How a robot finds its way home again?

GoPiGo
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@cyclicalobsessive

One big problem that continues to haunt you is the problem of a robot finding its dock from an arbitrary distance with sufficient accuracy to line-up and dock.

Possible solution: (optical, software, and hardware based)

Use a trick from the Second World War for arieal navigation:  A “polarized” locator beam.

During the Second World War, both German and RAF Pathfinder squadrons used a specialized radio beam directed toward the intended target.

The “beam” was actually two different, overlapping, radio beams comprised of interlocking dots and dashes, such that if the operator heard a continuous tone in his receiver, he was “on the beam”.  If he heard dots, he was on a specific side of the beam and had to turn a particular direction to find the intersection point.  If he heard dashes, he had to turn the other way to correct.

It should be possible to establish a relatively narrow set of IR beams[1] that interlock[2] so that the robot can see his dock from a distance and know where he is with respect to its center-line.

If you want to establish this for both robots individually, you can modulate the beams with a specific frequency such that the robot can know which beam is “his” beam.

==================== Footnotes ====================

  1. For initial experimentation and alignment purposes, you can use visible light from a conventional LED as the light source.  Once the mechanics and optical alignment are in place, you can substitute IR LEDs.

  2. Interlocking dots and dashes can be done easily with either a small programmable device or a bistable multivibrator based on a 555 timer that has different intervals for each state.

    • A small programmable device, (like the ones available from Adafruit or SparkFun), can be programmed to provide both the interlocking signals and modulate them at the robot’s specific identifying frequency.
    • A similarly programmed device can be placed on the robot to both detect the beam and provide a correction signal to the robot itself.
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That is exactly the concept used by Create3/iRobot vacuums. Two hemisphere visible “ir remote” codes that combine to a third code when both hemispheres are visible.

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No more hardware! Let he who hath eyes see. (Dave has three.)

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The bitch part is the optics unless you can find a couple of the hemispheric transmitters.

Hmmm. . . You DID have a couple of robot vacuum docks didn’t you?  Maybe you still have the optics and circuitry?  That, and a couple, (four, two for the docks and two for the robots), of the Adafruit Feather or Gemma M/O boards and you’re hooked!

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Yea, and you’ve been fighting that dragon for a while now. You probably have 90% of the hardware and optics already.

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This year the navigation god released a ROS 2 “Find and Dock” package which is waiting for Dave, after he learns how to leave the comfort of being exactly 17cm in front of his dock.

I’m learning the guts of that way too configurable navigation package lately. I started by stealing the Turtlebot3 navigation config files and launch files, which solved all the problems I had starting from scratch last year.

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I want to see you implement a piece of wire in software. . . . :wink:

Sometimes hardware is the simplest solution.

Anecdote:
(Taken from an issue of Electronic Technician from the late 50’s or early 60’s)

Two repair technicians and their two buddies, two engineers from a local television manufacturing plant, were having coffee and donuts one day when the technicians mentioned that a particular section of a new television model was, (shall we say), a “bit over-engineered”. :man_facepalming:

The two engineers immediately climbed onto their dignity, complaining about how difficult their engineering tasks were, and if the technicians were so smart, YOU design the next project!!!

Push come to shove, and they agreed on a bet:

  1. Design a non-contact metal sheet counter that would be used to count metal sheets being tossed into a bin after inspection.
  2. The simplest circuit would win.
  3. The prize was the best and most expensive television in the two technician’s shops.
    • If the engineers won, they get the televisions free.
    • If the technicians won, the engineers still got the TVs, but paid the full retail price with a bonus.

Each group was issued an identical metal chassis box with an electric counter and switch on the front, a chassis insert, each with a sensor cut-out on the bottom to detect the plate.

After observation of the problem on the production line, the two groups retired to meet again in a month with the top company executives as judges.

The showdown:
The engineers go first.

