Calculated 100% rise time value different than matlab value

I calculated a rise time of 1.96s while matlab says it’s 0.974s. I used the equation: Tr=(pi x angle)/wd the calculated angle value is 1.23 rad and the calculated wd is 1.97rad. I tried using the values from matlab to calculate the rise time but nothing comes close unless I use an equation I’ve never seen in class before. I’ve attached it. Any idea why this is would be greatly appreciated. Thanks

Answer 1

[Sam Chak]

Hi @Caleb

Since and , then

% Parameters
theta = 1.23;               % rad
wd    = 1.97;               % rad

% Rise time
tr_CK = (pi * theta)/wd     % rise time by CK

tr_CK = 1.9615

tr_ML = (pi - theta)/wd     % rise time by MATLAB

tr_ML = 0.9704

[Caleb]

Thanks for showing me that I’m supposed to subtract instead of multiply the pi and theta