How do I find the Time at which an Event occurs?

For my data, I have Throttle Position vs. Time. (sampled at 80Hz).

For most of the run, throttle position is varying around 30%, then near the end of the run throttle is quickly advanced to 100% (sometimes to 150%).

I need to find the time at which the throttle is starting to advance to 100%.

Here's what I'm trying, but I can't get it to work for me (etr_cmd is Throttle Position):

    for x = 1:size(etr_cmd,1)
        wave_start = diff(etr_cmd);

        if (wave_start == 1.0)
            time_row1 = x;
        end
    end

Any Help would be greatly appriciated.

[Thomas]

can you show your data?

Answer 1

[Pan]

In my studies, I use a function named "GetSecs", which returns "the time in seconds (with high precision)". Plus, "GetSecs uses the highest precision realtime clock on each operating system."

Answer 2

[Walter Roberson]

Will the change in throttle really be 1.0 exactly? Is your data quadrature encoded or something like that? It would seem more likely that etr_cmd would become 1.0 or greater when the throttle reaches 100%, but that the immediately previous position could be anywhere from ~0.3 upwards, leading to a diff() of 0.7 downward ??

find(etr_cmd >= 1.0, 1)

would seem like what you want.