Equipment fitting system that compares swing metrics
An equipment fitting system that measures swings by a user of different pieces of equipment with inertial sensors, and analyzes sensor data to recommend which piece of equipment is optimal for the user from among those tested. Illustrative applications include fitting of baseball bats and golf clubs. Swing metrics calculated from sensor data may include an acceleration metric, a speed metric, and a momentum metric; these metrics may be combined into a metrics score for each piece of equipment. Other factors may be included in an overall score, such as the user's subjective score for each piece of equipment, and ratings from experts or other consumers. Users may assign the relative importance for the different factors to calculate an overall equipment score.
1. An equipment fitting system that compares swing metrics, comprising:
one or more inertial sensors, wherein
each inertial sensor of said one or more inertial sensors comprises
an accelerometer;
a gyroscope;
each inertial sensor is coupled to one or more pieces of equipment of a plurality of pieces of equipment used by a user;
each inertial sensor is configured to capture inertial sensor data at a sequence of times during a swing of each piece of equipment of said one or more pieces of equipment to which said each inertial sensor is coupled;
a processor configured to
receive said inertial sensor data associated with said swing of said each piece of equipment of said one or more pieces of equipment;
for said each piece of equipment,
calculate one or more swing metrics based on said inertial sensor data; and
calculate a metrics score from said one or more swing metrics; and,
access a database for at least one similar metrics score and recommend an optimal piece of equipment of said plurality of pieces of equipment for said user based on said metrics score of another user.
2. The equipment fitting system of claim 1 , wherein said one or more swing metrics comprise an acceleration metric or a speed metric or a momentum metric.
3. The equipment fitting system of claim 2 , wherein said each piece of equipment of said plurality of pieces of equipment is associated with
a longitudinal axis;
a sweet spot position; and
an effective mass.
4. The equipment fitting system of claim 3 , wherein said acceleration metric comprises a rate of change of a centripetal acceleration of said each piece of equipment along said longitudinal axis.
5. The equipment fitting system of claim 4 , wherein
said processor is further configured to partition said sequence of times into phases, wherein said phases comprise
a load phase ending when said centripetal acceleration changes from positive to negative;
an accelerate phase following said load phase;
a peak phase following said accelerate phase; and
a transfer phase following said peak phase and ending at an endpoint of said swing;
said acceleration metric comprises an average rate of change of said centripetal acceleration during said accelerate phase.
6. The equipment fitting system of claim 3 , wherein said momentum metric equals said effective mass multiplied by said speed metric.
7. The equipment fitting system of claim 6 , wherein
said each piece of equipment is a bat; and,
said effective mass comprises 0.75 times a mass of said bat.
8. The equipment fitting system of claim 3 , wherein said speed metric comprises a speed of said sweet spot position at an endpoint of said swing.
9. The equipment fitting system of claim 8 , wherein said endpoint of said swing comprises a time of said sequence of times of an impact between said each piece of equipment and an object.
10. The equipment fitting system of claim 8 , wherein said endpoint of said swing comprises a time of said sequence of times when a rotational velocity magnitude of said each piece of equipment is maximum.
11. The equipment fitting system of claim 1 , wherein said one or more swing metrics comprises a rotational profile used to calculated said metrics score to recommend said optimal piece of equipment of said plurality of pieces of equipment.
12. The equipment fitting system of claim 11 , further comprising
said database comprising
said rotational profile associated with each user of a plurality of users, wherein said plurality of users comprises said user; and,
a swing analysis system coupled to said database and configured to compare said rotational profile across said plurality of users.
13. The equipment fitting system of claim 1 , wherein said processor is further configured to partition said sequence of times into phases, wherein said phases comprise
a load phase ending when a centripetal acceleration changes from positive to negative;
an accelerate phase following said load phase;
a peak phase following said accelerate phase; and,
a transfer phase following said peak phase and ending at an end of said swing when said each piece of equipment impacts a ball.
14. The equipment fitting system of claim 13 , wherein said one or more swing metrics are calculated from one or more of
said inertial sensor data;
a body rotation rate at said sequence of times;
an equipment rotation rate at said sequence of times; and,
said centripetal acceleration at said sequence of times.
15. The equipment fitting system of claim 14 , wherein said one or more swing metrics comprise one or more of
a peak loading acceleration, comprising a maximum positive centripetal acceleration during said load phase;
a rate of acceleration, comprising an average rate of change of said centripetal acceleration during said accelerate phase;
a peak acceleration, comprising a minimum negative centripetal acceleration after said load phase and before said end of said swing;
an acceleration impulse, comprising an integral of said centripetal acceleration between a start of said accelerate phase and said end of swing;
a time to peak force, comprising a time difference between a start of said accelerate phase and a time when said centripetal acceleration reaches a minimum negative value after said start of said accelerate phase;
a peak equipment rotation rate, comprising a maximum value of said equipment rotation rate between a start of said load phase and said end of said swing;
a peak body rotation rate, comprising a maximum value of said body rotation rate between a start of said load phase and said end of said swing;
a ratio between said peak equipment rotation rate and said peak body rotation rate.
16. The equipment fitting system of claim 1 , wherein said one or more pieces of equipment comprise a hand position or a sweet spot position.
17. The equipment fitting system of claim 16 , wherein said processor is further configured to
based on said inertial sensor data, calculate a trajectory of said each piece of equipment comprising a trajectory of said sweet spot position at said sequence of times;
determine a time of impact of said swing from said inertial sensor data;
calculate a swing plane from said inertial sensor data, wherein said swing plane is spanned by a velocity vector of said sweet spot position at said time of impact; and,
wherein said calculate said swing metrics is further based on one or more of
said time of impact;
said trajectory of said sweet spot position; and,
said swing plane.
18. The equipment fitting system of claim 16 , wherein said processor is further configured to
based on said inertial sensor data, calculate a trajectory of said each piece of equipment comprising a trajectory of said hand position at said sequence of times;
determine a time of impact of said swing from said inertial sensor data;
wherein said calculate said swing metrics is further based on
said trajectory of said hand position.
19. The equipment fitting system of claim 1 , wherein said processor is further configured to calculate said metrics score as a weighted sum of said one or more swing metrics.
20. The equipment fitting system of claim 1 , wherein said recommend said optimal piece of equipment is further based on one or more of
a user feel score provided by said user for said each piece of equipment;
an expert opinion score provided by one or more experts for said each piece of equipment; and,
a consumer comparison score provided by one or more consumers for said each piece of equipment.
21. The equipment fitting system of claim 20 , wherein said processor is further configured to
calculate an overall score for said each piece of equipment based on
said metrics score;
said user feel score;
said expert opinion score; and
said consumer comparison score; and,
select said optimal piece of equipment as a piece of equipment having a highest overall score.
22. The equipment fitting system of claim 21 , wherein said processor is further configured to
calculate said overall score as a weighted sum of
said metrics score;
said user feel score;
said expert opinion score; and
said consumer comparison score.
23. The equipment fitting system of claim 22 , wherein said processor is further configured to
obtain or calculate weights for said weighted sum based on input from said user.
24. The equipment fitting system of claim 1 , wherein said each piece of equipment is a bat.
25. The equipment fitting system of claim 1 , wherein said each piece of equipment is a golf club.