Advanced ultrasonic technology proved to be themost reliable and error-free system for use in anautomatic pin scoring application.

An Automatic UltrasonicBowling Scoring SystemDonald P. Massa, Massa Products Corporation

Over the past several years, thebowling industry has undergonemajor modernization. With the introduc­tion of computer-controlled automaticscoring, systems now automatically detectboth the number and locations of the pinsleft standing after each bowling ball isrolled. The following article describes onesuch system-an automatic ultrasonicscoring system that was developed and isbeing mass produced by Massa ProductsCorporation for use by the AMF BowlingCompanies, Inc. to locate the positions ofall standing pins, no matter where theyslide over the pindeck.

DEFINING THE PROBLEMPhoto 1 shows a typical pinspotting

machine located at the end of a bowlingalley. At the start of a game, ten pins arepositioned on the alley under the pinspot­ter in a triangular pattern. When a bowlerrolls a ball down the alley, some of the pinsare usually knocked down and others slideto different positions over the pindeck. Aneffective automatic scoring system mustquickly and accurately determine the ex­act number and position of the pins leftstanding, no matter where the pins mayhave slid over the pindeck.

WHY ULTRASONICS?Ultrasonics is sound of a frequency

above the range of human hearing, usu­ally considered to be greater than 20 kHz.The microphones and loudspeakers usedto receive and transmit ultrasonic soundare called transducers. Ultrasonic trans-

Photo I. An AMF Pinspotter is shown with the Massa

Ultrasonic Array mounted above and in front of the ten

standing pins.

ducers can be combined with special elec­tronic circuits to provide systems that areideally suited for noncontact sensing andhigh-precision mechanical position deter­mination in many industrial applications.Because of the relatively low velocity ofsound in air (343 ms at 20°C), ultrasonicsystems can easily be designed to very ac­curately measure the exact distance to areflecting object by simply transmitting asound pulse from the ultrasonic transducerand measuring the elapsed time for thereflected echo to return.

~ Range and Bearing. The ability to ob­tain accurate range and bearing of targetsmakes ultrasonics an ideal sensing technol­ogy for inexpensive automatic bowling pindetection over optical systems, which haveseveral drawbacks. Exact pin positions can-

not be determined with an inexpensive op­tical system because the range informationcannot be easily obtained. These systemsonly scan the pindeck and attempt tocount the number of light reflecting tar­gets that appear in the field of view. In thebowling industry, however, it's importantto know the positions of the standing pins;in addition to the number, so that thebowler can better determine where thesecond ball should be tolled to have the

best chance of obtaining a spare. An ultra­sonic system measures the time for thesound to travel from the transducer to the

target and back again, thus the position ofthe pins can easily be determined. How­ever, with an optical method, that useslight, which travels at approximately onemillion times the speed of sound, themeasurement of position of the bowlingpin would require the measurement ofecho time intervals with an accuracy bet­ter than one millionth of a millisecond,

which is impractical.Optical systems have two other draw­

backs when compared to ultrasonic pinsensors. First, if the standing pins slide sothat one pin is directly behind another, theoptical sensor will only "see" and countone pin. Ultrasonic sensors, however, arepositioned to look down over the tops ofthe pins, so they will all be accuratelycounted.

Secondly, an optical system will fail ifthe pins are dirty or if any backgroundwalls or surfaces are good light reflectors.Consequently, the entire background areamust be painted flat black and the bowl-

SENSORS October 1987

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Figure 2. The side view of the back of a bowling aile)' shows the four rows of pins and the location of the uTTa)'.

0Q0a>

0

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a

0Q;

...Q):::: 0--:J t

'50 016.5"

~-~ Massa

UltrasonicArray,"

Figure 1. This plan view of the back of a bowling alley

shows the spots for the ten pins and the location of the

Massa Ultrasonic Array in front of the pin triangle.

ing pins must be washed on a regular basisto ensure high reflection of light from theirsurfaces. With the ultrasonic system, thepins will reflect the sound no matter howdirty or "banged up" they are.

SYSTEM DESCRIPTIONEach ultrasonic system is designed to in­

dependently control two bowling lanes andconsists of two ultrasonic arrays connectedto a common ZSO-basedelectronic control

board. An ultrasonic array is mountedunder each pinspotter machine above andin front of the pins. Each array is located16.5 in. in front of the number one pin,as shown in Figure I, and 22 in. above thepindeck, as shown in Figure 2.

