[Dprglist] Compass heading using gyroscopes?

[John Swindle]

A quick note: A one-degree error is two inches after ten feet. Not good enough for small robot navigation unless something is constantly providing better pointing accuracy. Even for the contests, if the robot depends on that amount of error, it would miss the goal in 6 Can, might hit the cone in Square Dance, etc. Outdoors, the accuracy has to be a lot better. I think you will be very unhappy with 11.25 degree resolution. And be careful that resolution and accuracy are not the same thing.
Later,John Swindle


-----Original Message-----
From: Murray Altheim via DPRGlist <dprglist at lists.dprg.org>
To: Doug Paradis <paradug at gmail.com>
Cc: DPRG <dprglist at lists.dprg.org>
Sent: Fri, May 15, 2020 2:21 am
Subject: Re: [Dprglist] Compass heading using gyroscopes?

Hi Doug,

That's a good point. I frankly can't imagine why I'd need degree-perfect
accuracy on a moving robot, where the heading is changing quite a lot,
all the time. Now I suppose if one was using the heading reading to
*maintain* heading an accuracy of a few degrees would be valuable. So
there's two purposes: 1) basic directional navigation (e.g., pointing
the robot roughly north); and 2) heading with accuracy for holding a
bearing.

For directional navigation increasing resolution allows me to go from an
8-wind compass rose (an accuracy of 45° allows a determination of which
of the 8 directions we're aiming); 16-wind compass rose (22.5° accuracy);
32-wind compass rose (11.25°). So basically anything better than 11.25°
gives me a 32-wind compass rose for directional navigation. I think that's
easily doable.

For holding a bearing the more accuracy the better, though I doubt degree
accuracy is all that important in a small robot (a container ship, yes).
Since the robot is going to be reading the IMU and correcting its heading
continually a few degrees inaccuracy might be somewhat "self-correcting",
dunno. 2-3-5 degrees would probably be fine, but I won't know until I
try it out. The overall behaviour of the robot will be altered by that
difference but in either case I don't think it would be "wrong"; slow-
motion film of bumble bees shows they're hardly accurate navigators and
they seem to get along just fine.

Cheers,

Murray

On 15/05/20 6:26 pm, Doug Paradis wrote:
> Murray,
>     I think it also depends on the degree of accuracy you want. If you want your compass to tell you N,NE,E,SE,S,SW,W,NW 'ish, you calibration doesn't need to be as complete as if you want +/- 0.1 degree.
> 
> Regards,
> Doug P>
...........................................................................
Murray Altheim <murray18 at altheim dot com>                      = =  ===
http://www.altheim.com/murray/                                     ===  ===
                                                                    = =  ===
    In the evening
    The rice leaves in the garden
    Rustle in the autumn wind
    That blows through my reed hut.
            -- Minamoto no Tsunenobu

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