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Re: Forward Error Correction and under-runs at speed
Well...
I ran the tests again.
Four squares forward at 0.5, 1.5 and 2.5m/s/s
Top speed was limited to 2 m/s so it will never have been reached.
The mouse was run back-heavy, balanced and front-heavy. The front and
back-heavy runs were about the same level of imbalance.
At the lowest acceleration, the actual distance travelled is measured.
at the middle acceleration setting, the mouse stops short by about 4mm.
At the highest acceleration, the mouse stops short by about 10mm.
The same results were obtained with all three setups although I did not
measure the distance in each case to the nearest anything - just marked
lines on the maze floor.
Adding more weight to the rear does, however, seem to make things worse.
While the front and rear skid are similar (cheap domed drawing pins),
the rear skid is more worn than the front one and may well present a
greater friction.
I shall have to perform all the tests in reverse to be sure. Maybe
tomorrow as everyone has gone to bed early.
For background:
Acceleration and velocity are stored as 8.8 fixed point values, distance
as a 24.8 fixed point value. Simple additions accumulate acceleration to
speed and speed to distance. The mouse is stepper driven with 16x
microstepping giving a resolution on the ground of about 0.05mm per
step. Distance travelled can be determined from a counter attached to
each wheel pulse generator or from the accumulated speed. In either case
the result comes out the same. The mouse thinks it has gone so far but
reality falls a little short with greater acceleration.
Pete Harrison