Simulink "Sum" block giving wrong result
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I ran a simulation that produced an unnexpected result. It was supposed to be just a noise floor, but for some periods this signal seems to stay constane and then spike before returning to normal. And it happened twice in this particular length of simulation:
I tried the debugger and found an error in a sum block. I've tried re-running multiple times, the error occurs at the same timestep (my noise input didn't change between these runs). If I change the tolerance, it still occurs, but at a different time step.
Example, in this step, the result of the sum of this two signals is correct 1.9794e-11 - 1.905161e-11 = 7.43e-13;
As well as in the next step, -9.639417e-13 + 3.0406e-12 = 2.07e-12
however, at the next step, the signals are updated, but the sum, wrongly, still displays the previous value:
It continues for several steps. If I choose to run the remaining of the simulation, eventually it just "explodes" after a while and goes back to normal.
What could be going on?
3 个评论
Youssef Noureddine
2022-11-9
Hi Arthur,
Can you log the value of the three signals that go into the add block and save it to a .MAT file and attach it here so that I can take a look at it and try it on my end? I can take a look at it tomorrow, but having the signal value history will greatly assist me in determining what could be causing what you are encountering.
Sincerely,
Youssef
Sure thing.
If I import them into matlab and try to sum them, the result is different from what simulink has calculated.
input1 = load('input1.mat').data;
input2 = load('input2.mat').data;
input3 = load('input3.mat').data;
output_from_add = load('output_from_add.mat').data;
input3.Data %input3 is a constant 0;
sumofinputs = input1 + input2;
df = sumofinputs - output_from_add;
plot(df);
Arthur Reis
2022-11-14
编辑：Arthur Reis
2022-11-14
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