Problem with running simulink block diagram in discrete mode

I tried to run a Simulink block diagram which consists three difference blocks ... but it's not working properly ... I tried to diagnose the problem by monitoring the signal values. I found that the output value for the difference blocks is not used. I don't know what is this and what's the problem ... please help me

[Sachin Ganjare]

Please elaborate your question. For example: Configuration of the block, error received etc.

[Pouya Jamali]

just no error received ... the block diagram run properly but the output is always zero which must be not. the configuration for the difference blocks is as follow: Initial condition for previous input: 0.0 Input processing: inherited

[Sachin Ganjare]

Which matlab version & from which toolbox this block comes from?

[Pouya Jamali]

It comes from Simulink main library from discrete branch in MATLAB R2012b.

[Pouya Jamali]

no, the solver is variable-step discrete time...

[Sachin Ganjare]

What is output datatype & rounding method? And what is nature of your input data, is it a matrix of fractional values less than one?

[Pouya Jamali]

the output data type is Inherit: Inherit via internal rule and also the rounding mode is floor. the input signal is a scalar which is very small maybe in order of 1e-6.

[Sachin Ganjare]

Did you check output after first sample time is executed?

[Sachin Ganjare]

Probabaly you did not check your output in scope correctly, rather take it in workspace & check, you will find non zero value as initial output

[Pouya Jamali]

Ow, I think the problem is misunderstood ... I should explain it more efficient! using show port values I've monitored all the signals in my block diagram. all the signals are working properly just before passing through difference block. The output of the difference block is not used all the time during simulation. and I think it cause the final output to be zero which must be not.

Answer 1

[Sachin Ganjare]

Check your output min & max values in block configuration.

[Pouya Jamali]

I haven't specified min and max for the output... every thing is by default.