hi i read this Warning: Unable to determine a fixed step size based on the sample times in the model 'doc_pnseq2', because the model does not have any discrete sample times. Picking a fixed step size of (1.6) based on simulation start and stop times. You can disable this diagnostic by explicitly specifying a fixed step size in the Solver pane of the Configuration Parameters dialog box, or setting the 'Automatic solver parameter selection' diagnostic to 'none' in the Solver group on the Diagnostics pane of the Configuration Parameters dialog box.
the problem is solved thank