Golf swing sensing device

Abstract

First and second pairs of receivers are utilized to detect and process signals from a club head mounted transmitter. The first pair of receivers are located equidistant from an inclined plane corresponding to the proper swing plane for the golfer. A phase comparator produces a voltage output whenever the transmitter deviates from the desired swing plane. The comparator voltage output may be utilized to drive visual and an aural indicator, also a recorder, producing a tone which is indicative of the magnitude and direction of deviation of the club head from the swing plane. The second set of receivers is located along a line corresponding to the nominal horizontal flight path for the golf ball so that the golf club head has a maximum relative velocity to the two receivers at the point of ball impact. The difference in apparent frequencies detected at the two spaced antennas is converted into a voltage analog of velocity. A resetable maximum indicating meter may be utilized to indicate the club head velocity at impact.

Description

BACKGROUND OF THE INVENTION

For many years golf has been one of the most highly competitive of sports. The game is played by an extremely large number of individuals, with varying amounts of time to devote to the game. However, all serious golfers are constantly training themselves to play the game better and are concerned with all aspects of the game. However, no single aspect of the game is generally considered to be more important to a golfer's performance than the characteristics of his "swing." There are almost as many different methods of teaching the development of a proper swing as there are instructors. However there is general agreement that the ideal swing is conducted with the head of the golf club moving in an arc that lies in a single plane. That is the golf club is swung primarily with the arms and wrists and the combination of those actions produces a club head path that varies in the instantaneous radius of curvature, but which at all times, with minor variations, lies within a single plane. Such a perfect swing is less susceptible to the variations that produce inaccurate shots and unsatisfactory ball travel distances. Therefore, all of the aspects of a golfer's address to the ball, of back swing, and of follow-through, can be related to the ultimate objective of obtaining a smooth planar swing. This would include the objectives of holding the trunk and head of the body relatively stable, of a smooth acceleration from the back swing, and a smooth and complete follow-through.

Various golf swing testing devices have been developed in the prior art. Typically, such devices employ some type of a dummy ball which is mounted on a pivoted mounting and includes a plurality of sensors which are capable of detecting the club head velocity and angle at impact. Such devices cannot provide any information on the early stages of club head travel, and thus deal in results of improper swing procedure, rather than in identifying where the improper club head movement took place, or its magnitude. The use of the dummy golf ball necessitates an attachment that interferes with the normal feel of striking a golf ball and produces a deceptive distorted appearance. Further, the velocity measurements measured by such a device are not totally dependant upon the accuracy of calibration of the device and do not otherwise represent acutual velocities.

Other devices have been proposed that would constrain the golfer's head or constrain the path of the golf club so that the golfer would experience proper position during swing or a proper swing path. However, these devices do not provide any mechanism by which the unconstrained swing of the golfer may be critically analyzed instantaneously and in detail.

Another prior art teaching technique which has enjoyed relatively widespread acceptance is the use of a video tape recorder and associated playback equipment. By the use of such a technique a golfer may make his usual swing and then may see the swing played back at critical angles so that he may analyze deficiencies in his swing. Such techniques are not entirely accurate since television is basically two dimensional, and does not provide precise information on the deviation of the club head. Further, since the information is not provided until after the completion of the swing, there is no way for the golfer to test by the appropriate position of the golf club at various points in the swing or to obtain real time information on the "feel" of a proper swing.

Another technique in prior art devices has been to provide a specially designed and highly instrumented club including instrumented club head and shaft which includes information on the strain induced in the shaft by the acceleration of the shaft, club head, and like parameters from which, indirectly, certain information regarding the swing may be obtained. However, club mounted instrumentation in itself is not capable of producing an accurate record of the club head path.

Therefore, it is desirable to have a golf ball swing sensing device for sensing the swing path and striking velocity of the club head, especially where such a device enables the golfer to use his own equipment without substantial modification, and where the golfer obtains an instantaneous indication of the correctness of his swing as well as a permanent record of the entire swing for later analysis. Such a device is particularly desirable where it is relatively low in cost and easy to operate.

