System and method for a quantitative detection of a movement
A system for a quantitative detection of a movement. The system includes a signal emitter and two signal receivers, positioned in series, along a first axis parallel to a second axis of movement of a reflective marker provided on a moving object. The reflective marker is configured to reflect a signal emitted by the signal emitter towards the two signal receivers. The two receivers have a signal reception coverage such that allows existence of a reflective marker position, on the second axis, in which the reflective marker of a given size is recognized simultaneously by the two signal receivers.
1 . A system for a quantitative detection of a movement, the system comprising:
a signal emitter and two signal receivers, positioned in series, along a first axis parallel to a second axis of movement of a reflective marker provided on a moving object, wherein the reflective marker is configured to reflect a signal emitted by the signal emitter towards the two signal receivers;
wherein the two receivers have a signal reception coverage such that allows existence of a reflective marker position, on the second axis, in which the reflective marker of a given size is recognized simultaneously by the two signal receivers;
wherein the size H m of the reflective marker in the second axis is calculated as a function of:
a distance D em between the first axis and the second axis,
a distance D er0 between the signal emitter and the first signal receiver,
a distance D er1 between the signal emitter and the second signal receiver,
a signal emitting angle β e of the signal emitter,
a signal reception angle α r0 of the first signal receiver, and
a signal reception angle α r1 of the second signal receiver;
and wherein:
H
m
≥
D
er
0
+
D
er
1
2
for
D
em
≥
D
er
0
2
·
tan
min
(
β
e
,
α
r
0
)
2
and
D
em
≥
D
er
1
2
·
tan
min
(
β
e
,
α
r
1
)
2
whereas when D er0 is different from D er1 , the greater one of the two is applied to determine D em .
2 . The system according to claim 1 wherein the distance (D er0 ) between the signal emitter and the first signal receiver is equal to the distance (D er1 ) between the signal emitter and the second signal receiver.
3 . The system according to claim 1 wherein the signal reception angle (α r0 ) of the first signal receiver is equal to the signal reception angle (α r1 ) of the second signal receiver.
4 . The system according to claim 1 wherein at a position wherein the signals reported by said two signal receivers are the same, their waveforms cross while their respective values are at more than 25% of a maximum value reported for the reflective marker.
5 . A weightlifting system comprising a weight stack having at least one weight plate comprising the system according to claim 1 wherein the reflective marker in affixed to the at least one weight plate.
6 . A method for determining a direction of movement in the system of claim 1 , the method comprising:
determining that both signals from the two signal receivers have a predefined Low value (T 1 );
determining that one of the signals has assumed a predefined High value while the other signal has maintained said Low value (T 2 );
subsequently, checking whether the respective signals have assumed the values of the other signal at (T 2 ) thereby reversing the values of the signals (T 3 );
checking whether both signals have the Low level again (T 5 );
determining a direction of movement, of said reflective marker, based on the first and the last signal having said High level.
7 . The method according to claim 6 further comprising:
estimating a value (W tr ) of the signals at a time (T 3 ) when the signals values cross;
determining a maximum value (W max ) registered by the signal receivers and if
W
t
r
W
m
ax
≥
threshold
then accepting a pass of the reflective marker by the system.
8 . A computer program comprising program code means for performing all the steps of the method of claim 6 when said program is run on a computer.
9 . A computer readable medium storing computer-executable instructions performing all the steps of the method of claim 6 when executed on a computer.