Ball spin rate measurement

• US 9,868,044 B2
• Filed: 04/20/2016
• Issued: 01/16/2018
• Est. Priority Date: 01/10/2013
• Status: Active Grant

• Current Assignee: EDH US LLC
• Original Assignee: EDH US LLC
• Inventors: Johnson, Henri, Johnson, Thomas, Rust, Robert William
• Primary Examiner(s): Bythrow, Peter M
• Application Number:
  US15/133,744
• Publication Number:
  US 20160339320A1
• Time in Patent Office: 636 Days
• CPC Class Codes: A63B 2024/0034 during flight
• CPC Class Codes: A63B 2071/0625 Emitting sound, noise or music
• CPC Class Codes: A63B 2071/0694 Visual indication, e.g. Indicia
• CPC Class Codes: A63B 2220/35 Spin
• CPC Class Codes: A63B 2220/803 Motion sensors
• CPC Class Codes: A63B 2220/805 Optical or opto-electronic sensors
• CPC Class Codes: A63B 2220/806 Video cameras
• CPC Class Codes: A63B 2220/833 Sensors arranged on the exercise apparatus or sports implement
• CPC Class Codes: A63B 2220/89 Field sensors, e.g. radar systems
• CPC Class Codes: A63B 2225/20 with means for remote communication, e.g. internet or the like
• CPC Class Codes: A63B 2225/50 Wireless data transmission, e.g. by radio transmitters or telemetry
• CPC Class Codes: A63B 2225/52 modulated by measured values
• CPC Class Codes: A63B 69/3658 Means associated with the ball for indicating or measuring, e.g. speed, direction
• CPC Class Codes: A63B 71/0622 Visual, audio or audio-visual systems for entertaining, instructing or motivating the user
• CPC Class Codes: G01S 13/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 13/581 using transmission of interrupted pulse modulated waves and based upon the Doppler effect resulting from movement of targets
• CPC Class Codes: G01S 7/285 Receivers
• CPC Class Codes: G01S 7/352 Receivers
• CPC Class Codes: G06F 1/1626 with a single-body enclosure integrating a flat display, e.g. Personal Digital Assistants [PDAs]

Abstract

Systems and methods for ball spin rate measurement are described. Some embodiments provide a method whereby a phase-demodulated difference signal of a projectile in flight is received, such as from a Doppler radar system. A first periodic component of the phase-demodulated signal is detected, the first periodic component having a plurality of bipolar pulses, with each of the pulses having a first portion during which an apparent speed of the projectile is greater than a nominal speed of the projectile, and each of the pulses having a second portion during which the apparent speed of the projectile is less that the nominal speed of the projectile. A period of the first periodic component is detected, and the spin rate of the projectile in flight is determined based on the period of the first periodic component.

Claims

1. A system for determining a spin rate of a projectile in flight, the system comprising:

a signal transmitter to transmit a microwave signal toward the projectile in flight;

a signal receiver to receive a reflected signal from the projectile in flight, the reflected signal caused by at least a portion of the microwave signal incident on the projectile in flight;

a signal mixer to mix the received signal with a comparison signal based on the transmitted microwave signal to yield a difference signal;

a demodulator to demodulate the difference signal to generate a demodulated signal comprising at least one periodic component indicating phase variations between the received signal and the comparison signal; and

a frequency analyzer to detect a first periodic component of the demodulated signal, the first periodic component including a first time portion indicating a first apparent speed of the projectile greater than a nominal speed of the projectile, and including a second time portion indicating a second apparent speed of the projectile less than the nominal speed of the projectile, the frequency analyzer to determine a period of the first periodic component, and to determine the spin rate of the projectile in flight based on the period of the first periodic component.

2. The system of claim 1, the first periodic component generated by rotation of a structural feature of an outer layer of the projectile in flight, the structural feature extending along an equator of the projectile in flight, and the frequency analyzer to determine the spin rate as corresponding to a period equal to an even multiple of the period of the first periodic component.

3. The system of claim 2, the structural feature comprising a seam at which two cover half-shells of a golf ball are coupled together to cover a core of the golf ball, the core operating as a lens to create a magnifying zone for the reflected signal, the increase and decrease in the apparent speed caused by the seam passing through the magnifying zone.