SUMMARY OF THE INVENTION

In an exemplary embodiment of the invention, a battery-powered transmitter is secured to the head of a conventional golf club. The transmitter can operate at extremely low power levels and therefore may be entirely solid state integrated circuit construction with no projecting antennas. The weight of such a device is not sufficient to throw off the normal feel of the golf club and thus the golfer is able to utilize his own equipment in training.

First and second pairs of antennas are mounted on a cradle. The cradle is mounted under a platform which receives the golfer and the golf ball tee. The first antennas are spaced by approximately 5 feet and lie along a line transverse to the nominal horizontal flight path. The nominal horizontal flight path refers to the direction of intended flight of a golf ball, assuming the golfer is able to complete a perfect swing, and refers to a horizontal path of the ball over level ground. The antennas are mounted for pivotal movement about an axis parallel to the nominal flight path so that a plane defined by points equidistant from the two antennas may be inclined from the vertical. In the environment of the invention, the plane is inclined toward the golfer and passes through the golf ball positioned on the ball tee. Thus, the plane may be adjusted to correspond with the swing plane for a particular golfer, depending upon his height, stance, club length and other considerations. A second pair of spaced antennas is mounted on another portion of the cradle and generally along the axis of rotation an said cradle such that tilting of the cradle does not substantially affect the position of the second pair of antennas. The antennas are therefore arranged as closely as is practical to the nominal horizontal flight path of the ball. The line connecting the second pair of antennas is parallel to a tangent to the arc of swing at the point of impact of the ball. Thus a vector representative of the velocity of the club head will be parallel to, and substantially directly in opposition to, the pair of antennas at the point that the club head strikes the ball. Since this corresponds to the maximum velocity portion of the swing, the sensing by the antennas of the doppler shaft at this point will correspond to the maximum actual velocity of the club head. The use of two antennas makes it possible to incorporate relatively simple circuitry since all non-relevant variations are balanced out and the differences in apparent frequency of the club head mounted transmitter is solely attributable to doppler effects. The difference in frequency is an analog of club head velocity. By converting this frequency into a voltage, a maximum indicating and resetable meter may be driven to indicate the absolute value of maximum velocity reached. The expected voltage generated by a particular club head velocity can be calculated according to the expected doppler shift in frequency together with known circuit parameters. Thus, it is possible to obtain an absolute value for club head velocity and it need not be derived by indirect means or initial calibration. Since the voltage output of the system is independent of the transmitter frequency, the system will accept variations in the transmitter frequency based upon temperature changes, impact, and aging without deteriorating in accuracy. In addition, the system for processing the signals detected by the antennas is not critical as to sensitivity, band width, or stability.

A number of different indicators may be utilized with the swing plane portion of the system, however an aural indicator utilized in conjunction with a chart recorder has special advantages. With an aural and visual indication the golfer may obtain instantaneous information about the correctness of the positioning of the club in the back swing, the practice swings, and in the positioning of the club in termination of the follow-through. The audio frequency selected for the position of the club head in the swing plane is approximately 500Hz. The human ear is able to detect very small variations from this frequency. By providing a reference point such as by insuring that the swing plane passes through the golf ball carried on the ball tee, it is possible for the golfer to attune his ears to the 500Hz note merely be positioning the golf club head directly behind the ball. The signal he then hears is the signal he should hear at all points throughout his swing, with variations depending on his instructor's directions such as a slight deviation at each end of the swing corresponding to the generation of a desirable hook. The record produced by a chart recorder will be a record of deviation from the swing plane versus time and therefore completely charts the progress of the golf club through the swing. The record enables the instructor to critique each swing by refering to the chart after the swing has taken place. Maximum swing velocity is displayed on a digital meter located to be easily readable by the golfer and instructor. The maximum velocity of the previous swing is displayed until the meter is reset.

It is therefore an object of the invention to provide a new and improved golf swing sensing device.

It is another object of the invention to provide a new and improved golf swing sensing device that provides an instantaneous indication of deviation from the desired swing plane.

