Dear Mohamed, your system becomes then hybrid system, but I do not how did you create your system in order to help you?

i am working on speed control of induction motor . i designed sliding mode control as a continuous time control . i have implemented the system on matlab/simulink using simpowersystems induction motor block but with sampling time 2 microsecond.

Ok Mohamed I think your simulation is correct because you used 2 micro-seconds as sampling time which is nearly continuous, as you reduce the sampling time your discrete system approaches the continuous one. If for example the time constant for a control system is in the order of seconds, then the sampling with microseconds creates quasi-continuous system. I hope this answer helps you.

thank you prof ashraf , can i ask if you have any paper addressed this point . i want to cite it in my work.