Tracking the Baseball with the Track Man Doppler

Tracking the Baseball with the Track. Man Doppler Radar A Brief Introduction Busch Petco

The Doppler Technique Doppler Frequency Shift f. D = Doppler Shift = FTX - FRX = 2 FTX(VR/c) VR = dr/dt = rate of change of distance of ball from TM 2

Frequency/Velocity vs. Time Doppler shift Radial velocity Batted ball Bat Bounce Pitched ball Time 3

Slightly More Detail • Want to determine location of baseball as function of time – TM determines r, , • r = distance from TM • , =orientation angles wrt TM

Summary of TM Technique: r, , • Determining r(t) – Doppler shift determines dr/dt – Two-frequency phase shift determines r(0)

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

Measuring angles Phase Shift Between Detectors Angles Extra distance = Dsin( ) phase shift 8

Three Detectors ,

Summary of Technique Doppler shift determines dr/dt Two wavelength phase shift determines r(0) + dr/dt r(t) 3 -detector array phase shifts determine (t), (t) r(t), (t) gives full 3 D trajectory Need to convert to field coordinates using location and orientation of TM 10

Measurement Principle: Spin Doppler frequency modulated by rotation frequency Sidebands separated by n 11

Track. Man Capabilities I: Full 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 12

Track. Man Capabilities II: Full 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 13