How to give a step input for a function?

Hi, I am trying to solve a system, with the formulae:

Here (theta double dot) is acceleration component whicch is a positive step from time -0,053 to 0,090 and a negative step from time 0,090 to 0,190 seconds. The system is a rotary flexible arm, that makes a 90 degree rotation from rest and then stops. The code I used is:

The nature of the curve I am expecting is as shown below:

The result that I get is different. As shown below:

Can someone please help me to rectify the problem. Thanks in advance. NOTE: please ignore the values in codes. Those may not match with the oscilloscope image uploaded. I hope however, that the idea is conveyed properly.