Electronic Golf Swing Analysis - eSwing

[eswing]

I'd appreciate any feedback about our proprietary trajectory model, which is the guts of eSwing's 3D display of ball flight. Check out our website at www.eSwingGolf.com for a complete description of our eSwing Analyzer and (under development) integrated, photo-based launch monitor as an optional accessory. Both products will be available to ship to customers not later than April 1, 2012. Pre-sale of units is available at a significant discount for a limited period. Call or email for details. Thanks for your time, consideration and interest in eSwing!

A short video (4:00 min) is available from our website explaining and animating eSwing's patented "opto-acoustic" technology.

Attachments:

[cwdlaw223]

Does it capture attack angle of the clubhead?

Is attack angle factored into the clubpath determination of the clubhead?

[eswing]

The eSwing Analyzer, by itself, does not measure AOA. With the integrated Launch Monitor, we will calculate (not measure directly) AOA as the difference between assumed Launch Angle (taking into account "roll up" to create backspin) and measured launch angle.

[eswing]

Club speed is not adjusted for AOA, but the distance over which club speed is measured (2.5", between two sets of IR sensors, ahead of impact) would not significantly change club speed even if it was considered.

[cwdlaw223]

How can you get an accurate club path measurement without incorporating an angle of attack measurement?

[eswing]

We use two (2) high frequency ultrasonic (U/S) sensors to measure the distance that the toe of the club passes in front of each of the U/S transducers, 3 inches ahead of the ball center and 3 inches after impact. If the echo time received from the sensors (in pulse-echo mode) is the same for both sensors, then over the 6 inch interval that the transducers are separated, the club is travelling parallel to the target line. That's swing path, totally independent of face angle.

[eswing]

AOA is measured in the vertical plane; swing path is measured in the horizontal plane. Two different, independent measurements.

[roh]

So I live in the north east and I am considering various simulators/monitors to get thru the winter. what is available now, just the club monitor without the launch monitor? If I was hitting balls on it indoors, is there an interface with a computer that would show me the ball flight. I am currently considering the Foresight GC2 launch monitor. It only reads the ball, as I understand it, but a club monitoring add-on is supposedly coming. I'm getting the sense that this is not the year to buy something as the technology is still progressing and the prices will be significantly lower not long from now. Any advice would be appreciated.
Bob

[cwdlaw223]

Dec 3, 2011 17:59:39 GMT -5 eswing said:

AOA is measured in the vertical plane; swing path is measured in the horizontal plane. Two different, independent measurements.

So you don't believe the attack angle affects club path?

[eswing]

Before getting too far into this discussion, we probably ought to agree what we mean by swing path angle and AOA. Are we on the same page? Please see attached PDF. Rick

Attachments:

[cwdlaw223]

I define club path and attack angle the same as Trackman and club path has both and vertical and horizontal component that is three dimensional. It seems like your device is calculating club path as two dimensional.

[natep]

cwd,

Trackman will spit out a number like +4 for club path. Thats just a horizontal measurement, not a 3d measurement.

[cwdlaw223]

I stand corrected. However, doesn't attack angle, VSP and HSP affect the calculation for club path? If attack angle isn't calculated wouldn't that throw off the club path?

[natep]

Im not sure how it calculates something like HSP. I'm not sure how it could unless it caught true low point. In fact I dont know how it calculates anything!

[eswing]

A little basic aerodynamics may be useful in this discussion to set the bar. Doesn't matter whether you're flying an airplane (my background) or trying to make a golf ball or baseball or Frisbee fly, they all fly using the same principles.

Ball displacement, after impact, in the world of golf is defined in terms of X,Y, and Z. X is usually defined as the horizontal displacement vector in the direction of the target line; Y is the vertical displacement vector (up and down) 90 degrees relative to target line; and Z is the horizontal displacement vector (left or right of the target line and perpendicular to it, sometimes called azimuth). Simulation programs use a step time increment, STI, (eSwing uses 0.05 sec) between displacement calculations, along with other inputs such as the Aerodynamic Constant, Ka, (a function of air density and surface area of the golf ball), instantaneous Spin Rate and Vb, which determine coefficients of lift (CL) and drag (CD) for the ball. Wind speed and wind direction are also factored into these displacement calculations. Bottom line is that ball flight (displacement after impact) for each STI is calculated and ball flight can be displayed as 2D or 3D ball flight.

Swing Path, relative to the target line at impact, is measured in the horizontal plane (X-Z). Club head Angle of Attack (AOA), in most systems, is measured in the vertical plane (X-Y), after impact. Super high speed digital and video cameras are capable of actually capturing and measuring the club head path at impact, but these systems are too expensive to build into most monitoring systems. These two measures, Swing Path and AOA, are independent and unrelated. The AOA is simply a measure of what actual ball launch angle was measured relative to the horizon to expected launch angle, which is the loft of the club reduced slightly for "roll-up" as energy is consumed to create backspin, resulting in an expected launch angle slightly less than club loft.

There's a great explanation of this, far better than I can explain in a few sentences, available at: www.golf-simulators.com/physics.htm. Also, a good book on the subject is "The Physics of Golf", 2nd Edition (1999), by Theodore P. Jorgensen, a must read for anyone who wants to really understand the dynamics of how a golf ball flies.