the integration block with limitation saturate your values. You are limiting the answer of the integration to a certain range of numbers. Your original system might be singular, the limitation bound the values to keep the answer in an acceptable range

Dear Colleague,

Good Day,

The Integrator block outputs the value of the integral of its input signal with respect to time.

The Integrator Limited block is identical to the Integrator block with the exception that the output of the block is limited based on the upper and lower saturation limits. See Limiting the Integral for details. ( 1st link ).

Limiting the Integral

To prevent the output from exceeding specifiable levels, select the Limit output check box and enter the limits in the appropriate parameter fields. This action causes the block to function as a limited integrator. When the output reaches the limits, the integral action is turned off to prevent integral wind up. During a simulation, you can change the limits but you cannot change whether the output is limited. The block determines output as follows:

When the integral is less than or equal to the Lower saturation limit, the output is held at the Lower saturation limit.

When the integral is between the Lower saturation limit and the Upper saturation limit, the output is the integral.

When the integral is greater than or equal to the Upper saturation limit, the output is held at the Upper saturation limit.

To generate a signal that indicates when the state is being limited, select the Show saturation port check box. A saturation port appears below the block output port.

Please, see the attached links for detail:

http://www.mathworks.com/help/simulink/slref/integrator.html

http://radio.feld.cvut.cz/matlab/toolbox/simulink/ug/integrator.html

http://www-rohan.sdsu.edu/doc/matlab/toolbox/simulink/slref/integrator.html

http://www-rohan.sdsu.edu/doc/matlab/toolbox/simulink/slref/discretetimeintegrator.html