4. The system of claim 1, the first periodic component generated by rotation of a feature coupled to a cover covering a core of a golf ball, and the frequency analyzer to determine the spin rate as having a period equal to the period of the first periodic component.

5. The system of claim 4, the feature comprising a conductive marker, the core operating as a lens to create a magnifying zone for the reflected signal, the increase and decrease in the apparent speed caused by the conductive marker passing through the magnifying zone.

6. The system of claim 1, the signal transmitter comprising a transmitter for a Doppler radar system, and the signal receiver comprising a receiver for the Doppler radar system.

7. The system of claim 1, further comprising:

a signal filter to filter the demodulated signal to yield a filtered signal, the signal filter comprising at last one of a signal sampler, a band-pass filter, and a band-limiting filter, the frequency analyzer to detect the first periodic component in the filtered signal.

8. The system of claim 1, the demodulator comprising a first demodulator, the system further comprising a second demodulator to demodulate the filtered signal to produce a second demodulated signal, the frequency analyzer to detect the first periodic component in the second demodulated signal.

9. The system of claim 1, the frequency analyzer to perform a fast Fourier transform to detect the first periodic component.

10. The system of claim 1, the frequency analyzer to detect the first periodic component of the demodulated signal based on at least one rule associated with a physical configuration of the projectile in flight.

11. The system of claim 1, further comprising a low-pass filter to filter the difference signal, the demodulator to demodulate the filtered difference signal.

12. The system of claim 1, the comparison signal having a frequency equal to a frequency of the transmitted microwave signal.

13. The system of claim 1, the projectile in flight traveling away from the transmitter and the receiver, the first time period occurring immediately before the second time period during the period of the first periodic component.

14. The system of claim 1, the sum of the first time period and the second timer period being less than the period of the first periodic component.

15. A method of determining a spin rate of a projectile in flight, the method comprising:

transmitting a microwave signal toward a projectile in flight;

receiving a reflected signal from the projectile in flight, the reflected signal being a reflected portion of the microwave signal incident on the projectile in flight;

mixing the received signal with a comparison signal based on the transmitted microwave signal to yield a difference signal;

demodulating the difference signal to generate a demodulated signal comprising at least one periodic component indicating phase variations between the received signal and the comparison signal;

detecting a first periodic component of the demodulated signal, the first periodic component comprising a repeating bipolar pulse having a first portion during which an apparent speed of the projectile is greater than a preceding speed of the projectile, the bipolar pulse having a second portion during which the apparent speed of the projectile is less than the preceding speed of the projectile;

determining a period of the first periodic component; and

determining the spin rate of the projectile in flight based on the period of the first periodic component.

16. The method of claim 15, a period of the spin rate of the projectile in flight being an even multiple of the period of the first periodic component based on the projectile in flight comprising a signal-reflective feature forming a loop about the projectile in flight.

17. The method of claim 15, a period of the spin rate of the projectile in flight being equal to the period of the first periodic component based on the projectile in flight comprising a signal-reflective feature not forming a loop about the projectile in flight.

18. A system for determining a spin rate of a projectile in flight, the system comprising:

at least one hardware processor; and

a memory including instructions that, when executed by the at least one hardware processor, cause the system to perform operations comprising;

receiving a phase-demodulated difference signal of a projectile in flight from a Doppler radar system;

detecting a first periodic component of the phase-demodulated signal, the first periodic component comprising a plurality of bipolar pulses, each of the plurality of bipolar pulses having a first portion during which an apparent speed of the projectile is greater than a nominal speed of the projectile between consecutive ones of the bipolar pulses, and each of the plurality of bipolar pulses having a second portion during which the apparent speed of the projectile is less that the nominal speed of the projectile between consecutive ones of the bipolar pulses;

determining a period of the first periodic component; and

determining the spin rate of the projectile in flight based on the period of the first periodic component.

19. The system of claim 18, the determining of the spin rate of the projectile in flight being based in part on at least one rule relating the spin rate of the projectile in flight to the period of the first periodic component according to a configuration of a signal-reflective physical feature of the projectile in flight.

20. The system of claim 19, the operations further comprising correlating a point in time between the first portion and the second portion of each of the plurality of bipolar pulses with a at least a portion of the signal-reflective physical feature being positioned opposite the projectile in flight from the Doppler radar system.