Each array contains 14 ultrasonic trans­ducers precisely positioned so that the en­tire pindeck is insonified by 14 accurate

ultrasonic beams. The array bar is a rigidaluminum extrusion with 14precision cav­ities machined into the front edge to holdthe transducers. The axis of each cavityis machined at a different angle in boththe horizontal and vertical planes so thatthe entire pindeck will be insonified by the14 separate sound pulses (see Photo 2).

A circuit board containing both the am­plifier and detection circuits is also located

in the array bar. This allows the signals tobe processed inside a completely shieldedenclosure. All of the signals going in andout of the grounded array housing are dig­ital, eliminating any possibility of pickingup the transient electromagnetic noisethat can occur on low-level analog signalleads.

SENSORS October 1987

~ Ultrasonic Transducers. The heart of

the pin sensing system is the ultrasonictransducers that operate at 150 kHz. Theoptimum frequency of operation was cho­sen after considering several design cri­teria. As the frequency of sound increases,the sound absorption increases as thesound wave travels along the air path fromthe transducer to the pin and back again.The attenuation at 150 kHz is 2 dBIft.

Since the maximum round-trip distancebetween a transducer and the farthest pinis S ft, the maximum total attenuation at150 kHz is 16 dB, which is acceptable fordetecting the echo. However, any spuriousultrasonic sounds generated more than Sft away would be very greatly attenuatedbefore reaching the array, and thereforewould not be detected as false echoes.

The wavelength of sound is also a func­tion of frequency. The higher the fre­quency, the shorter the wavelength. Inorder for a target to produce a good echoin an ultrasonic ranging system, the reflect­ing surface must be several wavelengthsin dimension. At 150 kHz, the wavelengthof sound is approximately %2 in., which issufficiently small compared to the size ofa bowling pin to ensure a good echoreflection.

The choice of frequency of operationis also critical in ensuring a reasonable sizefor the transducer. The system design re­quires that the transducers produce nar­row beams of sound that contain the trans­

mitted sound within a 12-degree conicalangle. To produce such narrow radiationbeam patterns, the radiating surface of thetransducer must be large compared to thewavelength of sound being transmitted.The larger the ratio of diameter of theradiating surface of the transducer to the

wavelength, the narrower the beam angle.To produce a 12-degree beam angle, theradiating surface of the transducer must

~ iMassaUltrasonicArray

22"

j

be six wavelengths in diameter. The 150kHz transducers designed for the systemare slightly over 1/2 in. in diameter. If thefrequency was much lower, the trans­ducers would become too large to fit intothe space allotted.

A more critical aspect of the beam pat­tern concerned the side lobes that are

generated in the transducers. A conven­

tional narrow-beam transducer producesadditional radiation lobes outside the main

beam as shown in Figure 3. Although theside lobes are reduced in amplitude, a pinlocated along an axis of the secondary lobeof a conventional transducer could still

produce a large enough echo to be de­tected. This would be interpreted by thesensing system as a pin standing along theaxis of the primary beam, which would,therefore, incorrectly register an extra pin,..causmg a sconng error.

To eliminate the side lobe problem,Massa developed the Model TR-2404 ul­trasonic transducer, which produces a nar­row 12-degree beam of sound. Its construc­tion, however, eliminates all side lobes, sothat only the primary beam of sound isproduced (see Figure 4).

The resonant frequency of the trans­ducers must be very accurately controlledduring the manufacturing process to en­sure optimum system operation. Withineach array, the resonant frequencies of all14 transducers are held within a tolerance

of ± 0.3 percent. The ruggedly con­structed transducer is also shockproof, soit can survive high-impact hits by flyingpins without damage, and will not pick upbowling machine vibrations. The trans­ducer is completely sealed so that it isunaffected by the dusty environment.

METHOD OF OPERATIONThe ultrasonic scoring system is com­

pletely automatic, and even self-calibrates

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Photo 2. The Ultrasonic Array consists of 14 precision 150 kHz narrow·beam transducers mounted in an aluminum channel. The circuit board is shown mounted in the channel.

to compensate: for any variations causedby changes in the velocity of sound at dif·ferent temperatures. At the start of agame, the pinspotter sets up ten pins ina triangular pattern. To calibrate thevelocity of sound, the control electronicsnext cause one of the transducers that in­

sonifies the pindeck area in the vicinity ofthe number five and nine pins to initiatean ultrasonic pulse. A 130 V, peak-to-peak150 kHz tone burst is applied to the trans­ducer, which in turn sends out a soundpulse that travels through space. A portionof this sound reflects from the number five

pin; another portion reflects from thenumber nine pin. These two acousticechoes return to the transducer and are

converted into an electrical signal that isamplified by the electronics in the array.If the echo signal exceeds the system de­tection threshold, a 5 V digital signal isgenerated. This digital signal is then trans­mitted by the interconnection cable to thecontrol electronics.

