Measurement of the coefficient of restitution of a golf club

• US 6,527,648 B2
• Filed: 04/04/2001
• Issued: 03/04/2003
• Est. Priority Date: 04/04/2001
• Status: Expired due to Term

• Current Assignee: Callaway Golf Company (Topgolf Callaway Brands Corp.)
• Original Assignee: Callaway Golf Company (Topgolf Callaway Brands Corp.)
• Inventors: Erickson, Matthew J., Kosmatka, John B., Ehlers, Steven M., Fan, Frank H.
• Primary Examiner(s): NGUYEN, KIM T
• Application Number:
  US09/826,544
• Publication Number:
  US 20030004007A1
• Time in Patent Office: 699 Days
• Field of Search: 473/221, 473/290, 473/291, 473/282, 473/329, 473/332, 473/342, 473/559, 473/351, 73/13.7, 73/13.8, 73/13.9, 73/542.3, 73/650.3, 73/78, 73/82, 735/70, 735/79, 736/59, 736/62, 737/78, 738/44
• US Class Current: 473/221
• CPC Class Codes: A63B 60/42 Devices for measuring, verifying, correcting or customising the inherent characteristics of golf clubs, bats, rackets or the like, e.g. measuring the maximum torque a batting shaft can withstand
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/269 Various geometry objects
• CPC Class Codes: G01N 29/045 by imparting shocks to the workpiece and detecting the vibrations or the acoustic waves caused by the shocks measuring resonant frequency G01H13/00; measuring strength properties by application of mechanical stress G01N3/00

Abstract

A method (100) and system (20) for predicting a coefficient of restitution (COR) of a golf club (30) or golf club head (36) is disclosed herein. The system (20) and method (100) are able to predict the COR in a non-destructive manner for a particular golf ball and impact speed. The system (20) and method (100) utilize a vibration sensor (24) attached to the face (34) of a golf club (30). The vibration sensor (24) is excited with an excitation device (26), and data is transmitted to an analyzer (22). A mathematical model of the golf club (30) is created allowing for the coefficient of restitution to be predicted without destroying the golf club (30).

Claims

1. A method for predicting a coefficient of restitution (COR) of a golf club, the method comprising:

attaching a vibration sensor to a face of the golf club;

impacting the attached vibration sensor with an excitation device to generate vibrations in the face;

transmitting a force of excitation from the excitation device and the vibrations measured by the vibration sensor to an analyzer to generate frequency domain data for the golf club;

transforming the frequency domain data for the golf club into a transfer function for the golf club; and

inputting a golf ball model for a specific golf ball and an impact speed into the transfer function in order to generate a predicted COR for the golf club at the impact speed with the specific golf ball, the golf ball model comprising a contact duration of the specific ball, a contact force of the specific ball, and a COR of the specific ball.

2. The method according to claim 1 wherein the impact speed is a club speed.

3. The method according to claim 1 wherein the impact speed is a ball speed.

4. The method according to claim 1 wherein the vibration sensor is an accelerometer with the capability of transmitting data to the analyzer.

5. The method according to claim 1 wherein the excitation device is an impact device with the capability of generating the force of excitation and transmitting the force of excitation to the analyzer.

6. The method according to claim 1 wherein transforming the frequency domain data comprises:

generating a graph of frequency;

analyzing the phase of the graph of frequency to determine when the face of the golf club is traveling inward and outward for determining a contact point velocity;

selecting a frequency band to minimize noise; and

calculating the transfer function.

7. The method according to claim 6 wherein the frequency band is from 500 Hertz to a first inflection point of the graph.

8. The method according to claim 6 further comprising inputting an effective mass of the golf club into the transfer function, the effective mass calculated from the graph of frequency at 0 Hertz.

9. The method according to claim 1 wherein a system identification is used to generate the transfer function.

10. A method for predicting a coefficient of restitution (COR) of a golf club head, the method comprising:

attaching a vibration sensor to a face of the golf club head;

impacting the attached vibration sensor with an impact device to generate vibrations in the face;

transmitting a force of impact from the impact device and the vibrations measured by the vibration sensor to an analyzer to generate frequency domain data for the golf club head;

transforming the frequency domain data for the golf club head into a transfer function for the golf club head; and

inputting a golf ball model for a specific golf ball and an impact speed into the transfer function in order to generate a predicted COR for the golf club head at the impact speed with the specific golf ball, the golf ball model comprising a contact duration of the specific ball, a contact force of the specific ball, and a COR of the specific ball.

11. The method according to claim 10 wherein transforming the frequency domain data comprises:

generating a graph of frequency;

analyzing the phase of the graph of frequency to determine when the face of the golf club is traveling inward and outward for determining a contact point velocity;

selecting a frequency band to minimize noise; and

calculating the transfer function.

12. The method according to claim 11 wherein the frequency band is from 500 Hertz to a first inflection point of the graph.

13. The method according to claim 11 further comprising inputting an effective mass of the golf club head into the transfer function, the effective mass calculated from the graph of frequency at 0 Hertz.

14. A method for predicting a coefficient of restitution (COR) of a golf club, the method comprising:

attaching a vibration sensor to a face of the golf club;

exciting the attached vibration sensor with an excitation device to generate vibrations in the face;

transmitting a force of excitation from the excitation device and the vibrations measured by the vibration sensor to an analyzer to generate time domain data for the golf club;

transforming the time domain data for the golf club into a transfer function of the golf club; and

inputting a golf ball model for a specific golf ball and an impact speed into the transfer function of the golf club in order to generate a predicted COR for the golf club at the specified impact speed with the specific golf ball, the golf ball model comprising a contact duration of the specific ball, a contact force of the specific ball, and a COR of the specific ball.

15. The method according to claim 14 wherein the golf club is unshafted.