System and method for characterizing tire uniformity machines

1. A method for characterizing spindle forces of a tire uniformity machine, comprising:

receiving a tire in an apparatus having an upper spindle with an upper rim and a lower spindle with a lower rim, wherein said rims capture the tire therebetween;

applying a load wheel to the tire and collecting a measurement data waveform;

determining an angular offset of said lower rim in relation to said upper rim so as to define an engagement position among a plurality of engagement positions;

designating said measurement data waveform as a tire result waveform;

appending said measurement data waveform to a collection of measurement data waveforms for at least a predetermined number of measurement data waveforms for said engagement position;

determining whether said predetermined number of measurement data waveforms for said engagement position has been obtained and if not, storing said tire result waveform as a tire test result for said engagement position, and if said predetermined number of measurement data waveforms for said engagement position has been obtained:

computing an average waveform for said engagement position;

generating a characterization waveform for each average waveform;

calculating a final tire waveform by subtracting the characterization waveform from said tire result waveform; and

storing said final tire waveform as the tire test result.

2. The method according to claim 1 , further comprising:

comparing said tire test result to a predetermined threshold.

3. The method according to claim 1 , further comprising:

subtracting a load wheel characterization waveform from said measurement data waveform so as to obtain said tire result waveform prior to the appending step.

4. The method according to claim 3 , further comprising:

continuing to append said measurement data waveforms to said collection of measurement data waveforms for said engagement position and updating said average waveform even after sufficient data for said engagement positions has been obtained.

5. The method according to claim 1 , further comprising:

associating a tire encoder with said spindle to monitor a rotational position of the tire and said upper spindle with an upper rim;

associating a flag with said lower rim; and

positioning a proximity switch so as to detect said flag and a rotational position of said lower rim, wherein said engagement position is determined from said rotational positions of said lower rim and said upper rim.

6. The method according to claim 1 , further comprising:

re-setting said average waveform values for each said engagement position to null whenever any mechanical component of the tire uniformity machine is replaced.

7. The method according to claim 6 wherein said any mechanical component is selected from the group consisting of an upper spindle chuck assembly, a lower spindle chuck assembly, a nose cone, a nose cone cup, a removable rim, a spindle, a rim adapter, and spindle bearings.

8. The method according to claim 1 , further comprising:

setting said predetermined number of engagement positions to at least two.

9. The method according to claim 1 , further comprising:

computing at least a first harmonic of said average waveform to generate said characterization waveform.

10. The method according to claim 9 , further comprising:

filtering said characterization waveform for all engagement positions for use as said characterization waveform.

11. The method according to claim 1 , further comprising:

removing said measurement data waveform for an oldest tested tire for each newly tested tire once a predetermined number of said measurement data waveforms have been collected.

12. The method according to claim 1 , wherein said characterization waveform is a lateral force characterization waveform.

13. The method according to claim 1 , further comprising:

determining a load wheel characterization waveform of said load wheel;

calculating a spring rate of the tire;

subtracting said load wheel characterization from said measurement data waveform and storing as said tire result waveform;

normalizing said tire result waveform based on said spring rate of the tire and storing as a normalized waveform; and

appending said normalized waveforms to a collection of normalized waveforms for at least a predetermined number for said engagement position;

wherein if said predetermined number of normalized waveforms for said engagement position has not been obtained, storing said tire result waveform as said tire test result.

14. The method according to claim 13 , further comprising:

continuing to append said normalized waveforms for said engagement positions and computing said characterization waveform even after said predetermined number of said normalized waveforms for each said engagement position has been obtained.

15. The method according to claim 14 , further comprising:

multiplying all points in said characterization waveform by said spring rate prior to calculating said final tire waveform.

16. The method according to claim 13 , further comprising:

computing at least a first harmonic of said average waveform to generate said characterization waveform.

17. The method according to claim 16 , further comprising:

filtering said characterization waveform for all engagement positions for use as said characterization waveform.

18. The method according to claim 13 , wherein said characterization waveform is a radial force characterization waveform.