Technical Field

The invention generally relates to systems to detect the impact of an object with a surface and to determine the location of a specific part of the object relative to a defined spatial position on the surface when the impact occurs. In particular, it can relate to a system for detecting the spatial and temporal relationship of a specific part of a person’s foot relative to a defined location on the ground.

The invention is, for instance, applicable to the detection of no halls when bowling in the game of cricket, to the detection of the impact of a ball with a person relative to a goal line and to the detection of foot faults when serving in the game of tennis.

More particularly the invention relates to no bail detection with equipment detecting the position of the bowler’s leading (front) foot in relation to the popping crease during the delivery stride. Other judgements relating to the position of part of something relative to a surface are also included.

Background Art

A cricket pitch has a white line known as the“crease” or“popping crease” 1.2m forwards of the line of the stumps. The crease is actually the rearward edge of the white line.

In accordance with Law 21.5.2 of cricket, a bowler’s front foot, in his delivery, must land with some part, whether grounded or raised, behind the popping crease. An umpire must w'atch the bowler’s foot to see where it lands. However, it is often difficult to see clearly if the foot has landed legally due to the speed of delivery. This difficulty is furthered by the umpire having to quickly direct attention to the other end of the pitch as soon as the bowler releases the ball.

There are currently multiple solutions to certain aspects of the problem.

For televised matches the umpire (either on-field or TV umpire) can request a video review on a wicket ball to see if the bowler’s delivery _' was legal. However, the issue with this approach is that this option is only available to umpires for wicket balls rather than for all balls bowled, it disturbs the flow of the game and creates delays and still requires the on-fteld umpire to attempt to determine if the delivery is legal as he will not know whether the review option would be available on that particular ball until after the ball is bowled.

The advantage of this replay system is that the foot can be watched from side on and, depending on the footage quality, can be very accurate in determining a no-ball.

However, some illegal deliveries would remain difficult to call accurately (including close calls and when the back of the foot is in the air)

A number of automatic detectors have already been developed that function through the use of optical lasers and receivers. For instance, one of the detectors functions with a set of lasers/receivers on either side of the popping crease, if the set on the batman’s side of the crease is triggered without the set on the umpire’s side of the crease being triggered, an alarm sounds to indicate a no-ball. The problems with this are: back of foot may still be in the air behind the crease when the toes touch the ground on the other side, foot may pass below the level of the receivers (in the footmarks) and trigger the receivers before the foot has actually landed, will not detect a foot that lands so far past the crease that it is past the receivers.

The other automatic detector which is currently available for use in training sessions uses a single set of lasers/receivers and is placed a foot length past the crease on the batman’s side. This will sound an alarm once an object cutting the beam triggers it. The problem with this is not everyone has the same size foot, the foot doesn’t always land perpendicular to the crease, and someone could bowl from well behind the crease then trigger the receiver in his or her follow-through.

Other proposed systems relate to detection of the foot by radio signal measurement from the bowlers shoe to sensors in known relation to the popping crease (Automated Decisions in Aware Cricket Ground; A Proposal by P. Ashok Kumar, Member, IACSIT - International Journal of Information and Education Technology, Vol. 2, No. 3, June 2012), detection of a foot using on-ground sensors (US application 2018 0326284) which is one example of using a contact mat.

Therefore a need exists for a solution to the problem of detecting when and where the bowler’s foot is in relation to the crease. Therefore a need exists for a solution to the problem of detecting when and where the server’s foot is in relation to the baseline.

In the game of Australian Football there may sometimes be difficulty in determining whether a player touched a ball passing the goal or behind posts before or after it passed the posts. There is currently no quick way of determining this and the current rules rely on an umpires perception.

The present invention provides a solution to these and other problems which offers advantages over the prior art or which will at least provide the public with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowl edge in the art, in Australia, New Zealand or in any other country.