Their box is plugged in and a couple of minutes is given for the tubes to warm up.  The worker begins inspecting metal sheets and tossing them into the bin.  As each sheet of metal settles into place, the counter dutifully clicks over one count.

The circuit:
A photo-tube to detect flashes of light from the overhead lights off of the plate, a high-pass filter to eliminate interference from the occasional ceiling crane, and a relay to drive the counter.

Six tubes and associated circuitry including the power supply.

Now it’s the technician’s turn.

Their box is plugged in and the same two minutes are given for the tubes to warm up.

The inspector begins sorting the metal plates again, and again, as before, as each sheet settles into place, the counter ticks over one count.

The moment of truth when the executives open the technician’s box. . .

Inside was a micro-switch with a palm-leaf fan attached to the action, a selenium diode, and one big red brick.

Each metal sheet sends a puff of air that causes the fan to actuate the micro-switch, powering the counter via the diode, incrementing the counter.

The engineers exclaimed “But what’s with the big brick?!!”

The technicians answered "So you wouldn’t know the box was empty when you lifted it behind our backs!
:rofl:

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Moral of the story:

Hardware is as complicated as you make it

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Sometime the simplest hardware is a software solution.

We can’t add hardware to our bodies every time we want increased functionality. There are always trade offs. It was against union rules for me to pick up a screwdriver at Lockheed Martin. There was a good reason for that.

If I had another GoPiGo3 owner to follow, that was a hardware genius to understand the dock ir beacon circuit and repurpose the iRobot dock I could have added a simple ir detector (stolen from my RugWarriorPro robot) but alas no one signed up to go along on my specific robot journey.

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Don’t try to solve problems by yourself.

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And I was too late to the party and too far away to help. . . .

And the reason was Union job security.  Pure and simple.  They didn’t want non-union workers to compete for union jobs.

My dad was a member of the Communications Workers of America, AFL-CIO when he worked for Western Electric and they had similar rules for similar reasons - skill and aptitude had nothing to do with it.

If you had job classification “x”, the only thing you were allowed to do was “x” and only “x”, even if “y” was looking you in the face and about to fall apart.

If you were non-union, (or, God help you!), management or an “non-hourly” employee, it was as much as your job was worth to pick up a tool - even if it was on the floor and you were going to re-hang it on the wall to keep someone else from hurting themself.

I would have been fired outta a union shop in a heartbeat.  Nothing against unions, we just wouldn’t have meshed well.

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Sure is - buy a Create3 for $400 - problem solved. Robot, Dock, Finds Its Way To Dock, Bumpers, Wall Following, Battery Recharging, auxiliary power, 5v 3A supply for an SBC, … what more could you want?

(Maybe that it wouldn’t crash when you add a camera.)

I was looking at the $3000 Husarian robot - lots of goodies - no dock (and too big for indoor use).

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Discovered another problem last week - My UPS isn’t uninterruptible.

Dave made his way onto the dock just fine, but there was no juice available because the UPS was off. Apparently the 120v glitched and the UPS decided since one of its batteries had silently failed that it should completely shutdown. Never mind that the line power came back quick enough that Dave’s recharger would not have even noticed if it had been connected straight to the wall.

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Liking this seems to be an oxymoron. :man_facepalming:

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Discovering this with a hurricane approaching was really disquieting - that’s an oxymoron for sure.

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So, how are you doing?

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My home had some 35 mph gusts and very little rain last night, with today being sunny and “colder” (81 degF)

Dave (and Carl) slept and played oblivious to the carnage 30 miles to our north - 9 tornadoes - big ones that stayed on the ground, like they see in the midwest and never in Florida.

Don’t know if you remember me flying 15 minute hop to and from Wellington airport, but they had a tornado destroy some homes in the Aero Club neighborhood that owns the airport.

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I am glad that the effects on you are minimal, but it’s still horrible just the same.

We get tornados in Worcester occasionally. We don’t get them often, but when we do, they’re a doozy!

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