetic it would be though...
-Phil
To detect the wire signal from the robot, I'd need to build some type of circuit, perhaps including a 'antenna coil'?
It is most likely an AC signal so you may be able to pick it up with an AM/FM radio or a Propscope with a simple antenna. Might even have the frequency listed in the manual.
Enough information there to build a perimeter sensor for your project I think.
Found a patent that might not be for this exact model but at least from same company (Friendlyrobotics). A schema on pg 23 seems to cover the signal sensor which by the way also can measure the strength of the signal even far away from the wire.
Now I'm mainly interested in knowing if the robot passes over the signal wire or not, the signal strength is of less importance.
There also needs to be some tolerance for other items like metal pipes or grates, or simply cable depth.
Yes, good to see they used a crystal, which makes the chirp very precise and suits a narrow band analog filter (that can dig into the noise floor).
Probably easiest to make one of those with another crystal, and a switched-capacitor filter/detector, tied to a sensor head that is broadly resonant at the 8kHz.
You really don't need an external filter. The Propeller can do the filtering all by itself:
http://forums.parallax.com/discussion/133173/fir2pasm-automatic-fir-filter-code-generator/p1
And a narrow bandpass filter for 8 kHz should be a piece of cake.
-Phil
Well, maybe on paper...
The issues arise when you seek to tunnel into the noise.
Running an oversampled ADC and then hoping to find a signal below the noise, runs into LSB quanta effects.
If you instead use external analog elements, that quanta effect is not present until you apply the ADC.
The type of filter/sync detector I have in mind, gives I & Q signals that are envelope based, but can be built with a Prop's timers and simple analog switches (4066 class). The ADC applies to the post-filter/envelope detector.
Nett result: Better noise floor.
http://forums.parallax.com/discussion/105674/hook-an-antenna-to-your-propeller-and-listen-to-the-radio-new-shortwave-prog/p1
8 kHz is slow enough -- and the integration times long enough -- that the S/N should be quite high.
-Phil
Sounds worth trying, and it may prove 'good enough'.
I have also done some thinking on small scale outdoor localization similar to your lawnmower robot application.
GPS is too rough, but Differential GPS can give sub-100mm accuracy. There is a nice hackaday article exactly this issue;
http://hackaday.com/2017/03/01/where-are-the-autonomous-lawnmowers/
Alternatively, you can try some sort of triangulation beacons similar to the Vive Lighthouse interior system (the problem would be sunlight interference);
http://www.theverge.com/circuitbreaker/2016/7/6/12109880/htc-vive-lighthouse-hack-diy-positional-tracking
Has anyone compared this 1pps, with the 1pps from say Adafruit or other GPS ?