Method, apparatus, and computer program product for measuring and interpreting metrics of an athletic action and an object associated therewith
Embodiments provided herein measure metrics of an athletic action and an object associated therewith, and more particularly, to measuring the metrics and characteristics of a baseball during the wind-up, release, flight, and catch of a pitch sequence. Methods may include: receiving, from at least one motion sensor associated with an object, acceleration data and angular velocity data of the object in response to an athletic action performed on the object; processing the acceleration data to establish vector rotation data between a frame of reference of the object and an Earth frame of reference; applying the vector rotation data to the acceleration data to obtain acceleration of the object in the Earth frame of reference; applying the vector rotation data to the angular velocity data to obtain angular velocity of the object in the Earth frame of reference.
1. An apparatus comprising;
at least one accelerometer;
at least one gyroscope;
at least one processor; and
at least one magnetometer,
wherein in response to rotation of the apparatus relative to an Earth frame of reference, the at least one processor is configured to:
process data received from the at least one accelerometer, and the at least one gyroscope to determine a rotation of the apparatus in the Earth frame of reference;
determine, based on a magnetometer sinusoidal signal from the at least one magnetometer, a period of the magnetometer sinusoidal signal representing a spin rate;
generate from the period of the magnetometer sinusoidal signal, a finite impulse response high pass filter; and
implement the finite impulse response high pass filter as a moving average window filter on the signal from the at least one accelerometer to isolate a lift force and a drag force acting on an object associated with the apparatus.
2. The apparatus of claim 1 , wherein an orientation of the apparatus in the Earth frame is maintained in quaternion form.
3. The apparatus of claim 1 , wherein rotation of the apparatus relative to the Earth frame of reference is established in response to a gravitational force detected by the accelerometer.
4. The apparatus of claim 1 , wherein the apparatus further comprises a communications interface, wherein the communications interface outputs position, angular velocity, and angular acceleration in the Earth frame of reference to a remote device.
5. The apparatus of claim 4 , wherein the angular velocity and angular acceleration are compared against historical data, wherein the remote device provides for display of feedback to improve at least one of the angular velocity and the angular acceleration relative to the historical data.
6. The apparatus of claim 1 , wherein the processor is further configured to isolate the lift force from the drag force based, at least in part, on a drag coefficient and a surface area of the object associated with the apparatus.
7. The apparatus of claim 1 , wherein the processor is further configured to:
receive three channels of data from the at least one magnetometer;
determine zero crossings of a sinusoidal signal from each channel of data;
average a time difference of two adjacent pairs of zero crossings of each of the three channels of data; and
determine a period of spin from the averaged time difference.
8. The apparatus of claim 1 , wherein in response to an object associated with the apparatus being thrown by a user, the processor is further configured to:
receive a signal from the at least one gyroscope;
obtain a second derivative of the signal from the at least one gyroscope to establish an angular jerk signal having a value along a time axis; and
determine on the time axis a beginning of a Snap phase of a throw in response to a statistically significant increase in the value of the angular jerk signal.
9. The apparatus of claim 8 , wherein the processor is further configured to:
determine on the time axis a latter portion of the Snap phase of the throw in response to a change in the angular jerk signal from a positive value to a negative value; and
determine an end of the Snap phase on the time axis in response to an angular jerk value of zero following the beginning of the Snap phase and the latter portion of the Snap phase.
10. The apparatus of claim 9 , wherein the processor is further configured to, based on a signal from the at least one accelerometer, determine a distance traveled by the object during the Snap phase.
11. The apparatus of claim 9 , wherein the processor is further configured to, based on a signal from the at least one accelerometer, determine a change in speed of the object during the Snap phase.
12. The apparatus of claim 9 , wherein the processor is further configured to, based on a signal from the at least one gyroscope, determine a change in spin axis of the object during the Snap phase.
13. An apparatus comprising;
at least one accelerometer;
at least one gyroscope;
at least one magnetometer; and
at least one processor,
wherein in response the apparatus being thrown and experiencing rotation of the apparatus relative to an Earth frame of reference, the apparatus at least one processor is configured to:
process data received from the at least one accelerometer, the at least one gyroscope, and the at least one magnetometer to determine a rotation of the apparatus in the Earth frame of reference;
determine, from the rotation of the apparatus in the Earth frame of reference, a lift force and a drag force acting on the apparatus; and
isolate the lift force from the drag force based, at least in part, on a drag coefficient and a surface area of an object associated with the apparatus.
14. The apparatus of claim 13 , wherein rotation of the apparatus relative to the Earth frame of reference is established in response to a gravitational force detected by the accelerometer.
15. The apparatus of claim 14 , wherein an angular velocity and an angular acceleration are compared against historical data, wherein a remote device provides for display of feedback to improve at least one of the angular velocity and the angular acceleration relative to the historical data.
16. The apparatus of claim 13 , wherein the processor is further configured to:
receive three channels of data from the at least one magnetometer;
determine zero crossings of a sinusoidal signal from each channel of data;
average a time difference of two adjacent pairs of zero crossings of each of the three channels of data; and
determine a period of spin from the averaged time difference.
17. The apparatus claim 13 , wherein in response to the apparatus being thrown, the processor is further configured to:
receive a signal from the at least one gyroscope;
obtain a second derivative of the signal from the at least one gyroscope to establish an angular jerk signal having a value along a time axis;
determine on the time axis a beginning of a Snap phase of the throw in response to a statistically significant increase in the value of the angular jerk signal;
determine on the time axis a latter portion of the Snap phase of a throw in response to a change in the angular jerk signal from a positive value to a negative value; and
determine an end of the Snap phase on the time axis in response to an angular jerk value of zero following the beginning of the Snap phase and the latter portion of the Snap phase wherein the end of the Snap phase defines a release of the thrown apparatus.
18. The apparatus of claim 13 , wherein the processor configured to determine, from the rotation of the object in the Earth frame of reference, lift and drag forces acting on the apparatus comprises the apparatus configured to:
determine, based on a sinusoidal signal from the at least one accelerometer or at least one magnetometer, a period of the sinusoid representing a spin rate;
generate from the period of the sinusoidal signal, a high pass filter; and
implement the high pass filter as a moving average window filter on a signal from the at least one accelerometer to isolate lift and drag forces acting on an object associated with the apparatus.
19. An apparatus comprising;
at least one accelerometer;
at least one gyroscope;
at least one processor; and
at least one magnetometer,
wherein in response to rotation of the apparatus relative to an Earth frame of reference, the at least one processor is configured to:
process data received from the at least one accelerometer, and the at least one gyroscope to determine a rotation of the apparatus in the Earth frame of reference;
receive three channels of data from the at least one magnetometer;
determine zero crossings of a sinusoidal signal from each channel of data;
average a time difference of two adjacent pairs of zero crossings of each of the three channels of data; and
determine a period of spin from the averaged time difference.
20. The apparatus of claim 19 , wherein rotation of the apparatus relative to the Earth frame of reference is established in response to a gravitational force detected by the at least one accelerometer.