two intervals const a p3

• Position $$\tag{D3} x(t) = \left\{ \begin{array}{cc} x_0 + v_0(t - t_0) + \tfrac12 a_0(t - t_0)^2, & t_0 \le t < t_1, \\[0.5em] x_1 + v_1(t - t_1) + \tfrac12 a_1(t - t_1)^2, & t_1 \le t < t_2, \end{array} \right. $$ with $t_{n+1} = t_n + \tau_n$, where $\tau_n$ is $n$-th time interval.
• Initial conditions
  • $x(t_0) = x_0$,
  • $x(t_1) = x_1$ and $x(t_1) = x_0 + v_0(t_1 - t_0) + \tfrac12 a_0(t_1 - t_0)^2$.