Figure 5 is an oscillogram of the signals

produced by the reflected echoes frompins five and nine when they arrive at theappropriate receiving channels. The toptrace shows the amplified received analogacoustic signal. The large pulse at the leftof the trace is caused by the 130 V, peak­to-peak transmit tone burst. The first echosignal, which arrives at approximately 51/2

ms, is caused by the reflection from thenumber five pin, and the second echo,which arrives at approximately 71/4 ms, iscaused by the reflection from the numbernine pin, which is farther away. The bot­tom trace on Figure 5 is the output of thedetection circuit. A 5 V signal appears dur­ing the time that the two large echoesfrom pins five and nine remain above thethreshold.

The control electronics measure the

time period from the start of the acousticpulse to the return of the reflected echo.Since the speed of sound is a function oftemperature, the system must be cali­brated for the temperature of the bowlinglane. Because the computer knows that

the number five pin is on its spot at thistime, it also knows the exact distance from

the transducer to the pin. The computerthen automatically adjusts the processingalgorithms to compensate for any variationin the speed of sound as required to main­tain the correct pin measurement over thepindeck during bowling.

~ Operation. The system automaticallycalibrates for speed of sound variationseach time ten pins are placed by the pin­spotter. When the bowler rolls the firstball, it knocks down several pins and thenhits a switch at the back of the lane. This

switch sends a signal to the control elec­tronics board indicating a ball has just beenbowled. The computer waits 1.7 s to allowfor late falling pins, and then sequentiallypulses each of the 14 transducer channelsin the array. Each channel sends a digitalsignal to the control electronics wheneverany echoes are received. Since the com­puter knows in which direction each of thenarrow-beam transducers is pointing, it is

Figurc 3. Secondary lobes are shown on either side of the primary beam in this radia­

tion pattern from a standard narrow-beam tr'l1!sducer.

Figurc -I. The special design of the ,\lode! TR-2-10-l ultrasonic tralISducer eliminates

,Ill secondary lobes_

SENSORS October 1987

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Figure 5. This output signal of one of the 14 ultrasonic channels shows the return echoes from pins five and

nine. The top signal is the ilnalog output and the bottom signal is the digital output. The hori~ontal scale is 1

ms per division.

able to calculate the exact range and bear­ing of the reflected echoes and, therefore,the exact location of each standing pin.

It takes OJ s to accumulate the datafrom the 14 channels and determine

which pins are standing. For increasedreliability, all areas of the pindeck are in­sonified by at least two transducers in thearray. In addition, all the transducers aresequentially pulsed a second time. A pin

must be detected during both detection se­quences in order to be called standing.

The control electronics then send the

standing pin information to the graphicscomputer, which displays on a screen inproper scoring format the number of pinsknocked down. In addition, the positionsof the standing pins are displayed, togetherwith an indication of where the second ball

should be rolled in order to obtain a spare.

Meanwhile, the pinspotter is sweeping thedeadwood from the pindeck and replacingthe standing pins. The bowler then rollsthe next ball, and the exact sequence isrepeated, except that all pins are sweptand ten new pins are placed on the pin­deck. In this manner, the score is automat­icallyupdated and continuously displayedto the bowler.

An additional benefit occurs when astrike is bowled. The control electronics

recognize the strike and instantly signalthe pinspotter to sweep the pindeck anddrop ten new pins, rather than waste time

by first going through its normal cycle oftrying to pick up any pins that might beleft standing.

CONCLUSIONSl'vlassa has been manufacturing large

quantities of ultrasonic scoring systems forseveral years and successful installationshave been made in over 24,000 bowlinglanes. The system speeds up bowlinggames by as much as 25 percent. The Ac­cuSonic Automatic Scoring System paysfor itself in a relatively short period of timebecause of the additional number of gamesthat can be played during a given periodof time.

Donald P. Massa is President. !ldassa Products Cor·

poration, 280 Lincoln St., Hingham, \1:\ 02043.

Reprinted from Sensors, October 1987Copyright© 1987 by Helmers Publishing, Inc.174 Concord St., Peterborough NH 03458

All Rights Reserved

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