Velocity from acceleration data

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nur yusof 2015-6-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/225692-velocity-from-acceleration-data

编辑： Walter Roberson 2015-6-29

Hi all,

I have an acceleration data from accelerometers. I want to get velocity from the data by integrate it using matlab. Here my coding :-

%clear
clc;
%Create a baseline sinusoidal signal
ch1_100mss = ch1_100ms
xdata = ch1_100mss;
y0 = sin(xdata);
%Add noise to the signal
noise = 2*y0.*randn(size(y0));    % Response-dependent 
ydata = y0 + noise;               % Gaussian noise
% %Fit the noisy data with a custom sinusoidal model
f = fittype('a*sin(b*x)');
fit1 = fit(xdata,ydata,f,'StartPoint',[1 1]);
%Find the integral of the fit at the predictors
int = integrate(fit1,xdata,0);
%Plot the data, the fit, and the integral
subplot(2,1,1)
plot(fit1,xdata,ydata)    % cfit plot method
subplot(2,1,2)
plot(xdata,int,'m')      % double plot method
grid on
legend('integral')
plot(fit1,xdata,ydata,{'fit','integral'})

and the plot is

my question are:-

1) When i run the coding below warning is appear

      Warning: Minimum step size reached; singularity possible.
  > In quad at 103
    In cfit.integrate at 42
    In integration at 23
  Warning: Minimum step size reached; singularity possible.
  > In quad at 103
    In cfit.integrate at 40
    In cfit.plot at 138
    In integration at 33
  Warning: Minimum step size reached; singularity possible.
  > In quad at 103
    In cfit.integrate at 42
    In cfit.plot at 138
    In integration at 33