Summary of the Invention

In its broadest form, the invention consists in an impact detector detecting the impact of an object with a surface area and determining the position of a specific part of the object relative to a defined spatial position on the surface area when the impact is detected including:

an acceleration detector mounted in or on the object to detect the moment of impact of the object with the surface area,

at least one ultrasonic transmiter on the object in a known location and emitting an ultrasonic signal upon the detection of an impact by the acceleration detector;

multiple detectors external to the object and acting to detect the ultrasonic signal and its time of occurrence and to transmit that time to a comparator; the comparator acting to compare output fro the detectors to determine where the specific part of the object was located relative to the defined spatial position at the time of impact,

an indicator to indicate the location of the specific part of the object as derived from the comparator at the time of detection of an impact.

Preferably the acceleration detector is attached to the heel of a shoe in co-location with two ultrasonic transmitters.

Preferably at least some of the multiple detectors detecting the ultrasonic signal are located around the defined spatial position and are substantially flush with the surface area.

Preferably the comparator receives transmitted information from all the multiple detectors and transmits information to the indicator.

Preferably the object is a bowlers shoe, the multiple detectors are in the area of a bowling crease and the indicator is a display available to a cricket umpire indicating whether a bowled ball is a "no ball".

Preferably the at least one ultrasonic transmitter is attached to the persons foot, and the calculation from the detection of the ultrasonic sound allows the calculation of the inclination of the persons foot at impact relative to the ground.

In a further embodiment the invention relates to a method of detecting the placement of an object impacting a surface by:

providing an acceleration detector and at least one ultrasonic sound pulse emitter on the object,

emitting an ultrasonic pulse from the at least one ultrasonic sound pulse emitter when an impact of the object with the surface is detected,

providing at least three ultrasonic sound detectors and receiving the emitted ultrasonic pulse in at least three of the ultrasonic sound detectors,

deri ving the time of receipt of the ultrasonic pulse at the at least three ultrasoni c sound detectors, calculating the placement of the at least one ultrasonic pulse transmitter relative the surface at the time of impact.

In a third embodiment the invention relates to a system for detecting the spatial and temporal relationship of the impact of the a person’s shoe relative to a defined location on the ground including:

an impact detector detecting the contact of the person’s shoe with the ground in the area of the defined location,

at least one ultrasonic sound transmitter attached to the person's shoe,

a plurality of ultrasonic sound receivers positioned around the defined location, the impact detector causing the at least one ultrasonic sound transmitter to emit an ultrasonic sound pulse, the sound pulse being receivable by at least some of the plurality of ultrasonic sound receivers,

the ultrasonic sound receivers receiving the sound pulse and providing the time of receipt of the pulse to a calculator,

the calculator receiving the time of the detection of the ultrasonic sound at the at least some of the plurality of ultrasonic sound receivers and calculating where a portion of the person's shoe was when the person's shoe impacted the ground within the area of the defined location,

an indicator indicating whether or not the calculation from the calculator indicates that the portion of a persons foot was within or without a specified part of the area of the defined location.

In a more particular embodiment the invention relates to a no ball indicator for use in the game of cricket in a cricket field including a popping crease and including:

a foot mounted impact detector detecti ng the contact of the bowlers leadi ng foot with the ground in the area of the popping crease,

at least one ultrasonic transmitter attached to the heel of the shoe of the bowlers l eading foot, the impact detector on detection of an impact causing the ultrasonic transmitter to transmit at least one pulse of ultrasonic sound,

a plurality of ultrasonic sound receivers placed in the area of the popping crease, at least some of the plurality of the ultrasonic sound receivers receiving the at least one pulse of ultrasonic sound,

a calculator receiving from the at least some of the plurality of ultrasonic sound receivers an indicator of the time of receipt of the at least one pulse of ultrasonic sound, the calculator resolving the location of the heel of the bowlers shoe relative to the popping crease and determining whether the location of the bowlers shoe at the time of impact was beyond the popping crease.

These and other features of as well as advantages which characterise the present invention will be apparent upon reading of the following detailed description and review of the associated drawings of the exemplification the invention consisting in a no ball indicator for use in the game of cri cket.

The features required to apply the invention to the exemplification of a foot fault indicator for use in the game of tennis will become apparent to a person skilled in the art by extrapolation from the said detailed description of the exemplification the no ball indicator for use in the game of cricket.

Brief Description of the Drawings

FIGs. 1 are general perspective views of a bowier’s leading foot at the time of bowling a bail.