It is another object of the invention to provide a new and improved golf swing sensing device that provides an immediate indication of maximum club head velocity.

It is another object of the invention to provide a new and improved golf swing sensing device that is relatively low in clost.

It is another object of the invention to provide a new and improved golf swing sensing device that enables the golfer to train using any standard club.

It is another object of the invention to provide a new and improved golf swing sensing device that produces a permanent record of the deviation from the desired swing plane throughout the entire swing.

It is another object of the invention to provide a new and improved golf swing sensing device that is easily adaptable to golfers of varying height and stance.

It is another object of the invention to provide a new and improved golf swing sensing device that is able to utilize relatively low cost electronic components with no sacrifice in accuracy.

Other objects and many attendant advantages of the invention will become more apparent upon a reading of the following detailed description, together with the drawings in which like reference numerals refer to like parts throughout and in which:

FIG. 1 is a perspective view of the apparatus as used. FIG. 2 is an end view illustrating the antenna and swing plane alignment.

FIG. 3 is an enlarged end view partially cut away.

FIG. 4 is a block diagram of the swing plane deviation sensing means.

FIG. 5 is a block diagram of the swing velocity sensing means.

Referring now to the drawings, FIG. 1 illustrates a typical installation of the invention. An elevated platform 10 incorporates a ball tee 12 and golfer support portion of the platform 14. The particular swing plane 16 for a illustrated golfer 18 is diagrammatically presented, as is the ideal swing path 20. When swung along the arc 20, the club 22, having a head 24, could be expected to drive ball 26 so that the horizontal projection of its flight path corresponds to the nominal horizontal flight path 30.

As is best illustrated in FIG. 2, the battery-operated transmitter 32 is taped in position on the after portion of the club head 24 so that it lies precisely on the swing plane 16 with the golf club in striking position. Two phantom position 34 illustrates a deviation of the club head below the swing plane 16 in an incorrectly positioned back swing. The phantom position 36 illustrates an improper follow through which results in the club head position deviating from the swing plane 16 on the upper side thereof.

As will more particularly appear by additional reference to FIG. 3, a first pair of receivers 38 and 40 are mounted on a cradle 42 that includes a cross arm 44. A first pair of receiving antennas 50 and 52 are carried on the respective receivers 38 and 40 and are equally spaced from a central pivot 54 on cross arm 44. The orientation of the cross arm 44 is such that a line connecting the antennas 50 and 52 passes directly below the ball tee 12. A vertical plane through the antennas is transverse to the nominal horizontal flight path 30. Further, a plane described by points equidistant from the antennas 50 and 52 will pass through the center of the ball and, by inclination of the cross arm 44 the plane can be made to correspond in angulation to the ideal swing plane for a selected golfer. The cross arm 44 is supported on arcuate tracks 60 having their center of radius at the center of ball 26, the tracks riding on rollers 62 on brackets 64 are fixed to the platform 14. By this mechanism the position of the golf ball 26 is made at all times to correspond to a point in the plane 16, thus if the golfer positions himself correctly with respect to the ball 26 the desired swing plane for the golfer will correspond with that swing plane described by points equidistant from antennas 50 and 52. The selected adjustment of the cross arm 44 is held by tightening a nut 66 on fixed bracket 65 against a clamp bar 68 pivotally attached to the cross arm. The front and top portions of platform 14 have a slot 69 for clearance of cross arm 44 and for access to nut 66. The cradle 42 also mounts a second cross arm 70 which is transverse to the cross arm 44, parallel to plane 16.

Cross arm 70 extends beyond the ends of the platform 10 and mounts a second pair of receivers 72 and 74 which have mounted at their upper ends a second pair of antennas 76 and 78. A line connecting the antennas 76 and 78 is parallel to and closely below the nominal horizontal flight path 30. Since the path of the club head, in a proper swing, substantially corresponds to the nominal flight path 30 at the point of impact with the ball 26 and since the maximum velocity of th club head is obtained in this vicinity, then each antenna 76 and 78 will "see" a vector component of velocity substantially equal to the absolute value of velocity. Since the antennas 76 and 78 are fixed for rotation about the axis of pivot 54 the antennas are maintained on the plane 16 despite the angle of inclination chosen.

