Simulink: Sine wave generation. Configuration problem.

Hi, While using Simulink, I simply connect a 'sine wave generator' (picked from Simulink>>Sources) to the scope and set the frequency at 100*pi rad/s.

However, on running the simulation, I get a randomly increasing waveform and not a sinusoidal signal of above freq. However, if I set a frequcny such as 1 rad/s, a perfect sine wave is obtained.

I think I must choose a 'continuous' scale to run it and right now maybe a 'discrete scale' is chosen with large step size. May someone suggest a possible remedy?

Thanks.

[yassine amine]

exempel: tried with time=10s , Amplitude=200 , Frequency=100*pi , sample time=0.00001 it gives you a better result

Answer 1

[Guy Rouleau]

By default, the Simulink solver chooses the time steps using:

dt = (t_stop-t_start)/50

With the default parameters, it gives 50 Hz, or a period of 0.02. this is why you do not see the 100rad/s sine way proprerly... Nyquist criteria and aliasing!

I made the following blog post exactly on this topic:

http://blogs.mathworks.com/seth/2009/07/14/refining-the-output-of-a-simulation/

[ANUBHAV SINHA]

Thank you. But please also tell about how i can switch from running the simulation from continuous to discrete mode(where i would further choose the step size) and vice versa.

Earlier when i used to run simulation, a block used to appear on top left corner of the screen. However, it seems to have mysteriously dissappeared since last few days! w

Thanks.

[Guy Rouleau]

Is that a real question? You are using SimPowerSystems and the block you are talking about is the POWERGUI block!

Make yourself a gift and please read the Getting Started section of the SimPowerSystems documentation:

http://www.mathworks.com/help/toolbox/physmod/powersys/ug/f10-1368.html

[Giovanni]

Thank you!!! It helped a lot! :)))))

[ARYA VIJAYAN]

Thank you...you helped me..!!