| Plotting Results Error +/- 0.02”
(approx. 1 1/4 sixty fourths of an inch). All the error is from plotting.
Some deviations are small but they are exact values. A difference of
0.04” is real.
All lengths are in inches and all angles in degrees.
R = right
L = left
S = step length
C = carry length
St = stride length
str = straddle length
WB = walking base length
o = offset
d = degree
(2d) = foot offset given as degree leg angle
L30R30str3 = left step length = 30”: right step length = 30”:
straddle length = 3”
L(2d)oL-2dL:R(4d)oR = left foot (2d leg angle) offset CCW and 2
deg CCW foot angle: right foot (4d leg angle) offset CW (This person would
be walking straight.)
Standard lengths
-L30R30
-straddle length = 3”
-step out length = 15” (So, 3.822deg leg angle/inch foot offset or
0.2617”foot offset/deg leg angle)
-rear stretch length = 15”
-foot model length = 6”
A 2 deg CCW leg angle for the left leg corresponds to a 0.52” foot offset
left for the left foot. Using leg angle for plotting is much, much, much
easier.
Plotting Results Analysis
Observations
-
Step Length:
-
Different step lengths for the left and right foot
does not cause an angular change in the DOT.
-
Angular changes in the DOT do not affect step
length.
-
Stride Length:
-
Stride length for the other foot increases with
external angular rotations, and decreases with internal angular
rotations.
-
A person can be turning with every step, but still
walking straight.
-
R/L Distances: (normal straight R/L – 0.l5”/30” step
length, or about 5/32”, a 0.5% increase)
-
Increasing straddle distance increases R/L lengths.
R/L values increase about 0.15”/1”str; constant over 28-30” step
length.
-
Foot offset is shown in the forward foot. ie. if the
left foot had a foot offset left, the L-R distance wouldn’t change,
but the R-L distance increases. (External rotation - I-0.025”/deg
leg angle; Internal rotation - D-0.01” or 0.02”/deg leg angle).
-
Shorter step length is shown in the forward foot. ie.
if the left foot had a shorter step length, the L-R distance
wouldn’t change, but the R-L distance would decrease.
For small changes, the R/L distance decrease equals the actual step
length decrease.
-
Foot angles do not change the R/L distances.
So, foot angle vs. foot offset rotations have a different effect on
the R/L distance.
-
Walking Base: (data not shown)
-
Walking base increases with internal angular
rotations, and decreases with external.
Final Words
Even with only the relatively few plots here, I've had to
leave out many explanations and discussions or I would never get this out.
This is the major theoretical section. Even if some of the
details change over time, I believe that any understanding of path deviation
must use this general framework.
Please make your own plots and try to find more information
in the standard footfall patterns. Also, try to find better and quicker ways
to do it.
The best thing to do is make plot models that are in a
series, like in the Tables, so it's easier to see regular variations. The
good thing about computer modeling is that anyone can make and use the
models, and they are all directly comparable. This has great potential.
Once a large number of different standard plots are made,
maybe we’ll figure out something new and be able to create tables of
standard values, or equations and relationships to determine accurate values
from real footfall patterns.
The last part of this work, Part III, will show how the plot
model can be modified to produce an analytical model to facilitate the
analysis of field patterns, and will discuss experimental procedures.
Have a go at making an analytical model and see what you
come up with. Maybe it will be better than mine.
I hope everyone looks on this as a group effort and tries to
contribute. As far as I know, all this is a new way to look at it, and it
will take time to fine tune.
So, please be critical about the work, but not unreasonable.
Show how it’s wrong and I’ll change it. I have no pet theories, I'm just
looking for the truth.
I consider this method always under development.
Regards,
Mike Mouck
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1, Page 2) Part IIa Part IIb
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Part IIc Part III
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