Signals from the first and second pairs of antennas are processed such that an aural signal indicative of position relative to swing plane 16 is delivered to the loudspeaker 80, and a chart recorder 82 is driven to produce a record of the deviations from the swing plane throughout the duration of the swing. The maximum velocity of the club head is displayed at the digital readout 84 which is reactivated for a second swing by the reset button 86 as will appear more fully hereinafter.

Referring now to FIG. 4 the system block diagram for the swing path indicating means is illustrated. The antennas 50 and 52 feed RF amplifiers 100 and 102. The battery operated transmitter 30 is selected to operate at a frequency in the range of 1 to 5 GHz. The frequency is not critical as will appear more fully hereinafter. A local oscillator 104 is selected to operate at a frequency which differs from the nominal frequency of the transmitter 30 by a convenient IF frequency difference. The local oscillator 104 is common to both channels of the system and thus any variation in the local oscillator frequency will equally effect both sides of the system and will produce equal amplitude variations which will cancel out. Mixers 106 and 108 develop a difference frequency in the band pass of the IF amplifiers 110 and 112. The output of the IF amplifiers 110 and 112 has the same phase relationship as the sensed RF signals at antennas 76 and 78.

The phase of the signals from the IF amplifiers 110 and 112 are compared in a standard phase comparitor 114 which is selected to have an indicator output that varies from a negative voltage for lagging phase angles and a positive voltage for leading phase angles. Thus in a given system, club head positions below the swing plane will produce a negative voltage and a club head position above the swing plane will produce a positive voltage. The magnitude of this voltage is a measure of the deviation from the plane. In the preferred embodiment, such a voltage is utilized to drive a voltage variable audio oscillator 116 which produces a deviation from the nominal audio oscillator frequency of 500 Hz in the direction of a higher frequency with positive voltages, and in the direction of a lower frequency with negative voltages. The audio oscillator 116 drives a speaker 80 which speaker is mounted on the platform 10 as has been previously described.

The output of phase comparator 114 also drives a standard chart recorder 82. For purposes of the preferred embodiment, the chart recorder is wired to produce a deviation above a central position on the chart with positive voltages and a deviation below the central position on the chart with negative voltages. The chart drive speed is selected to produce an appropriate time base. Motion of the chart is commenced by depression of the reset button 86 and interrupted after a pre-determined time delay introduced by recyclable delay 120.

Referring to FIG. 5 the system block diagram for the swing velocity indicating means is illustrated. Signals from the transmitter 30 at the antennas 76 and 78 are amplified by RF amplifiers 122 and 124. The frequency of a local oscillator 126 is selected to be different from the nominal frequency of transmitter 30 by the frequency of the IF amplifiers 128 and 130. The difference frequency corresponding to the IF band is produced in the mixers 132 and 134, amplified by IF amplifiers 128 and 130, and mixed in mixer 136. The difference signal from mixer 136 corresponds with the sum of the doppler frequency shifts introduced by the velocity of the transmitter with respect to the antennas 76 and 78. Low pass filter 138 passes only this frequency, which is converted by frequency to voltage converter 140 into a voltage suitable for driving a maximum voltage display 142. In the preferred embodiment, maximum voltage display 142 is a digital display device with a readout head 84. The maximum voltage, and therefore the maximum velocity, is displayed by the readout 84 until the device is recycled by reset 86, which resets the maximum voltage display 84 and the recorder 82 at the same time.

OPERATION

In use, a golfer 18 positions himself on the platform 10 so as to properly address a golf ball 26 on ball tee 12. With the club head in the full line position illustrated in FIG. 2, the signal being delivered to the speaker 80 will correspond to the nominal frequency of the audio frequency oscillator 116. In the preferred embodiment this frequency is 500 Hz. Thus the golfer determines the pitch of the tone head on the speaker 80 and then moves the golf club to the proper position for the height of the back swing. If the same tone is not heard when in proper position on the back swing, then the tilt of the arm 44 is adjusted until the same pitch is heard. Once the golfer has determined that all positions in his swing produce a proper pitch in the tone from speaker 80 he is ready to take a practice stroke.

