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From: Klaus Vestergaard Kragelund <klauskvik@hotmail.com>
Newsgroups: sci.electronics.design
Subject: Re: IR detector system, biasing of photo diode
Date: Tue, 29 Oct 2024 00:52:43 +0100
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On 28-10-2024 13:01, Don Y wrote:
> On 10/28/2024 3:17 AM, Klaus Vestergaard Kragelund wrote:
>>>>>> A IR transmitter on the docking station transmits a beam, and 2 IR 
>>>>>> detectors on the robot detects the beam and lets the robot 
>>>>>> navigate towards the target. The working distance is a couple of 
>>>>>> meters.
>>>>>
>>>>> Can the robot ALWAYS see the docking station?  What happens if an
>>>>> obstacle (wall?) comes between the two?
>>>>
>>>> Yes, we have RTK GPS to position it within a cm at a location right 
>>>> in front of the docking, 2 meters away.
>>>
>>> Then why can't you move to the GPS location of the dock with the
>>> same degree of accuracy?
>>
>> The docking station is typically in a shed, or close to a building 
>> where the GPS signal disappears.
> 
> Ah, OK.
> 
>>>>> Can either device (robot/dock) ever slip out of the shared plane?
>>>>
>>>> No, should be locked
>>>
>>> "Outdoors" (from below).  Presumably on pavement/concrete (not a "lawn")
>>> that wouldn't have dips and bumps?
>>
>> It's moving on grass, and can have bumps etc, so for IR the lope needs 
>> to be perhaps 20degrees to avoid loss of signal
> 
> And, presumably, they are short (time and space) transients?  *Faster*
> than the response time of the robots controls?
>

Yes, the inner loop must be a lot faster than the control time of the 
robot, or it will oscillate ;-)

>>>>> I have become particularly fond of using cameras to interface with
>>>>> the real world.  Of course, it requires a bit more horsepower but
>>>>> seems to be able to overcome all of the issues that have crept up...
>>>>
>>>> That's also a solution we have been working on. The Worx Vision uses 
>>>> that
>>>>
>>>> https://eu.worx.com/da-dk/landroid/vision-technology/
>>>>
>>>> That is for a future version. Cameras can also be blinded, lenses 
>>>> needs to be cleaned etc
>>>
>>> Yes, but a camera can be "queried" to verify that it is functioning
>>> correctly:  "What do you see?  Is it THIS?"
>>>
>>> I test my cameras by storing previously viewed scenes to verify they
>>> are still "reasonably" intact.  Ideally, I would move something into
>>> the field of view but that requires additional capabilities.
>>>
>>> You, however, could move the robot (assuming IT has the eyes) and
>>> verify that the scene changes accordingly.
>>
>> Could be done. The guys in charge are worried with change of 
>> environment, so what happens when it snows heavily, fog or other 
>> surroundings changing effects.
> 
> You extract salient "features" from the scene and use them.
> The robot doesn't need to be concerned about whether the ground is
> green, brown or white.  Or, if the shed is in shade, blanketed
> with snow, etc.
> 
> E.g., I use them to "watch" the garage door rails (which have a specific
> shape) to see if any objects have come between the camera and the rails.
> (The rails define the plane that the garage door will occupy as
> it closes)  Of course, everything around the rails is highly variable
> as garages are notorious for clutter and dynamism.
> 
> Another camera "watches" the mailbox by the road.  In addition to
> the surroundings changing, there can be pedestrian and vehicular
> traffic passing at any time.  In our case, it is illegal to
> drive while using a phone so folks often pull over to answer
> phone calls -- our mailbox is in a shaded area that seems to be
> highly desirable to such motorists-in-need.  But, *their*
> vehicles don't look like "mail trucks" so no chance of thinking that
> *they* are delivering our mail...
> 
> As I said before, it is a really great "sensor"!  The downside is
> that you need resources to use it (your optical approach is likely
> possible with far less resources -- think of how robot vaccuum cleaners
> operate wrt their charging docks)
> 

Correct, all though high resolutionn cameraes are very cheap nowadays. 
And they have a Linux maching running the application SW, so adding a 
camera does not add much extra cost, just a camera interface IC.