JPS596080A - Swing measuring apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a swing measuring device that uses ultrasonic waves to measure the swing angle and speed of a baseball bat passing through a predetermined space.

A conventional device of this kind has ultrasonic transducers (1a) and (1b) installed a certain distance apart, as shown in FIG.
Sharp directional ultrasonic pulse beams (2a) and (2b) were emitted from each of them in the same direction and at the same frequency. Then, the ultrasonic pulse beams (2a) and (2
The swing angle and speed of the bat (31) were determined by signal processing the echo reflected from the bat (3) that was swung by b).

Now, in Fig. 1, transducers (1a) and (1b)
The distance between is l, and the distance from the point where the bat (3) swinging from left to right in Figure 1 crosses the ultrasonic pulse beam (2a) to the transducer (1a) is khtt. The transducer (
1b) as h2. Further, the angle between the swing trajectory of the bat (3) and the horizontal plane is defined as the swing angle θ. At this time, the signals detected by the transducers (1a) and (ib) are shown in FIGS. 2a and 2b. In Fig. 2, the horizontal axis t is time, the vertical axis I is intensity, and the pulse shown by the solid line is the ultrasonic pulse oscillated by the transducer (1a) and (1b), and the pulse batt (3 ) is an echo from In addition, in Fig. 2, ta is the transducer (1a
) and (1b) are the periods of the synchronously oscillated ultrasonic pulses, ts and tb are the transducer (1a), respectively.
and (1b) transmits an ultrasonic pulse and then bats (
3), and tc is the time from when the transducer (1a) receives the first echo until the transducer (1b) receives the first echo. It is.

Here, if the speed of the ultrasonic wave is ga, then the distances h1 and hz
is determined by the formula %'tl1 and the formula (2).

hl = ve * ta/2 ・・・・・・・・・
・・・・・・River・・・・・・ il+hz=ga・
t b/2 ・・・・・・・・・・・・・・・・・・
(21 Therefore, the swing angle θ is hx and hz of the 11th) equation and the 2nd equation.
and the distance l between the transducers (1a) and (1b)
) can be found using the formula.

θ=actan((hz ht)/A') −・−
+31 Furthermore, the speed τ of bat 3) is hz−stone<hl ・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・When (4), No. (5)
v=J/(tc-residence θ)...music/music...+5 found by the formula
1. However, in order to measure θ and Θ as described above, equations (6) and (71) must hold true.

ta < ts・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・16+
ta < im ・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・(7
1. However, when measuring the swing of a professional baseball player, it is necessary to measure the swing angle and speed of a bat that moves at a speed of nearly 40 m/see over a height of about 1 m. At this time, since hl and bz are about 1 m, tl and tb take about 6 m5ec, and
In order to apply the ultrasonic pulse to the bat moving at high speed as mentioned above, the reflection cross section of the bat is small, so the number 1 is required.
0 IG(z, that is, ts of several hundred μSec is required. At this pulse frequency, equation (6) and equation (
Since the condition of formula 7) does not hold, it has been difficult to measure the swing angle and speed of a bat swung at high speed using conventional devices of this type.

In order to eliminate this drawback, the present invention installs two ultrasonic transducers on the ground at a predetermined interval so that the axes of the oscillating beams of each transmitter intersect at a height near the impact point of the pole. This device generates high-speed ultrasonic pulse beams and processes the echoes to determine the swing angle and speed of a bat that swings at high speed.

The drawings will be described and explained in detail below.

FIG. 3 is a block diagram of an embodiment of the present invention. In Figure 3, the oscillation circuit (4) is a transmitter (5a) with sharp directivity.
Ultrasonic pulses are transmitted at the same frequency from (5b) and (5b). The receivers (6a) and (6b) detect the echoes of the ultrasonic pulses transmitted by the transmitters (5a) and (5b), respectively, and are reflected by the bat, and activate the threshold circuits (7a) and (7b). ), only echoes having an intensity exceeding a preset threshold are extracted, and this number is counted by counters (8a) and (8b). The angle calculation circuit (9) has the above-mentioned counters (8a) and (8
Find the ratio of the number of echoes counted in b).

Angle memo I of the swing angle of the bat corresponding to this ratio
Choose from J Qω. On the other hand, the echoes detected by the above threshold circuits (7a) and (7b) are processed by the maximum echo detection circuit (
Ila) and (Ilb) and detect the echo with its maximum intensity. This detection pulse is sent to a timer (
13, timer az is set to maximum echo detection circuit (l
Measure the time difference between the pulses coming from la) and (Ilb). Using the time difference thus measured and the swing angle determined by the angle calculation circuit (9), the speed calculation circuit f131 calculates the swing speed of the bat.

Now, as shown in Figure 4, the transmitter (5
a) and a transmitter (6a) installed adjacent to the receiver (6a).
5b) and the receiver (6b) are installed on the ground with a distance of 2W in the swing direction of the bat, and the transmitter (5a)
The axes of the ultrasonic pulse beams shown by the dashed line in FIG. 4 transmitted from (5b) intersect at a point at a height h close to the impact point of the ball on the midpoint of the distance 2W. Note that the directivity centers of the receivers (6a) and (6b) are directed toward the intersection. The angle at which the sound pressure becomes % of the value on the beam axis is the directivity angle θ%, which represents the spread of the beam.