The reset button is depressed to reset the velocity indication and start the chart reader, and the swing is immediately commenced. Assuming during the actual practice stroke that the golfer's club head deviates from the proper plane 16, as at 34 and 36 in FIG. 2, then the golfer will hear a change in pitch from the speaker 80 during the swing which will vary from a pitch below the proper pitch at the initiation of the swing to a pitch above a proper pitch at the terminus of the swing. The precise deviation of the club head 24 at every point along the path 20 will be recorded on the chart recorder 82. Display 84 will present and hold a digital number corresponding to the maximum velocity in feet per second of the club head relative to the antennas 76 and 78.

Claims

Having described my invention I now claim:

1. A device for sensing the swinging path and striking velocity of the head of a golf club comprising:

a golf club,

a battery-powered radio frequency transmitter secured to the head of said golf club,

a golfer supporting platform having a ball tee positioned along the nominal horizontal flight path and a golfer supporting position spaced from said ball tee,

a first pair of antennas mounted in association with said platform substantially equidistant from said ball tee,

a vertical plane passing through said first antennas is substantially transverse to said nominal horizontal flight path,

a plane defined by all points equidistant from said first antennas is inclined from the vertical toward said golfer supporting position,

a second pair of spaced antennas positioned along a substantially horizontal line parallel to said nominal horizontal flight path,

swing path indicating means for comparing the phase of the detected signals from said first antennas, converting the phase difference into a voltage analogue of phase, and indicating the magnitude of said voltage analogue, and

swing velocity indicating means for comparing the detected apparant frequencies at said second pair of antennas, converting the difference frequency into a voltage analogue of said difference frequency, and indicating the maximum value of said voltage analogue.

2. The golf swing sensing device according to claim 1, wherein:

said first pair of antennas are mounted on a pivoting cradle,

said pivoting cradle having an axis of rotation substantially parallel with and substantially directly below said nominal horizontal flight path,

whereby the inclination of said plane defined by point equidistant from said first antennas may be adjusted to individual golfers using the device.

3. The golf swing sensing device according to claim 2, wherein:

said second antennas are mounted on said pivoting cradle and on said plane defined by points equidistant from said first antennas.

4. The golf swing sensing device according to claim 1, wherein:

a line between said second set of antennas passes through the position of a ball supported on said ball tee,

whereby the maximum relative doppler effect is produced by a club head during that portion of the swing that the club head is striking a ball.

5. The golf swing sensing device according to claim 1, wherein:

said first antennas are spaced, one from the other, by approximately 5 feet.

6. The golf swing sensing device according to claim 1, wherein:

said swing path indicating means comprises a phase comparator having a voltage output that is negative for sensed deviation on one side of said plane defined by points equidistant from said first antennas and positive for sensed deviation on the opposite sides of said plane.

7. The golf swing sensing device according to claim 1, wherein:

said swing path indicating means comprises a common local oscillator, signals from said local oscillator are mixed with RF signals from said antennas to produce an IF frequency corresponding to that of separate IF amplifiers.

8. The golf swing sensing device according to claim 1, wherein:

said swing velocity indicating means comprises a mixer for developing a difference signal between the RF detected at individual ones of said second pair of antennas, and a low pass filter having an upper cut off frequency above the range of doppler frequencies developed in the difference signals from said mixer, but below the primary frequency of the transmitter.