FIG. 2 is a diagram of the bowling end of a cricket pitch with ultrasonic detectors.

FIG. 3 is a perspective view' of an ultrasonic sound detector suitable for detecting the distance to an ultrasonic source..

FIG. 4 is a perspective view of a ultrasonic transmitter suitable for mounting on a bowler’s shoe

FIG 5 is a flow diagram of the detection of a no bail for an ultrasonic system

FIG. 6 is a view showing the footfall of a bowler on the crease

FIG. 7 is a flow diagram of the detection of whether a ball is impacted before or after a line event

FIG. 8 is a perspective view of a beam detector suitable for mounting on a bowler’s shoe. FIG 9 is diagram of the bowling end of a cricket pi tch with light detectors.

FIG 10 is a flow diagram of the detection of a no ball for a light detection

FIG. 11 is a perspective view of a beam emitter suitable for creating a beam of light over the popping crease.

FIG. 12 is a diagram of the modular construction of the equipment of the invention

Description of the invention

Referring now to FIGs. I A to IE where the drawings show the white line 101 of the popping crease and a bowler’s foot 102 as the ball is bowled. In FIG. 1A the entire bowler’s foot 102 is behind the popping crease at the rear edge of the white line 101. This is therefore not a no ball.

FIG. IB show's the bowler’s foot on the white line with the heel extending behind the popping crease. Again this is not a no ball.

FIG. 1C shows the bowler’s foot 102 mostly in front of the white line 101 with the heel raised above it but still extending past the rear edge of the while line. This is still not a no ball because the heel of the shoe is above the popping crease at the rear of the white line.

FIG. ID shows the bowler’s foot 102 impacting on the forward part of the white line 101. This is ahead of the popping crease, so this is a no bail.

FIG IE shows the bowler’s foot 102 in front of the white line 101. This is a no ball.

FIG.2 show's details of a cricket pitch 201 at the bowler’s end where stumps 202 have bails 203 and are located on the bowler’s crease 204. A bowling crease is indicated by a white line 204, a popping crease by white line 205, and return creases 206 on either side of the stumps. An additional line 207 indicates the centreline between the two sets of stumps.

A bowler, in the final delivery' stride, must not put the back foot on or over the return crease, must not place a foot beyond the centreline 207 and must have at least part of the delivery foot behind the popping crease (the law' states part of the foot must be behind the popping crease, therefore it can be completely behind the popping crease in a legal delivery'). To allow judgement of this there are provided multiple ultrasonic detectors 208, 209, 210 on one side of the popping crease 205 and both before and after it outside the return creases 206 A second set 21 1, 212, 213 are located on the other side of the pitch beside the popping crease 205 and both before and after it and outside the return crease 206. Another may be located at 214 behind the wicket. These ultrasonic detectors are preferably located in the ground with the top surface flush or slightly proud of ground level. The top of the ultrasonic detectors may be flexible and rounded both to reduce damage and to remove any tripping hazard. Optionally the ultrasonic detectors may be remotely controlled to telescope upwards for the bowlers run to improve detection of the ultrasound.

FIG.3 shows at 300 in general an ultrasonic sound detector having a lower portion 301 and an upper portion 302 hole 303 behind which an ultrasonic detector may be positioned. Portion 301 may include battery and a solenoid to raise portion 302 for the bowling run. A radio transmitter in each sound detector 300 may issue a measurement of the detected time of occurrence of the ultrasonic pulses to a remote receiver which may calculate the distance of the foot from the sound detectors 300 and thence the position of the heel of the foot at the impact closest to the popping crease 205.

A remote receiver may receive any indications from all of the detectors at the bowling end and resolve them to provide the position of the bowlers heel at foot impact.

Each ultrasonic sensor may also contain a radio receiver for controlling the extension and retraction of the top portion 302 of the sensor for a bowling run.

Located on the bowlers heel or elsewhere on the foot is an impact triggered ultrasonic transmitter.

