On Fri, Aug 31, 2001 at 03:50:40PM -0500, Lawrence Lile wrote:
> Y'know, with all this talk about optical sensors, keep this in mind: Cutting
> grass is a dirty job.  If you are not careful, any optical sensor is going
> to soon be covered in gook.  I nixed several ideas for optical grass height
> gauging, concrete sensing, edge sensing etc. after watching the bits of
> juicy stick grass flying all around a mower.   That's why I keep coming back
> to my axiom - Cochroach Stupid! or Keep It Simple Stupid!  Cochroaches have
> feelers that are more use than their eyes, if they even have eyes.

I understand. Since I posed this query I just wanted to update my thoughts.

I always liked the beacon idea. The problem I always had with it was trying
to figure out how to sense on a moving plane. Between hills, valleys, and
obstacles, along with a continuous slope in the yard it will be very very
difficult to sync the transmitter and receiver. But the discussion on the
rotating VOR mirrors I realized that creating a verticle sweep could help
quite a bit because then the receiver could sense the transmission even
with a height disparity.

After thinking about it some more, I realized that putting a complex motorized
mechanism on a number of stationary beacons probably isn't a good idea. The
stationary part of the system needs to be as simple and reliable as possible.
I also figured that the mowbot really only needs to know which beacon it's
talking to and the angle of the front of the bot relative to that beacon.

So here my idea:

1) Flip flop the system and make the mowbot the transmitter and have stationary
receivers mounted that detects the transmittions.

2) Design a two dimensional sweep. The transmitter will rotate horizontally
360 degrees. On this platform have a vertically rotating light transmitter.

3) The receiver system will passivly wait for transmittions and then
transmit their id when they detect a transmission. Thinking of using wireless
for that.

4) So the way it'll work is that the mowbot does a 360 degree horizontal
sweep with vertical sweeps up and down. When a receiver detects it transmits
its ID to the mowbot. The mowbot can then record the angular position of
the receiver and move on. The set of angles uniquely identifies the position
presuming you have a minimum of two receivers.

After that you can use the data for tracking, planning, etc. You can dead
reckon based on the angular data from the stationary receivers. You can define
spots that are out of bounds, the home position, the start position, where to
turn, etc.

Since the receivers are no longer actively transmitting, they may be low power
enough that they can be solar powered. The receivers do not have to interact
with one another, simply report that they are currently receiving a signal.

Maybe it's time to start some testing of the idea...

BAJ

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