9. A device for sensing the swing path of the head of a golf club comprising:

a golfer supporting platform having a ball tee positioned along the nominal horizontal flight path of a golf ball, and a golfer supporting position spaced from said ball tee,

a golf club,

a battery-powered radio frequency transmitter secured to the head of said golf club,

a first pair of antennas mounted in association with said platform substantially equidistant from said ball tee,

a vertical plane passing through said first antennas being substantially transverse to said nominal horizontal flight path,

the plane defined by all points equadistant from said first antennas being inclined from the vertical toward said golfer supporting position,

a second pair of spaced antennas positioned along a substantially horizontal line parallel to said nominal horizontal flight path,

swing path indicating means for comparing the relative phase of the detected signal from said first antennas,

converting the phase difference into a voltage analogue of phase and indicating the magnitude of said voltage analogue,

swing velocity indicating means for comparing the detected apparent frequencies at said second pair of antennas, converting the difference frequency into a voltage analogue of said difference frequency, and indicating the maximum value of said voltage analogue.

10. The golf swing sensing device according to claim 9, wherein:

said first pair of antennas are mounted on a pivoting frame,

said pivoting frame having an axis of rotation substantially parallel with and substantially directly below said nominal horizontal flight path,

whereby the inclination of said plane defined by point equidistant from said first antennas may be adjusted to individual golfers using the device.

11. The golf swing sensing device according to claim 9, wherein:

said first antennas are spaced from one another by approximately five feet.

12. The golf swing sensing device according to claim 9, wherein:

said swing path indicating means comprises a phase comparator having a voltage output that is negative for sensed deviations on one side of said plane defined by points equidistant from said first antennas and positive for sensed deiviations on the opposite sides of said plane.

13. A device for sending the swing path of the head of a golf club, comprising:

a golfer supporting platform having a ball tee positioned along the nominal horizontal flight path for a golf ball, and a golfer supporting position spaced from said ball tee,

a golf club,

a battery-powered radio frequency transmitter secured to the head of said club,

a first pair of antennas mounted in association with said platforms substantially equidistant from said ball tee,

a vertical plane passing through said first antennas being substantially transverse to said nominal horizontal flight path,

the plane defined by all points equadistant from said first antennas being inclined from the vertical toward said golfer supporting position,

a second pair of spaced antennas positioned along a substantially horizontal line parallel to said nominal horizontal flight path,

swing path indicating means for comparing the relative phase of the detected signal from said first antennas, converting the phase difference into a voltage analogue of phase, and indicating the magnitude of said voltage analogue,

swing velocity indicating means for comparing the detected apparent frequencies at said second pair of antennas, converting the difference frequency into a voltage analogue of said difference frequency, and indicating the maximum value of said voltage analogue,

said swing path indicating means comprising a common local oscillator, signals from said local oscillator being mixed with RF signals from each of said first pair of antennas to produce an IF frequency corresponding to that of separate IF amplifiers.

14. A device for sensing the striking velocity of the head of a golf club comprising:

a golfer supporting platform having a ball tee positioned along the normal horizontal flight path for a golf ball and a golfer supporting position spaced from said ball tee,

a golf club,

a battery-powered radio frequency transmitter secured to the head of said club,

a first pair of antennas mounted in association with said platform substantially equidistant from said ball tee,

a second pair of antennas positioned along a substantially horizontal line parallel to said nominal horizontal flight path,

a vertical plane passing through said first antennas being substantially tranverse to said nominal horizontal flight path,

the plane defined by all points equadistant from said first antennas being inclined from the vertical towards said golfer supporting position,

swing velocity indicating means for comparing the detected apparent frequencies at said second pair of antennas, converting the difference frequency into a voltage analogue of said difference frequency, and indicating the maximum value of said voltage analogue.

15. The golf swing sensing device according to claim 14, wherein:

said second antennas are mounted on said pivoting cradle and on said plane defined by points equidistant from said first antennas.

16. The golf swing sensing device according to claim 14, wherein:

a line between said second set of antennas passes through the position of a ball supported on said ball tee,

whereby the maximum relative doppler effect is produced by a club head during that portion of the swing that the club head is striking a ball.

17. The golf swing sensing device according to claim 14, wherein:

said swing velocity indicating means comprises a mixer for developing a difference signal between the RF detected at individual ones of said second pair of antennas, and a low pass filter having an upper cut off frequency above the range of doppler frequencies developed in the difference signals from said mixer, but below the primary frequency of the transmitter.