FIG. 4 shows a curved casing 401 suitable for attachment to the heel of the foot with a pair of ultrasonic transmitters 402, 403 pointing in opposite directions. Also in casing 401 is a battery _' and an accelerometer with an output triggered by the deceleration of the bowlers foot at the impact of the bowlers foot with the ground. This acts as an impact detector to activate the ultrasonic transmitters and create a short ultrasonic pulse. The ultrasonic transmitter frequency may be in the 40kHz to 50kHz range.

This ultrasonic pulse will be picked up by at least some of the ultrasonic detectors 208 to 213. The onset of these signals will be timed and notified to a monitoring system. The monitoring system may take the variables into account (the current temperature as the major variant which will affect the speed of sound, the transmitter velocity relative to each sensor at the time of signal transmission) and can be used to calculate the position of the transmitter when the impact of the bowlers foot with the ground

5 occurred. Because the bowlers heel may be in the air at the time of impact the

calculations must take this into account by calculating the three dimensional position of the ultrasonic transmitter or transmitters and translating this to a position on the ground.

To measure the location of the transmitter on the foot in three dimensions without lu ambiguity it must be detected by four sensors. In normal circumstances three sensors is enough since the ambiguity produced by the lack of one sensor resolves to two positions, one of which is under the ground and can be discarded. The received sensor signals may include reflections of the ultrasonic sound emitted by the transmitters, for instance from the stumps, the bowlers rear foot or the umpire, which would be

15 discarded in processing.

Typically the bowlers front foot will contact the ground near the popping crease with the heel, but the toe may also be the first part of the foot to touch the ground before ball release. The toe to heel measurement of the bowlers foot may then also be required to be estimated to get the precise location of the bowlers foot at the time of impact since there is a propagation time from toe to heel.

The speed of sound in air at 20°C is 343 m/sec, falling with a temperature decrease. It may be calculated as Cair = (331.3 + (0.606 x 0))m/sec where Q is the temperature in degrees °C. Typically the speed at 10 degrees is 337.3 Im/s and at 30 degrees

349.02m/s giving approximately a 2% change in the speed of sound for a 20 degree change in temperature. In addition to this where the toe of the bowlers foot touches the ground before the remainder of the foot the shock must propagate through the foot to the heel to trigger the ultrasonic transmitter. The conduction is mainly through bone and flesh and will be at a speed between 300m/s and 6Q0m/s. Where the distance calculations between transmitter and acoustic sensors show that the heel is in the air

30 the distance of the foot from the sensors may need to be corrected for the delay

between the foot hitting the ground and the impact shock reaching the transmitter accelerometer in addition to the correction for the angled position from the portion of the foot which is impacting the ground.

The sensors may also detect the speed at which the bowlers foot was moving when the ultrasonic pulse occurs because there will be a Doppler effect change of frequency detected at the sensors from the frequency with the foot at a rest state. A measurement of this could be resolved in both the vertical and horizontal planes. This may assist in detecting the rotational movement of the grounded foot.

The calculations for determining the position of a radiating object in three dimensions using multiple sensors are well known. In this case there may be a need to add an additional acoustic delay factor in the equations if the radiating object (the heel of the bowlers foot) is determined to be above the ground by more than the mounted height of the ultrasonic transmitters. This delay is effectively a measurement of the distance from the heel to the toe at the angle which is shown by the transmitter position. This allows the position of the toe to be calculated if a foot orientation is assumed and can act as a confirmation of the accuracy of any calibration

FIG. 5 shows a flowchart for the detection of a no ball with at 501 the ball being placed in play. At 502 the delivery is selected as either around or over the wicket so that the correct side of the wicket is determined. The system then awaits the detection of an ultrasonic signal at 503 and when one is detected the location from wiiich it w ^? as sent is calculated at 504.

The attitude of the foot at the time of impact is also determined at 505 and from this the location of the heel of the foot when the foot impacted the ground is calculated. If that location is not beyond the bowling crease a comparison at 506 returns the system to detecting the next ultrasonic signal. Where the foot impact was past the rear edge of the bowling crease it is determined at 507 whether the heel of the impacting foot was behind the edge of the popping crease or ahead of it. If the heel is resolved as being ahead of the edge of the crease at the time of impact by a comparator then the ball is signalled at 508 as a no ball

At 509 it is calculated by a comparator whether the impact of the foot was beyond the midline of the crease. If so then the ball is again signalled at 508 as a no ball. Otherwise the ball is signalled at 510 as fair and for both the no ball and the fair ball the play ends at 511.

