Tracking the Baseball with the TrackMan Doppler Radar

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Tracking the Baseball with the TrackMan Doppler
Radar

• A Brief Introduction

Petco
Busch
2
The Doppler Technique

• Doppler Frequency Shift

fD Doppler Shift FTX - FRX ? 2FTX(VR/c)
VR dr/dt rate of change of distance of ball
from TM
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Frequency/Velocity vs. Time
Doppler shift
Radial velocity
Time ?
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Slightly More Detail

• Want to determine location of baseball as
  function of time
• TM determines r,?,?
• r distance from TM
• ?,?orientation angles wrt TM

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Summary of TM Technique r,?,?

• Determining r(t)
• Doppler shift determines dr/dt
• Two-frequency phase shift determines r(0)

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Determining r(0)

• Transmit two wavelengths ?1 and ?2
• Initially in phase
• After reflection and detection, out of phase by
  2r(1/ ?1 - 1/ ?2)
• Measuring phase shift at t0 determines r(0)

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Summary of TM Technique r,?,?

• Determining r(t)
• Doppler shift determines dr/dt
• Two-frequency phase shift determines r(0)
• Determining ?(t),?(t)
• Phase shift between pairs of detectors

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Measuring angles

• Phase Shift Between Detectors? Angles

Extra distance Dsin(?) ? phase shift
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Three Detectors ? ?,?
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Summary of Technique
Doppler shift determines dr/dt Two wavelength
phase shift determines r(0) r(0) dr/dt ?
r(t) 3-detector array phase shifts determine
?(t), ?(t) r(t), ?(t), ?(t) gives full 3D
trajectory Need to convert to field coordinates
using location and orientation of TM
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Measurement Principle Spin
Doppler frequency modulated by rotation frequency
? Sidebands separated by n?
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TrackMan Capabilities IFull pitched ball
trajectory

• Everything PITCHf/x gives plus.
• Actual release point (extension)
• ? perceived velocity
• Total spin (including gyro component)
• Many more points on the trajectory
• Utility of more points under study

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TrackMan Capabilities IIFull batted ball
trajectory

• Batted ball speed, launch spray angles
• Equivalent to HITf/x
• Landing point coordinates at ground level and
  hang time
• Equivalent to Hittracker
• Initial spin
• and more, if you want it