Friday, January 28, 2011

Damping

A difficult decision to make when displaying measurement values is how much damping to apply. Too much damping and you will miss rapid changes in conditions. No damping and quickly changing digital displays become very difficult to interpret. One solution to this dilemma is to dampen all digital numbers, but to show both dampened and undampened values on analog displays. In this system, we use by default a running average over the last 4 seconds for damping. The running averages are recalculated each time a new value is received (10 times per second).
The following figures present around 19 seconds of data recorded during a beat (in an under-canvassed and badly trimmed boat, I must admit...). The dampened data is plotted in red over the real-time data.


Apparent wind angle (AWA)
True wind angle (TWA)



 
Speed through water (STW)
Velocity made good (VMG)



Apparent wind speed (AWS)
True wind speed (TWS)

Custom software (written in C++) has been developed for the notebook to build displays using the real-time data received through the USB port. The only limit here is imagination. The following clip shows how the data presented above look like in the chosen display (the background image can be changed to any one of your preferred vendor or your own). The analog display shows both dampened and umdampened apparent wind angle (AWA), with the dampened true wind speed (TWS) number in the center. In the right column, we find the following dampened numbers: speed through water (STW), VMG, wind direction and heel angle. Two analog sliders also repeat the STW and VMG values.


video 

This other clip shows a debugging display receiving most of the same real-time data, undampened.

video

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