Hello, I have a state space equation at hand.. This attached with this... Now the term (theta double dot) is a positive step for 0,136 milli seconds and negative step for next 0,136 millisecond and 0 at all other times. So that when I simulate I will get a graph as below: This is the nature of the graph I am expecting. Iam using Matlab ODE45 to solve this. It is pretty easy I think, but I cant figure out how to give this acceleration function. I hope the question is clear. The values are Omega = 219, Zeta = 0,03 Gamma(i) divided by M(i)=0,01 theta double dot = -63 and +63 in the above said intervals respectively.