If the beam is cut on a horizontal plane with height h, the length of the cross section is 2
8. Note that here, the transmitters (5a) and (5b
) have the same directivity. It is assumed that the bat (3) crosses these two beams at an angle θ and a speed ν with respect to the horizontal direction. That is, as shown in FIG. 4, the bat (3) passes through the beam transmitted by the transmitter (5a) by a distance of line segment 17, and passes through the beam transmitted by the transmitter (5b) by a line. It passes only the distance of the branch market. Here, while the bat (3) passes through the line segments m and ■, the counter (8
Let Na and Nb be the number of echoes counted in a) and (8b), and let ts be the period of the ultrasonic pulse, then the (8th
) and equation (9) hold true.

aa' = Na・1. @τ ・・・・・・・・・・・・
・・・・・・・・・・・・(8) bd=Nb@tsIIτ
・・・・・・・・・・・・・・・・・・・・・(91 In reality, the beam is wider than the divergence angle θ%, so the distance that the bat (3) passes through the beam is m and city, and the number of echoes detected at receivers (6a) and (6b) is greater than Na and Nb. However, the intensity of echoes detected at receivers (6a) and (6b) is largest when reflected at the beam axis, and becomes smaller as it is reflected farther from the beam axis, so that reflected outside the range of line m and the city is equal to that reflected within the above range. Therefore, only echoes reflected within the above range can be extracted by performing threshold processing using threshold circuits (7a) and (7b).

As an example h = 1 m, W = 20 am, S
= 15 cm, a directivity angle θ% = 8.45° is required, and this directivity angle can be achieved by using a disc-shaped vibrator with a diameter of 33nwn. At this time, ip1 and the swing angle θ have the relationship shown in FIG. In FIG. 5, the horizontal axis is the swing angle of 0. The vertical axis is b'i7/aa
' is the value of '. Furthermore, the first generation is established from equations (8) and (9).

Therefore, by storing the relationship shown in Figure 5 in the angle memory (1G), the angle calculation circuit (9
The swing angle θ corresponding to the value of Nb/Na calculated in ) can be selected from the angle memory uti.

On the other hand, the maximum echo detection circuits (lla) and (Ilb)
Since the maximum echo detected by the bat (3) is reflected when the bat (3) passes through the beam axis, the timer O2
The time difference tp measured at is the time it takes for the bat (31 to pass through distance 1 of line segment 7 in Figure 4.
The speed calculation circuit 03 calculates the swing speed, V, using the anth equation using θ obtained by the angle calculation circuit (9) and ip obtained by the timer tta. The anth equation gives a good approximation when the swing angle θ is 20° or less.

In addition, in the present invention, when an ultrasonic pulse with a frequency of 50 KHz or more is used, the swing angle of a bat swung at a speed of 40 m/sec or less can be determined with an accuracy of 1''.

Additionally, the swing speed can be determined with an accuracy of 0.5%.

As described above, in the swing measuring device according to the present invention, two ultrasonic transducers are installed on the ground at a predetermined interval, and the axes of the excavation beams of each transmitter intersect at a height near the impact point of the ball. There is an advantage in that the swing angle and speed of a bat swinging at high speed can be determined by transmitting an ultrasonic pulse beam in this manner and processing the echoes as signals.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of measuring the azimuth angle and velocity of a bat in a conventional swing measuring device. 2(a) and 2(b) schematically show signals detected by the transducer, FIG. 3 is a block diagram of an embodiment of the device according to the present invention, and FIG. 4 is a diagram schematically showing the signals detected by the transducer. An explanatory diagram of the principle of measuring the swing angle and velocity of a bat in this invention device, Figure 5 is a diagram showing the relationship between bb7aa' and the swing angle θ. In the figure, (la) and (xb) are transducers, (2a
) and (2b) are ultrasonic pulse beams, (3) are rosettes), t41 is an oscillation circuit, (5a) and (5b) are transmitters, (6a) and (6b) are transfer devices, (7a)
and (7b) are value circuits, (8a) and (81)
) is a counter, (9I is an angle calculation circuit, (101 is an angle memory, (Ila) and 01b) is a maximum echo detection circuit. a is a timer, and α is a speed calculation circuit. In the two figures, the same or Equivalent parts are indicated with the same reference numerals. Fig. 3 Fig. 4

Claims (1)

[Claims] In a swing measuring device that measures the swing trajectory angle and swing speed of a baseball bat passing through a predetermined space, two sets of ultrasonic transducers are installed on the ground at a predetermined interval, and each transmitter transmits the It transmits a sharply directional ultrasonic pulse beam that intersects at an arbitrary height above the midpoint of the installation interval of the ultrasonic transducer, and also transmits the ultrasonic pulse reflected by the bat to the adjacent transducer. A swing measurement device characterized by receiving waves with a receiver having directivity in the same direction.