FIG. 6 shows the footfall of a bowlers leading foot at the crease and shows how the angle may vary from a left splayed foot at 601, through a normal delivery at 602 to a right splayed foot at 603. The mounting of the transmitting device 401 may be varied so that it is normally at the rearmost position on a particular bowlers foot.

FIG 7 shows the flow diagram to be used for the detection of line events such as the detection of a hand to the bail before or after it crosses the goal line in Australian Rules.

At 701 a ball with an accelerometer embedded to monitor the impacts on the bail is put in play. At 702 the line detector is set, preferably this is a light curtain above a football goal line. The flag for the detector is then set to 1 at 703 and a loop entered to detect an appropriate line break. In the loop any impact of the ball is detected at 704, if none is present the flag stays at 1 while if an impact is detected the flag is set to 0 at 705.

At 706 the line break reading is checked to see if any line break event has occurred. If it has the flag setting is checked at 707. If the setting is 1 then no impact has been detected before the line was broken and the result is satisfactory at 708 If, however, the flag is zero then the impact has happened before the line was broken, and this is indicated as an error at 709.

In a. cricket system the umpire has a controller display for the system (not shown) having, as a minimum: a switch to activate the system, a button to announce the ball as being in play, a selector for the bowler’s side of the wicket and an indicator for a fair ball or a no ball. The controller may also include the ability to choose which bowler is active. Preferably the no ball indicator has some audio accompaniment indicating a no ball.

Where the system is being used for training the umpires display may be replaced by a more overt system including lights and an audible sound, and optionally a display of where the bowler’s feet were placed.

The display controller communicates with the ultrasonic sensors, the radio

communications in the heel of the shoes of various bowlers, and any device initiating the detection of the bowler during runup to the crease. In a fully provisioned system the umpire may also have a display showing the bowler’s foot impact points within range of the sensors, the number of halls and no balls bowled in an over, and the state of the system as regards the various battery levels. The umpire device may also include a manual override to adjust the ball count.

5 FIG.8 shows at 800 an electronics block to be attached to the heel of a bowler’s shoe.

It consists of a cuneiform slim container having projecting sideways optical sensors 802. These sensors connect to amplifiers on a curved or flexible circuit board inside the container 801 with the sensing of the detecti on of a light beam by one of the optical sensors being transmitted by an inbuilt radio transmitter such as a Bluetooth device to lu an umpire visible display device. The container may also include a rechargeable

battery and may include ultrasonic pulse transmitters and an impact detecting accelerometer or momentary switch to trigger the transmission of ultrasonic pulses.

FIG.9 shows details of a cricket pitch 901 at the bowler’s end where stumps 902 have bails 903 and are located on the bowler’s crease. A bowling crease is indicated by a

15 white line 904, a popping crease by white line 905, and return creases 906 on either side of the stumps. An additional line 907 indicates the centreline between the two sets of stumps.

A bowler, in the final delivery stride, must not put the back foot on or over the return crease, must not place a foot beyond the centreline 907 and must have at least part of the delivery foot behind the popping crease (the law states part of the foot must be behind the crease, therefore it can be completely behind the crease in a legal delivery).

To allow judgement of this there may be provided beam emitters 908 and 909 on either side of the popping crease and outside the return creases. These emitters are located in the ground with the top surface flush with the ground level but one or both are

5 intended to pop up during a bowler’s delivery run and emit a fan of light along the popping crease. The frequency or modulation of the light beam is chosen to allow as little interference from sunlight as possible.

This light may be detected by a light detector secured to the heel of the shoe of the bowler’s leading foot. This light detector may additionally have an acceleration sensor

30 to aid in determining when the bowler’s foot impacts the ground and a radio transmitter to forward these indications to the umpire either directly or via a receiver in the beam emitters.

Optionally the rearmost heel of the bowler’s leading foot may have retro-reflectors attached to it, and the beam emitter may have detectors for any light reflected from the retro-reflectors.

