Inexpensive dynamic balancer for helicopter rotor system

[JMarkWolf]

I'm investigating the feasability of building an inexpensive instrument for capturing the maximum instantaneous acceleration generated by a helicopter main rotor, relative to the rotational phase angle of the rotor.

Commercially available (read expensive) instruments utilize analog accelerometers and ultimately provide velocity data in IPS (inches-per-second at a phase angle). This "dot" is then manually plotted on a polar chart, then extending radii from the dot to the margins of the polar chart provides suggested corrective action. The object is to iteratively "move" the dot as close as possible to the center of the chart.

I'm considering new accelerometer modules from Analog Devices (ADXL series modules) which provide a PWM signal that corresponds directly to the applied acceleration. This signal lends itself to very easy measurement with any common micro-controller, bypassing the need for the low level signal conditioning and A-to-D converters, etc. Capturing the phase angle of the rotor is also very easy using similar pulse duration counting techniques.

Can anyone comment on common pitfalls I may encounter with this approach, and offer any suggestions?

 

[nbucska]

I think it would be cost effective to use 188 based

http://www.bagotronix.com

's DOS - stamp (<$170.- with 8 ch. ADC)
You can compile/assemble on any PC in BASIC, C, FORTRAN
etc. Add 2 acc.meters, 2 op-amps, it is still cheap...

Small, too.
<nbucska@pcperipherals.com>