A Performance Analysis System for the Sport of Bowling

2.8.1 Detecting Release
Detecting the point of release by using a RELEASE light level has been quite effective.
Since the bowler must cover up the light sensor when placing their fingers in the ball, the
module sees a very low level of light (essentially 0) while the bowler is gripping the ball.
There are circumstances when, as part of a bowler's normal ritual, they insert and remove
their fingers in the ball several times before commencing their delivery. SMARTDOT
detects each of these as a release, assuming enough pressure has been applied to activate
the module, but the discrimination routine is intended to recognize, and ignore, such
behavior.
Pre-sampling of the waveform helps capture the moment of release - that point when the
light samples start to increase from their dark pre-release levels. Although the module
uses the configured RELEASE level to detect release (at which time it writes the eight
pre-samples to EEPROM), the MASTER program determines the exact moment of release
from those pre-sample values, which might differ from the time the module used by one
or two sample times. Referring to Figure 2-7, which zooms in on the first 400 msecs of
the waveform shown in Figure 2-6, the pre-sample light level is actually 0 (completely
dark) until the bowler starts to release the ball at -17 msecs. Release occurs between -8
msecs and 0 msecs, where a sharp increase in the light level is evident.
70
60
50
Impact with Lane
(ball loft)
Light Level
40
30
20
Release
Point
Finger Pressure
at Release
10
0
-50
0 50 100 150 200 250 300 350
Milliseconds (since Release)
Figure 2-7: Raw Data Release Region (400 ms)
2.8.2 Detecting Impacts
The piezoelectric film sensor and the comparator circuitry are more than adequate for
detecting the various impacts the ball experiences. Several impacts are shown in Figure
2-7, which presents the first few hundred milliseconds after release. At two consecutive
sample times, -8 msecs and 0 msecs, the sudden pressure that the bowler applied to the
finger insert while releasing the ball is indicated. At 183 msecs, the graph indicates the
ball contacting the lane. The module consistently records both the pressure applied at
release and the impact generated when the ball hits the lane.
At the other end of the lane, the module has no problem detecting multiple impacts with
the pins, as seen in Figure 2-8 (an expansion of the waveform in Figure 2-6). This
particular waveform is from a ball that hit the 1-3 pocket and resulted in a strike. A good
pocket hit generally results in the ball hitting four pins on its way through the rack, and
there are four impacts indicated on the graph. Throughout testing, solid pocket hits
tended to generate four impacts, while light pocket hits, and high hits resulted in three
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