FIG. 10 shows the flow' of sequence of operations with the no ball detector. At 1001 the umpire sets the ball as being in play, and at 1002 selects for either an around the wicket bowler approach or an over wicket approach.

The syste is then set up to expect the bowler’s back foot or leading foot in an area on the appropriate side of the wicket and to allo this to be detected at 1003, either by detection of a radio transmission from the leading foot shoe heel fitment or by the detection of foot impacts by any in-ground sensors in the stumps or by beam emitters being detected by the optical sensors on the shoe heel.

Once an approaching foot impact or shoe passing is detected the beam emitter is raised at 1004 and a flag indicating detection of the leading foot near the popping crease is set to zero at 1005.

The system now monitors continuously at 1006 for a detection of the heel of the leading foot on or over the popping crease and at 1009 for the impact of the bowler’s leading foot.

If the shoe heel has not yet passed the crease then at 1007 the flag is set to 1 (although it will normally still be set to 1). Should the leading shoe have been detected as past the popping crease (that is, the heel detector has detected and passed through the popping crease beam from the beam emitter and has detected the secondary beam adjacent the popping crease beam without a later second detection of the popping crease beam) then the flag is set to zero at 1008. If at 1009 a leading foot impact is detected the flag is checked at 1010 and if at zero the bail is indicated as a no bail at 101 1

If the flag is at zero 1010 then the leading shoe has either never passed the popping crease or has returned behind it before the foot impacted the ground. This is flagged as a fair ball at 1012 and at 1013 the beam emitter is dropped, awaiting next use. FIG I 1 shows at I 100 in general the telescoping optical beam emitter having a lower portion I I0l and an upper portion 1102 with a slot 1103 from which a fan beam may be emitted. Portion I I0l may include battery and a solenoid to raise portion 1102 for the bowling run. The raising turns on the beam emiter which is preferably a laser

5 beam, diffracted from a mirror and through a beam diffractor in slot 1103 which forms a fan array. An LED 1 104 in the top of portion 1104 may indicate such things as correct reception of a beam from the counterpart emitter at the opposing end of the popping crease or battery state

FIG. 12 shows an accelerometer 1201 as mounted to a shoe in combination with lu ultrasonic transmitters such as 1202. The ultrasound pulse created by the transmitter or transmitters is broadcast to in-ground receivers such as 1204, 1205, 1206, 1207 which transmit the time of receipt of an ultrasonic pulse to comparator 1208. The comparator 1208 compares the relative time of receipt of the pulse with the known positions of the in ground receivers 1204 - 1207 and the popping crease and resolves

15 the position of the shoe heel relative to the popping crease as a "ball" or a "no ball" which decision is sent to the display 1209. This display may be held by an umpire and may additionally show a count of at least balls and no balls and preferably overs, wides etc. from an external scoring system.

Where a light beam system is used the light beam may be infra-red or any other light frequency which will not disturb the bowler and may be modulated to allow

identification of a particular light beam.

The light beam emitter or in-ground ultrasonic transmitter may contain a radio receiver and transmitter for indicating to an umpire held display the state of the

transmitter/beam emitter, and for controlling the retraction of the top portion 1 102 when the rear of the bowler’s foot has been detected. The extension and retraction of top portion 1102 may be by a screw ⁷ action solenoid or by direct extension and retraction.

The beam emitter may equally contain a receiver of the ultrasonic pulses emitted by a transmitter or transmitters in the bowlers shoe and the radio transmitter may indicate

30 the timing of the pulses to the detection and display system used by the umpires. The various radio devices required to link the parts of the system together may form a small radio network and may make use of Bluetooth 4.0 capability, since the total range required must be small and the security of the system must be good.

Typically if the game is Australian Football the ball impact is with an item which is the player or the players hand.

It is to be understood that even though numerous characteristics and advantages of the various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functioning of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail so long as the functioning of the invention is not adversely affected.

For example the particular elements of the no ball detector may vary dependent on the particular application for which it is used without variation in the spirit and scope of the present invention.

In addition, although the preferred embodiments described herein are directed to the detection of no balls for use in a cricket game, it will be appreciated by those skilled in the art that variations and modification s are possible within the scope of the appended claims