modern techniques for evaluating hitting alan m. nathan university of illinois batted ball analysis...
TRANSCRIPT
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Modern Techniques for Evaluating Hitting
Alan M. NathanUniversity of Illinois
• Batted ball analysis– Initial speed and angles– Landing point and hang time
• Swing analysis– Bat speed– Swing plane– Timing– “squaring up” 1
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Introductory Remarks
• Tradition techniques are “outcome-based”–BA, SLG, OPS, BABIP, …
• Modern techniques are “process-based”, independent of outcome–What constitutes a well-hit ball?–What constitutes a good swing?
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Tools for Modern Technique
• Baseball Info Solutions (BIS)–Batted ball landing point and hang time
• Hitf/x– Initial batted ball speed and angles
• TrackMan or Fieldf/x–All of the above (i.e., full trajectory)
• Physics–Relating batted ball to swing parameters
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Example: HITf/x Analysis
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See Mike Fast, BPro, Nov. 16 & 22, 2011
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• ~50% of balls hit with BBS90 mph are safe hits, regardless of VLA
• ~37% of balls hit with BBS 90 mph and 250≤VLA≤350 are HR
BABIP
HR
What Constitutes “Good Contact”? Hitf/x from April 2009
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BABIP
HR
What Constitutes “Good Contact”? Hitf/x from April 2009
• ~80% of balls hit with 100≤VLA≤150 are safe hits, regardless of BBS
• ~68% of balls hit with 100≤VLA≤250 and 60≤BBS≤80 mph are safe hits
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Potential of These Data
• Quantify “good contact” (GC)• Establish outcome-inpependent metrics for
hitting based on GC• Investigate relationship between GC and
pitching metrics• Small sample size and sustainability• Potential even greater if landing point &
hang time are known– Ben Jedlovic’s talk at 2013 SABR Analytics
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Example
Divide BBS-VLA space into rectangles• For each rectangle, assign a value
based on some useful metric–e.g., BA, SLG, Linear Weights, …
• For any hitter, weighted average can be computed to arrive at overall metric
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Landing Point/Hang Time(image courtesy of BIS)
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Small horiz speed
Large horiz speed
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Ex: Two MLB Hitters(images courtesy of BIS)
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Batter #1 Batter #2
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tof:R:bbs
bbs:vla:R
Comparing the two methods using TrackMan dataBBS
R
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tof:R:bbs
bbs:vla:R
BBS
R
Comparing the two methods using TrackMan data
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(bbs,vla) (tof,R)?
13Considerable variation of R for fixed bbs,vla.
All stadiums
covered stadiums
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Why does initial velocity not determine landing point
accurately?• Variation in air density
– Easy to control• Variation in wind
– Not so easy to control, except for covered• Variation in spin
– More in a mintue• Variation in surface properties of ball
– A topic of intense interest (to me!)14
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Related question: Is greater “carry” a skill?
• In particular, is ability to put backspin on ball a skill?
• With both initial velocity vector and landing point/hang time, we can address this question for individual batters
• Related to swing parameters
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New Research Project
• Can batted ball data determine swing parameters?
• A very challenging physics problem• In this talk I will
– State the problem– Discuss progress in solving
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Bat Swing Parameters• Bat speed determined by pitch and
batted ball speed• Fan: timing of swing• Tilt: to swing plane• Offset: “squaring up”
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fan
tiltE = offset
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Current State
• Bat swing parameters can predict batted ball parameters.– fan+tilt+offset HLA+VLA+spin axis
• Can batted ball parameters determine bat swing parameters?
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Simple Example:Straight Pitch, RHH, Tilt=00
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E=0”
E=-1”
E=0
E=+1”
Fan=00 Fan=-150Fan=150
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Simple Example:Straight Pitch, RHH, Tilt=450
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E=-1”
E=0
E=+1”
Fan=00
Fan=-150
Fan=150
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A Brief Aside:Spin of a Batted Baseball
2000 fps120 mph
friction
normal force
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Fly balls break toward foul line
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450-450
00
LF
RF
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Effect of tilt on spin axis
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Tilt Balls hit to CF slice
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RHH
LHH
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Current State of Affairs
Spin axis might be able to determine tilt angle
Spin axis can be determined from trajectory
hang time backspin
lateral deflectionsidespin
spin axis ~ tan-1(sidespin/backspin)
Work still in progress but It looks promising that
HLA+VLA+spin axis fan+tilt+offset25
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Summary/Outlook
• We have some new tools for evaluating batting based on process rather than outcome
• Determining swing parameters from batted ball data looks promising but still a work in progress
• Progress on both fronts would benefit greatly from existing data that are not readily available
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